aboutsummaryrefslogtreecommitdiff
path: root/ext/bg/js/backend.js
blob: 407dc965bc54ac4a0dd57bc9e2a3aea6c128b4ea (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
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
/*
 * Copyright (C) 2016-2020  Alex Yatskov <alex@foosoft.net>
 * Author: Alex Yatskov <alex@foosoft.net>
 *
 * 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 Backend {
    constructor() {
        this.translator = new Translator();
        this.anki = new AnkiNull();
        this.mecab = new Mecab();
        this.options = null;
        this.optionsSchema = null;
        this.optionsContext = {
            depth: 0,
            url: window.location.href
        };

        this.isPreparedResolve = null;
        this.isPreparedPromise = new Promise((resolve) => (this.isPreparedResolve = resolve));

        this.clipboardPasteTarget = document.querySelector('#clipboard-paste-target');
        this.popupWindow = null;
        this.clipboardPopupTimerId = null;
        this.clipboardInterval = 250;
        this.clipboardPreviousText = null;

        this.apiForwarder = new BackendApiForwarder();
    }

    async prepare() {
        await this.translator.prepare();

        this.optionsSchema = await requestJson(chrome.runtime.getURL('/bg/data/options-schema.json'), 'GET');
        this.options = await optionsLoad();
        try {
            this.options = JsonSchema.getValidValueOrDefault(this.optionsSchema, this.options);
        } catch (e) {
            // This shouldn't happen, but catch errors just in case of bugs
            logError(e);
        }

        this.onOptionsUpdated('background');

        if (isObject(chrome.commands) && isObject(chrome.commands.onCommand)) {
            chrome.commands.onCommand.addListener((command) => this._runCommand(command));
        }
        if (isObject(chrome.tabs) && isObject(chrome.tabs.onZoomChange)) {
            chrome.tabs.onZoomChange.addListener((info) => this._onZoomChange(info));
        }
        chrome.runtime.onMessage.addListener(this.onMessage.bind(this));

        const options = this.getOptionsSync(this.optionsContext);
        if (options.general.showGuide) {
            chrome.tabs.create({url: chrome.runtime.getURL('/bg/guide.html')});
        }

        this.isPreparedResolve();
        this.isPreparedResolve = null;
        this.isPreparedPromise = null;
    }

    onOptionsUpdated(source) {
        this.applyOptions();

        const callback = () => this.checkLastError(chrome.runtime.lastError);
        chrome.tabs.query({}, (tabs) => {
            for (const tab of tabs) {
                chrome.tabs.sendMessage(tab.id, {action: 'optionsUpdate', params: {source}}, callback);
            }
        });
    }

    onMessage({action, params}, sender, callback) {
        const handler = Backend._messageHandlers.get(action);
        if (typeof handler !== 'function') { return false; }

        try {
            const promise = handler(this, params, sender);
            promise.then(
                (result) => callback({result}),
                (error) => callback({error: errorToJson(error)})
            );
            return true;
        } catch (error) {
            callback({error: errorToJson(error)});
            return false;
        }
    }

    _onZoomChange({tabId, oldZoomFactor, newZoomFactor}) {
        const callback = () => this.checkLastError(chrome.runtime.lastError);
        chrome.tabs.sendMessage(tabId, {action: 'zoomChanged', params: {oldZoomFactor, newZoomFactor}}, callback);
    }

    applyOptions() {
        const options = this.getOptionsSync(this.optionsContext);
        if (!options.general.enable) {
            this.setExtensionBadgeBackgroundColor('#555555');
            this.setExtensionBadgeText('off');
        } else if (!dictConfigured(options)) {
            this.setExtensionBadgeBackgroundColor('#f0ad4e');
            this.setExtensionBadgeText('!');
        } else {
            this.setExtensionBadgeText('');
        }

        this.anki = options.anki.enable ? new AnkiConnect(options.anki.server) : new AnkiNull();

        if (options.parsing.enableMecabParser) {
            this.mecab.startListener();
        } else {
            this.mecab.stopListener();
        }

        window.clearInterval(this.clipboardPopupTimerId);
        if (options.general.enableClipboardPopups) {
            this.clipboardPopupTimerId = setInterval(() => {
                this._onApiClipboardGet()
                .then((result) => {
                    if (this.clipboardPreviousText === result) {
                        return;
                    }
                    this._onCommandSearch({mode: 'popup', query: result});
                    this.clipboardPreviousText = result;
                });
            }, this.clipboardInterval);
        }
    }

