Video message recording improvements

submodules/TelegramUI/Components/VideoMessageCameraScreen/Sources/ResultPreviewView.swift

@@ -0,0 +1,119 @@
+import Foundation
+import UIKit
+import AVFoundation
+
+final class ResultPreviewView: UIView {
+    let composition: AVComposition
+    
+    let player: AVPlayer
+    let playerLayer: AVPlayerLayer
+    
+    var didPlayToEndTimeObserver: NSObjectProtocol?
+    
+    var trimRange: Range<Double>? {
+        didSet {
+            if let trimRange = self.trimRange {
+                self.player.currentItem?.forwardPlaybackEndTime = CMTime(seconds: trimRange.upperBound, preferredTimescale: CMTimeScale(1000))
+            } else {
+                self.player.currentItem?.forwardPlaybackEndTime = .invalid
+            }
+        }
+    }
+    
+    init(composition: AVComposition) {
+        self.composition = composition
+        
+        self.player = AVPlayer(playerItem: AVPlayerItem(asset: composition))
+        self.player.isMuted = true
+        
+        self.playerLayer = AVPlayerLayer(player: self.player)
+        
+        super.init(frame: .zero)
+        
+        self.layer.addSublayer(self.playerLayer)
+        
+        self.didPlayToEndTimeObserver = NotificationCenter.default.addObserver(forName: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: self.player.currentItem, queue: nil, using: { [weak self] notification in
+            guard let self else {
+                return
+            }
+            var start: Double = 0.0
+            if let trimRange = self.trimRange {
+                start = trimRange.lowerBound
+            }
+            self.player.pause()
+            self.seek(to: start, andPlay: true)
+        })
+        
+        self.player.play()
+    }
+    
+    required public init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+    
+    deinit {
+        if let didPlayToEndTimeObserver = self.didPlayToEndTimeObserver {
+            NotificationCenter.default.removeObserver(didPlayToEndTimeObserver)
+        }
+    }
+    
+    func updateTrimRange(start: Double, end: Double, updatedEnd: Bool, apply: Bool) {
+        if !apply {
+            self.player.pause()
+        } else {
+            self.trimRange = start..<end
+        }
+        let seekTo: Double
+        if updatedEnd && !apply {
+            seekTo = end
+        } else {
+            seekTo = start
+        }
+        self.seek(to: seekTo, andPlay: apply)
+    }
+    
+    func play() {
+        self.player.play()
+    }
+    
+    func pause() {
+        self.player.pause()
+    }
+    
+    private var targetTimePosition: (CMTime, Bool)?
+    private var updatingTimePosition = false
+    func seek(to seconds: Double, andPlay play: Bool) {
+        let position = CMTime(seconds: seconds, preferredTimescale: CMTimeScale(1000.0))
+        self.targetTimePosition = (position, play)
+        
+        if !self.updatingTimePosition {
+            self.updateVideoTimePosition()
+        }
+    }
+    
+    private func updateVideoTimePosition() {
+        guard let (targetPosition, _) = self.targetTimePosition else {
+            return
+        }
+        self.updatingTimePosition = true
+        
+        self.player.seek(to: targetPosition, toleranceBefore: .zero, toleranceAfter: .zero, completionHandler: { [weak self] _ in
+            if let self {
+                if let (currentTargetPosition, play) = self.targetTimePosition, currentTargetPosition == targetPosition {
+                    self.updatingTimePosition = false
+                    self.targetTimePosition = nil
+                    
+                    if play {
+                        self.player.play()
+                    }
+                } else {
+                    self.updateVideoTimePosition()
+                }
+            }
+        })
+    }
+    
+    override func layoutSubviews() {
+        self.playerLayer.frame = self.bounds
+    }
+}