Separate core classes into separate files (#545)

81 files changed, 923 insertions, 812 deletions

diff --git a/ext/js/accessibility/accessibility-controller.js b/ext/js/accessibility/accessibility-controller.js
index 3cc400e4..b2785893 100644
--- a/ext/js/accessibility/accessibility-controller.js
+++ b/ext/js/accessibility/accessibility-controller.js
@@ -17,7 +17,7 @@
  */
 
 import {isContentScriptRegistered, registerContentScript, unregisterContentScript} from '../background/script-manager.js';
-import {log} from '../core.js';
+import {log} from '../core/logger.js';
 
 /**
  * This class controls the registration of accessibility handlers.
diff --git a/ext/js/app/content-script-main.js b/ext/js/app/content-script-main.js
index e640dc3c..c0bea73c 100644
--- a/ext/js/app/content-script-main.js
+++ b/ext/js/app/content-script-main.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log} from '../core.js';
+import {log} from '../core/logger.js';
 import {HotkeyHandler} from '../input/hotkey-handler.js';
 import {yomitan} from '../yomitan.js';
 import {Frontend} from './frontend.js';
diff --git a/ext/js/app/frontend.js b/ext/js/app/frontend.js
index 8ac3acc3..13d2d9d8 100644
--- a/ext/js/app/frontend.js
+++ b/ext/js/app/frontend.js
@@ -16,8 +16,10 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection, log, promiseAnimationFrame} from '../core.js';
 import {createApiMap, invokeApiMapHandler} from '../core/api-map.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
+import {log} from '../core/logger.js';
+import {promiseAnimationFrame} from '../core/utilities.js';
 import {DocumentUtil} from '../dom/document-util.js';
 import {TextSourceElement} from '../dom/text-source-element.js';
 import {TextSourceRange} from '../dom/text-source-range.js';
diff --git a/ext/js/app/popup-factory.js b/ext/js/app/popup-factory.js
index 14fc4617..f9eec913 100644
--- a/ext/js/app/popup-factory.js
+++ b/ext/js/app/popup-factory.js
@@ -17,7 +17,7 @@
  */
 
 import {FrameOffsetForwarder} from '../comm/frame-offset-forwarder.js';
-import {generateId} from '../core.js';
+import {generateId} from '../core/utilities.js';
 import {yomitan} from '../yomitan.js';
 import {PopupProxy} from './popup-proxy.js';
 import {PopupWindow} from './popup-window.js';
diff --git a/ext/js/app/popup-proxy.js b/ext/js/app/popup-proxy.js
index 66c91994..fa4a448b 100644
--- a/ext/js/app/popup-proxy.js
+++ b/ext/js/app/popup-proxy.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, log} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {log} from '../core/logger.js';
 import {yomitan} from '../yomitan.js';
 
 /**
diff --git a/ext/js/app/popup-window.js b/ext/js/app/popup-window.js
index ff8a1273..60d99612 100644
--- a/ext/js/app/popup-window.js
+++ b/ext/js/app/popup-window.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
 import {yomitan} from '../yomitan.js';
 
 /**
diff --git a/ext/js/app/popup.js b/ext/js/app/popup.js
index d83618d3..0a84f3f7 100644
--- a/ext/js/app/popup.js
+++ b/ext/js/app/popup.js
@@ -17,8 +17,11 @@
  */
 
 import {FrameClient} from '../comm/frame-client.js';
-import {DynamicProperty, EventDispatcher, EventListenerCollection, deepEqual} from '../core.js';
+import {DynamicProperty} from '../core/dynamic-property.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {ExtensionError} from '../core/extension-error.js';
+import {deepEqual} from '../core/utilities.js';
 import {DocumentUtil} from '../dom/document-util.js';
 import {loadStyle} from '../dom/style-util.js';
 import {yomitan} from '../yomitan.js';
diff --git a/ext/js/background/backend.js b/ext/js/background/backend.js
index f2f2fda9..38d82496 100644
--- a/ext/js/background/backend.js
+++ b/ext/js/background/backend.js
@@ -22,10 +22,11 @@ import {AnkiConnect} from '../comm/anki-connect.js';
 import {ClipboardMonitor} from '../comm/clipboard-monitor.js';
 import {ClipboardReader} from '../comm/clipboard-reader.js';
 import {Mecab} from '../comm/mecab.js';
-import {clone, deferPromise, isObject, log, promiseTimeout} from '../core.js';
 import {createApiMap, invokeApiMapHandler} from '../core/api-map.js';
 import {ExtensionError} from '../core/extension-error.js';
 import {readResponseJson} from '../core/json.js';
+import {log} from '../core/logger.js';
+import {clone, deferPromise, isObject, promiseTimeout} from '../core/utilities.js';
 import {AnkiUtil} from '../data/anki-util.js';
 import {OptionsUtil} from '../data/options-util.js';
 import {PermissionsUtil} from '../data/permissions-util.js';
diff --git a/ext/js/background/offscreen-proxy.js b/ext/js/background/offscreen-proxy.js
index abd3fa37..77f5448a 100644
--- a/ext/js/background/offscreen-proxy.js
+++ b/ext/js/background/offscreen-proxy.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {isObject} from '../core.js';
+import {isObject} from '../core/utilities.js';
 import {ExtensionError} from '../core/extension-error.js';
 import {ArrayBufferUtil} from '../data/sandbox/array-buffer-util.js';
 
diff --git a/ext/js/comm/clipboard-monitor.js b/ext/js/comm/clipboard-monitor.js
index c4381910..a1ea3362 100644
--- a/ext/js/comm/clipboard-monitor.js
+++ b/ext/js/comm/clipboard-monitor.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
 
 /**
  * @augments EventDispatcher<import('clipboard-monitor').Events>
diff --git a/ext/js/comm/cross-frame-api.js b/ext/js/comm/cross-frame-api.js
index ab21967a..fca7c84d 100644
--- a/ext/js/comm/cross-frame-api.js
+++ b/ext/js/comm/cross-frame-api.js
@@ -16,10 +16,12 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, EventListenerCollection, log} from '../core.js';
 import {extendApiMap, invokeApiMapHandler} from '../core/api-map.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {ExtensionError} from '../core/extension-error.js';
 import {parseJson} from '../core/json.js';
+import {log} from '../core/logger.js';
 import {yomitan} from '../yomitan.js';
 
 /**
diff --git a/ext/js/comm/frame-ancestry-handler.js b/ext/js/comm/frame-ancestry-handler.js
index a9e49a6e..31739654 100644
--- a/ext/js/comm/frame-ancestry-handler.js
+++ b/ext/js/comm/frame-ancestry-handler.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {generateId} from '../core.js';
+import {generateId} from '../core/utilities.js';
 import {yomitan} from '../yomitan.js';
 
 /**
diff --git a/ext/js/comm/frame-client.js b/ext/js/comm/frame-client.js
index aadb4f08..62db1edd 100644
--- a/ext/js/comm/frame-client.js
+++ b/ext/js/comm/frame-client.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {deferPromise, generateId, isObject} from '../core.js';
+import {deferPromise, generateId, isObject} from '../core/utilities.js';
 
 export class FrameClient {
     constructor() {
diff --git a/ext/js/comm/frame-endpoint.js b/ext/js/comm/frame-endpoint.js
index bf5efdd4..0008417d 100644
--- a/ext/js/comm/frame-endpoint.js
+++ b/ext/js/comm/frame-endpoint.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection, generateId} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
+import {generateId} from '../core/utilities.js';
 import {yomitan} from '../yomitan.js';
 
 export class FrameEndpoint {
diff --git a/ext/js/comm/mecab.js b/ext/js/comm/mecab.js
index 57d97e98..1ff3f066 100644
--- a/ext/js/comm/mecab.js
+++ b/ext/js/comm/mecab.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {toError} from '../core/to-error.js';
 
