Critical performance fix for UI freezes when receiving media:
Problem: mediaAttachment(for:) was called during every SwiftUI render,
performing synchronous disk I/O on main thread:
- FileManager.fileExists() called 2-6x per message (checking subdirs)
- applicationFilesDirectory() creating directories on every call
- With multiple media messages, this meant 20-100+ disk ops per render
Solution:
1. Remove fileExists checks - construct URLs directly
- Files are validated during playback/display (fail gracefully if missing)
- Sender determines subdirectory (outgoing vs incoming)
2. Cache applicationFilesDirectory() result
- Static cache prevents repeated FileManager.url() calls
- Directory created only once
3. Remove redundant playback.replaceURL() in VoiceNoteView.onAppear
- Controller already initialized with correct URL
This eliminates ALL disk I/O from the view rendering hot path.
Fixes:
1. Post-playback freeze: audioPlayerDidFinishPlaying now dispatches to main
thread before updating @Published properties (Swift concurrency violation)
2. Unbounded waveform cache: Implement LRU eviction with 20-entry limit
- Track last access time for each cached waveform
- Evict oldest entry when cache is full
- Prevents unlimited memory growth as voice notes accumulate
3. Audio buffer memory leaks: Wrap computeWaveform in autoreleasepool
- AVAudioPCMBuffer allocations are autoreleased
- Pool ensures buffers are freed promptly
4. Image processing memory: Add autoreleasepool around compression loops
- Each jpegData() call creates temporary objects
- Inner pool per iteration prevents memory spikes during quality search
Memory should now remain stable during extended use.
Problem: AVAudioPlayer initialization in VoiceNotePlaybackController.init()
was running synchronously on main thread during view creation, blocking
UI for 50-200ms per voice note.
Solution:
- Remove eager preparePlayer() call from init
- Load duration asynchronously on background queue
- Player is only prepared when playback is actually requested via ensurePlayerReady()
This prevents UI freezes when voice notes appear in the chat.
