aboutsummaryrefslogtreecommitdiff
path: root/ext/js/core.js
blob: cdac20200ba9bb94bd341e07cb9a8ad7a803eb03 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
/*
 * Copyright (C) 2023  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 `JSON.parse(JSON.stringify(value))`.
 * @template T
 * @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 const clone = (() => {
    /**
     * @template T
     * @param {T} value
     * @returns {T}
     */
    // eslint-disable-next-line no-shadow, @typescript-eslint/no-shadow
    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);
        }
    }

    return clone;
})();

/**
 * 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 const deepEqual = (() => {
    /**
     * @param {unknown} value1
     * @param {unknown} value2
     * @returns {boolean}
     */
    // eslint-disable-next-line no-shadow, @typescript-eslint/no-shadow
    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;
    }

    return deepEqual;
})();

/**
 * 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
 * @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 {?number} */
        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);
        }
    });
}

/**
 * Invokes a standard message handler. This function is used to react and respond
 * to communication messages within the extension.
 * @template {import('core').SafeAny} TParams
 * @param {import('core').MessageHandlerDetails} details Details about how to handle messages.
 * @param {TParams} params Information which was passed with the original message.
 * @param {(response: import('core').Response) => void} callback A callback function which is invoked after the handler has completed. The value passed
 *   to the function is in the format:
 *   - `{result: unknown}` if the handler invoked successfully.
 *   - `{error: object}` if the handler thew an error. The error is serialized.
 * @param {...*} extraArgs Additional arguments which are passed to the `handler` function.
 * @returns {boolean} `true` if the function is invoked asynchronously, `false` otherwise.
 */
export function invokeMessageHandler({handler, async}, params, callback, ...extraArgs) {
    try {
        let promiseOrResult = handler(params, ...extraArgs);
        if (async === 'dynamic') {
            ({async, result: promiseOrResult} = promiseOrResult);
        }
        if (async) {
            /** @type {Promise<any>} */ (promiseOrResult).then(
                (result) => { callback({result}); },
                (error) => { callback({error: ExtensionError.serialize(error)}); }
            );
            return true;
        } else {
            callback({result: promiseOrResult});
            return false;
        }
    } catch (error) {
        callback({error: ExtensionError.serialize(error)});
        return false;
    }
}

/**
 * @template {string} TEventName
 * Base class controls basic event dispatching.
 */
export class EventDispatcher {
    /**
     * Creates a new instance.
     */
    constructor() {
        /** @type {Map<string, ((details: import('core').SafeAny) => void)[]>} */
        this._eventMap = new Map();
    }

    /**
     * Triggers an event with the given name and specified argument.
     * @param {TEventName} eventName The string representing the event's name.
     * @param {unknown} [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.
     * @param {TEventName} eventName The string representing the event's name.
     * @param {(details: import('core').SafeAny) => void} 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.
     * @param {TEventName} eventName The string representing the event's name.
     * @param {(details: import('core').SafeAny) => void} 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.
     * @param {TEventName} 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 {string} TEventName
     * @param {EventDispatcher<TEventName>} target The object to add the event listener to.
     * @param {TEventName} eventName The string representing the event's name.
     * @param {(details: import('core').SafeAny) => void} 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
 * @augments EventDispatcher<import('dynamic-property').EventType>
 */
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', /** @type {import('dynamic-property').ChangeEventDetails<T>} */ ({value}));
    }
}

/**
 * This class handles logging of messages to the console and triggering
 * an event for log calls.
 * @augments EventDispatcher<import('log').LoggerEventType>
 */
export class Logger extends EventDispatcher {
    /**
     * Creates a new instance.
     */
    constructor() {
        super();
        /** @type {string} */
        this._extensionName = 'Yomichan';
        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';

        switch (level) {
            case 'info': console.info(message); break;
            case 'debug': console.debug(message); break;
            case 'warn': console.warn(message); break;
            case 'error': console.error(message); break;
            default: console.log(message); break;
        }

        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);
    }
}

/**
 * This object is the default logger used by the runtime.
 */
export const log = new Logger();