fixed bugs

ios/OralTrainer/Player/PlayerController.swift

@@ -31,8 +31,9 @@ final class PlayerController: ObservableObject {
     private var swipeBackAnchorTime: TimeInterval = 0
     private var speedBeforeLongPress: Float?
     private var transientTask: Task<Void, Never>?
-    private var cacheSwapTask: Task<Void, Never>?
+    private var cacheFallbackTask: Task<Void, Never>?
     private var activePlaybackURL: URL?
+    private var didAttemptFullFileFallback = false
     private var sentenceEndTimeObserver: Any?
     private var sentenceEndGuardToken = 0
 
@@ -91,8 +92,9 @@ final class PlayerController: ObservableObject {
     @MainActor
     func load(_ item: TrainingMediaItem) {
         cancelSentenceBoundaryGuard()
-        cacheSwapTask?.cancel()
-        cacheSwapTask = nil
+        cacheFallbackTask?.cancel()
+        cacheFallbackTask = nil
+        didAttemptFullFileFallback = false
         lastSentenceIndex = nil
         swipeBackAnchorIndex = nil
         pendingSeekPositionMs = nil
@@ -110,12 +112,8 @@ final class PlayerController: ObservableObject {
             cacheState = .ready
             preparePlaybackItem(with: cachedURL)
         } else {
-            // 关键约束：云端视频没有完整本地文件前，不把 remote URL 交给 AVPlayer。
-            activePlaybackURL = nil
-            cacheState = .downloading
-            player.replaceCurrentItem(with: nil)
-            tick()
-            scheduleFullFileDownload(for: item)
+            cacheState = .notRequired
+            preparePlaybackItem(with: item.url)
         }
     }
 
@@ -480,39 +478,8 @@ final class PlayerController: ObservableObject {
         pendingSeekPositionMs ?? currentPositionMs()
     }
 
-    @MainActor
-    private func scheduleFullFileDownload(for item: TrainingMediaItem) {
-        let remoteURL = item.url
-        cacheSwapTask = Task { [weak self] in
-            let cachedURL: URL
-            do {
-                cachedURL = try await StreamingVideoCache.shared.prefetch(remoteURL)
-            } catch is CancellationError {
-                return
-            } catch {
-                self?.cacheState = .failed(message: error.localizedDescription)
-                self?.showTransientMessage("视频缓存失败：\(error.localizedDescription)")
-                return
-            }
-            self?.prepareDownloadedFileIfNeeded(remoteURL: remoteURL, cachedURL: cachedURL)
-        }
-    }
-
-    @MainActor
-    private func prepareDownloadedFileIfNeeded(remoteURL: URL, cachedURL: URL) {
-        guard !Task.isCancelled,
-              mediaItem?.url == remoteURL,
-              activePlaybackURL == nil else {
-            return
-        }
-
-        cacheState = .ready
-        preparePlaybackItem(with: cachedURL)
-        showTransientMessage("视频已完整缓存，可以播放")
-    }
-
     private func preparePlaybackItem(with playbackURL: URL) {
-        let newItem = AVPlayerItem(url: playbackURL)
+        let newItem = makePlayerItem(url: playbackURL)
         activePlaybackURL = playbackURL
         attachItemObservers(to: newItem)
         player.replaceCurrentItem(with: newItem)
@@ -524,6 +491,19 @@ final class PlayerController: ObservableObject {
         tick()
     }
 
+    private func makePlayerItem(url: URL) -> AVPlayerItem {
+        guard !url.isFileURL else {
+            return AVPlayerItem(url: url)
+        }
+        var options: [String: Any] = [:]
+        let ext = url.pathExtension.lowercased()
+        if ext.isEmpty || ["mp4", "m4v", "mov"].contains(ext) {
+            options["AVURLAssetOverrideMIMETypeKey"] = "video/mp4"
+        }
+        let asset = AVURLAsset(url: url, options: options.isEmpty ? nil : options)
+        return AVPlayerItem(asset: asset, automaticallyLoadedAssetKeys: ["playable", "tracks", "duration"])
+    }
+
     /// AVPlayer 的 seek 是异步的；所有 seek 必须统一走这里，避免播放循环、
     /// 用户手势和 seek 完成回调交错后把位置拉回旧句子。
     private func performSeek(
@@ -844,12 +824,57 @@ final class PlayerController: ObservableObject {
                 if item.status == .failed {
                     let message = item.error?.localizedDescription ?? "未知错误"
                     self.showTransientMessage("播放失败：\(message)")
+                } else if item.status == .readyToPlay {
+                    self.considerFullFileFallback(for: item)
                 }
                 self.tick()
             }
         }
     }
 
+    private func considerFullFileFallback(for item: AVPlayerItem) {
+        guard !didAttemptFullFileFallback,
+              let media = mediaItem,
+              !media.isLocalFile,
+              !(activePlaybackURL?.isFileURL ?? false) else {
+            return
+        }
+        let hasVisibleVideo = item.presentationSize.height >= 2 && item.presentationSize.width >= 2
+        if hasVisibleVideo {
+            return
+        }
+        didAttemptFullFileFallback = true
+        cacheFallbackTask?.cancel()
+        cacheFallbackTask = Task { @MainActor [weak self] in
+            try? await Task.sleep(nanoseconds: 800_000_000)
+            guard let self, !Task.isCancelled else {
+                return
+            }
+            guard self.mediaItem?.id == media.id,
+                  self.player.currentItem === item,
+                  item.presentationSize.height < 2 else {
+                return
+            }
+            do {
+                let cachedURL = try await StreamingVideoCache.shared.prefetch(media.url)
+                guard self.mediaItem?.id == media.id else {
+                    return
+                }
+                let shouldPlay = self.playbackIntent
+                let positionMs = self.pendingSeekPositionMs ?? self.currentPositionMs()
+                self.preparePlaybackItem(with: cachedURL)
+                self.cacheState = .ready
+                if positionMs > 0 {
+                    self.performSeek(to: positionMs, resumePlayback: shouldPlay)
+                }
+            } catch is CancellationError {
+                return
+            } catch {
+                self.showTransientMessage("视频画面加载失败：\(error.localizedDescription)")
+            }
+        }
+    }
+
     private func configureAudioSession() {
         let session = AVAudioSession.sharedInstance()
         try? session.setCategory(.playback, mode: .moviePlayback)