camera: Android video recording (Phase 4b)

CameraX VideoCapture<Recorder> wired alongside Preview + ImageCapture
in a single bindToLifecycle call. Mirrors the iOS surface contract:

  startVideoRecording(handle, snapshotOrientation) → null
    Records to a UUID-named MP4 in cacheDir. Audio enabled iff the
    instance was created with enableAudio: true AND RECORD_AUDIO has
    been granted (no SecurityException if the user denied mic but
    asked for audio — recording proceeds silent). targetRotation set
    per-call so the file's rotation metadata matches how the device
    was held at recording start.

  stopVideoRecording(handle) → {path}
    Resolves when CameraX delivers the VideoRecordEvent.Finalize.

Telegram-fidelity mirror: VideoCapture.Builder.setMirrorMode(MIRROR_MODE_OFF)
overrides CameraX's default MIRROR_MODE_ON_FRONT_ONLY so selfie
videos record the raw sensor feed ("as others see you"). Preview-side
mirror stays a CameraX-managed SurfaceTexture transform; the recorded
file is independent.

Quality: Quality.HD (720p) — keeps file sizes reasonable for chat
composer use and well within mid-range Android devices' budget for
binding all three use cases (Preview + ImageCapture + VideoCapture).
Fallback for devices that reject the 3-use-case bind would be next
iteration.

instance.dispose() now hard-cancels any in-flight recording (drops
file, no caller waiting) — matches iOS' recorder.cancel() path.

android/src/main/kotlin/io/swipelab/ux/camera/CameraInstance.kt

@@ -30,6 +30,7 @@ class CameraInstance(
     private val lifecycleOwner = CustomLifecycleOwner()
     private val previewSink = PreviewSink(registry, context)
     private val photo = PhotoCapture()
+    private val video = VideoCapture()
     private val orientation = DeviceOrientationBridge(context)
 
     private var cameraProvider: ProcessCameraProvider? = null
@@ -113,6 +114,10 @@ class CameraInstance(
     fun dispose() {
         if (disposed) return
         disposed = true
+        // Mirror iOS' dispose: any in-flight recording is hard-cancelled
+        // (file discarded) rather than left to flush, since there's no
+        // caller waiting on the result anymore.
+        if (video.isRecording) video.cancel()
         orientation.stop()
         cameraProvider?.unbindAll()
         cameraProvider = null
@@ -150,6 +155,26 @@ class CameraInstance(
         photo.take(context, snapshotRotation, onResult)
     }
 
+    /// Begin recording. [snapshotRotation] is baked into the file's
+    /// rotation metadata; the file plays back rotated even if the
+    /// device returns to portrait mid-recording. [onStartResult] fires
+    /// when CameraX's `Recording.start()` returns (immediately on
+    /// success), not when the first frame lands.
+    fun startVideoRecording(
+        snapshotRotation: Int,
+        onStartResult: (Result<Unit>) -> Unit,
+    ) {
+        check(!disposed)
+        video.start(context, enableAudio, snapshotRotation, onStartResult)
+    }
+
+    /// Stop the in-flight recording. [onResult] fires asynchronously
+    /// when CameraX delivers the Finalize event.
+    fun stopVideoRecording(onResult: (Result<String>) -> Unit) {
+        check(!disposed)
+        video.stop(onResult)
+    }
+
     private fun bind(provider: ProcessCameraProvider) {
         provider.unbindAll()
 
@@ -167,11 +192,17 @@ class CameraInstance(
             .also { it.setSurfaceProvider(previewSink::provideSurface) }
         this.preview = preview
 
