feat(player): simplifies text track handling

Resolves #35 by adding the `textTrack` function to simplify
text track retrieval and selection. This function allows to:

- retrieve the currently active text track
- activate a text track based on `language` and `kind` properties

Also, when selecting a text track, if the `kind` property is not satisfied,
the first text track satisfying the `language` condition will be returned,
or `undefined` if no condition is satisfied. During this process,
all text tracks in mode `showing` are `disabled`.

```javascript
// Get the current text track
player.textTrack();

// Activate a text track
player.textTrack({language:'en', kind:'captions'})

// Disable all text tracks
player.textTrack('off')
```

- add `textTrack` function
- export the registered component directly
- add test coverage

src/components/player.js

@@ -41,9 +41,65 @@ class Player extends videojs.getComponent('player') {
 
     return audioTrack;
   }
+
+  /**
+   * A getter/setter for the media's text track.
+   * Activates the text track according to the language and kind properties.
+   * Falls back on the first text track found if the kind property is not satisfied.
+   * Disables all subtitle tracks that are `showing` if the `trackSelector` is truthy but does not satisfy any condition.
+   *
+   * @param {TrackSelector} [trackSelector]
+   *
+   * @example
+   * // Get the current text track
+   * player.textTrack();
+   *
+   * @example
+   * // Disable all text tracks has a side effect
+   * player.textTrack('off');
+   * player.textTrack({});
+   *
+   * @example
+   * // Activate an text track based on language and kind properties
+   * player.textTrack({language:'en', kind:'captions'});
+   *
+   * @example
+   * // Activate first text track found corresponding to language
+   * player.textTrack({language:'fr'});
+   *
+   * @return { import('video.js/dist/types/tracks/audio-track').default|undefined }
+   */
+  textTrack(trackSelector) {
+    const textTracks = Array.from(this.player().textTracks()).filter(
+      (textTrack) => !['chapters', 'metadata'].includes(textTrack.kind)
+    );
+
+    if (!trackSelector) {
+      return textTracks.find((textTrack) => textTrack.mode === 'showing');
+    }
+
+    textTracks.forEach((textTrack) => (textTrack.mode = 'disabled'));
+
+    const { kind, language } = trackSelector;
+    const textTrack =
+      textTracks.find((textTrack) => {
+        if (textTrack.language === language && textTrack.kind === kind) {
+          textTrack.mode = 'showing';
+        }
+
+        return textTrack.mode === 'showing';
+      }) ||
+      textTracks.find((textTrack) => {
+        if (textTrack.language === language) {
+          textTrack.mode = 'showing';
+        }
+
+        return textTrack.mode === 'showing';
+      });
+
+    return textTrack;
+  }
 }
 
 // Overrides the default video.js player component
-videojs.registerComponent('player', Player);
-
-export default Player;
+export default videojs.registerComponent('player', Player);

test/components/player.spec.js

@@ -61,4 +61,63 @@ describe('Player', () => {
       expect(player.audioTrack({ language: 'fr' })).toBeUndefined();
     });
   });
+
+  describe('textTrack', () => {
+    const player = new Player(videoEl);
+
+    player.textTracks = jest.fn(() => ({
+      0: {
+        mode: 'showing',
+        id: '1',
+        kind: 'subtitles',
+        label: 'English',
+        language: 'en',
+      },
+      1: {
+        mode: 'disabled',
+        id: '2',
+        kind: 'descriptions',
+        label: 'English AD',
+        language: 'en',
+      },
+      length: 2,
+    }));
+
+    it('should return the currently active text track if the function parameter is undefined', () => {
+      expect(player.textTrack()).toMatchObject({
+        mode: 'showing',
+        id: '1',
+        kind: 'subtitles',
+        label: 'English',
+        language: 'en',
+      });
+    });
+    it('should enable and return the text track according to the language and kind properties', () => {
+      expect(
+        player.textTrack({ language: 'en', kind: 'descriptions' })
+      ).toMatchObject({
+        mode: 'showing',
+        id: '2',
+        kind: 'descriptions',
+        label: 'English AD',
+        language: 'en',
+      });
+    });
+    it('should enable and return the text track according to the language property if the kind property does not satisfy the condition', () => {
+      expect(
+        player.textTrack({ language: 'en', kind: 'invalid' })
+      ).toMatchObject({
+        mode: 'showing',
+        id: '1',
+        kind: 'subtitles',
+        label: 'English',
+        language: 'en',
+      });
+    });
+    it('should return undefined and disable every active text track if the language and kind properties do not satisfy the condition', () => {
+      expect(player.textTrack({ language: 'fr' })).toBeUndefined();
+      expect(player.textTracks.mock.results[0].value[0].mode).toBe('disabled');
+      expect(player.textTracks.mock.results[0].value[1].mode).toBe('disabled');
+    });
+  });
 });