refactor: extract shared mixins and helpers, drop dead abstractions

Introduces shared seams for paginated views, D-pad reorder, media control
routing, async singletons and the device method channel, then points the
open-coded copies at them.

Also removes unused models and duplicated provider/server plumbing, folds
the twice-implemented artifact store in the server, and factors the
repeated Flutter toolchain prologue in CI into a composite action.

android/app/src/main/kotlin/com/edde746/plezy/exoplayer/ExoPlayerCore.kt

@@ -77,6 +77,7 @@ import com.edde746.plezy.shared.FlutterOverlayHelper
 import com.edde746.plezy.shared.FrameRateManager
 import com.edde746.plezy.shared.MediaCodecQuery
 import com.edde746.plezy.shared.PlayerSurfaceHost
+import com.edde746.plezy.shared.SurfacePlayerCore
 import java.util.concurrent.Executors
 import java.util.concurrent.atomic.AtomicLong
 import org.chromium.net.CronetEngine
@@ -102,7 +103,7 @@ interface ExoPlayerDelegate : com.edde746.plezy.shared.PlayerDelegate {
 internal fun playbackMimeType(isLive: Boolean): String? = if (isLive) MimeTypes.APPLICATION_M3U8 else null
 
 @OptIn(UnstableApi::class)
-class ExoPlayerCore(private val activity: Activity) : Player.Listener {
+class ExoPlayerCore(private val activity: Activity) : Player.Listener, SurfacePlayerCore {
 
   companion object {
     private const val TAG = "ExoPlayerCore"
@@ -3400,7 +3401,7 @@ class ExoPlayerCore(private val activity: Activity) : Player.Listener {
     else -> null
   }
 
-  fun setVisible(visible: Boolean) {
+  override fun setVisible(visible: Boolean) {
     if (disposing) return
     currentVisible = visible
     activity.runOnUiThread {
@@ -3493,7 +3494,7 @@ class ExoPlayerCore(private val activity: Activity) : Player.Listener {
     }
   }
 
-  fun onPipModeChanged(isInPipMode: Boolean) {
+  override fun onPipModeChanged(isInPipMode: Boolean) {
     if (disposing) return
     activity.runOnUiThread {
       if (disposing) return@runOnUiThread
@@ -3509,7 +3510,7 @@ class ExoPlayerCore(private val activity: Activity) : Player.Listener {
     }
   }
 
-  fun updateFrame() {
+  override fun updateFrame() {
     if (disposing) return
     activity.runOnUiThread {
       if (disposing) return@runOnUiThread
@@ -3524,15 +3525,15 @@ class ExoPlayerCore(private val activity: Activity) : Player.Listener {
 
   // Audio Focus
 
-  fun requestAudioFocus(): Boolean = audioFocusManager?.requestAudioFocus() ?: false
+  override fun requestAudioFocus(): Boolean = audioFocusManager?.requestAudioFocus() ?: false
 
-  fun abandonAudioFocus() {
+  override fun abandonAudioFocus() {
     audioFocusManager?.abandonAudioFocus()
   }
 
   // Frame Rate Matching
 
-  fun setVideoFrameRate(
+  override fun setVideoFrameRate(
     fps: Float,
     videoDurationMs: Long,
     extraDelayMs: Long,
@@ -3548,7 +3549,7 @@ class ExoPlayerCore(private val activity: Activity) : Player.Listener {
     mgr.setVideoFrameRate(fps, videoDurationMs, extraDelayMs, videoWidth, videoHeight, onComplete)
   }
 
-  fun clearVideoFrameRate() {
+  override fun clearVideoFrameRate() {
     frameRateManager?.clearVideoFrameRate()
   }
 

android/app/src/main/kotlin/com/edde746/plezy/exoplayer/ExoPlayerPlugin.kt

@@ -12,6 +12,7 @@ import com.edde746.plezy.shared.MpvContentUriResolver
 import com.edde746.plezy.shared.PlayerChannelBinding
 import com.edde746.plezy.shared.PlayerDelegate
 import com.edde746.plezy.shared.ResolvedMpvUri
+import com.edde746.plezy.shared.SurfacePlayerCore
 import io.flutter.embedding.engine.plugins.FlutterPlugin
 import io.flutter.embedding.engine.plugins.activity.ActivityAware
 import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
@@ -45,6 +46,10 @@ class ExoPlayerPlugin :
   private var activity: Activity? = null
   private var activityBinding: ActivityPluginBinding? = null
 