 /**
diff --git a/ext/js/core.js b/ext/js/core.js
deleted file mode 100644
index 1c2ff06b..00000000
--- a/ext/js/core.js
+++ /dev/null
@@ -1,737 +0,0 @@
-/*
- * Copyright (C) 2023-2024  Yomitan Authors
- * Copyright (C) 2019-2022  Yomichan Authors
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
-
-import {ExtensionError} from './core/extension-error.js';
-
-/**
- * Checks whether a given value is a non-array object.
- * @param {unknown} value The value to check.
- * @returns {boolean} `true` if the value is an object and not an array, `false` otherwise.
- */
-export function isObject(value) {
-    return typeof value === 'object' && value !== null && !Array.isArray(value);
-}
-
-/**
- * Converts any string into a form that can be passed into the RegExp constructor.
- * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
- * @param {string} string The string to convert to a valid regular expression.
- * @returns {string} The escaped string.
- */
-export function escapeRegExp(string) {
-    return string.replace(/[.*+\-?^${}()|[\]\\]/g, '\\$&');
-}
-
-/**
- * Reverses a string.
- * @param {string} string The string to reverse.
- * @returns {string} The returned string, which retains proper UTF-16 surrogate pair order.
- */
-export function stringReverse(string) {
-    return [...string].reverse().join('');
-}
-
-/**
- * Creates a deep clone of an object or value. This is similar to `parseJson(JSON.stringify(value))`.
- * @template [T=unknown]
- * @param {T} value The value to clone.
- * @returns {T} A new clone of the value.
- * @throws An error if the value is circular and cannot be cloned.
- */
-export function clone(value) {
-    if (value === null) { return /** @type {T} */ (null); }
-    switch (typeof value) {
-        case 'boolean':
-        case 'number':
-        case 'string':
-        case 'bigint':
-        case 'symbol':
-        case 'undefined':
-            return value;
-        default:
-            return cloneInternal(value, new Set());
-    }
-}
-
-/**
- * @template [T=unknown]
- * @param {T} value
- * @param {Set<unknown>} visited
- * @returns {T}
- * @throws {Error}
- */
-function cloneInternal(value, visited) {
-    if (value === null) { return /** @type {T} */ (null); }
-    switch (typeof value) {
-        case 'boolean':
-        case 'number':
-        case 'string':
-        case 'bigint':
-        case 'symbol':
-        case 'undefined':
-            return value;
-        case 'object':
-            return /** @type {T} */ (
-                    Array.isArray(value) ?
-                    cloneArray(value, visited) :
-                    cloneObject(/** @type {import('core').SerializableObject} */ (value), visited)
-            );
-        default:
-            throw new Error(`Cannot clone object of type ${typeof value}`);
-    }
-}
-
-/**
- * @param {unknown[]} value
- * @param {Set<unknown>} visited
- * @returns {unknown[]}
- * @throws {Error}
- */
-function cloneArray(value, visited) {
-    if (visited.has(value)) { throw new Error('Circular'); }
-    try {
-        visited.add(value);
-        const result = [];
-        for (const item of value) {
-            result.push(cloneInternal(item, visited));
-        }
-        return result;
-    } finally {
-        visited.delete(value);
-    }
-}
-
-/**
- * @param {import('core').SerializableObject} value
- * @param {Set<unknown>} visited
- * @returns {import('core').SerializableObject}
- * @throws {Error}
- */
-function cloneObject(value, visited) {
-    if (visited.has(value)) { throw new Error('Circular'); }
-    try {
-        visited.add(value);
-        /** @type {import('core').SerializableObject} */
-        const result = {};
-        for (const key in value) {
-            if (Object.prototype.hasOwnProperty.call(value, key)) {
-                result[key] = cloneInternal(value[key], visited);
-            }
-        }
-        return result;
-    } finally {
-        visited.delete(value);
-    }
-}
-
-/**
- * Checks if an object or value is deeply equal to another object or value.
- * @param {unknown} value1 The first value to check.
- * @param {unknown} value2 The second value to check.
- * @returns {boolean} `true` if the values are the same object, or deeply equal without cycles. `false` otherwise.
- */
-export function deepEqual(value1, value2) {
-    if (value1 === value2) { return true; }
-
-    const type = typeof value1;
-    if (typeof value2 !== type) { return false; }
-
-    switch (type) {
-        case 'object':
-        case 'function':
-            return deepEqualInternal(value1, value2, new Set());
-        default:
-            return false;
-    }
-}
-
-/**
- * @param {unknown} value1
- * @param {unknown} value2
- * @param {Set<unknown>} visited1
- * @returns {boolean}
- */
-function deepEqualInternal(value1, value2, visited1) {
-    if (value1 === value2) { return true; }
-
-    const type = typeof value1;
-    if (typeof value2 !== type) { return false; }
-
-    switch (type) {
-        case 'object':
-        case 'function':
-        {
-            if (value1 === null || value2 === null) { return false; }
-            const array = Array.isArray(value1);
-            if (array !== Array.isArray(value2)) { return false; }
-            if (visited1.has(value1)) { return false; }
-            visited1.add(value1);
-            return (
-                    array ?
-                    areArraysEqual(/** @type {unknown[]} */ (value1), /** @type {unknown[]} */ (value2), visited1) :
-                    areObjectsEqual(/** @type {import('core').UnknownObject} */ (value1), /** @type {import('core').UnknownObject} */ (value2), visited1)
-            );
-        }
-        default:
-            return false;
-    }
-}
-
-/**
- * @param {import('core').UnknownObject} value1
- * @param {import('core').UnknownObject} value2
- * @param {Set<unknown>} visited1
- * @returns {boolean}
- */
-function areObjectsEqual(value1, value2, visited1) {
-    const keys1 = Object.keys(value1);
-    const keys2 = Object.keys(value2);
-    if (keys1.length !== keys2.length) { return false; }
-
-    const keys1Set = new Set(keys1);
-    for (const key of keys2) {
-        if (!keys1Set.has(key) || !deepEqualInternal(value1[key], value2[key], visited1)) { return false; }
-    }
-
-    return true;
-}
-
-/**
- * @param {unknown[]} value1
- * @param {unknown[]} value2
- * @param {Set<unknown>} visited1
- * @returns {boolean}
- */
-function areArraysEqual(value1, value2, visited1) {
-    const length = value1.length;
-    if (length !== value2.length) { return false; }
-
-    for (let i = 0; i < length; ++i) {
-        if (!deepEqualInternal(value1[i], value2[i], visited1)) { return false; }
-    }
-
-    return true;
-}
-
-/**
- * Creates a new base-16 (lower case) string of a sequence of random bytes of the given length.
- * @param {number} length The number of bytes the string represents. The returned string's length will be twice as long.
- * @returns {string} A string of random characters.
- */
-export function generateId(length) {
-    const array = new Uint8Array(length);
-    crypto.getRandomValues(array);
-    let id = '';
-    for (const value of array) {
-        id += value.toString(16).padStart(2, '0');
-    }
-    return id;
-}
-
-/**
- * Creates an unresolved promise that can be resolved later, outside the promise's executor function.
- * @template [T=unknown]
- * @returns {import('core').DeferredPromiseDetails<T>} An object `{promise, resolve, reject}`, containing the promise and the resolve/reject functions.
- */
-export function deferPromise() {
-    /** @type {((value: T) => void)|undefined} */
-    let resolve;
-    /** @type {((reason?: import('core').RejectionReason) => void)|undefined} */
-    let reject;
-    const promise = new Promise((resolve2, reject2) => {
-        resolve = resolve2;
-        reject = reject2;
-    });
-    return {
-        promise,
-        resolve: /** @type {(value: T) => void} */ (resolve),
-        reject: /** @type {(reason?: import('core').RejectionReason) => void} */ (reject)
-    };
-}
-
-/**
- * Creates a promise that is resolved after a set delay.
- * @param {number} delay How many milliseconds until the promise should be resolved. If 0, the promise is immediately resolved.
- * @returns {Promise<void>} A promise with two additional properties: `resolve` and `reject`, which can be used to complete the promise early.
- */
-export function promiseTimeout(delay) {
-    return delay <= 0 ? Promise.resolve() : new Promise((resolve) => { setTimeout(resolve, delay); });
-}
-
-/**
- * Creates a promise that will resolve after the next animation frame, using `requestAnimationFrame`.
- * @param {number} [timeout] A maximum duration (in milliseconds) to wait until the promise resolves. If null or omitted, no timeout is used.
- * @returns {Promise<{time: number, timeout: boolean}>} A promise that is resolved with `{time, timeout}`, where `time` is the timestamp from `requestAnimationFrame`,
- *   and `timeout` is a boolean indicating whether the cause was a timeout or not.
- * @throws The promise throws an error if animation is not supported in this context, such as in a service worker.
- */
-export function promiseAnimationFrame(timeout) {
-    return new Promise((resolve, reject) => {
-        if (typeof cancelAnimationFrame !== 'function' || typeof requestAnimationFrame !== 'function') {
-            reject(new Error('Animation not supported in this context'));
-            return;
-        }
-
-        /** @type {?import('core').Timeout} */
-        let timer = null;
-        /** @type {?number} */
-        let frameRequest = null;
-        /**
-         * @param {number} time
-         */
-        const onFrame = (time) => {
-            frameRequest = null;
-            if (timer !== null) {
-                clearTimeout(timer);
-                timer = null;
-            }
-            resolve({time, timeout: false});
-        };
-        const onTimeout = () => {
-            timer = null;
-            if (frameRequest !== null) {
-                // eslint-disable-next-line no-undef
-                cancelAnimationFrame(frameRequest);
-                frameRequest = null;
-            }
-            resolve({time: performance.now(), timeout: true});
-        };
-
-        // eslint-disable-next-line no-undef
-        frameRequest = requestAnimationFrame(onFrame);
-        if (typeof timeout === 'number') {
-            timer = setTimeout(onTimeout, timeout);
-        }
-    });
-}
-
-/**
- * The following typedef is required because the JSDoc `implements` tag doesn't work with `import()`.
- * https://github.com/microsoft/TypeScript/issues/49905
- * @typedef {import('core').EventDispatcherOffGeneric} EventDispatcherOffGeneric
- */
-
-/**
- * Base class controls basic event dispatching.
- * @template {import('core').EventSurface} TSurface
- * @implements {EventDispatcherOffGeneric}
- */
-export class EventDispatcher {
-    /**
-     * Creates a new instance.
-     */
-    constructor() {
-        /** @type {Map<import('core').EventNames<TSurface>, import('core').EventHandlerAny[]>} */
-        this._eventMap = new Map();
-    }
-
-    /**
-     * Triggers an event with the given name and specified argument.
-     * @template {import('core').EventNames<TSurface>} TName
-     * @param {TName} eventName The string representing the event's name.
-     * @param {import('core').EventArgument<TSurface, TName>} details The argument passed to the callback functions.
-     * @returns {boolean} `true` if any callbacks were registered, `false` otherwise.
-     */
-    trigger(eventName, details) {
-        const callbacks = this._eventMap.get(eventName);
-        if (typeof callbacks === 'undefined') { return false; }
-
-        for (const callback of callbacks) {
-            callback(details);
-        }
-        return true;
-    }
-
-    /**
-     * Adds a single event listener to a specific event.
-     * @template {import('core').EventNames<TSurface>} TName
-     * @param {TName} eventName The string representing the event's name.
-     * @param {import('core').EventHandler<TSurface, TName>} callback The event listener callback to add.
-     */
-    on(eventName, callback) {
-        let callbacks = this._eventMap.get(eventName);
-        if (typeof callbacks === 'undefined') {
-            callbacks = [];
-            this._eventMap.set(eventName, callbacks);
-        }
-        callbacks.push(callback);
-    }
-
-    /**
-     * Removes a single event listener from a specific event.
-     * @template {import('core').EventNames<TSurface>} TName
-     * @param {TName} eventName The string representing the event's name.
-     * @param {import('core').EventHandler<TSurface, TName>} callback The event listener callback to add.
-     * @returns {boolean} `true` if the callback was removed, `false` otherwise.
-     */
-    off(eventName, callback) {
-        const callbacks = this._eventMap.get(eventName);
-        if (typeof callbacks === 'undefined') { return false; }
-
-        const ii = callbacks.length;
-        for (let i = 0; i < ii; ++i) {
-            if (callbacks[i] === callback) {
-                callbacks.splice(i, 1);
-                if (callbacks.length === 0) {
-                    this._eventMap.delete(eventName);
-                }
-                return true;
-            }
-        }
-        return false;
-    }
-
-    /**
-     * Checks if an event has any listeners.
-     * @template {import('core').EventNames<TSurface>} TName
-     * @param {TName} eventName The string representing the event's name.
-     * @returns {boolean} `true` if the event has listeners, `false` otherwise.
-     */
-    hasListeners(eventName) {
-        const callbacks = this._eventMap.get(eventName);
-        return (typeof callbacks !== 'undefined' && callbacks.length > 0);
-    }
-}
-
-/**
- * Class which stores event listeners added to various objects, making it easy to remove them in bulk.
- */
-export class EventListenerCollection {
-    /**
-     * Creates a new instance.
-     */
-    constructor() {
-        /** @type {import('event-listener-collection').EventListenerDetails[]} */
-        this._eventListeners = [];
-    }
-
-    /**
-     * Returns the number of event listeners that are currently in the object.
-     * @type {number}
-     */
-    get size() {
-        return this._eventListeners.length;
-    }
-
-    /**
-     * Adds an event listener using `object.addEventListener`. The listener will later be removed using `object.removeEventListener`.
-     * @param {import('event-listener-collection').EventTarget} target The object to add the event listener to.
-     * @param {string} type The name of the event.
-     * @param {EventListener | EventListenerObject | import('event-listener-collection').EventListenerFunction} listener The callback listener.
-     * @param {AddEventListenerOptions | boolean} [options] Options for the event.
-     */
-    addEventListener(target, type, listener, options) {
-        target.addEventListener(type, listener, options);
-        this._eventListeners.push({type: 'removeEventListener', target, eventName: type, listener, options});
-    }
-
-    /**
-     * Adds an event listener using `object.addListener`. The listener will later be removed using `object.removeListener`.
-     * @template {import('event-listener-collection').EventListenerFunction} TCallback
-     * @template [TArgs=unknown]
-     * @param {import('event-listener-collection').ExtensionEvent<TCallback, TArgs>} target The object to add the event listener to.
-     * @param {TCallback} callback The callback.
-     * @param {TArgs[]} args The extra argument array passed to the `addListener`/`removeListener` function.
-     */
-    addListener(target, callback, ...args) {
-        target.addListener(callback, ...args);
-        this._eventListeners.push({type: 'removeListener', target, callback, args});
-    }
-
-    /**
-     * Adds an event listener using `object.on`. The listener will later be removed using `object.off`.
-     * @template {import('core').EventSurface} TSurface
-     * @template {import('core').EventNames<TSurface>} TName
-     * @param {EventDispatcher<TSurface>} target The object to add the event listener to.
-     * @param {TName} eventName The string representing the event's name.
-     * @param {import('core').EventHandler<TSurface, TName>} callback The event listener callback to add.
-     */
-    on(target, eventName, callback) {
-        target.on(eventName, callback);
-        this._eventListeners.push({type: 'off', eventName, target, callback});
-    }
-
-    /**
-     * Removes all event listeners added to objects for this instance and clears the internal list of event listeners.
-     */
-    removeAllEventListeners() {
-        if (this._eventListeners.length === 0) { return; }
-        for (const item of this._eventListeners) {
-            switch (item.type) {
-                case 'removeEventListener':
-                    item.target.removeEventListener(item.eventName, item.listener, item.options);
-                    break;
-                case 'removeListener':
-                    item.target.removeListener(item.callback, ...item.args);
-                    break;
-                case 'off':
-                    item.target.off(item.eventName, item.callback);
-                    break;
-            }
-        }
-        this._eventListeners = [];
-    }
-}
-
-/**
- * Class representing a generic value with an override stack.
- * Changes can be observed by listening to the 'change' event.
- * @template [T=unknown]
- * @augments EventDispatcher<import('dynamic-property').Events<T>>
- */
-export class DynamicProperty extends EventDispatcher {
-    /**
-     * Creates a new instance with the specified value.
-     * @param {T} value The value to assign.
-     */
-    constructor(value) {
-        super();
-        /** @type {T} */
-        this._value = value;
-        /** @type {T} */
-        this._defaultValue = value;
-        /** @type {{value: T, priority: number, token: string}[]} */
-        this._overrides = [];
-    }
-
-    /**
-     * Gets the default value for the property, which is assigned to the
-     * public value property when no overrides are present.
-     * @type {T}
-     */
-    get defaultValue() {
-        return this._defaultValue;
-    }
-
-    /**
-     * Assigns the default value for the property. If no overrides are present
-     * and if the value is different than the current default value,
-     * the 'change' event will be triggered.
-     * @param {T} value The value to assign.
-     */
-    set defaultValue(value) {
-        this._defaultValue = value;
-        if (this._overrides.length === 0) { this._updateValue(); }
-    }
-
-    /**
-     * Gets the current value for the property, taking any overrides into account.
-     * @type {T}
-     */
-    get value() {
-        return this._value;
-    }
-
-    /**
-     * Gets the number of overrides added to the property.
-     * @type {number}
-     */
-    get overrideCount() {
-        return this._overrides.length;
-    }
-
-    /**
-     * Adds an override value with the specified priority to the override stack.
-     * Values with higher priority will take precedence over those with lower.
-     * For tie breaks, the override value added first will take precedence.
-     * If the newly added override has the highest priority of all overrides
-     * and if the override value is different from the current value,
-     * the 'change' event will be fired.
-     * @param {T} value The override value to assign.
-     * @param {number} [priority] The priority value to use, as a number.
-     * @returns {import('core').TokenString} A string token which can be passed to the clearOverride function
-     *   to remove the override.
-     */
-    setOverride(value, priority = 0) {
-        const overridesCount = this._overrides.length;
-        let i = 0;
-        for (; i < overridesCount; ++i) {
-            if (priority > this._overrides[i].priority) { break; }
-        }
-        const token = generateId(16);
-        this._overrides.splice(i, 0, {value, priority, token});
-        if (i === 0) { this._updateValue(); }
-        return token;
-    }
-
-    /**
-     * Removes a specific override value. If the removed override
-     * had the highest priority, and the new value is different from
-     * the previous value, the 'change' event will be fired.
-     * @param {import('core').TokenString} token The token for the corresponding override which is to be removed.
-     * @returns {boolean} `true` if an override was returned, `false` otherwise.
-     */
-    clearOverride(token) {
-        for (let i = 0, ii = this._overrides.length; i < ii; ++i) {
-            if (this._overrides[i].token === token) {
-                this._overrides.splice(i, 1);
-                if (i === 0) { this._updateValue(); }
-                return true;
-            }
-        }
-        return false;
-    }
-
-    /**
-     * Updates the current value using the current overrides and default value.
-     * If the new value differs from the previous value, the 'change' event will be fired.
-     */
-    _updateValue() {
-        const value = this._overrides.length > 0 ? this._overrides[0].value : this._defaultValue;
-        if (this._value === value) { return; }
-        this._value = value;
-        this.trigger('change', {value});
-    }
-}
-
-/**
- * This class handles logging of messages to the console and triggering
- * an event for log calls.
- * @augments EventDispatcher<import('log').Events>
- */
-export class Logger extends EventDispatcher {
-    /**
-     * Creates a new instance.
-     */
-    constructor() {
-        super();
-        /** @type {string} */
-        this._extensionName = 'Yomitan';
-        try {
-            const {name, version} = chrome.runtime.getManifest();
-            this._extensionName = `${name} ${version}`;
-        } catch (e) {
-            // NOP
-        }
-    }
-
-    /**
-     * Logs a generic error. This will trigger the 'log' event with the same arguments as the function invocation.
-     * @param {unknown} error The error to log. This is typically an `Error` or `Error`-like object.
-     * @param {import('log').LogLevel} level The level to log at. Values include `'info'`, `'debug'`, `'warn'`, and `'error'`.
-     *   Other values will be logged at a non-error level.
-     * @param {?import('log').LogContext} [context] An optional context object for the error which should typically include a `url` field.
-     */
-    log(error, level, context = null) {
-        if (typeof context !== 'object' || context === null) {
-            context = {url: location.href};
-        }
-
-        let errorString;
-        try {
-            if (typeof error === 'string') {
-                errorString = error;
-            } else {
-                errorString = (
-                    typeof error === 'object' && error !== null ?
-                    error.toString() :
-                    `${error}`
-                );
-                if (/^\[object \w+\]$/.test(errorString)) {
-                    errorString = JSON.stringify(error);
-                }
-            }
-        } catch (e) {
-            errorString = `${error}`;
-        }
-
-        let errorStack;
-        try {
-            errorStack = (
-                error instanceof Error ?
-                (typeof error.stack === 'string' ? error.stack.trimEnd() : '') :
-                ''
-            );
-        } catch (e) {
-            errorStack = '';
-        }
-
-        let errorData;
-        try {
-            if (error instanceof ExtensionError) {
-                errorData = error.data;
-            }
-        } catch (e) {
-            // NOP
-        }
-
-        if (errorStack.startsWith(errorString)) {
-            errorString = errorStack;
-        } else if (errorStack.length > 0) {
-            errorString += `\n${errorStack}`;
-        }
-
-        let message = `${this._extensionName} has encountered a problem.`;
-        message += `\nOriginating URL: ${context.url}\n`;
-        message += errorString;
-        if (typeof errorData !== 'undefined') {
-            message += `\nData: ${JSON.stringify(errorData, null, 4)}`;
-        }
-        message += '\n\nIssues can be reported at https://github.com/themoeway/yomitan/issues';
-
-        /* eslint-disable no-console */
-        switch (level) {
-            case 'log': console.log(message); break;
-            case 'info': console.info(message); break;
-            case 'debug': console.debug(message); break;
-            case 'warn': console.warn(message); break;
-            case 'error': console.error(message); break;
-        }
-        /* eslint-enable no-console */
-
-        this.trigger('log', {error, level, context});
-    }
-
-    /**
-     * Logs a warning. This function invokes `log` internally.
-     * @param {unknown} error The error to log. This is typically an `Error` or `Error`-like object.
-     * @param {?import('log').LogContext} context An optional context object for the error which should typically include a `url` field.
-     */
-    warn(error, context = null) {
-        this.log(error, 'warn', context);
-    }
-
-    /**
-     * Logs an error. This function invokes `log` internally.
-     * @param {unknown} error The error to log. This is typically an `Error` or `Error`-like object.
-     * @param {?import('log').LogContext} context An optional context object for the error which should typically include a `url` field.
-     */
-    error(error, context = null) {
-        this.log(error, 'error', context);
-    }
-
-    /**
-     * @param {import('log').LogLevel} errorLevel
-     * @returns {import('log').LogErrorLevelValue}
-     */
-    getLogErrorLevelValue(errorLevel) {
-        switch (errorLevel) {
-            case 'log':
-            case 'info':
-            case 'debug':
-                return 0;
-            case 'warn': return 1;
-            case 'error': return 2;
-        }
-    }
-}
-
-/**
- * This object is the default logger used by the runtime.
- */
-export const log = new Logger();
diff --git a/ext/js/core/dynamic-property.js b/ext/js/core/dynamic-property.js
new file mode 100644
index 00000000..5d8b4716
--- /dev/null
+++ b/ext/js/core/dynamic-property.js
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2023-2024  Yomitan Authors
+ * Copyright (C) 2019-2022  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {EventDispatcher} from './event-dispatcher.js';
+import {generateId} from './utilities.js';
+
+/**
+ * Class representing a generic value with an override stack.
+ * Changes can be observed by listening to the 'change' event.
+ * @template [T=unknown]
+ * @augments EventDispatcher<import('dynamic-property').Events<T>>
+ */
+export class DynamicProperty extends EventDispatcher {
+    /**
+     * Creates a new instance with the specified value.
+     * @param {T} value The value to assign.
+     */
+    constructor(value) {
+        super();
+        /** @type {T} */
+        this._value = value;
+        /** @type {T} */
+        this._defaultValue = value;
+        /** @type {{value: T, priority: number, token: string}[]} */
