10 files changed, 357 insertions, 93 deletions
diff --git a/ext/js/background/backend.js b/ext/js/background/backend.js
index e246f0bb..31191612 100644
--- a/ext/js/background/backend.js
+++ b/ext/js/background/backend.js
@@ -34,6 +34,7 @@ import {DictionaryDatabase} from '../dictionary/dictionary-database.js';
 import {Environment} from '../extension/environment.js';
 import {ObjectPropertyAccessor} from '../general/object-property-accessor.js';
 import {distributeFuriganaInflected, isCodePointJapanese, isStringPartiallyJapanese, convertKatakanaToHiragana as jpConvertKatakanaToHiragana} from '../language/ja/japanese.js';
+import {getLanguageSummaries} from '../language/languages.js';
 import {Translator} from '../language/translator.js';
 import {AudioDownloader} from '../media/audio-downloader.js';
 import {getFileExtensionFromAudioMediaType, getFileExtensionFromImageMediaType} from '../media/media-util.js';
@@ -183,7 +184,8 @@ export class Backend {
             ['textHasJapaneseCharacters',    this._onApiTextHasJapaneseCharacters.bind(this)],
             ['getTermFrequencies',           this._onApiGetTermFrequencies.bind(this)],
             ['findAnkiNotes',                this._onApiFindAnkiNotes.bind(this)],
-            ['openCrossFramePort',           this._onApiOpenCrossFramePort.bind(this)]
+            ['openCrossFramePort',           this._onApiOpenCrossFramePort.bind(this)],
+            ['getLanguageSummaries',         this._onApiGetLanguageSummaries.bind(this)]
         ]);
         /* eslint-enable @stylistic/no-multi-spaces */
 
@@ -906,6 +908,11 @@ export class Backend {
         return {targetTabId, targetFrameId};
     }
 
+    /** @type {import('api').ApiHandler<'getLanguageSummaries'>} */
+    _onApiGetLanguageSummaries() {
+        return getLanguageSummaries();
+    }
+
     // Command handlers
 
     /**
@@ -2361,15 +2368,9 @@ export class Backend {
         if (typeof deinflect !== 'boolean') { deinflect = true; }
         const enabledDictionaryMap = this._getTranslatorEnabledDictionaryMap(options);
         const {
-            general: {mainDictionary, sortFrequencyDictionary, sortFrequencyDictionaryOrder},
+            general: {mainDictionary, sortFrequencyDictionary, sortFrequencyDictionaryOrder, language},
             scanning: {alphanumeric},
             translation: {
-                convertHalfWidthCharacters,
-                convertNumericCharacters,
-                convertAlphabeticCharacters,
-                convertHiraganaToKatakana,
-                convertKatakanaToHiragana,
-                collapseEmphaticSequences,
                 textReplacements: textReplacementsOptions,
                 searchResolution
             }
@@ -2394,16 +2395,11 @@ export class Backend {
             sortFrequencyDictionary,
             sortFrequencyDictionaryOrder,
             removeNonJapaneseCharacters: !alphanumeric,
-            convertHalfWidthCharacters,
-            convertNumericCharacters,
-            convertAlphabeticCharacters,
-            convertHiraganaToKatakana,
-            convertKatakanaToHiragana,
-            collapseEmphaticSequences,
             searchResolution,
             textReplacements,
             enabledDictionaryMap,
-            excludeDictionaryDefinitions
+            excludeDictionaryDefinitions,
+            language
         };
     }
 
diff --git a/ext/js/comm/api.js b/ext/js/comm/api.js
index b4fdbeb5..40b8e252 100644
--- a/ext/js/comm/api.js
+++ b/ext/js/comm/api.js
@@ -361,6 +361,13 @@ export class API {
         return this._invoke('openCrossFramePort', {targetTabId, targetFrameId});
     }
 
+    /**
+     * @returns {Promise<import('api').ApiReturn<'getLanguageSummaries'>>}
+     */
+    getLanguageSummaries() {
+        return this._invoke('getLanguageSummaries', void 0);
+    }
+
     // Utilities
 
