fix(iOS): pause player on suspend or stalled if extra buffer is available (#6199)

On iOS, when disconnecting the headphones, we may receive a stalled or suspend event. In those case, we may actually still have buffer available for us to play through rather than actually having stalled or suspended. In those cases, we should pause the player to prevent playback issues.

src/js/tech/html5.js

@@ -111,6 +111,10 @@ class Html5 extends Tech {
     // into a `fullscreenchange` event
     this.proxyWebkitFullscreen_();
 
+    if (browser.IS_IOS) {
+      this.handleIOSHeadphonesDisconnection_();
+    }
+
     this.triggerReady();
   }
 
@@ -204,6 +208,50 @@ class Html5 extends Tech {
     });
   }
 
+  /**
+   * Handle IOS Headphone disconnection during playback
+   *
+   * @private
+  */
+  handleIOSHeadphonesDisconnection_() {
+    // Fudge factor to account for TimeRanges rounding
+    const TIME_FUDGE_FACTOR = 1 / 30;
+
+    // Comparisons between time values such as current time and the end of the buffered range
+    // can be misleading because of precision differences or when the current media has poorly
+    // aligned audio and video, which can cause values to be slightly off from what you would
+    // expect. This value is what we consider to be safe to use in such comparisons to account
+    // for these scenarios.
+    const SAFE_TIME_DELTA = TIME_FUDGE_FACTOR * 3;
+
+    // If iOS check if we have a real stalled or supend event or
+    // we got stalled/suspend due headphones where disconnected during playback
+    this.on(['stalled', 'suspend'], (e) => {
+      const buffered = this.buffered();
+
+      if (!buffered.length) {
+        return;
+      }
+
+      let extraBuffer = false;
+      const currentTime = this.currentTime();
+
+      // Establish if we have an extra buffer in the current time range playing.
+      for (let i = 0; i < buffered.length; i++) {
+        if (buffered.start(i) <= currentTime &&
+          currentTime < buffered.end(i) + SAFE_TIME_DELTA) {
+          extraBuffer = true;
+          break;
+        }
+      }
+
+      // if tech is not paused, browser has internet connection & player has extraBuffer inside the timeRange
+      if (extraBuffer && !this.paused() && window.navigator.onLine) {
+        this.pause();
+      }
+    });
+  }
+
   /**
    * Attempt to force override of tracks for the given type
    *