+        // Preview + ImageCapture + VideoCapture as a single binding.
+        // CameraX 1.4 supports this combination on essentially every
+        // device that supports video — if a device can't deliver all
+        // three simultaneously, `bindToLifecycle` throws and we'd
+        // need to fall back. Not observed on Pixel-class hardware.
         camera = provider.bindToLifecycle(
             lifecycleOwner,
             selector,
             preview,
             photo.useCase,
+            video.useCase,
         )
     }
 

android/src/main/kotlin/io/swipelab/ux/camera/CameraPlugin.kt

@@ -135,12 +135,8 @@ class CameraPlugin :
             "lockCaptureOrientation" -> result.success(null) // preview always portrait
             "unlockCaptureOrientation" -> result.success(null)
             "takePicture" -> handleTakePicture(call, result)
-            "startVideoRecording" -> result.error(
-                "unsupported_format", "video recording not yet on Android", null,
-            )
-            "stopVideoRecording" -> result.error(
-                "unsupported_format", "video recording not yet on Android", null,
-            )
+            "startVideoRecording" -> handleStartVideo(call, result)
+            "stopVideoRecording" -> handleStopVideo(call, result)
             "audioPermissionStatus" -> result.success(isAudioGranted())
             "openSettings" -> handleOpenSettings(result)
             else -> result.notImplemented()
@@ -314,6 +310,36 @@ class CameraPlugin :
         }
     }
 
+    private fun handleStartVideo(call: MethodCall, result: MethodChannel.Result) {
+        val args = call.arguments as? Map<*, *>
+            ?: return result.error("bad_args", "startVideoRecording", null)
+        val snapshotRaw = args["snapshotOrientation"] as? String ?: "portraitUp"
+        withInstance(call, result) { instance ->
+            instance.startVideoRecording(flutterToSurfaceRotation(snapshotRaw)) {
+                outcome ->
+                outcome.fold(
+                    onSuccess = { result.success(null) },
+                    onFailure = { t ->
+                        result.error("recorder_failed", t.localizedMessage, null)
+                    },
+                )
+            }
+        }
+    }
+
+    private fun handleStopVideo(call: MethodCall, result: MethodChannel.Result) {
+        withInstance(call, result) { instance ->
+            instance.stopVideoRecording { outcome ->
+                outcome.fold(
+                    onSuccess = { path -> result.success(mapOf("path" to path)) },
+                    onFailure = { t ->
+                        result.error("recorder_failed", t.localizedMessage, null)
+                    },
+                )
+            }
+        }
+    }
+
     private fun handleOpenSettings(result: MethodChannel.Result) {
         val act = activity
             ?: return result.error("no_activity", "plugin not attached", null)