     /**
diff --git a/ext/js/data/options-util.js b/ext/js/data/options-util.js
index 1644df2f..7952eafc 100644
--- a/ext/js/data/options-util.js
+++ b/ext/js/data/options-util.js
@@ -522,7 +522,8 @@ export class OptionsUtil {
             this._updateVersion22,
             this._updateVersion23,
             this._updateVersion24,
-            this._updateVersion25
+            this._updateVersion25,
+            this._updateVersion26
         ];
         /* eslint-enable @typescript-eslint/unbound-method */
         if (typeof targetVersion === 'number' && targetVersion < result.length) {
@@ -1155,6 +1156,31 @@ export class OptionsUtil {
     }
 
     /**
+     * - Added general.language.
+     * - Modularized text preprocessors.
+     * @type {import('options-util').UpdateFunction}
+     */
+    _updateVersion26(options) {
+        const textPreprocessors = [
+            'convertHalfWidthCharacters',
+            'convertNumericCharacters',
+            'convertAlphabeticCharacters',
+            'convertHiraganaToKatakana',
+            'convertKatakanaToHiragana',
+            'collapseEmphaticSequences'
+        ];
+
+        for (const {options: profileOptions} of options.profiles) {
+            profileOptions.general.language = 'ja';
+
+            for (const preprocessor of textPreprocessors) {
+                delete profileOptions.translation[preprocessor];
+            }
+        }
+    }
+
+
+    /**
      * @param {string} url
      * @returns {Promise<chrome.tabs.Tab>}
      */
diff --git a/ext/js/language/en/language-english.js b/ext/js/language/en/language-english.js
new file mode 100644
index 00000000..8268653f
--- /dev/null
+++ b/ext/js/language/en/language-english.js
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2024  Yomitan 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 {capitalizeFirstLetter, decapitalize} from '../text-preprocessors.js';
+
+/** @type {import('language-english').EnglishLanguageDescriptor} */
+export const descriptor = {
+    name: 'English',
+    iso: 'en',
+    exampleText: 'read',
+    textPreprocessors: {
+        capitalizeFirstLetter,
+        decapitalize
+    }
+};
diff --git a/ext/js/language/ja/language-japanese.js b/ext/js/language/ja/language-japanese.js
new file mode 100644
index 00000000..ced34bcd
--- /dev/null
+++ b/ext/js/language/ja/language-japanese.js
@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2024  Yomitan 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 {basicTextPreprocessorOptions} from '../text-preprocessors.js';
+import {convertAlphabeticToKana} from './japanese-wanakana.js';
+import {collapseEmphaticSequences, convertHalfWidthKanaToFullWidth, convertHiraganaToKatakana, convertKatakanaToHiragana, convertNumericToFullWidth} from './japanese.js';
+
+/** @type {import('language-japanese').JapaneseLanguageDescriptor} */
+export const descriptor = {
+    name: 'Japanese',
+    iso: 'ja',
+    exampleText: '読め',
+    textPreprocessors: {
+        convertHalfWidthCharacters: {
+            name: 'Convert half width characters to full width',
+            description: 'ﾖﾐﾁｬﾝ → ヨミチャン',
+            options: basicTextPreprocessorOptions,
+            /** @type {import('language').TextPreprocessorFunction<boolean>} */
+            process: (str, setting, sourceMap) => (setting ? convertHalfWidthKanaToFullWidth(str, sourceMap) : str)
+        },
+        convertNumericCharacters: {
+            name: 'Convert numeric characters to full width',
+            description: '1234 → １２３４',
+            options: basicTextPreprocessorOptions,
+            /** @type {import('language').TextPreprocessorFunction<boolean>} */
+            process: (str, setting) => (setting ? convertNumericToFullWidth(str) : str)
+        },
+        convertAlphabeticCharacters: {
+            name: 'Convert alphabetic characters to hiragana',
+            description: 'yomichan → よみちゃん',
+            options: basicTextPreprocessorOptions,
+            /** @type {import('language').TextPreprocessorFunction<boolean>} */
+            process: (str, setting, sourceMap) => (setting ? convertAlphabeticToKana(str, sourceMap) : str)
+        },
+        convertHiraganaToKatakana: {
+            name: 'Convert hiragana to katakana',
+            description: 'よみちゃん → ヨミチャン',
+            options: basicTextPreprocessorOptions,