    async getOptionsSchema() {
        if (this.isPreparedPromise !== null) {
            await this.isPreparedPromise;
        }
        return this.optionsSchema;
    }

    async getFullOptions() {
        if (this.isPreparedPromise !== null) {
            await this.isPreparedPromise;
        }
        return this.options;
    }

    async setFullOptions(options) {
        if (this.isPreparedPromise !== null) {
            await this.isPreparedPromise;
        }
        try {
            this.options = JsonSchema.getValidValueOrDefault(this.optionsSchema, utilIsolate(options));
        } catch (e) {
            // This shouldn't happen, but catch errors just in case of bugs
            logError(e);
        }
    }

    async getOptions(optionsContext) {
        if (this.isPreparedPromise !== null) {
            await this.isPreparedPromise;
        }
        return this.getOptionsSync(optionsContext);
    }

    getOptionsSync(optionsContext) {
        return this.getProfileSync(optionsContext).options;
    }

    getProfileSync(optionsContext) {
        const profiles = this.options.profiles;
        if (typeof optionsContext.index === 'number') {
            return profiles[optionsContext.index];
        }
        const profile = this.getProfileFromContext(optionsContext);
        return profile !== null ? profile : this.options.profiles[this.options.profileCurrent];
    }

    getProfileFromContext(optionsContext) {
        for (const profile of this.options.profiles) {
            const conditionGroups = profile.conditionGroups;
            if (conditionGroups.length > 0 && Backend.testConditionGroups(conditionGroups, optionsContext)) {
                return profile;
            }
        }
        return null;
    }

    static testConditionGroups(conditionGroups, data) {
        if (conditionGroups.length === 0) { return false; }

        for (const conditionGroup of conditionGroups) {
            const conditions = conditionGroup.conditions;
            if (conditions.length > 0 && Backend.testConditions(conditions, data)) {
                return true;
            }
        }

        return false;
    }

    static testConditions(conditions, data) {
        for (const condition of conditions) {
            if (!conditionsTestValue(profileConditionsDescriptor, condition.type, condition.operator, condition.value, data)) {
                return false;
            }
        }
        return true;
    }

    setExtensionBadgeBackgroundColor(color) {
        if (typeof chrome.browserAction.setBadgeBackgroundColor === 'function') {
            chrome.browserAction.setBadgeBackgroundColor({color});
        }
    }

    setExtensionBadgeText(text) {
        if (typeof chrome.browserAction.setBadgeText === 'function') {
            chrome.browserAction.setBadgeText({text});
        }
    }

    checkLastError() {
        // NOP
    }

    _runCommand(command, params) {
        const handler = Backend._commandHandlers.get(command);
        if (typeof handler !== 'function') { return false; }

        handler(this, params);
        return true;
    }

    // Message handlers

    _onApiOptionsSchemaGet() {
        return this.getOptionsSchema();
    }

    _onApiOptionsGet({optionsContext}) {
        return this.getOptions(optionsContext);
    }

    _onApiOptionsGetFull() {
        return this.getFullOptions();
    }

    async _onApiOptionsSet({changedOptions, optionsContext, source}) {
        const options = await this.getOptions(optionsContext);

        function getValuePaths(obj) {
            const valuePaths = [];
            const nodes = [{obj, path: []}];
            while (nodes.length > 0) {
                const node = nodes.pop();
                for (const key of Object.keys(node.obj)) {
                    const path = node.path.concat(key);
                    const obj = node.obj[key];
                    if (obj !== null && typeof obj === 'object') {
                        nodes.unshift({obj, path});
                    } else {
                        valuePaths.push([obj, path]);
                    }
                }
            }
            return valuePaths;
        }

        function modifyOption(path, value, options) {
            let pivot = options;
            for (const key of path.slice(0, -1)) {
                if (!hasOwn(pivot, key)) {
                    return false;
                }
                pivot = pivot[key];
            }
            pivot[path[path.length - 1]] = value;
            return true;
        }

        for (const [value, path] of getValuePaths(changedOptions)) {
            modifyOption(path, value, options);
        }

        await this._onApiOptionsSave({source});
    }

    async _onApiOptionsSave({source}) {
        const options = await this.getFullOptions();
        await optionsSave(options);
        this.onOptionsUpdated(source);
    }