android/src/main/kotlin/io/swipelab/ux/camera/VideoCapture.kt

@@ -0,0 +1,148 @@
+package io.swipelab.ux.camera
+
+import android.Manifest
+import android.annotation.SuppressLint
+import android.content.Context
+import android.content.pm.PackageManager
+import androidx.camera.core.MirrorMode
+import androidx.camera.video.FileOutputOptions
+import androidx.camera.video.Quality
+import androidx.camera.video.QualitySelector
+import androidx.camera.video.Recorder
+import androidx.camera.video.Recording
+import androidx.camera.video.VideoRecordEvent
+import androidx.core.content.ContextCompat
+import java.io.File
+import java.util.UUID
+
+/// Wraps CameraX `VideoCapture<Recorder>`. One per [CameraInstance];
+/// the use case is bound alongside Preview + ImageCapture in
+/// `CameraInstance.bind`. Telegram-fidelity mirror policy: raw sensor
+/// feed in the recorded MP4 (no `MIRROR_MODE_ON_FRONT_ONLY` default
+/// CameraX would otherwise apply).
+class VideoCapture {
+    private val recorder = Recorder.Builder()
+        // HD (720p) matches iOS' AVCaptureSession.Preset.high default
+        // negotiation for 1280×720; keeps file sizes reasonable for
+        // chat composer use and well within the 3-use-case binding
+        // budget for mid-range Android devices.
+        .setQualitySelector(QualitySelector.from(Quality.HD))
+        .build()
+
+    val useCase: androidx.camera.video.VideoCapture<Recorder> =
+        androidx.camera.video.VideoCapture.Builder(recorder)
+            // Raw sensor capture — selfie videos are "as others see
+            // you"; the preview-only mirror lives in UxCameraPreview.
+            .setMirrorMode(MirrorMode.MIRROR_MODE_OFF)
+            .build()
+
+    private var recording: Recording? = null
+    private var stopCompletion: ((Result<String>) -> Unit)? = null
+    private var outFile: File? = null
+
+    val isRecording: Boolean get() = recording != null
+
+    /// Begin recording into a UUID-named MP4 in [context]'s cache dir.
+    /// [snapshotRotation] is a `Surface.ROTATION_*`. Audio is enabled
+    /// only when [enableAudio] AND the RECORD_AUDIO permission is
+    /// already granted — calling `withAudioEnabled()` without the
+    /// permission throws `SecurityException`.
+    ///
+    /// [onStartResult] fires synchronously after `Recording.start()`
+    /// returns (with success) — CameraX's `Recording` is "live" by
+    /// then; the asynchronous Start/Status/Finalize events still flow
+    /// to our listener but the caller has already moved on. Any
+    /// failure raised by `start()` is surfaced as a failed result.
+    /// The eventual Finalize event flows to the [stop] completion.
+    @SuppressLint("MissingPermission")
+    fun start(
+        context: Context,
+        enableAudio: Boolean,
+        snapshotRotation: Int,
+        onStartResult: (Result<Unit>) -> Unit,
+    ) {
+        if (recording != null) {
+            onStartResult(Result.failure(
+                IllegalStateException("Recording already in flight"),
+            ))
+            return
+        }
+
+        useCase.targetRotation = snapshotRotation
+
+        val file = File(context.cacheDir, "ux_camera_${UUID.randomUUID()}.mp4")
+        outFile = file
+        val options = FileOutputOptions.Builder(file).build()
+
+        val audioGranted = ContextCompat.checkSelfPermission(
+            context, Manifest.permission.RECORD_AUDIO,
+        ) == PackageManager.PERMISSION_GRANTED
+
+        var pending = recorder.prepareRecording(context, options)
+        if (enableAudio && audioGranted) {
+            pending = pending.withAudioEnabled()
+        }
+
+        try {
+            recording = pending.start(
+                ContextCompat.getMainExecutor(context),
+            ) { event ->
+                if (event is VideoRecordEvent.Finalize) {
+                    val cb = stopCompletion
+                    stopCompletion = null
+                    recording = null
+                    val target = outFile
+                    outFile = null
+                    if (event.hasError()) {
+                        cb?.invoke(Result.failure(
+                            RuntimeException(
+                                "VideoRecordEvent.Finalize error " +
+                                    "${event.error}: ${event.cause?.localizedMessage}",
+                            ),
+                        ))
+                    } else {
+                        cb?.invoke(Result.success(target?.absolutePath ?: ""))
+                    }
+                }
+            }
+            onStartResult(Result.success(Unit))
+        } catch (t: Throwable) {
+            recording = null
+            outFile = null
+            onStartResult(Result.failure(t))
+        }
+    }
+
+    /// Stop the in-flight recording. [onResult] fires when the
+    /// Finalize event lands — typically within ~100–300 ms of the
+    /// stop call. If no recording is in flight, fires failure.
+    fun stop(onResult: (Result<String>) -> Unit) {
+        val r = recording
+        if (r == null) {
+            onResult(Result.failure(IllegalStateException("No recording in flight")))
+            return
+        }
+        // Stash the completion BEFORE telling the recorder to stop —
+        // the Finalize callback can fire before `stop()` returns on
+        // fast hardware.
+        stopCompletion = onResult
+        r.stop()
+    }
+
+    /// Drop any in-flight recording without delivering its file.
+    /// Used by [CameraInstance.dispose] when the instance is torn
+    /// down mid-recording — mirrors the iOS path's `recorder.cancel()`.
+    fun cancel() {
+        val r = recording
+        if (r != null) {
+            recording = null
+            r.stop()
+        }
+        stopCompletion?.invoke(Result.failure(
+            RuntimeException("Recording cancelled"),
+        ))
+        stopCompletion = null
+        outFile?.delete()
+        outFile = null
+    }
+}