+            /** @type {import('language').TextPreprocessorFunction<boolean>} */
+            process: (str, setting) => (setting ? convertHiraganaToKatakana(str) : str)
+        },
+        convertKatakanaToHiragana: {
+            name: 'Convert katakana to hiragana',
+            description: 'ヨミチャン → よみちゃん',
+            options: basicTextPreprocessorOptions,
+            /** @type {import('language').TextPreprocessorFunction<boolean>} */
+            process: (str, setting) => (setting ? convertKatakanaToHiragana(str) : str)
+        },
+        collapseEmphaticSequences: {
+            name: 'Collapse emphatic character sequences',
+            description: 'すっっごーーい → すっごーい / すごい',
+            options: [[false, false], [true, false], [true, true]],
+            /** @type {import('language').TextPreprocessorFunction<[collapseEmphatic: boolean, collapseEmphaticFull: boolean]>} */
+            process: (str, setting, sourceMap) => {
+                const [collapseEmphatic, collapseEmphaticFull] = setting;
+                if (collapseEmphatic) {
+                    str = collapseEmphaticSequences(str, collapseEmphaticFull, sourceMap);
+                }
+                return str;
+            }
+        }
+    }
+};
diff --git a/ext/js/language/languages.js b/ext/js/language/languages.js
new file mode 100755
index 00000000..f51ca163
--- /dev/null
+++ b/ext/js/language/languages.js
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2024  Yomitan 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 {descriptor as descriptorEnglish} from './en/language-english.js';
+import {descriptor as descriptorJapanese} from './ja/language-japanese.js';
+
+const languageDescriptors = [
+    descriptorEnglish,
+    descriptorJapanese
+];
+
+/** @type {Map<string, typeof languageDescriptors[0]>} */
+const languageDescriptorMap = new Map();
+for (const languageDescriptor of languageDescriptors) {
+    languageDescriptorMap.set(languageDescriptor.iso, languageDescriptor);
+}
+
+/**
+ * @returns {import('language').LanguageSummary[]}
+ */
+export function getLanguageSummaries() {
+    const results = [];
+    for (const {name, iso, exampleText} of languageDescriptorMap.values()) {
+        results.push({name, iso, exampleText});
+    }
+    return results;
+}
+
+/**
+ * @returns {import('language').LanguageAndPreprocessors[]}
+ * @throws {Error}
+ */
+export function getAllLanguageTextPreprocessors() {
+    const results = [];
+    for (const {iso, textPreprocessors} of languageDescriptorMap.values()) {
+        /** @type {import('language').TextPreprocessorWithId<unknown>[]} */
+        const textPreprocessorsArray = [];
+        for (const [id, textPreprocessor] of Object.entries(textPreprocessors)) {
+            textPreprocessorsArray.push({
+                id,
+                textPreprocessor: /** @type {import('language').TextPreprocessor<unknown>} */ (textPreprocessor)
+            });
+        }
+        results.push({iso, textPreprocessors: textPreprocessorsArray});
+    }
+    return results;
+}
diff --git a/ext/js/language/text-preprocessors.js b/ext/js/language/text-preprocessors.js
new file mode 100755
index 00000000..12b3d1b6
--- /dev/null
+++ b/ext/js/language/text-preprocessors.js
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2024  Yomitan 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/>.
+ */
+
+/** @type {import('language').TextPreprocessorOptions<boolean>} */
+export const basicTextPreprocessorOptions = [false, true];
+
+/** @type {import('language').TextPreprocessor<boolean>} */
+export const decapitalize = {
+    name: 'Decapitalize text',
+    description: 'CAPITALIZED TEXT → capitalized text',
+    options: basicTextPreprocessorOptions,
+    process: (str, setting) => (setting ? str.toLowerCase() : str)
+};
+
+/** @type {import('language').TextPreprocessor<boolean>} */
+export const capitalizeFirstLetter = {
+    name: 'Capitalize first letter',
+    description: 'lowercase text → Lowercase text',
+    options: basicTextPreprocessorOptions,
+    process: (str, setting) => (setting ? str.charAt(0).toUpperCase() + str.slice(1) : str)
+};
diff --git a/ext/js/language/translator.js b/ext/js/language/translator.js
index b2342e8d..4f9304b5 100644
--- a/ext/js/language/translator.js
+++ b/ext/js/language/translator.js
@@ -18,9 +18,9 @@
 