    async _onApiKanjiFind({text, optionsContext}) {
        const options = await this.getOptions(optionsContext);
        const definitions = await this.translator.findKanji(text, options);
        definitions.splice(options.general.maxResults);
        return definitions;
    }

    async _onApiTermsFind({text, details, optionsContext}) {
        const options = await this.getOptions(optionsContext);
        const [definitions, length] = await this.translator.findTerms(text, details, options);
        definitions.splice(options.general.maxResults);
        return {length, definitions};
    }

    async _onApiTextParse({text, optionsContext}) {
        const options = await this.getOptions(optionsContext);
        const results = [];
        while (text.length > 0) {
            const term = [];
            const [definitions, sourceLength] = await this.translator.findTermsInternal(
                text.substring(0, options.scanning.length),
                dictEnabledSet(options),
                {},
                options
            );
            if (definitions.length > 0) {
                dictTermsSort(definitions);
                const {expression, reading} = definitions[0];
                const source = text.substring(0, sourceLength);
                for (const {text, furigana} of jpDistributeFuriganaInflected(expression, reading, source)) {
                    const reading = jpConvertReading(text, furigana, options.parsing.readingMode);
                    term.push({text, reading});
                }
                text = text.substring(source.length);
            } else {
                const reading = jpConvertReading(text[0], null, options.parsing.readingMode);
                term.push({text: text[0], reading});
                text = text.substring(1);
            }
            results.push(term);
        }
        return results;
    }

    async _onApiTextParseMecab({text, optionsContext}) {
        const options = await this.getOptions(optionsContext);
        const results = {};
        const rawResults = await this.mecab.parseText(text);
        for (const mecabName in rawResults) {
            const result = [];
            for (const parsedLine of rawResults[mecabName]) {
                for (const {expression, reading, source} of parsedLine) {
                    const term = [];
                    if (expression !== null && reading !== null) {
                        for (const {text, furigana} of jpDistributeFuriganaInflected(
                            expression,
                            jpKatakanaToHiragana(reading),
                            source
                        )) {
                            const reading = jpConvertReading(text, furigana, options.parsing.readingMode);
                            term.push({text, reading});
                        }
                    } else {
                        const reading = jpConvertReading(source, null, options.parsing.readingMode);
                        term.push({text: source, reading});
                    }
                    result.push(term);
                }
                result.push([{text: '\n'}]);
            }
            results[mecabName] = result;
        }
        return results;
    }

    async _onApiDefinitionAdd({definition, mode, context, optionsContext}) {
        const options = await this.getOptions(optionsContext);
        const templates = Backend._getTemplates(options);

        if (mode !== 'kanji') {
            await audioInject(
                definition,
                options.anki.terms.fields,
                options.audio.sources,
                optionsContext
            );
        }

        if (context && context.screenshot) {
            await this._injectScreenshot(
                definition,
                options.anki.terms.fields,
                context.screenshot
            );
        }

        const note = await dictNoteFormat(definition, mode, options, templates);
        return this.anki.addNote(note);
    }

    async _onApiDefinitionsAddable({definitions, modes, optionsContext}) {
        const options = await this.getOptions(optionsContext);
        const templates = Backend._getTemplates(options);
        const states = [];

        try {
            const notes = [];
            for (const definition of definitions) {
                for (const mode of modes) {
                    const note = await dictNoteFormat(definition, mode, options, templates);
                    notes.push(note);
                }
            }

            const cannotAdd = [];
            const results = await this.anki.canAddNotes(notes);
            for (let resultBase = 0; resultBase < results.length; resultBase += modes.length) {
                const state = {};
                for (let modeOffset = 0; modeOffset < modes.length; ++modeOffset) {
                    const index = resultBase + modeOffset;
                    const result = results[index];
                    const info = {canAdd: result};
                    state[modes[modeOffset]] = info;
                    if (!result) {
                        cannotAdd.push([notes[index], info]);
                    }
                }

                states.push(state);
            }

            if (cannotAdd.length > 0) {
                const noteIdsArray = await this.anki.findNoteIds(cannotAdd.map((e) => e[0]));
                for (let i = 0, ii = Math.min(cannotAdd.length, noteIdsArray.length); i < ii; ++i) {
                    const noteIds = noteIdsArray[i];
                    if (noteIds.length > 0) {
                        cannotAdd[i][1].noteId = noteIds[0];
                    }
                }
            }
        } catch (e) {
            // NOP
        }

