Make panic wipe deterministic and device-bound (#1431)

* Make panic wipe deterministic and device-bound

* Scope install markers to iOS

* Harden panic recovery and service shutdown

* Invalidate queued BLE ingress during panic

* Harden panic keychain and media cleanup

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: jack <jack@deck.local>

bitchat/ViewModels/ChatMediaTransferCoordinator.swift

@@ -72,15 +72,98 @@ extension ChatViewModel: ChatMediaTransferContext {
     }
 }
 
+/// Synchronous boundary between detached image writers and panic deletion.
+///
+/// Invalidation closes admission before waiting for writers that already
+/// entered. Those writers never need the main actor while inside the boundary,
+/// so a synchronous panic transaction can safely join them and then delete
+/// every output before reporting completion.
+private final class ImagePreparationBarrier: @unchecked Sendable {
+    private let condition = NSCondition()
+    private var generation: UInt64 = 0
+    private var activeOperations = 0
+
+    var currentGeneration: UInt64 {
+        condition.lock()
+        defer { condition.unlock() }
+        return generation
+    }
+
+    func isCurrent(_ candidate: UInt64) -> Bool {
+        condition.lock()
+        defer { condition.unlock() }
+        return generation == candidate
+    }
+
+    func performIfCurrent<T>(
+        generation candidate: UInt64,
+        operation: () throws -> T
+    ) rethrows -> T? {
+        condition.lock()
+        guard generation == candidate else {
+            condition.unlock()
+            return nil
+        }
+        activeOperations += 1
+        condition.unlock()
+
+        defer {
+            condition.lock()
+            activeOperations -= 1
+            if activeOperations == 0 {
+                condition.broadcast()
+            }
+            condition.unlock()
+        }
+        return try operation()
+    }
+
+    func invalidateAndWait() {
+        condition.lock()
+        generation &+= 1
+        while activeOperations > 0 {
+            condition.wait()
+        }
+        condition.unlock()
+    }
+}
+
+/// Runs synchronous media encoding and file I/O on a dispatch worker.
+///
+/// These operations can legitimately block. Keeping them off Swift's
+/// cooperative executor preserves forward progress when several transfers or
+/// test doubles wait at the same time.
+private func runBlockingMediaPreparation<T>(
+    _ operation: @escaping @Sendable () throws -> T
+) async throws -> T {
+    try await withCheckedThrowingContinuation { continuation in
+        DispatchQueue.global(qos: .userInitiated).async {
+            do {
+                continuation.resume(returning: try operation())
+            } catch {
+                continuation.resume(throwing: error)
+            }
+        }
+    }
+}
+
 @MainActor
 final class ChatMediaTransferCoordinator {
     private unowned let context: any ChatMediaTransferContext
+    private let prepareImagePacket: @Sendable (URL) throws -> ChatPreparedImage
+    private let imagePreparationBarrier = ImagePreparationBarrier()
 
     private(set) var transferIdToMessageIDs: [String: [String]] = [:]
     private(set) var messageIDToTransferId: [String: String] = [:]
 
-    init(context: any ChatMediaTransferContext) {
+    init(
+        context: any ChatMediaTransferContext,
+        prepareImagePacket: @escaping @Sendable (URL) throws -> ChatPreparedImage = {
+            try ChatMediaPreparation.prepareImagePacket(from: $0)
+        }
+    ) {
         self.context = context
+        self.prepareImagePacket = prepareImagePacket
     }
 
     func sendVoiceNote(at url: URL) {
@@ -98,13 +181,19 @@ final class ChatMediaTransferCoordinator {
         )
         let messageID = message.id
         let transferId = makeTransferID(messageID: messageID)
+        let generation = imagePreparationBarrier.currentGeneration
 
         Task.detached(priority: .userInitiated) { [weak self] in
             do {
-                let packet = try ChatMediaPreparation.prepareVoiceNotePacket(at: url)
+                let packet = try await runBlockingMediaPreparation {
+                    try ChatMediaPreparation.prepareVoiceNotePacket(at: url)
+                }
 