 import {applyTextReplacement} from '../general/regex-util.js';
 import {TextSourceMap} from '../general/text-source-map.js';
-import {convertAlphabeticToKana} from './ja/japanese-wanakana.js';
-import {collapseEmphaticSequences, convertHalfWidthKanaToFullWidth, convertHiraganaToKatakana, convertKatakanaToHiragana, convertNumericToFullWidth, isCodePointJapanese} from './ja/japanese.js';
+import {isCodePointJapanese} from './ja/japanese.js';
 import {LanguageTransformer} from './language-transformer.js';
+import {getAllLanguageTextPreprocessors} from './languages.js';
 
 /**
  * Class which finds term and kanji dictionary entries for text.
@@ -41,6 +41,8 @@ export class Translator {
         this._stringComparer = new Intl.Collator('en-US'); // Invariant locale
         /** @type {RegExp} */
         this._numberRegex = /[+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?/;
+        /** @type {Map<string, {textPreprocessors: import('language').TextPreprocessorWithId<unknown>[], optionSpace: import('translation-internal').PreprocessorOptionsSpace}>} */
+        this._textPreprocessors = new Map();
     }
 
     /**
@@ -49,6 +51,14 @@ export class Translator {
      */
     prepare(descriptor) {
         this._languageTransformer.addDescriptor(descriptor);
+        for (const {iso, textPreprocessors} of getAllLanguageTextPreprocessors()) {
+            /** @type {Map<string, import('language').TextPreprocessorOptions<unknown>>} */
+            const optionSpace = new Map();
+            for (const {id, textPreprocessor} of textPreprocessors) {
+                optionSpace.set(id, textPreprocessor.options);
+            }
+            this._textPreprocessors.set(iso, {textPreprocessors, optionSpace});
+        }
     }
 
     /**
@@ -415,51 +425,45 @@ export class Translator {
         }
     }
 
-    // Deinflections and text transformations
+    // Deinflections and text preprocessing
 
     /**
      * @param {string} text
      * @param {import('translation').FindTermsOptions} options
      * @returns {import('translation-internal').DatabaseDeinflection[]}
+     * @throws {Error}
      */
     _getAlgorithmDeinflections(text, options) {
-        /** @type {import('translation-internal').TextDeinflectionOptionsArrays} */
-        const textOptionVariantArray = [
-            this._getTextReplacementsVariants(options),
-            this._getTextOptionEntryVariants(options.convertHalfWidthCharacters),
-            this._getTextOptionEntryVariants(options.convertNumericCharacters),
-            this._getTextOptionEntryVariants(options.convertAlphabeticCharacters),
-            this._getTextOptionEntryVariants(options.convertHiraganaToKatakana),
-            this._getTextOptionEntryVariants(options.convertKatakanaToHiragana),
-            this._getCollapseEmphaticOptions(options)
-        ];
+        const {language} = options;
+        const info = this._textPreprocessors.get(language);
+        if (typeof info === 'undefined') { throw new Error(`Unsupported language: ${language}`); }
+        const {textPreprocessors, optionSpace: textPreprocessorOptionsSpace} = info;
+
+        /** @type {Map<string, import('language').TextPreprocessorOptions<unknown>>} */
+        const variantSpace = new Map();
+        variantSpace.set('textReplacements', this._getTextReplacementsVariants(options));
+        for (const [key, value] of textPreprocessorOptionsSpace) {
+            variantSpace.set(key, value);
+        }
 