+        this._overrides = [];
+    }
+
+    /**
+     * Gets the default value for the property, which is assigned to the
+     * public value property when no overrides are present.
+     * @type {T}
+     */
+    get defaultValue() {
+        return this._defaultValue;
+    }
+
+    /**
+     * Assigns the default value for the property. If no overrides are present
+     * and if the value is different than the current default value,
+     * the 'change' event will be triggered.
+     * @param {T} value The value to assign.
+     */
+    set defaultValue(value) {
+        this._defaultValue = value;
+        if (this._overrides.length === 0) { this._updateValue(); }
+    }
+
+    /**
+     * Gets the current value for the property, taking any overrides into account.
+     * @type {T}
+     */
+    get value() {
+        return this._value;
+    }
+
+    /**
+     * Gets the number of overrides added to the property.
+     * @type {number}
+     */
+    get overrideCount() {
+        return this._overrides.length;
+    }
+
+    /**
+     * Adds an override value with the specified priority to the override stack.
+     * Values with higher priority will take precedence over those with lower.
+     * For tie breaks, the override value added first will take precedence.
+     * If the newly added override has the highest priority of all overrides
+     * and if the override value is different from the current value,
+     * the 'change' event will be fired.
+     * @param {T} value The override value to assign.
+     * @param {number} [priority] The priority value to use, as a number.
+     * @returns {import('core').TokenString} A string token which can be passed to the clearOverride function
+     *   to remove the override.
+     */
+    setOverride(value, priority = 0) {
+        const overridesCount = this._overrides.length;
+        let i = 0;
+        for (; i < overridesCount; ++i) {
+            if (priority > this._overrides[i].priority) { break; }
+        }
+        const token = generateId(16);
+        this._overrides.splice(i, 0, {value, priority, token});
+        if (i === 0) { this._updateValue(); }
+        return token;
+    }
+
+    /**
+     * Removes a specific override value. If the removed override
+     * had the highest priority, and the new value is different from
+     * the previous value, the 'change' event will be fired.
+     * @param {import('core').TokenString} token The token for the corresponding override which is to be removed.
+     * @returns {boolean} `true` if an override was returned, `false` otherwise.
+     */
+    clearOverride(token) {
+        for (let i = 0, ii = this._overrides.length; i < ii; ++i) {
+            if (this._overrides[i].token === token) {
+                this._overrides.splice(i, 1);
+                if (i === 0) { this._updateValue(); }
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Updates the current value using the current overrides and default value.
+     * If the new value differs from the previous value, the 'change' event will be fired.
+     */
+    _updateValue() {
+        const value = this._overrides.length > 0 ? this._overrides[0].value : this._defaultValue;
+        if (this._value === value) { return; }
+        this._value = value;
+        this.trigger('change', {value});
+    }
+}
diff --git a/ext/js/core/event-dispatcher.js b/ext/js/core/event-dispatcher.js
new file mode 100644
index 00000000..75f2fdd3
--- /dev/null
+++ b/ext/js/core/event-dispatcher.js
@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2023-2024  Yomitan Authors
+ * Copyright (C) 2019-2022  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * The following typedef is required because the JSDoc `implements` tag doesn't work with `import()`.
+ * https://github.com/microsoft/TypeScript/issues/49905
+ * @typedef {import('core').EventDispatcherOffGeneric} EventDispatcherOffGeneric
+ */
+
+/**
+ * Base class controls basic event dispatching.
+ * @template {import('core').EventSurface} TSurface
+ * @implements {EventDispatcherOffGeneric}
+ */
+export class EventDispatcher {
+    /**
+     * Creates a new instance.
+     */
+    constructor() {
+        /** @type {Map<import('core').EventNames<TSurface>, import('core').EventHandlerAny[]>} */
+        this._eventMap = new Map();
+    }
+
+    /**
+     * Triggers an event with the given name and specified argument.
+     * @template {import('core').EventNames<TSurface>} TName
+     * @param {TName} eventName The string representing the event's name.
+     * @param {import('core').EventArgument<TSurface, TName>} details The argument passed to the callback functions.
+     * @returns {boolean} `true` if any callbacks were registered, `false` otherwise.
+     */
+    trigger(eventName, details) {
+        const callbacks = this._eventMap.get(eventName);
+        if (typeof callbacks === 'undefined') { return false; }
+
+        for (const callback of callbacks) {
+            callback(details);
+        }
+        return true;
+    }
+
+    /**
+     * Adds a single event listener to a specific event.
+     * @template {import('core').EventNames<TSurface>} TName
+     * @param {TName} eventName The string representing the event's name.
+     * @param {import('core').EventHandler<TSurface, TName>} callback The event listener callback to add.
+     */
+    on(eventName, callback) {
+        let callbacks = this._eventMap.get(eventName);
+        if (typeof callbacks === 'undefined') {
+            callbacks = [];
+            this._eventMap.set(eventName, callbacks);
+        }
+        callbacks.push(callback);
+    }
+
+    /**
+     * Removes a single event listener from a specific event.
+     * @template {import('core').EventNames<TSurface>} TName
+     * @param {TName} eventName The string representing the event's name.
+     * @param {import('core').EventHandler<TSurface, TName>} callback The event listener callback to add.
+     * @returns {boolean} `true` if the callback was removed, `false` otherwise.
+     */
+    off(eventName, callback) {
+        const callbacks = this._eventMap.get(eventName);
+        if (typeof callbacks === 'undefined') { return false; }
+
+        const ii = callbacks.length;
+        for (let i = 0; i < ii; ++i) {
+            if (callbacks[i] === callback) {
+                callbacks.splice(i, 1);
+                if (callbacks.length === 0) {
+                    this._eventMap.delete(eventName);
+                }
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Checks if an event has any listeners.
+     * @template {import('core').EventNames<TSurface>} TName
+     * @param {TName} eventName The string representing the event's name.
+     * @returns {boolean} `true` if the event has listeners, `false` otherwise.
+     */
+    hasListeners(eventName) {
+        const callbacks = this._eventMap.get(eventName);
+        return (typeof callbacks !== 'undefined' && callbacks.length > 0);
+    }
+}
diff --git a/ext/js/core/event-listener-collection.js b/ext/js/core/event-listener-collection.js
new file mode 100644
index 00000000..87d18a90
--- /dev/null
+++ b/ext/js/core/event-listener-collection.js
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2023-2024  Yomitan Authors
+ * Copyright (C) 2019-2022  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * Class which stores event listeners added to various objects, making it easy to remove them in bulk.
+ */
+export class EventListenerCollection {
+    /**
+     * Creates a new instance.
+     */
+    constructor() {
+        /** @type {import('event-listener-collection').EventListenerDetails[]} */
+        this._eventListeners = [];
+    }
+
+    /**
+     * Returns the number of event listeners that are currently in the object.
+     * @type {number}
+     */
+    get size() {
+        return this._eventListeners.length;
+    }
+
+    /**
+     * Adds an event listener using `object.addEventListener`. The listener will later be removed using `object.removeEventListener`.
+     * @param {import('event-listener-collection').EventTarget} target The object to add the event listener to.
+     * @param {string} type The name of the event.
+     * @param {EventListener | EventListenerObject | import('event-listener-collection').EventListenerFunction} listener The callback listener.
+     * @param {AddEventListenerOptions | boolean} [options] Options for the event.
+     */
+    addEventListener(target, type, listener, options) {
+        target.addEventListener(type, listener, options);
+        this._eventListeners.push({type: 'removeEventListener', target, eventName: type, listener, options});
+    }
+
+    /**
+     * Adds an event listener using `object.addListener`. The listener will later be removed using `object.removeListener`.
+     * @template {import('event-listener-collection').EventListenerFunction} TCallback
+     * @template [TArgs=unknown]
+     * @param {import('event-listener-collection').ExtensionEvent<TCallback, TArgs>} target The object to add the event listener to.
+     * @param {TCallback} callback The callback.
+     * @param {TArgs[]} args The extra argument array passed to the `addListener`/`removeListener` function.
+     */
+    addListener(target, callback, ...args) {
+        target.addListener(callback, ...args);
+        this._eventListeners.push({type: 'removeListener', target, callback, args});
+    }
+
+    /**
+     * Adds an event listener using `object.on`. The listener will later be removed using `object.off`.
+     * @template {import('core').EventSurface} TSurface
+     * @template {import('core').EventNames<TSurface>} TName
+     * @param {import('./event-dispatcher.js').EventDispatcher<TSurface>} target The object to add the event listener to.
+     * @param {TName} eventName The string representing the event's name.
+     * @param {import('core').EventHandler<TSurface, TName>} callback The event listener callback to add.
+     */
+    on(target, eventName, callback) {
+        target.on(eventName, callback);
+        this._eventListeners.push({type: 'off', eventName, target, callback});
+    }
+
+    /**
+     * Removes all event listeners added to objects for this instance and clears the internal list of event listeners.
+     */
+    removeAllEventListeners() {
+        if (this._eventListeners.length === 0) { return; }
+        for (const item of this._eventListeners) {
+            switch (item.type) {
+                case 'removeEventListener':
+                    item.target.removeEventListener(item.eventName, item.listener, item.options);
+                    break;
+                case 'removeListener':
+                    item.target.removeListener(item.callback, ...item.args);
+                    break;
+                case 'off':
+                    item.target.off(item.eventName, item.callback);
+                    break;
+            }
+        }
+        this._eventListeners = [];
+    }
+}
diff --git a/ext/js/core/logger.js b/ext/js/core/logger.js
new file mode 100644
index 00000000..165e1ae2
--- /dev/null
+++ b/ext/js/core/logger.js
@@ -0,0 +1,157 @@
+/*
+ * Copyright (C) 2023-2024  Yomitan Authors
+ * Copyright (C) 2019-2022  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {EventDispatcher} from './event-dispatcher.js';
+import {ExtensionError} from './extension-error.js';
+
+/**
+ * This class handles logging of messages to the console and triggering
+ * an event for log calls.
+ * @augments EventDispatcher<import('log').Events>
+ */
+export class Logger extends EventDispatcher {
+    /**
+     * Creates a new instance.
+     */
+    constructor() {
+        super();
+        /** @type {string} */
+        this._extensionName = 'Yomitan';
+        try {
+            const {name, version} = chrome.runtime.getManifest();
+            this._extensionName = `${name} ${version}`;
+        } catch (e) {
+            // NOP
+        }
+    }
+
+    /**
+     * Logs a generic error. This will trigger the 'log' event with the same arguments as the function invocation.
+     * @param {unknown} error The error to log. This is typically an `Error` or `Error`-like object.
+     * @param {import('log').LogLevel} level The level to log at. Values include `'info'`, `'debug'`, `'warn'`, and `'error'`.
+     *   Other values will be logged at a non-error level.
+     * @param {?import('log').LogContext} [context] An optional context object for the error which should typically include a `url` field.
+     */
+    log(error, level, context = null) {
+        if (typeof context !== 'object' || context === null) {
+            context = {url: location.href};
+        }
+
+        let errorString;
+        try {
+            if (typeof error === 'string') {
+                errorString = error;
+            } else {
+                errorString = (
+                    typeof error === 'object' && error !== null ?
+                    error.toString() :
+                    `${error}`
+                );
+                if (/^\[object \w+\]$/.test(errorString)) {
+                    errorString = JSON.stringify(error);
+                }
+            }
+        } catch (e) {
+            errorString = `${error}`;
+        }
+
+        let errorStack;
+        try {
+            errorStack = (
+                error instanceof Error ?
+                (typeof error.stack === 'string' ? error.stack.trimEnd() : '') :
+                ''
+            );
+        } catch (e) {
+            errorStack = '';
+        }
+
+        let errorData;
+        try {
+            if (error instanceof ExtensionError) {
+                errorData = error.data;
+            }
+        } catch (e) {
+            // NOP
+        }
+
+        if (errorStack.startsWith(errorString)) {
+            errorString = errorStack;
+        } else if (errorStack.length > 0) {
+            errorString += `\n${errorStack}`;
+        }
+
+        let message = `${this._extensionName} has encountered a problem.`;
+        message += `\nOriginating URL: ${context.url}\n`;
+        message += errorString;
+        if (typeof errorData !== 'undefined') {
+            message += `\nData: ${JSON.stringify(errorData, null, 4)}`;
+        }
+        message += '\n\nIssues can be reported at https://github.com/themoeway/yomitan/issues';
+
+        /* eslint-disable no-console */
+        switch (level) {
+            case 'log': console.log(message); break;
+            case 'info': console.info(message); break;
+            case 'debug': console.debug(message); break;
+            case 'warn': console.warn(message); break;
+            case 'error': console.error(message); break;
+        }
+        /* eslint-enable no-console */
+
+        this.trigger('log', {error, level, context});
+    }
+
+    /**
+     * Logs a warning. This function invokes `log` internally.
+     * @param {unknown} error The error to log. This is typically an `Error` or `Error`-like object.
+     * @param {?import('log').LogContext} context An optional context object for the error which should typically include a `url` field.
+     */
+    warn(error, context = null) {
+        this.log(error, 'warn', context);
+    }
+
+    /**
+     * Logs an error. This function invokes `log` internally.
+     * @param {unknown} error The error to log. This is typically an `Error` or `Error`-like object.
+     * @param {?import('log').LogContext} context An optional context object for the error which should typically include a `url` field.
+     */
+    error(error, context = null) {
+        this.log(error, 'error', context);
+    }
+
+    /**
+     * @param {import('log').LogLevel} errorLevel
+     * @returns {import('log').LogErrorLevelValue}
+     */
+    getLogErrorLevelValue(errorLevel) {
+        switch (errorLevel) {
+            case 'log':
+            case 'info':
+            case 'debug':
+                return 0;
+            case 'warn': return 1;
+            case 'error': return 2;
+        }
+    }
+}
+
+/**
+ * This object is the default logger used by the runtime.
+ */
+export const log = new Logger();
diff --git a/ext/js/core/utilities.js b/ext/js/core/utilities.js
new file mode 100644
index 00000000..1fc2da42
--- /dev/null
+++ b/ext/js/core/utilities.js
@@ -0,0 +1,319 @@
+/*
+ * Copyright (C) 2023-2024  Yomitan Authors
+ * Copyright (C) 2019-2022  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * Checks whether a given value is a non-array object.
+ * @param {unknown} value The value to check.
+ * @returns {boolean} `true` if the value is an object and not an array, `false` otherwise.
+ */
+export function isObject(value) {
+    return typeof value === 'object' && value !== null && !Array.isArray(value);
+}
+
+/**
+ * Converts any string into a form that can be passed into the RegExp constructor.
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
+ * @param {string} string The string to convert to a valid regular expression.
+ * @returns {string} The escaped string.
+ */
+export function escapeRegExp(string) {
+    return string.replace(/[.*+\-?^${}()|[\]\\]/g, '\\$&');
+}
+
+/**
+ * Reverses a string.
+ * @param {string} string The string to reverse.
+ * @returns {string} The returned string, which retains proper UTF-16 surrogate pair order.
+ */
+export function stringReverse(string) {
+    return [...string].reverse().join('');
+}
+
+/**
+ * Creates a deep clone of an object or value. This is similar to `parseJson(JSON.stringify(value))`.
+ * @template [T=unknown]
+ * @param {T} value The value to clone.
+ * @returns {T} A new clone of the value.
+ * @throws An error if the value is circular and cannot be cloned.
+ */
+export function clone(value) {
+    if (value === null) { return /** @type {T} */ (null); }
+    switch (typeof value) {
+        case 'boolean':
+        case 'number':
+        case 'string':
+        case 'bigint':
+        case 'symbol':
+        case 'undefined':
+            return value;
+        default:
+            return cloneInternal(value, new Set());
+    }
+}
+
+/**
+ * @template [T=unknown]
+ * @param {T} value
+ * @param {Set<unknown>} visited
+ * @returns {T}
+ * @throws {Error}
+ */
+function cloneInternal(value, visited) {
+    if (value === null) { return /** @type {T} */ (null); }
+    switch (typeof value) {
+        case 'boolean':
+        case 'number':
+        case 'string':
+        case 'bigint':
+        case 'symbol':
+        case 'undefined':
+            return value;
+        case 'object':
+            return /** @type {T} */ (
+                    Array.isArray(value) ?
+                    cloneArray(value, visited) :
+                    cloneObject(/** @type {import('core').SerializableObject} */ (value), visited)
+            );
+        default:
+            throw new Error(`Cannot clone object of type ${typeof value}`);
+    }
+}
+
+/**
+ * @param {unknown[]} value
+ * @param {Set<unknown>} visited
+ * @returns {unknown[]}
+ * @throws {Error}
+ */
+function cloneArray(value, visited) {
+    if (visited.has(value)) { throw new Error('Circular'); }
+    try {
+        visited.add(value);
+        const result = [];
+        for (const item of value) {
+            result.push(cloneInternal(item, visited));
+        }
+        return result;
+    } finally {
+        visited.delete(value);
+    }
+}
+
+/**
+ * @param {import('core').SerializableObject} value
+ * @param {Set<unknown>} visited
+ * @returns {import('core').SerializableObject}
+ * @throws {Error}
+ */
+function cloneObject(value, visited) {
+    if (visited.has(value)) { throw new Error('Circular'); }
+    try {
+        visited.add(value);
+        /** @type {import('core').SerializableObject} */
+        const result = {};
+        for (const key in value) {
+            if (Object.prototype.hasOwnProperty.call(value, key)) {
+                result[key] = cloneInternal(value[key], visited);
+            }
+        }
+        return result;
+    } finally {
+        visited.delete(value);
+    }
+}
+
+/**
+ * Checks if an object or value is deeply equal to another object or value.
+ * @param {unknown} value1 The first value to check.
+ * @param {unknown} value2 The second value to check.
+ * @returns {boolean} `true` if the values are the same object, or deeply equal without cycles. `false` otherwise.
+ */
+export function deepEqual(value1, value2) {
+    if (value1 === value2) { return true; }
+
+    const type = typeof value1;
+    if (typeof value2 !== type) { return false; }
+
+    switch (type) {
+        case 'object':
+        case 'function':
+            return deepEqualInternal(value1, value2, new Set());
+        default:
+            return false;
+    }
+}
+
+/**
+ * @param {unknown} value1
+ * @param {unknown} value2
+ * @param {Set<unknown>} visited1
+ * @returns {boolean}
+ */
+function deepEqualInternal(value1, value2, visited1) {
+    if (value1 === value2) { return true; }
+
+    const type = typeof value1;
+    if (typeof value2 !== type) { return false; }
+
+    switch (type) {
+        case 'object':
+        case 'function':
+        {
+            if (value1 === null || value2 === null) { return false; }
+            const array = Array.isArray(value1);
+            if (array !== Array.isArray(value2)) { return false; }
+            if (visited1.has(value1)) { return false; }
+            visited1.add(value1);
+            return (
+                    array ?
+                    areArraysEqual(/** @type {unknown[]} */ (value1), /** @type {unknown[]} */ (value2), visited1) :
+                    areObjectsEqual(/** @type {import('core').UnknownObject} */ (value1), /** @type {import('core').UnknownObject} */ (value2), visited1)
+            );
+        }
+        default:
+            return false;
+    }
+}
+
+/**
+ * @param {import('core').UnknownObject} value1
+ * @param {import('core').UnknownObject} value2
+ * @param {Set<unknown>} visited1
+ * @returns {boolean}
+ */
+function areObjectsEqual(value1, value2, visited1) {
+    const keys1 = Object.keys(value1);
+    const keys2 = Object.keys(value2);
+    if (keys1.length !== keys2.length) { return false; }
+
+    const keys1Set = new Set(keys1);
+    for (const key of keys2) {
+        if (!keys1Set.has(key) || !deepEqualInternal(value1[key], value2[key], visited1)) { return false; }
+    }
+
+    return true;
+}
+
+/**
+ * @param {unknown[]} value1
+ * @param {unknown[]} value2
+ * @param {Set<unknown>} visited1
+ * @returns {boolean}
+ */
+function areArraysEqual(value1, value2, visited1) {
+    const length = value1.length;
+    if (length !== value2.length) { return false; }
+
+    for (let i = 0; i < length; ++i) {
+        if (!deepEqualInternal(value1[i], value2[i], visited1)) { return false; }
+    }
+
+    return true;
+}
+
+/**
+ * Creates a new base-16 (lower case) string of a sequence of random bytes of the given length.
+ * @param {number} length The number of bytes the string represents. The returned string's length will be twice as long.
+ * @returns {string} A string of random characters.
+ */
+export function generateId(length) {
+    const array = new Uint8Array(length);
+    crypto.getRandomValues(array);
+    let id = '';
+    for (const value of array) {
+        id += value.toString(16).padStart(2, '0');
+    }
+    return id;
+}
+
+/**
+ * Creates an unresolved promise that can be resolved later, outside the promise's executor function.
+ * @template [T=unknown]
+ * @returns {import('core').DeferredPromiseDetails<T>} An object `{promise, resolve, reject}`, containing the promise and the resolve/reject functions.
+ */
+export function deferPromise() {
+    /** @type {((value: T) => void)|undefined} */
+    let resolve;
+    /** @type {((reason?: import('core').RejectionReason) => void)|undefined} */
+    let reject;
+    const promise = new Promise((resolve2, reject2) => {
+        resolve = resolve2;
+        reject = reject2;
+    });
+    return {
+        promise,
+        resolve: /** @type {(value: T) => void} */ (resolve),
+        reject: /** @type {(reason?: import('core').RejectionReason) => void} */ (reject)
+    };
+}
+
+/**
+ * Creates a promise that is resolved after a set delay.
+ * @param {number} delay How many milliseconds until the promise should be resolved. If 0, the promise is immediately resolved.
+ * @returns {Promise<void>} A promise with two additional properties: `resolve` and `reject`, which can be used to complete the promise early.
+ */
+export function promiseTimeout(delay) {
+    return delay <= 0 ? Promise.resolve() : new Promise((resolve) => { setTimeout(resolve, delay); });
+}
+
+/**
+ * Creates a promise that will resolve after the next animation frame, using `requestAnimationFrame`.
+ * @param {number} [timeout] A maximum duration (in milliseconds) to wait until the promise resolves. If null or omitted, no timeout is used.
+ * @returns {Promise<{time: number, timeout: boolean}>} A promise that is resolved with `{time, timeout}`, where `time` is the timestamp from `requestAnimationFrame`,
+ *   and `timeout` is a boolean indicating whether the cause was a timeout or not.
+ * @throws The promise throws an error if animation is not supported in this context, such as in a service worker.
+ */
+export function promiseAnimationFrame(timeout) {
+    return new Promise((resolve, reject) => {
+        if (typeof cancelAnimationFrame !== 'function' || typeof requestAnimationFrame !== 'function') {
+            reject(new Error('Animation not supported in this context'));
+            return;
+        }
+
+        /** @type {?import('core').Timeout} */
+        let timer = null;
+        /** @type {?number} */
+        let frameRequest = null;
+        /**
+         * @param {number} time
+         */
+        const onFrame = (time) => {
+            frameRequest = null;
+            if (timer !== null) {
+                clearTimeout(timer);
+                timer = null;
+            }
+            resolve({time, timeout: false});
+        };
+        const onTimeout = () => {
+            timer = null;
+            if (frameRequest !== null) {
+                // eslint-disable-next-line no-undef
+                cancelAnimationFrame(frameRequest);
+                frameRequest = null;
+            }
+            resolve({time: performance.now(), timeout: true});
+        };
+
+        // eslint-disable-next-line no-undef
+        frameRequest = requestAnimationFrame(onFrame);
+        if (typeof timeout === 'number') {
+            timer = setTimeout(onTimeout, timeout);
+        }
+    });
+}
diff --git a/ext/js/data/anki-note-builder.js b/ext/js/data/anki-note-builder.js
index 8577205e..48564d54 100644
--- a/ext/js/data/anki-note-builder.js
+++ b/ext/js/data/anki-note-builder.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {deferPromise} from '../core.js';
+import {deferPromise} from '../core/utilities.js';
 import {ExtensionError} from '../core/extension-error.js';
 import {yomitan} from '../yomitan.js';
 import {AnkiUtil} from './anki-util.js';
diff --git a/ext/js/data/anki-util.js b/ext/js/data/anki-util.js
index 1edbc58c..57684887 100644
--- a/ext/js/data/anki-util.js
+++ b/ext/js/data/anki-util.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {isObject} from '../core.js';
+import {isObject} from '../core/utilities.js';
 