        return states;
    }

    async _onApiNoteView({noteId}) {
        return this.anki.guiBrowse(`nid:${noteId}`);
    }

    async _onApiTemplateRender({template, data, dynamic}) {
        return (
            dynamic ?
            handlebarsRenderDynamic(template, data) :
            handlebarsRenderStatic(template, data)
        );
    }

    async _onApiCommandExec({command, params}) {
        return this._runCommand(command, params);
    }

    async _onApiAudioGetUrl({definition, source, optionsContext}) {
        const options = await this.getOptions(optionsContext);
        return await audioGetUrl(definition, source, options);
    }

    _onApiScreenshotGet({options}, sender) {
        if (!(sender && sender.tab)) {
            return Promise.resolve();
        }

        const windowId = sender.tab.windowId;
        return new Promise((resolve) => {
            chrome.tabs.captureVisibleTab(windowId, options, (dataUrl) => resolve(dataUrl));
        });
    }

    _onApiForward({action, params}, sender) {
        if (!(sender && sender.tab)) {
            return Promise.resolve();
        }

        const tabId = sender.tab.id;
        return new Promise((resolve) => {
            chrome.tabs.sendMessage(tabId, {action, params}, (response) => resolve(response));
        });
    }

    _onApiFrameInformationGet(params, sender) {
        const frameId = sender.frameId;
        return Promise.resolve({frameId});
    }

    _onApiInjectStylesheet({css}, sender) {
        if (!sender.tab) {
            return Promise.reject(new Error('Invalid tab'));
        }

        const tabId = sender.tab.id;
        const frameId = sender.frameId;
        const details = {
            code: css,
            runAt: 'document_start',
            cssOrigin: 'user',
            allFrames: false
        };
        if (typeof frameId === 'number') {
            details.frameId = frameId;
        }

        return new Promise((resolve, reject) => {
            chrome.tabs.insertCSS(tabId, details, () => {
                const e = chrome.runtime.lastError;
                if (e) {
                    reject(new Error(e.message));
                } else {
                    resolve();
                }
            });
        });
    }

    async _onApiGetEnvironmentInfo() {
        const browser = await Backend._getBrowser();
        const platform = await new Promise((resolve) => chrome.runtime.getPlatformInfo(resolve));
        return {
            browser,
            platform: {
                os: platform.os
            }
        };
    }

    async _onApiClipboardGet() {
        /*
        Notes:
            document.execCommand('paste') doesn't work on Firefox.
            This may be a bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1603985
            Therefore, navigator.clipboard.readText() is used on Firefox.

            navigator.clipboard.readText() can't be used in Chrome for two reasons:
            * Requires page to be focused, else it rejects with an exception.
            * When the page is focused, Chrome will request clipboard permission, despite already
              being an extension with clipboard permissions. It effectively asks for the
              non-extension permission for clipboard access.
        */
        const browser = await Backend._getBrowser();
        if (browser === 'firefox' || browser === 'firefox-mobile') {
            return await navigator.clipboard.readText();
        } else {
            const clipboardPasteTarget = this.clipboardPasteTarget;
            clipboardPasteTarget.value = '';
            clipboardPasteTarget.focus();
            document.execCommand('paste');
            const result = clipboardPasteTarget.value;
            clipboardPasteTarget.value = '';
            return result;
        }
    }

    async _onApiGetDisplayTemplatesHtml() {
        const url = chrome.runtime.getURL('/mixed/display-templates.html');
        return await requestText(url, 'GET');
    }

    _onApiGetZoom(params, sender) {
        if (!sender || !sender.tab) {
            return Promise.reject(new Error('Invalid tab'));
        }

        return new Promise((resolve, reject) => {
            const tabId = sender.tab.id;
            if (!(
                chrome.tabs !== null &&
                typeof chrome.tabs === 'object' &&
                typeof chrome.tabs.getZoom === 'function'
            )) {
                // Not supported
                resolve({zoomFactor: 1.0});
                return;
            }
            chrome.tabs.getZoom(tabId, (zoomFactor) => {
                const e = chrome.runtime.lastError;
                if (e) {
                    reject(new Error(e.message));
                } else {
                    resolve({zoomFactor});
                }
            });
        });
    }