+  /** Whichever core currently owns the surface; both expose [SurfacePlayerCore] identically. */
+  private val activeSurfaceCore: SurfacePlayerCore?
+    get() = if (usingMpvFallback) mpvCore else playerCore
+
   // Every Dart observeProperty registration, kept so an ExoPlayer→MPV
   // fallback can re-observe exactly what Dart asked for instead of
   // maintaining a parallel hard-coded list.
@@ -949,20 +954,12 @@ class ExoPlayerPlugin :
       return
     }
 
-    if (usingMpvFallback) {
-      mpvCore?.setVisible(visible)
-    } else {
-      playerCore?.setVisible(visible)
-    }
+    activeSurfaceCore?.setVisible(visible)
     result.success(null)
   }
 
   private fun handleUpdateFrame(result: MethodChannel.Result) {
-    if (usingMpvFallback) {
-      mpvCore?.updateFrame()
-    } else {
-      playerCore?.updateFrame()
-    }
+    activeSurfaceCore?.updateFrame()
     result.success(null)
   }
 
@@ -974,51 +971,31 @@ class ExoPlayerPlugin :
     val videoHeight = call.argument<Number>("videoHeight")?.toInt() ?: 0
 
     Log.d(TAG, "setVideoFrameRate: fps=$fps, duration=$duration, extraDelayMs=$extraDelayMs, video=${videoWidth}x$videoHeight")
-    val onComplete: (Boolean) -> Unit = { switched -> result.success(switched) }
-    if (usingMpvFallback) {
-      val core = mpvCore
-      if (core == null) {
-        result.success(false)
-      } else {
-        core.setVideoFrameRate(fps, duration, extraDelayMs, videoWidth, videoHeight, onComplete)
-      }
-    } else {
-      val core = playerCore
-      if (core == null) {
-        result.success(false)
-      } else {
-        core.setVideoFrameRate(fps, duration, extraDelayMs, videoWidth, videoHeight, onComplete)
-      }
+    val core = activeSurfaceCore
+    if (core == null) {
+      result.success(false)
+      return
+    }
+    core.setVideoFrameRate(fps, duration, extraDelayMs, videoWidth, videoHeight) { switched ->
+      result.success(switched)
     }
   }
 
   private fun handleClearVideoFrameRate(result: MethodChannel.Result) {
     Log.d(TAG, "clearVideoFrameRate")
-    if (usingMpvFallback) {
-      mpvCore?.clearVideoFrameRate()
-    } else {
-      playerCore?.clearVideoFrameRate()
-    }
+    activeSurfaceCore?.clearVideoFrameRate()
     result.success(null)
   }
 
   private fun handleRequestAudioFocus(result: MethodChannel.Result) {
     Log.d(TAG, "requestAudioFocus")
-    val granted = if (usingMpvFallback) {
-      mpvCore?.requestAudioFocus() ?: false
-    } else {
-      playerCore?.requestAudioFocus() ?: false
-    }
+    val granted = activeSurfaceCore?.requestAudioFocus() ?: false
     result.success(granted)
   }
 
   private fun handleAbandonAudioFocus(result: MethodChannel.Result) {
     Log.d(TAG, "abandonAudioFocus")
-    if (usingMpvFallback) {
-      mpvCore?.abandonAudioFocus()
-    } else {
-      playerCore?.abandonAudioFocus()
-    }
+    activeSurfaceCore?.abandonAudioFocus()
     result.success(null)
   }
 