         /** @type {import('translation-internal').DatabaseDeinflection[]} */
         const deinflections = [];
         const used = new Set();
-        for (const [textReplacements, halfWidth, numeric, alphabetic, katakana, hiragana, [collapseEmphatic, collapseEmphaticFull]] of /** @type {Generator<import('translation-internal').TextDeinflectionOptions, void, unknown>} */ (this._getArrayVariants(textOptionVariantArray))) {
+
+        for (const arrayVariant of this._generateArrayVariants(variantSpace)) {
+            const textReplacements = /** @type {import('translation').FindTermsTextReplacement[] | null} */ (arrayVariant.get('textReplacements'));
+
             let text2 = text;
             const sourceMap = new TextSourceMap(text2);
+
             if (textReplacements !== null) {
                 text2 = this._applyTextReplacements(text2, sourceMap, textReplacements);
             }
-            if (halfWidth) {
-                text2 = convertHalfWidthKanaToFullWidth(text2, sourceMap);
-            }
-            if (numeric) {
-                text2 = convertNumericToFullWidth(text2);
-            }
-            if (alphabetic) {
-                text2 = convertAlphabeticToKana(text2, sourceMap);
-            }
-            if (katakana) {
-                text2 = convertHiraganaToKatakana(text2);
-            }
-            if (hiragana) {
-                text2 = convertKatakanaToHiragana(text2);
-            }
-            if (collapseEmphatic) {
-                text2 = collapseEmphaticSequences(text2, collapseEmphaticFull, sourceMap);
+
+            for (const preprocessor of textPreprocessors.values()) {
+                const {id, textPreprocessor} = preprocessor;
+                const setting = arrayVariant.get(id);
+                text2 = textPreprocessor.process(text2, setting, sourceMap);
             }
 
             for (
@@ -527,36 +531,6 @@ export class Translator {
     }
 
     /**
-     * @param {import('translation').FindTermsVariantMode} value
-     * @returns {boolean[]}
-     */
-    _getTextOptionEntryVariants(value) {
-        switch (value) {
-            case 'true': return [true];
-            case 'variant': return [false, true];
-            default: return [false];
-        }
-    }
-
-    /**
-     * @param {import('translation').FindTermsOptions} options
-     * @returns {[collapseEmphatic: boolean, collapseEmphaticFull: boolean][]}
-     */
-    _getCollapseEmphaticOptions(options) {
-        /** @type {[collapseEmphatic: boolean, collapseEmphaticFull: boolean][]} */
-        const collapseEmphaticOptions = [[false, false]];
-        switch (options.collapseEmphaticSequences) {
-            case 'true':
-                collapseEmphaticOptions.push([true, false]);
-                break;
-            case 'full':
-                collapseEmphaticOptions.push([true, false], [true, true]);
-                break;
-        }
-        return collapseEmphaticOptions;
-    }
-
-    /**
      * @param {import('translation').FindTermsOptions} options
      * @returns {(import('translation').FindTermsTextReplacement[] | null)[]}
      */
@@ -1343,26 +1317,32 @@ export class Translator {
     }
 
     /**
-     * @param {[...args: unknown[][]]} arrayVariants
-     * @yields {[...args: unknown[]]}
-     * @returns {Generator<unknown[], void, unknown>}
+     * @param {Map<string, unknown[]>} arrayVariants
+     * @yields {Map<string, unknown>}
+     * @returns {Generator<Map<string, unknown>, void, void>}
      */
-    *_getArrayVariants(arrayVariants) {
-        const ii = arrayVariants.length;
-
-        let total = 1;
-        for (let i = 0; i < ii; ++i) {
-            total *= arrayVariants[i].length;
+    *_generateArrayVariants(arrayVariants) {
+        const variantKeys = [...arrayVariants.keys()];
+        const entryVariantLengths = [];
+        for (const key of variantKeys) {
+            const entryVariants = /** @type {unknown[]} */ (arrayVariants.get(key));
+            entryVariantLengths.push(entryVariants.length);
         }
+        const totalVariants = entryVariantLengths.reduce((acc, length) => acc * length, 1);
+
+        for (let variantIndex = 0; variantIndex < totalVariants; ++variantIndex) {
+            /** @type {Map<string, unknown>} */
+            const variant = new Map();
+            let remainingIndex = variantIndex;
 