 /**
  * This class has some general utility functions for working with Anki data.
diff --git a/ext/js/data/json-schema.js b/ext/js/data/json-schema.js
index 350ebbe5..9b7ea011 100644
--- a/ext/js/data/json-schema.js
+++ b/ext/js/data/json-schema.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {clone} from '../core.js';
+import {clone} from '../core/utilities.js';
 import {CacheMap} from '../general/cache-map.js';
 
 export class JsonSchemaError extends Error {
diff --git a/ext/js/data/options-util.js b/ext/js/data/options-util.js
index 42f82ca2..cbaeb92b 100644
--- a/ext/js/data/options-util.js
+++ b/ext/js/data/options-util.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {escapeRegExp, isObject} from '../core.js';
+import {escapeRegExp, isObject} from '../core/utilities.js';
 import {parseJson, readResponseJson} from '../core/json.js';
 import {TemplatePatcher} from '../templates/template-patcher.js';
 import {JsonSchema} from './json-schema.js';
diff --git a/ext/js/dictionary/dictionary-database.js b/ext/js/dictionary/dictionary-database.js
index 818392f4..1c52b7ab 100644
--- a/ext/js/dictionary/dictionary-database.js
+++ b/ext/js/dictionary/dictionary-database.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log, stringReverse} from '../core.js';
+import {log} from '../core/logger.js';
+import {stringReverse} from '../core/utilities.js';
 import {Database} from '../data/database.js';
 