@@ -1228,11 +1205,7 @@ class ExoPlayerPlugin :
 
   fun onPipModeChanged(isInPipMode: Boolean) {
     activity?.runOnUiThread {
-      if (usingMpvFallback) {
-        mpvCore?.onPipModeChanged(isInPipMode)
-      } else {
-        playerCore?.onPipModeChanged(isInPipMode)
-      }
+      activeSurfaceCore?.onPipModeChanged(isInPipMode)
     }
   }
 

android/app/src/main/kotlin/com/edde746/plezy/mpv/MpvPlayerCore.kt

@@ -19,6 +19,7 @@ import com.edde746.plezy.shared.AudioFocusManager
 import com.edde746.plezy.shared.FrameRateManager
 import com.edde746.plezy.shared.PlayerDelegate
 import com.edde746.plezy.shared.PlayerSurfaceHost
+import com.edde746.plezy.shared.SurfacePlayerCore
 import dev.jdtech.mpv.*
 import kotlinx.coroutines.*
 import kotlinx.coroutines.sync.Mutex
@@ -40,7 +41,7 @@ class MpvPlayerCore private constructor(
   private val audioOnly: Boolean,
   private val propertyWriterOverride: (suspend (String, String) -> Unit)?,
   initializedForTesting: Boolean
-) : SurfaceHolder.Callback {
+) : SurfaceHolder.Callback, SurfacePlayerCore {
   constructor(context: Context, audioOnly: Boolean = false) : this(context, audioOnly, null, false)
 
   internal constructor(
@@ -405,7 +406,7 @@ class MpvPlayerCore private constructor(
 
   // Audio Focus
 
-  fun requestAudioFocus(): Boolean {
+  override fun requestAudioFocus(): Boolean {
     val granted = audioFocusManager?.requestAudioFocus() ?: false
     if (granted && pausedForAudioFocusLoss) {
       resumeAfterAudioFocusGain("audio focus request granted")
@@ -413,7 +414,7 @@ class MpvPlayerCore private constructor(
     return granted
   }
 
-  fun abandonAudioFocus() {
+  override fun abandonAudioFocus() {
     audioFocusManager?.abandonAudioFocus()
   }
 
@@ -1042,7 +1043,7 @@ class MpvPlayerCore private constructor(
     }
   }
 
-  fun setVisible(visible: Boolean) {
+  override fun setVisible(visible: Boolean) {
     // Audio-only: no render layer to show or hide — tolerated no-op.
     if (audioOnly || disposing) return
     runOnMain {
@@ -1067,11 +1068,11 @@ class MpvPlayerCore private constructor(
     }
   }
 
-  fun onPipModeChanged(isInPipMode: Boolean) {
+  override fun onPipModeChanged(isInPipMode: Boolean) {
     // MPV handles aspect ratio internally via its own surface management
   }
 
-  fun updateFrame() {
+  override fun updateFrame() {
     // Audio-only: no surface to refresh — tolerated no-op.
     if (audioOnly || disposing) return
     runOnMain {
@@ -1106,7 +1107,7 @@ class MpvPlayerCore private constructor(
 
   // Frame Rate Matching
 
-  fun setVideoFrameRate(
+  override fun setVideoFrameRate(
     fps: Float,
     videoDurationMs: Long,
     extraDelayMs: Long,
@@ -1128,7 +1129,7 @@ class MpvPlayerCore private constructor(
     }
   }
 
-  fun clearVideoFrameRate() {
+  override fun clearVideoFrameRate() {
     frameRateManager?.clearVideoFrameRate()
   }
 

android/app/src/main/kotlin/com/edde746/plezy/shared/SurfacePlayerCore.kt

@@ -0,0 +1,27 @@
+package com.edde746.plezy.shared
+
+/**
+ * Surface and display concerns that the ExoPlayer and mpv cores implement
+ * identically, so a plugin holding either one dispatches without branching
+ * on which backend is active.
+ *
+ * Only backend-independent members belong here: playback control
+ * (play/seek/track selection) stays off this interface because mpv drives it
+ * through properties and commands where ExoPlayer uses direct method calls.
+ */
+interface SurfacePlayerCore {
+  fun setVisible(visible: Boolean)
+  fun updateFrame()
+  fun onPipModeChanged(isInPipMode: Boolean)
+  fun requestAudioFocus(): Boolean
+  fun abandonAudioFocus()
+  fun clearVideoFrameRate()
+  fun setVideoFrameRate(
+    fps: Float,
+    videoDurationMs: Long,
+    extraDelayMs: Long,
+    videoWidth: Int,
+    videoHeight: Int,
+    onComplete: (switched: Boolean) -> Unit
+  )
+}