    // Command handlers

    async _onCommandSearch(params) {
        const {mode, query} = params || {};

        const options = await this.getOptions(this.optionsContext);
        const {popupWidth, popupHeight} = options.general;

        const baseUrl = chrome.runtime.getURL('/bg/search.html');
        const queryString = (query && query.length > 0) ? `?query=${encodeURIComponent(query)}` : '';
        const url = baseUrl + queryString;

        switch (mode) {
            case 'sameTab':
                try {
                    const tab = await Backend._findTab(1000, (url2) => (
                        url2 !== null &&
                        url2.startsWith(url) &&
                        (url2.length === url.length || url2[url.length] === '?' || url2[url.length] === '#')
                    ));
                    if (tab !== null) {
                        await Backend._focusTab(tab);
                        return;
                    }
                } catch (e) {
                    // NOP
                }
                chrome.tabs.create({url});
                return;
            case 'newTab':
                chrome.tabs.create({url});
                return;
            case 'popup':
                if (this.popupWindow !== null) {
                    chrome.windows.remove(this.popupWindow.id);
                }
                chrome.windows.create(
                    {url, width: popupWidth, height: popupHeight, type: 'popup'},
                    (popupWindow) => { this.popupWindow = popupWindow; }
                );
                return;
        }
    }

    _onCommandHelp() {
        chrome.tabs.create({url: 'https://foosoft.net/projects/yomichan/'});
    }

    _onCommandOptions(params) {
        if (!(params && params.newTab)) {
            chrome.runtime.openOptionsPage();
        } else {
            const manifest = chrome.runtime.getManifest();
            const url = chrome.runtime.getURL(manifest.options_ui.page);
            chrome.tabs.create({url});
        }
    }

    async _onCommandToggle() {
        const optionsContext = {
            depth: 0,
            url: window.location.href
        };
        const source = 'popup';

        const options = await this.getOptions(optionsContext);
        options.general.enable = !options.general.enable;
        await this._onApiOptionsSave({source});
    }

    // Utilities

    async _injectScreenshot(definition, fields, screenshot) {
        let usesScreenshot = false;
        for (const name in fields) {
            if (fields[name].includes('{screenshot}')) {
                usesScreenshot = true;
                break;
            }
        }

        if (!usesScreenshot) {
            return;
        }

        const dateToString = (date) => {
            const year = date.getUTCFullYear();
            const month = date.getUTCMonth().toString().padStart(2, '0');
            const day = date.getUTCDate().toString().padStart(2, '0');
            const hours = date.getUTCHours().toString().padStart(2, '0');
            const minutes = date.getUTCMinutes().toString().padStart(2, '0');
            const seconds = date.getUTCSeconds().toString().padStart(2, '0');
            return `${year}-${month}-${day}-${hours}-${minutes}-${seconds}`;
        };

        const now = new Date(Date.now());
        const filename = `yomichan_browser_screenshot_${definition.reading}_${dateToString(now)}.${screenshot.format}`;
        const data = screenshot.dataUrl.replace(/^data:[\w\W]*?,/, '');

        try {
            await this.anki.storeMediaFile(filename, data);
        } catch (e) {
            return;
        }

        definition.screenshotFileName = filename;
    }

    static _getTabUrl(tab) {
        return new Promise((resolve) => {
            chrome.tabs.sendMessage(tab.id, {action: 'getUrl'}, {frameId: 0}, (response) => {
                let url = null;
                if (!chrome.runtime.lastError) {
                    url = (response !== null && typeof response === 'object' && !Array.isArray(response) ? response.url : null);
                    if (url !== null && typeof url !== 'string') {
                        url = null;
                    }
                }
                resolve({tab, url});
            });
        });
    }

    static async _findTab(timeout, checkUrl) {
        // This function works around the need to have the "tabs" permission to access tab.url.
        const tabs = await new Promise((resolve) => chrome.tabs.query({}, resolve));
        let matchPromiseResolve = null;
        const matchPromise = new Promise((resolve) => { matchPromiseResolve = resolve; });

        const checkTabUrl = ({tab, url}) => {
            if (checkUrl(url, tab)) {
                matchPromiseResolve(tab);
            }
        };

        const promises = [];
        for (const tab of tabs) {
            const promise = Backend._getTabUrl(tab);
            promise.then(checkTabUrl);
            promises.push(promise);
        }

        const racePromises = [
            matchPromise,
            Promise.all(promises).then(() => null)
        ];
        if (typeof timeout === 'number') {
            racePromises.push(new Promise((resolve) => setTimeout(() => resolve(null), timeout)));
        }