 export class DictionaryDatabase {
diff --git a/ext/js/dictionary/dictionary-importer-media-loader.js b/ext/js/dictionary/dictionary-importer-media-loader.js
index d94ff98e..86ed53f2 100644
--- a/ext/js/dictionary/dictionary-importer-media-loader.js
+++ b/ext/js/dictionary/dictionary-importer-media-loader.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 
 /**
  * Class used for loading and validating media during the dictionary import process.
diff --git a/ext/js/dictionary/dictionary-importer.js b/ext/js/dictionary/dictionary-importer.js
index 067c8a3a..c8f68d78 100644
--- a/ext/js/dictionary/dictionary-importer.js
+++ b/ext/js/dictionary/dictionary-importer.js
@@ -24,7 +24,7 @@ import {
     ZipReader as ZipReader0,
     configure
 } from '../../lib/zip.js';
-import {stringReverse} from '../core.js';
+import {stringReverse} from '../core/utilities.js';
 import {ExtensionError} from '../core/extension-error.js';
 import {parseJson} from '../core/json.js';
 import {toError} from '../core/to-error.js';
diff --git a/ext/js/dictionary/dictionary-worker-main.js b/ext/js/dictionary/dictionary-worker-main.js
index 16d013af..d63a3a20 100644
--- a/ext/js/dictionary/dictionary-worker-main.js
+++ b/ext/js/dictionary/dictionary-worker-main.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log} from '../core.js';
+import {log} from '../core/logger.js';
 import {DictionaryWorkerHandler} from './dictionary-worker-handler.js';
 
