[Videos] handle app backgrounding (#4912)

* play when returning from background

* play when unfullscreening

* play when entering fullscreen, just to be sure

* state -> ref

---------

Co-authored-by: Samuel Newman <10959775+mozzius@users.noreply.github.com>

src/view/com/util/post-embeds/VideoEmbedInner/VideoEmbedInnerNative.tsx

@@ -7,6 +7,7 @@ import {useLingui} from '@lingui/react'
 import {useIsFocused} from '@react-navigation/native'
 
 import {HITSLOP_30} from '#/lib/constants'
+import {useAppState} from '#/lib/hooks/useAppState'
 import {useVideoPlayer} from '#/view/com/util/post-embeds/VideoPlayerContext'
 import {android, atoms as a, useTheme} from '#/alf'
 import {Mute_Stroke2_Corner0_Rounded as MuteIcon} from '#/components/icons/Mute'
@@ -21,6 +22,18 @@ export function VideoEmbedInnerNative() {
   const player = useVideoPlayer()
   const ref = useRef<VideoView>(null)
   const isScreenFocused = useIsFocused()
+  const isAppFocused = useAppState()
+  const prevFocusedRef = useRef(isAppFocused)
+
+  // resume video when coming back from background
+  useEffect(() => {
+    if (isAppFocused !== prevFocusedRef.current) {
+      prevFocusedRef.current = isAppFocused
+      if (isAppFocused === 'active') {
+        player.play()
+      }
+    }
+  }, [isAppFocused, player])
 
   // pause the video when the screen is not focused
   useEffect(() => {
@@ -34,6 +47,10 @@ export function VideoEmbedInnerNative() {
     }
   }, [isScreenFocused, player])
 
+  const enterFullscreen = useCallback(() => {
+    ref.current?.enterFullscreen()
+  }, [])
+
   return (
     <View style={[a.flex_1, a.relative]}>
       <VideoView
@@ -50,14 +67,10 @@ export function VideoEmbedInnerNative() {
           PlatformInfo.setAudioCategory(AudioCategory.Ambient)
           PlatformInfo.setAudioMixWithOthers(true)
           player.muted = true
+          if (!player.playing) player.play()
         }}
       />
-      <Controls
-        player={player}
-        enterFullscreen={() => {
-          ref.current?.enterFullscreen()
-        }}
-      />
+      <Controls player={player} enterFullscreen={enterFullscreen} />
     </View>
   )
 }
@@ -102,6 +115,22 @@ function Controls({
     }
   }, [player])
 
+  const onPressFullscreen = useCallback(() => {
+    switch (player.status) {
+      case 'idle':
+      case 'loading':
+      case 'readyToPlay': {
+        if (!player.playing) player.play()
+        enterFullscreen()
+        break
+      }
+      case 'error': {
+        player.replay()
+        break
+      }
+    }
+  }, [player, enterFullscreen])
+
   const toggleMuted = useCallback(() => {
     const muted = !player.muted
     // We want to set this to the _inverse_ of the new value, because we actually want for the audio to be mixed when
@@ -150,7 +179,7 @@ function Controls({
         </Animated.View>
       )}
       <Pressable
-        onPress={enterFullscreen}
+        onPress={onPressFullscreen}
         style={a.flex_1}
         accessibilityLabel={_(msg`Video`)}
         accessibilityHint={_(msg`Tap to enter full screen`)}