-        for (let a = 0; a < total; ++a) {
-            const variant = [];
-            let index = a;
-            for (let i = 0; i < ii; ++i) {
-                const entryVariants = arrayVariants[i];
-                variant.push(entryVariants[index % entryVariants.length]);
-                index = Math.floor(index / entryVariants.length);
+            for (let keyIndex = 0; keyIndex < variantKeys.length; ++keyIndex) {
+                const key = variantKeys[keyIndex];
+                const entryVariants = /** @type {unknown[]} */ (arrayVariants.get(key));
+                const entryIndex = remainingIndex % entryVariants.length;
+                variant.set(key, entryVariants[entryIndex]);
+                remainingIndex = Math.floor(remainingIndex / entryVariants.length);
             }
+
             yield variant;
         }
     }
diff --git a/ext/js/pages/settings/languages-controller.js b/ext/js/pages/settings/languages-controller.js
new file mode 100755
index 00000000..78f036df
--- /dev/null
+++ b/ext/js/pages/settings/languages-controller.js
@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2023-2024  Yomitan Authors
+ * Copyright (C) 2021-2022  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 {querySelectorNotNull} from '../../dom/query-selector.js';
+
+export class LanguagesController {
+    /**
+     * @param {import('./settings-controller.js').SettingsController} settingsController
+     */
+    constructor(settingsController) {
+        /** @type {import('./settings-controller.js').SettingsController} */
+        this._settingsController = settingsController;
+    }
+
+    /** */
+    async prepare() {
+        const languages = await this._settingsController.application.api.getLanguageSummaries();
+        languages.sort((a, b) => a.iso.localeCompare(b.iso, 'en'));
+        this._fillSelect(languages);
+    }
+
+    /**
+     * @param {import('language').LanguageSummary[]} languages
+     */
+    _fillSelect(languages) {
+        const selectElement = querySelectorNotNull(document, '#language-select');
+        for (const {iso, name} of languages) {
+            const option = document.createElement('option');
+            option.value = iso;
+            option.text = `(${iso}) ${name}`;
+            selectElement.appendChild(option);
+        }
+    }
+}
diff --git a/ext/js/pages/settings/settings-main.js b/ext/js/pages/settings/settings-main.js
index dc4b36c9..0b115246 100644
--- a/ext/js/pages/settings/settings-main.js
+++ b/ext/js/pages/settings/settings-main.js
@@ -30,6 +30,7 @@ import {DictionaryImportController} from './dictionary-import-controller.js';
 import {ExtensionKeyboardShortcutController} from './extension-keyboard-shortcuts-controller.js';
 import {GenericSettingController} from './generic-setting-controller.js';
 import {KeyboardShortcutController} from './keyboard-shortcuts-controller.js';
+import {LanguagesController} from './languages-controller.js';
 import {MecabController} from './mecab-controller.js';
 import {ModalController} from './modal-controller.js';
 import {NestedPopupsController} from './nested-popups-controller.js';
@@ -137,6 +138,9 @@ await Application.main(async (application) => {
     const secondarySearchDictionaryController = new SecondarySearchDictionaryController(settingsController);
     secondarySearchDictionaryController.prepare();
 
+    const languagesController = new LanguagesController(settingsController);
+    languagesController.prepare();
+
     const translationTextReplacementsController = new TranslationTextReplacementsController(settingsController);
     translationTextReplacementsController.prepare();