                 await MainActor.run { [weak self] in
-                    guard let self else { return }
+                    guard let self,
+                          self.imagePreparationBarrier.isCurrent(generation) else {
+                        return
+                    }
                     self.registerTransfer(transferId: transferId, messageID: messageID)
                     if let peerID = targetPeer {
                         self.context.sendFilePrivate(packet, to: peerID, transferId: transferId)
@@ -116,13 +205,19 @@ final class ChatMediaTransferCoordinator {
                 SecureLogger.warning("Voice note exceeds size limit (\(size) bytes)", category: .session)
                 try? FileManager.default.removeItem(at: url)
                 await MainActor.run { [weak self] in
-                    guard let self else { return }
+                    guard let self,
+                          self.imagePreparationBarrier.isCurrent(generation) else {
+                        return
+                    }
                     self.handleMediaSendFailure(messageID: messageID, reason: String(localized: "content.delivery.reason.voice_too_large", comment: "Failure reason shown when a voice note exceeds the size limit"))
                 }
             } catch {
                 SecureLogger.error("Voice note send failed: \(error)", category: .session)
                 await MainActor.run { [weak self] in
-                    guard let self else { return }
+                    guard let self,
+                          self.imagePreparationBarrier.isCurrent(generation) else {
+                        return
+                    }
                     self.handleMediaSendFailure(messageID: messageID, reason: String(localized: "content.delivery.reason.voice_send_failed", comment: "Failure reason shown when a voice note could not be sent"))
                 }
             }
@@ -132,11 +227,27 @@ final class ChatMediaTransferCoordinator {
     #if os(iOS)
     func processThenSendImage(_ image: UIImage?) {
         guard let image else { return }
-        Task.detached { [weak self] in
+        let generation = imagePreparationBarrier.currentGeneration
+        let barrier = imagePreparationBarrier
+        Task.detached(priority: .userInitiated) { [weak self, barrier] in
             do {
-                let processedURL = try ImageUtils.processImage(image)
-                await MainActor.run { [weak self] in
-                    guard let self else { return }
+                let processedURL = try await runBlockingMediaPreparation {
+                    try barrier.performIfCurrent(
+                        generation: generation,
+                        operation: {
+                            try ImageUtils.processImage(image)
+                        }
+                    )
+                }
+                guard let processedURL else {
+                    return
+                }
+                await MainActor.run { [weak self, barrier] in
+                    guard let self,
+                          barrier.isCurrent(generation) else {
+                        try? FileManager.default.removeItem(at: processedURL)
+                        return
+                    }
                     self.sendImage(from: processedURL)
                 }
             } catch {
@@ -147,11 +258,27 @@ final class ChatMediaTransferCoordinator {
     #elseif os(macOS)
     func processThenSendImage(from url: URL?) {
         guard let url else { return }
-        Task.detached { [weak self] in
+        let generation = imagePreparationBarrier.currentGeneration
+        let barrier = imagePreparationBarrier
+        Task.detached(priority: .userInitiated) { [weak self, barrier] in
             do {
-                let processedURL = try ImageUtils.processImage(at: url)
-                await MainActor.run { [weak self] in
-                    guard let self else { return }
+                let processedURL = try await runBlockingMediaPreparation {
+                    try barrier.performIfCurrent(
+                        generation: generation,
+                        operation: {
+                            try ImageUtils.processImage(at: url)
+                        }
+                    )
+                }
+                guard let processedURL else {
+                    return
+                }
+                await MainActor.run { [weak self, barrier] in
+                    guard let self,
+                          barrier.isCurrent(generation) else {
+                        try? FileManager.default.removeItem(at: processedURL)
+                        return
+                    }
                     self.sendImage(from: processedURL)
                 }
             } catch {
@@ -170,6 +297,7 @@ final class ChatMediaTransferCoordinator {
         }
 
         let targetPeer = context.selectedPrivateChatPeer
+        let generation = imagePreparationBarrier.currentGeneration
 
         do {
             try ImageUtils.validateImageSource(at: sourceURL)
@@ -179,12 +307,28 @@ final class ChatMediaTransferCoordinator {
             return
         }
 
-        Task.detached(priority: .userInitiated) { [weak self] in
+        let prepareImagePacket = self.prepareImagePacket
+        let barrier = imagePreparationBarrier
+        Task.detached(priority: .userInitiated) { [weak self, barrier] in
             do {
-                let prepared = try ChatMediaPreparation.prepareImagePacket(from: sourceURL)
+                let prepared = try await runBlockingMediaPreparation {
+                    try barrier.performIfCurrent(
+                        generation: generation,
+                        operation: {
+                            try prepareImagePacket(sourceURL)
+                        }
+                    )
+                }
+                guard let prepared else {
+                    return
+                }
 
-                await MainActor.run { [weak self] in
-                    guard let self else { return }
+                await MainActor.run { [weak self, barrier] in
+                    guard let self,
+                          barrier.isCurrent(generation) else {
+                        try? FileManager.default.removeItem(at: prepared.outputURL)
+                        return
+                    }
                     let message = self.enqueueMediaMessage(
                         content: "\(MimeType.Category.image.messagePrefix)\(prepared.outputURL.lastPathComponent)",
                         targetPeer: targetPeer
@@ -200,14 +344,20 @@ final class ChatMediaTransferCoordinator {
                 }
             } catch ChatMediaPreparationError.imageTooLarge(let size) {
                 SecureLogger.warning("Processed image exceeds size limit (\(size) bytes)", category: .session)
-                await MainActor.run { [weak self] in
-                    guard let self else { return }
+                await MainActor.run { [weak self, barrier] in
+                    guard let self,
+                          barrier.isCurrent(generation) else {
+                        return
+                    }
                     self.context.addSystemMessage("Image is too large to send.")
                 }
             } catch {
                 SecureLogger.error("Image send preparation failed: \(error)", category: .session)
-                await MainActor.run { [weak self] in
-                    guard let self else { return }
+                await MainActor.run { [weak self, barrier] in
+                    guard let self,
+                          barrier.isCurrent(generation) else {
+                        return
+                    }
                     self.context.addSystemMessage("Failed to prepare image for sending.")
                 }
             }
@@ -341,6 +491,20 @@ final class ChatMediaTransferCoordinator {
         clearTransferMapping(for: messageID)
         context.removeMessage(withID: messageID, cleanupFile: true)
     }
+
+    /// Invalidates detached preparation work and cancels every transfer that
+    /// reached the transport. Closing image-preparation admission and joining
+    /// active synchronous writers ensures the following panic media deletion
+    /// is the last filesystem mutation before the transaction can complete.
+    func resetForPanic() {
+        imagePreparationBarrier.invalidateAndWait()
+        let transferIDs = Set(transferIdToMessageIDs.keys)
+        transferIdToMessageIDs.removeAll(keepingCapacity: false)
+        messageIDToTransferId.removeAll(keepingCapacity: false)
+        for transferID in transferIDs {
+            context.cancelTransfer(transferID)
+        }
+    }
 }
 
 private extension ChatMediaTransferCoordinator {