VEX-5938: Update resource loader to handle encrypted local files (24i#12

)

Adds offline decryption key and uses it to decrypt content during offline playback

Jira: VEX-5938
https://jira.tenkasu.net/browse/VEX-5938

- Update to accept scheme for key required to play offline playback
- Uses provided scheme to intercept call from player and return the key
- Fixes player item observer removal pattern

### Reviews
- Major reviewer (domain expert): @armadilio3

README.md

@@ -317,6 +317,7 @@ var styles = StyleSheet.create({
 * [trackId](#trackId)
 * [useTextureView](#usetextureview)
 * [volume](#volume)
+* [localSourceEncryptionKeyScheme](#localSourceEncryptionKeyScheme)
 
 ### Event props
 * [onAudioBecomingNoisy](#onaudiobecomingnoisy)
@@ -915,6 +916,18 @@ Adjust the volume.
 
 Platforms: all
 
+#### localSourceEncryptionKeyScheme
+Set the url scheme for stream encryption key for local assets
+
+Type: String
+
+Example:
+```
+localSourceEncryptionKeyScheme="my-offline-key"
+```
+
+Platforms: iOS
+
 
 ### Event props
 

Video.js

@@ -418,6 +418,7 @@ Video.propTypes = {
     certificateUrl: PropTypes.string,
     getLicense: PropTypes.func,
   }),
+  localSourceEncryptionKeyScheme: PropTypes.string,
   minLoadRetryCount: PropTypes.number,
   maxBitRate: PropTypes.number,
   resizeMode: PropTypes.string,

ios/Video/Features/RCTPlayerObserver.swift

@@ -28,39 +28,43 @@ class RCTPlayerObserver: NSObject {
     var _handlers: RCTPlayerObserverHandler!
 
     var player:AVPlayer? {
+        willSet {
+            removePlayerObservers()
+            removePlayerTimeObserver()
+        }
         didSet {
-            if player == nil {
-                removePlayerObservers()
-                removePlayerTimeObserver()
-            } else {
+            if player != nil {
                 addPlayerObservers()
                 addPlayerTimeObserver()
             }
         }
     }
     var playerItem:AVPlayerItem? {
+        willSet {
+            removePlayerItemObservers()
+        }
         didSet {
-            if playerItem == nil {
-                removePlayerItemObservers()
-            } else {
+            if playerItem != nil {
                 addPlayerItemObservers()
             }
         }
     }
     var playerViewController:AVPlayerViewController? {
+        willSet {
+            removePlayerViewControllerObservers()
+        }
         didSet {
-            if playerViewController == nil {
-                removePlayerViewControllerObservers()
-            } else {
+            if playerViewController != nil {
                 addPlayerViewControllerObservers()
             }
         }
     }
     var playerLayer:AVPlayerLayer? {
+        willSet {
+            removePlayerLayerObserver()
+        }
         didSet {
             if playerLayer == nil {
-                removePlayerLayerObserver()
-            } else {
                 addPlayerLayerObserver()
             }
         }
@@ -148,8 +152,8 @@ class RCTPlayerObserver: NSObject {
 
     /* Cancels the previously registered time observer. */
     func removePlayerTimeObserver() {
-        if let timeObserver = _timeObserver {
-            player?.removeTimeObserver(timeObserver)
+        if _timeObserver != nil {
+            player?.removeTimeObserver(_timeObserver)
             _timeObserver = nil
         }
     }

ios/Video/Features/RCTPlayerOperations.swift

@@ -1,5 +1,6 @@
 import AVFoundation
 import MediaAccessibility
+import Promises
 
 let RCTVideoUnset = -1
 
@@ -157,4 +158,23 @@ enum RCTPlayerOperations {
         }
 
     }
+
+    static func seek(player: AVPlayer, playerItem:AVPlayerItem, paused:Bool, seekTime:Float, seekTolerance:Float) -> Promise<Bool> {
+        let timeScale:Int = 1000
+        let cmSeekTime:CMTime = CMTimeMakeWithSeconds(Float64(seekTime), preferredTimescale: Int32(timeScale))
+        let current:CMTime = playerItem.currentTime()
+        let tolerance:CMTime = CMTimeMake(value: Int64(seekTolerance), timescale: Int32(timeScale))
+
+        return Promise<Bool>(on: .global()) { fulfill, reject in
+            guard CMTimeCompare(current, cmSeekTime) != 0 else {
+                reject(NSError())
+                return
+            }
+            if !paused { player.pause() }
+
+            player.seek(to: cmSeekTime, toleranceBefore:tolerance, toleranceAfter:tolerance, completionHandler:{ (finished:Bool) in
+                fulfill(finished)
+            })
+        }
+    }
 }