 /** Entry point. */
diff --git a/ext/js/dictionary/dictionary-worker-media-loader.js b/ext/js/dictionary/dictionary-worker-media-loader.js
index cc380c2f..5c18e184 100644
--- a/ext/js/dictionary/dictionary-worker-media-loader.js
+++ b/ext/js/dictionary/dictionary-worker-media-loader.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {generateId} from '../core.js';
+import {generateId} from '../core/utilities.js';
 import {ExtensionError} from '../core/extension-error.js';
 
 /**
diff --git a/ext/js/display/display-anki.js b/ext/js/display/display-anki.js
index 2c24bafb..c51ddfa2 100644
--- a/ext/js/display/display-anki.js
+++ b/ext/js/display/display-anki.js
@@ -16,8 +16,9 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection, deferPromise} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {toError} from '../core/to-error.js';
+import {deferPromise} from '../core/utilities.js';
 import {AnkiNoteBuilder} from '../data/anki-note-builder.js';
 import {AnkiUtil} from '../data/anki-util.js';
 import {PopupMenu} from '../dom/popup-menu.js';
diff --git a/ext/js/display/display-audio.js b/ext/js/display/display-audio.js
index 55f83a33..8cbfc83f 100644
--- a/ext/js/display/display-audio.js
+++ b/ext/js/display/display-audio.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {PopupMenu} from '../dom/popup-menu.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 import {AudioSystem} from '../media/audio-system.js';
diff --git a/ext/js/display/display-content-manager.js b/ext/js/display/display-content-manager.js
index 98b40aae..d13dffb3 100644
--- a/ext/js/display/display-content-manager.js
+++ b/ext/js/display/display-content-manager.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {ArrayBufferUtil} from '../data/sandbox/array-buffer-util.js';
 import {yomitan} from '../yomitan.js';
 
diff --git a/ext/js/display/display-generator.js b/ext/js/display/display-generator.js
index 96559910..7bf13b77 100644
--- a/ext/js/display/display-generator.js
+++ b/ext/js/display/display-generator.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {isObject} from '../core.js';
+import {isObject} from '../core/utilities.js';
 import {ExtensionError} from '../core/extension-error.js';
 import {DictionaryDataUtil} from '../dictionary/dictionary-data-util.js';
 import {HtmlTemplateCollection} from '../dom/html-template-collection.js';
diff --git a/ext/js/display/display-history.js b/ext/js/display/display-history.js
index 021a7bd0..255a8536 100644
--- a/ext/js/display/display-history.js
+++ b/ext/js/display/display-history.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, generateId, isObject} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {generateId, isObject} from '../core/utilities.js';
 