        return await Promise.race(racePromises);
    }

    static async _focusTab(tab) {
        await new Promise((resolve, reject) => {
            chrome.tabs.update(tab.id, {active: true}, () => {
                const e = chrome.runtime.lastError;
                if (e) { reject(e); }
                else { resolve(); }
            });
        });

        if (!(typeof chrome.windows === 'object' && chrome.windows !== null)) {
            // Windows not supported (e.g. on Firefox mobile)
            return;
        }

        try {
            const tabWindow = await new Promise((resolve, reject) => {
                chrome.windows.get(tab.windowId, {}, (tabWindow) => {
                    const e = chrome.runtime.lastError;
                    if (e) { reject(e); }
                    else { resolve(tabWindow); }
                });
            });
            if (!tabWindow.focused) {
                await new Promise((resolve, reject) => {
                    chrome.windows.update(tab.windowId, {focused: true}, () => {
                        const e = chrome.runtime.lastError;
                        if (e) { reject(e); }
                        else { resolve(); }
                    });
                });
            }
        } catch (e) {
            // Edge throws exception for no reason here.
        }
    }

    static async _getBrowser() {
        if (EXTENSION_IS_BROWSER_EDGE) {
            return 'edge';
        }
        if (typeof browser !== 'undefined') {
            try {
                const info = await browser.runtime.getBrowserInfo();
                if (info.name === 'Fennec') {
                    return 'firefox-mobile';
                }
            } catch (e) {
                // NOP
            }
            return 'firefox';
        } else {
            return 'chrome';
        }
    }

    static _getTemplates(options) {
        const templates = options.anki.fieldTemplates;
        return typeof templates === 'string' ? templates : profileOptionsGetDefaultFieldTemplates();
    }
}

Backend._messageHandlers = new Map([
    ['optionsSchemaGet', (self, ...args) => self._onApiOptionsSchemaGet(...args)],
    ['optionsGet', (self, ...args) => self._onApiOptionsGet(...args)],
    ['optionsGetFull', (self, ...args) => self._onApiOptionsGetFull(...args)],
    ['optionsSet', (self, ...args) => self._onApiOptionsSet(...args)],
    ['optionsSave', (self, ...args) => self._onApiOptionsSave(...args)],
    ['kanjiFind', (self, ...args) => self._onApiKanjiFind(...args)],
    ['termsFind', (self, ...args) => self._onApiTermsFind(...args)],
    ['textParse', (self, ...args) => self._onApiTextParse(...args)],
    ['textParseMecab', (self, ...args) => self._onApiTextParseMecab(...args)],
    ['definitionAdd', (self, ...args) => self._onApiDefinitionAdd(...args)],
    ['definitionsAddable', (self, ...args) => self._onApiDefinitionsAddable(...args)],
    ['noteView', (self, ...args) => self._onApiNoteView(...args)],
    ['templateRender', (self, ...args) => self._onApiTemplateRender(...args)],
    ['commandExec', (self, ...args) => self._onApiCommandExec(...args)],
    ['audioGetUrl', (self, ...args) => self._onApiAudioGetUrl(...args)],
    ['screenshotGet', (self, ...args) => self._onApiScreenshotGet(...args)],
    ['forward', (self, ...args) => self._onApiForward(...args)],
    ['frameInformationGet', (self, ...args) => self._onApiFrameInformationGet(...args)],
    ['injectStylesheet', (self, ...args) => self._onApiInjectStylesheet(...args)],
    ['getEnvironmentInfo', (self, ...args) => self._onApiGetEnvironmentInfo(...args)],
    ['clipboardGet', (self, ...args) => self._onApiClipboardGet(...args)],
    ['getDisplayTemplatesHtml', (self, ...args) => self._onApiGetDisplayTemplatesHtml(...args)],
    ['getZoom', (self, ...args) => self._onApiGetZoom(...args)]
]);

Backend._commandHandlers = new Map([
    ['search', (self, ...args) => self._onCommandSearch(...args)],
    ['help', (self, ...args) => self._onCommandHelp(...args)],
    ['options', (self, ...args) => self._onCommandOptions(...args)],
    ['toggle', (self, ...args) => self._onCommandToggle(...args)]
]);

window.yomichanBackend = new Backend();
window.yomichanBackend.prepare();