Store selected TTS voice in localStorage (#1241)

Author: sbwhitt

src/plugins/tts/AbstractTTSEngine.js

@@ -142,6 +142,10 @@ export default class AbstractTTSEngine {
     // MS Edge fires voices changed randomly very often
     this.events.off('voiceschanged', this.updateBestVoice);
     this.voice = this.getVoices().find(voice => voice.voiceURI === voiceURI);
+    // if the current book has a language set, store the selected voice with the book language as a suffix
+    if (this.opts.bookLanguage) {
+      localStorage.setItem(`BRtts-voice-${this.opts.bookLanguage}`, this.voice.voiceURI);
+    }
     if (this.activeSound) this.activeSound.setVoice(this.voice);
   }
 
@@ -221,17 +225,32 @@ export default class AbstractTTSEngine {
     // user languages that match the book language
     const matchingUserLangs = userLanguages.filter(lang => lang.startsWith(bookLanguage));
 
-    // Try to find voices that intersect these two sets
-    return AbstractTTSEngine.getMatchingVoice(matchingUserLangs, bookLangVoices) ||
+    // First try to find the last chosen voice from localStorage for the current book language
+    return AbstractTTSEngine.getMatchingStoredVoice(bookLangVoices, bookLanguage)
+        // Try to find voices that intersect these two sets
+        || AbstractTTSEngine.getMatchingVoice(matchingUserLangs, bookLangVoices)
         // no user languages match the books; let's return the best voice for the book language
-        (bookLangVoices.find(v => v.default) || bookLangVoices[0])
+        || (bookLangVoices.find(v => v.default) || bookLangVoices[0])
         // No voices match the book language? let's find a voice in the user's language
         // and ignore book lang
         || AbstractTTSEngine.getMatchingVoice(userLanguages, voices)
         // C'mon! Ok, just read with whatever we got!
         || (voices.find(v => v.default) || voices[0]);
   }
 
+  /**
+   * @private
+   * Get the voice last selected by the user for the book language from localStorage.
+   * Returns undefined if no voice is stored or found.
+   * @param {SpeechSynthesisVoice[]} voices  browser voices to choose from
+   * @param {ISO6391} bookLanguage  book language to look for
+   * @return {SpeechSynthesisVoice | undefined}
+   */
+  static getMatchingStoredVoice(voices, bookLanguage) {
+    const storedVoice = localStorage.getItem(`BRtts-voice-${bookLanguage}`);
+    return (storedVoice ? voices.find(v => v.voiceURI === storedVoice) : undefined);
+  }
+
   /**
      * @private
      * Get the best voice that matches one of the BCP47 languages (order by preference)

tests/jest/plugins/tts/AbstractTTSEngine.test.js

@@ -111,6 +111,26 @@ for (const dummyVoice of [dummyVoiceHyphens, dummyVoiceUnderscores]) {
 
       expect(getBestBookVoice(voices, 'en', ['en-CA', 'en'])).toBe(voices[0]);
     });
+
+    test('choose stored language from localStorage', () => {
+      const voices = [
+        dummyVoice({lang: "en-US", voiceURI: "English US", default: true}),
+        dummyVoice({lang: "en-GB", voiceURI: "English GB"}),
+        dummyVoice({lang: "en-CA", voiceURI: "English CA"}),
+      ];
+      class DummyEngine extends AbstractTTSEngine {
+        getVoices() { return voices; }
+      }
+      const ttsEngine = new DummyEngine({...DUMMY_TTS_ENGINE_OPTS, bookLanguage: 'en'});
+      // simulates setting default voice on tts startup
+      ttsEngine.updateBestVoice();
+      // simulates user choosing a voice that matches the bookLanguage
+      // voice will be stored in localStorage
+      ttsEngine.setVoice(voices[2].voiceURI);
+
+      // expecting the voice to be selected by getMatchingStoredVoice and returned as best voice
+      expect(getBestBookVoice(voices, 'en', [])).toBe(voices[2]);
+    });
   });
 }