 /**
  * @augments EventDispatcher<import('display-history').Events>
diff --git a/ext/js/display/display-notification.js b/ext/js/display/display-notification.js
index 6d7cb63e..a955f3fa 100644
--- a/ext/js/display/display-notification.js
+++ b/ext/js/display/display-notification.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 
 export class DisplayNotification {
diff --git a/ext/js/display/display-profile-selection.js b/ext/js/display/display-profile-selection.js
index 04d6d9e1..ff4fe6bf 100644
--- a/ext/js/display/display-profile-selection.js
+++ b/ext/js/display/display-profile-selection.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection, generateId} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
+import {generateId} from '../core/utilities.js';
 import {PanelElement} from '../dom/panel-element.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 import {yomitan} from '../yomitan.js';
diff --git a/ext/js/display/display-resizer.js b/ext/js/display/display-resizer.js
index 009b2195..7e346c7d 100644
--- a/ext/js/display/display-resizer.js
+++ b/ext/js/display/display-resizer.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 
 export class DisplayResizer {
     /**
diff --git a/ext/js/display/display.js b/ext/js/display/display.js
index c7d58497..677c7c4b 100644
--- a/ext/js/display/display.js
+++ b/ext/js/display/display.js
@@ -18,10 +18,14 @@
 
 import {ThemeController} from '../app/theme-controller.js';
 import {FrameEndpoint} from '../comm/frame-endpoint.js';
-import {DynamicProperty, EventDispatcher, EventListenerCollection, clone, deepEqual, log, promiseTimeout} from '../core.js';
 import {extendApiMap, invokeApiMapHandler} from '../core/api-map.js';
+import {DynamicProperty} from '../core/dynamic-property.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {ExtensionError} from '../core/extension-error.js';
+import {log} from '../core/logger.js';
 import {toError} from '../core/to-error.js';
+import {clone, deepEqual, promiseTimeout} from '../core/utilities.js';
 import {PopupMenu} from '../dom/popup-menu.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 import {ScrollElement} from '../dom/scroll-element.js';
diff --git a/ext/js/display/element-overflow-controller.js b/ext/js/display/element-overflow-controller.js
index 16ac4a7c..e0b9035e 100644
--- a/ext/js/display/element-overflow-controller.js
+++ b/ext/js/display/element-overflow-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../core.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 
 export class ElementOverflowController {
     constructor() {
diff --git a/ext/js/display/option-toggle-hotkey-handler.js b/ext/js/display/option-toggle-hotkey-handler.js
index d06be649..d9065e7f 100644
--- a/ext/js/display/option-toggle-hotkey-handler.js
+++ b/ext/js/display/option-toggle-hotkey-handler.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {generateId} from '../core.js';
+import {generateId} from '../core/utilities.js';
 import {ExtensionError} from '../core/extension-error.js';
 import {toError} from '../core/to-error.js';
 import {yomitan} from '../yomitan.js';
diff --git a/ext/js/display/popup-main.js b/ext/js/display/popup-main.js
index 251f35dc..d4f622f2 100644
--- a/ext/js/display/popup-main.js
+++ b/ext/js/display/popup-main.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log} from '../core.js';
+import {log} from '../core/logger.js';
 import {DocumentFocusController} from '../dom/document-focus-controller.js';
 import {HotkeyHandler} from '../input/hotkey-handler.js';
 import {JapaneseUtil} from '../language/sandbox/japanese-util.js';
diff --git a/ext/js/display/query-parser.js b/ext/js/display/query-parser.js
index c7ab77bf..e129e1be 100644
--- a/ext/js/display/query-parser.js
+++ b/ext/js/display/query-parser.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, log} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {log} from '../core/logger.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 import {TextScanner} from '../language/text-scanner.js';
 import {yomitan} from '../yomitan.js';
diff --git a/ext/js/display/search-display-controller.js b/ext/js/display/search-display-controller.js
index 638bc52c..594a80aa 100644
--- a/ext/js/display/search-display-controller.js
+++ b/ext/js/display/search-display-controller.js
@@ -18,8 +18,8 @@
 
 import * as wanakana from '../../lib/wanakana.js';
 import {ClipboardMonitor} from '../comm/clipboard-monitor.js';
-import {EventListenerCollection} from '../core.js';
 import {createApiMap, invokeApiMapHandler} from '../core/api-map.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 import {yomitan} from '../yomitan.js';
 
diff --git a/ext/js/display/search-main.js b/ext/js/display/search-main.js
index 4484f47c..3cdd1f25 100644
--- a/ext/js/display/search-main.js
+++ b/ext/js/display/search-main.js
@@ -17,7 +17,7 @@
  */
 
 import * as wanakana from '../../lib/wanakana.js';
-import {log} from '../core.js';
+import {log} from '../core/logger.js';
 import {DocumentFocusController} from '../dom/document-focus-controller.js';
 import {HotkeyHandler} from '../input/hotkey-handler.js';
 import {JapaneseUtil} from '../language/sandbox/japanese-util.js';
diff --git a/ext/js/display/search-persistent-state-controller.js b/ext/js/display/search-persistent-state-controller.js
index d34f8502..d1220184 100644
--- a/ext/js/display/search-persistent-state-controller.js
+++ b/ext/js/display/search-persistent-state-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
 
 /**
  * @augments EventDispatcher<import('search-persistent-state-controller').Events>
diff --git a/ext/js/dom/document-util.js b/ext/js/dom/document-util.js
index dc5393bf..235a42d0 100644
--- a/ext/js/dom/document-util.js
+++ b/ext/js/dom/document-util.js
@@ -386,7 +386,7 @@ export class DocumentUtil {
     /**
      * Adds a fullscreen change event listener. This function handles all of the browser-specific variants.
      * @param {EventListener} onFullscreenChanged The event callback.
-     * @param {?import('../core.js').EventListenerCollection} eventListenerCollection An optional `EventListenerCollection` to add the registration to.
+     * @param {?import('../core/event-listener-collection.js').EventListenerCollection} eventListenerCollection An optional `EventListenerCollection` to add the registration to.
      */
     static addFullscreenChangeEventListener(onFullscreenChanged, eventListenerCollection = null) {
         const target = document;
diff --git a/ext/js/dom/panel-element.js b/ext/js/dom/panel-element.js
index 8d05bae5..9c1289d7 100644
--- a/ext/js/dom/panel-element.js
+++ b/ext/js/dom/panel-element.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
 
 /**
  * @augments EventDispatcher<import('panel-element').Events>
diff --git a/ext/js/dom/popup-menu.js b/ext/js/dom/popup-menu.js
index 94b896f6..8a8a19ba 100644
--- a/ext/js/dom/popup-menu.js
+++ b/ext/js/dom/popup-menu.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, EventListenerCollection} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {querySelectorNotNull} from './query-selector.js';
 
 /**
diff --git a/ext/js/general/task-accumulator.js b/ext/js/general/task-accumulator.js
index bad20ffa..62f12869 100644
--- a/ext/js/general/task-accumulator.js
+++ b/ext/js/general/task-accumulator.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log} from '../core.js';
+import {log} from '../core/logger.js';
 
 /**
  * @template [K=unknown]
diff --git a/ext/js/input/hotkey-handler.js b/ext/js/input/hotkey-handler.js
index 6999e4de..3b40a86d 100644
--- a/ext/js/input/hotkey-handler.js
+++ b/ext/js/input/hotkey-handler.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, EventListenerCollection} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
 import {DocumentUtil} from '../dom/document-util.js';
 import {yomitan} from '../yomitan.js';
 
diff --git a/ext/js/input/hotkey-help-controller.js b/ext/js/input/hotkey-help-controller.js
index 62312298..4c4f56d5 100644
--- a/ext/js/input/hotkey-help-controller.js
+++ b/ext/js/input/hotkey-help-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {isObject} from '../core.js';
+import {isObject} from '../core/utilities.js';
 import {parseJson} from '../core/json.js';
 import {yomitan} from '../yomitan.js';
 import {HotkeyUtil} from './hotkey-util.js';
diff --git a/ext/js/language/text-scanner.js b/ext/js/language/text-scanner.js
index 639cf7d6..accb53fd 100644
--- a/ext/js/language/text-scanner.js
+++ b/ext/js/language/text-scanner.js
@@ -16,7 +16,10 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, EventListenerCollection, clone, log} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
+import {EventListenerCollection} from '../core/event-listener-collection.js';
+import {log} from '../core/logger.js';
+import {clone} from '../core/utilities.js';
 import {DocumentUtil} from '../dom/document-util.js';
 import {TextSourceElement} from '../dom/text-source-element.js';
 import {yomitan} from '../yomitan.js';
diff --git a/ext/js/media/audio-system.js b/ext/js/media/audio-system.js
index b479783f..3d861d35 100644
--- a/ext/js/media/audio-system.js
+++ b/ext/js/media/audio-system.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher} from '../core.js';
+import {EventDispatcher} from '../core/event-dispatcher.js';
 import {TextToSpeechAudio} from './text-to-speech-audio.js';
 
 /**
diff --git a/ext/js/pages/info-main.js b/ext/js/pages/info-main.js
index 33c82c8a..dd55ab4b 100644
--- a/ext/js/pages/info-main.js
+++ b/ext/js/pages/info-main.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log, promiseTimeout} from '../core.js';
+import {log} from '../core/logger.js';
+import {promiseTimeout} from '../core/utilities.js';
 import {DocumentFocusController} from '../dom/document-focus-controller.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 import {yomitan} from '../yomitan.js';
diff --git a/ext/js/pages/permissions-main.js b/ext/js/pages/permissions-main.js
index 82b8b653..38135689 100644
--- a/ext/js/pages/permissions-main.js
+++ b/ext/js/pages/permissions-main.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log, promiseTimeout} from '../core.js';
+import {log} from '../core/logger.js';
+import {promiseTimeout} from '../core/utilities.js';
 import {DocumentFocusController} from '../dom/document-focus-controller.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 import {yomitan} from '../yomitan.js';
diff --git a/ext/js/pages/settings/anki-controller.js b/ext/js/pages/settings/anki-controller.js
index 69e44aa8..f6e19e14 100644
--- a/ext/js/pages/settings/anki-controller.js
+++ b/ext/js/pages/settings/anki-controller.js
@@ -17,8 +17,9 @@
  */
 
 import {AnkiConnect} from '../../comm/anki-connect.js';
-import {EventListenerCollection, log} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {ExtensionError} from '../../core/extension-error.js';
+import {log} from '../../core/logger.js';
 import {toError} from '../../core/to-error.js';
 import {AnkiUtil} from '../../data/anki-util.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
diff --git a/ext/js/pages/settings/audio-controller.js b/ext/js/pages/settings/audio-controller.js
index 0b3a1b43..9633c4b3 100644
--- a/ext/js/pages/settings/audio-controller.js
+++ b/ext/js/pages/settings/audio-controller.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, EventListenerCollection} from '../../core.js';
+import {EventDispatcher} from '../../core/event-dispatcher.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {AudioSystem} from '../../media/audio-system.js';
 
diff --git a/ext/js/pages/settings/backup-controller.js b/ext/js/pages/settings/backup-controller.js
index ffc8384e..f2eccd1e 100644
--- a/ext/js/pages/settings/backup-controller.js
+++ b/ext/js/pages/settings/backup-controller.js
@@ -17,9 +17,10 @@
  */
 
 import {Dexie} from '../../../lib/dexie.js';
-import {isObject, log} from '../../core.js';
 import {parseJson} from '../../core/json.js';
+import {log} from '../../core/logger.js';
 import {toError} from '../../core/to-error.js';
+import {isObject} from '../../core/utilities.js';
 import {OptionsUtil} from '../../data/options-util.js';
 import {ArrayBufferUtil} from '../../data/sandbox/array-buffer-util.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
diff --git a/ext/js/pages/settings/collapsible-dictionary-controller.js b/ext/js/pages/settings/collapsible-dictionary-controller.js
index ab0ecd74..e6930049 100644
--- a/ext/js/pages/settings/collapsible-dictionary-controller.js
+++ b/ext/js/pages/settings/collapsible-dictionary-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {yomitan} from '../../yomitan.js';
 
diff --git a/ext/js/pages/settings/dictionary-controller.js b/ext/js/pages/settings/dictionary-controller.js
index 25d87707..10dfdcdc 100644
--- a/ext/js/pages/settings/dictionary-controller.js
+++ b/ext/js/pages/settings/dictionary-controller.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection, log} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
+import {log} from '../../core/logger.js';
 import {DictionaryWorker} from '../../dictionary/dictionary-worker.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {yomitan} from '../../yomitan.js';
diff --git a/ext/js/pages/settings/dictionary-import-controller.js b/ext/js/pages/settings/dictionary-import-controller.js
index bf878085..183c0ccd 100644
--- a/ext/js/pages/settings/dictionary-import-controller.js
+++ b/ext/js/pages/settings/dictionary-import-controller.js
@@ -16,8 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log} from '../../core.js';
 import {ExtensionError} from '../../core/extension-error.js';
+import {log} from '../../core/logger.js';
 import {toError} from '../../core/to-error.js';
 import {DictionaryWorker} from '../../dictionary/dictionary-worker.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
diff --git a/ext/js/pages/settings/extension-keyboard-shortcuts-controller.js b/ext/js/pages/settings/extension-keyboard-shortcuts-controller.js
index 92422ce7..61330bb8 100644
--- a/ext/js/pages/settings/extension-keyboard-shortcuts-controller.js
+++ b/ext/js/pages/settings/extension-keyboard-shortcuts-controller.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection, isObject} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
+import {isObject} from '../../core/utilities.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {HotkeyUtil} from '../../input/hotkey-util.js';
 import {yomitan} from '../../yomitan.js';
diff --git a/ext/js/pages/settings/keyboard-mouse-input-field.js b/ext/js/pages/settings/keyboard-mouse-input-field.js
index 89f77b4a..310cbb19 100644
--- a/ext/js/pages/settings/keyboard-mouse-input-field.js
+++ b/ext/js/pages/settings/keyboard-mouse-input-field.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, EventListenerCollection} from '../../core.js';
+import {EventDispatcher} from '../../core/event-dispatcher.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {DocumentUtil} from '../../dom/document-util.js';
 import {HotkeyUtil} from '../../input/hotkey-util.js';
 
diff --git a/ext/js/pages/settings/keyboard-shortcuts-controller.js b/ext/js/pages/settings/keyboard-shortcuts-controller.js
index 700fe54a..396b0cc2 100644
--- a/ext/js/pages/settings/keyboard-shortcuts-controller.js
+++ b/ext/js/pages/settings/keyboard-shortcuts-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {DocumentUtil} from '../../dom/document-util.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {ObjectPropertyAccessor} from '../../general/object-property-accessor.js';
diff --git a/ext/js/pages/settings/permissions-origin-controller.js b/ext/js/pages/settings/permissions-origin-controller.js
index 73b32e9c..a0f23af6 100644
--- a/ext/js/pages/settings/permissions-origin-controller.js
+++ b/ext/js/pages/settings/permissions-origin-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {toError} from '../../core/to-error.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 
diff --git a/ext/js/pages/settings/persistent-storage-controller.js b/ext/js/pages/settings/persistent-storage-controller.js
index 2a6d7d51..baffa969 100644
--- a/ext/js/pages/settings/persistent-storage-controller.js
+++ b/ext/js/pages/settings/persistent-storage-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {isObject} from '../../core.js';
+import {isObject} from '../../core/utilities.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {yomitan} from '../../yomitan.js';
 
diff --git a/ext/js/pages/settings/popup-preview-frame-main.js b/ext/js/pages/settings/popup-preview-frame-main.js
index 83428b31..e3d7d0ec 100644
--- a/ext/js/pages/settings/popup-preview-frame-main.js
+++ b/ext/js/pages/settings/popup-preview-frame-main.js
@@ -17,7 +17,7 @@
  */
 
 import {PopupFactory} from '../../app/popup-factory.js';
-import {log} from '../../core.js';
+import {log} from '../../core/logger.js';
 import {HotkeyHandler} from '../../input/hotkey-handler.js';
 import {yomitan} from '../../yomitan.js';
 import {PopupPreviewFrame} from './popup-preview-frame.js';
diff --git a/ext/js/pages/settings/profile-conditions-ui.js b/ext/js/pages/settings/profile-conditions-ui.js
index eac33004..d07751fb 100644
--- a/ext/js/pages/settings/profile-conditions-ui.js
+++ b/ext/js/pages/settings/profile-conditions-ui.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, EventListenerCollection} from '../../core.js';
+import {EventDispatcher} from '../../core/event-dispatcher.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {DocumentUtil} from '../../dom/document-util.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {KeyboardMouseInputField} from './keyboard-mouse-input-field.js';
diff --git a/ext/js/pages/settings/profile-controller.js b/ext/js/pages/settings/profile-controller.js
index bf8c2ae4..73926a69 100644
--- a/ext/js/pages/settings/profile-controller.js
+++ b/ext/js/pages/settings/profile-controller.js
@@ -16,7 +16,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {clone, EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
+import {clone} from '../../core/utilities.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {yomitan} from '../../yomitan.js';
 import {ProfileConditionsUI} from './profile-conditions-ui.js';
diff --git a/ext/js/pages/settings/recommended-permissions-controller.js b/ext/js/pages/settings/recommended-permissions-controller.js
index dd93582e..84a4ef10 100644
--- a/ext/js/pages/settings/recommended-permissions-controller.js
+++ b/ext/js/pages/settings/recommended-permissions-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {toError} from '../../core/to-error.js';
 
 export class RecommendedPermissionsController {
diff --git a/ext/js/pages/settings/scan-inputs-controller.js b/ext/js/pages/settings/scan-inputs-controller.js
index 2fb1082d..2dfa3de3 100644
--- a/ext/js/pages/settings/scan-inputs-controller.js
+++ b/ext/js/pages/settings/scan-inputs-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {DocumentUtil} from '../../dom/document-util.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {yomitan} from '../../yomitan.js';
diff --git a/ext/js/pages/settings/secondary-search-dictionary-controller.js b/ext/js/pages/settings/secondary-search-dictionary-controller.js
index 8e637890..592f5eeb 100644
--- a/ext/js/pages/settings/secondary-search-dictionary-controller.js
+++ b/ext/js/pages/settings/secondary-search-dictionary-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {yomitan} from '../../yomitan.js';
 
diff --git a/ext/js/pages/settings/sentence-termination-characters-controller.js b/ext/js/pages/settings/sentence-termination-characters-controller.js
index 1f982dec..c393aaa1 100644
--- a/ext/js/pages/settings/sentence-termination-characters-controller.js
+++ b/ext/js/pages/settings/sentence-termination-characters-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 
 export class SentenceTerminationCharactersController {
diff --git a/ext/js/pages/settings/settings-controller.js b/ext/js/pages/settings/settings-controller.js
index f448adcf..25f5e8ad 100644
--- a/ext/js/pages/settings/settings-controller.js
+++ b/ext/js/pages/settings/settings-controller.js
@@ -16,7 +16,9 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventDispatcher, EventListenerCollection, generateId, isObject} from '../../core.js';
+import {EventDispatcher} from '../../core/event-dispatcher.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
+import {generateId, isObject} from '../../core/utilities.js';
 import {OptionsUtil} from '../../data/options-util.js';
 import {PermissionsUtil} from '../../data/permissions-util.js';
 import {HtmlTemplateCollection} from '../../dom/html-template-collection.js';
diff --git a/ext/js/pages/settings/settings-main.js b/ext/js/pages/settings/settings-main.js
index 13c3d73a..7e458043 100644
--- a/ext/js/pages/settings/settings-main.js
+++ b/ext/js/pages/settings/settings-main.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log} from '../../core.js';
+import {log} from '../../core/logger.js';
 import {DocumentFocusController} from '../../dom/document-focus-controller.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 import {yomitan} from '../../yomitan.js';
diff --git a/ext/js/pages/settings/translation-text-replacements-controller.js b/ext/js/pages/settings/translation-text-replacements-controller.js
index 745011b3..98a16026 100644
--- a/ext/js/pages/settings/translation-text-replacements-controller.js
+++ b/ext/js/pages/settings/translation-text-replacements-controller.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {EventListenerCollection} from '../../core.js';
+import {EventListenerCollection} from '../../core/event-listener-collection.js';
 import {querySelectorNotNull} from '../../dom/query-selector.js';
 
 export class TranslationTextReplacementsController {
diff --git a/ext/js/pages/welcome-main.js b/ext/js/pages/welcome-main.js
index 86a57cce..35472ec2 100644
--- a/ext/js/pages/welcome-main.js
+++ b/ext/js/pages/welcome-main.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {log} from '../core.js';
+import {log} from '../core/logger.js';
 import {DocumentFocusController} from '../dom/document-focus-controller.js';
 import {querySelectorNotNull} from '../dom/query-selector.js';
 import {yomitan} from '../yomitan.js';
diff --git a/ext/js/templates/template-renderer-proxy.js b/ext/js/templates/template-renderer-proxy.js
index 0f2abf13..e4814ec4 100644
--- a/ext/js/templates/template-renderer-proxy.js
+++ b/ext/js/templates/template-renderer-proxy.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-import {generateId} from '../core.js';
+import {generateId} from '../core/utilities.js';
 import {ExtensionError} from '../core/extension-error.js';
 
 export class TemplateRendererProxy {
diff --git a/ext/js/yomitan.js b/ext/js/yomitan.js
index 190392d9..cd3f65fd 100644
--- a/ext/js/yomitan.js
+++ b/ext/js/yomitan.js
@@ -18,9 +18,11 @@
 
 import {API} from './comm/api.js';
 import {CrossFrameAPI} from './comm/cross-frame-api.js';
-import {EventDispatcher, deferPromise, log} from './core.js';
 import {createApiMap, invokeApiMapHandler} from './core/api-map.js';
+import {EventDispatcher} from './core/event-dispatcher.js';
 import {ExtensionError} from './core/extension-error.js';
+import {log} from './core/logger.js';
+import {deferPromise} from './core/utilities.js';
 
 /**
  * @returns {boolean}
diff --git a/test/core.test.js b/test/core.test.js
index c7370abf..0ddcc2d1 100644
--- a/test/core.test.js
+++ b/test/core.test.js
@@ -17,7 +17,8 @@
  */
 
 import {describe, expect, test} from 'vitest';
-import {DynamicProperty, deepEqual} from '../ext/js/core.js';
+import {DynamicProperty} from '../ext/js/core/dynamic-property.js';
+import {deepEqual} from '../ext/js/core/utilities.js';
 
 /** */
 function testDynamicProperty() {