queue: add ability to see previous items

Add the ability to see (but not edit) previous items.

This completes the new playback UI I've been working on for about 2
weeks now. I pray that there is no insane unfixable bug with this,
please please please please please

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueAdapter.kt

@@ -25,15 +25,15 @@ import android.view.View
 import androidx.core.view.isInvisible
 import androidx.recyclerview.widget.RecyclerView
 import com.google.android.material.shape.MaterialShapeDrawable
+import java.util.*
 import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.ItemQueueSongBinding
-import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.ui.recycler.*
 import org.oxycblt.auxio.util.*
 
 class QueueAdapter(listener: QueueItemListener) :
-    MonoAdapter<Song, QueueItemListener, QueueSongViewHolder>(listener) {
+    MonoAdapter<QueueViewModel.QueueSong, QueueItemListener, QueueSongViewHolder>(listener) {
     override val data = SyncBackingData(this, QueueSongViewHolder.DIFFER)
     override val creator = QueueSongViewHolder.CREATOR
 }
@@ -46,7 +46,7 @@ interface QueueItemListener {
 class QueueSongViewHolder
 private constructor(
     private val binding: ItemQueueSongBinding,
-) : BindingViewHolder<Song, QueueItemListener>(binding.root) {
+) : BindingViewHolder<QueueViewModel.QueueSong, QueueItemListener>(binding.root) {
     val bodyView: View
         get() = binding.body
     val backgroundView: View
@@ -58,6 +58,9 @@ private constructor(
             elevation = binding.context.getDimenSafe(R.dimen.elevation_normal) * 5
         }
 
+    val isEnabled: Boolean
+        get() = binding.songDragHandle.isEnabled
+
     init {
         binding.body.background =
             LayerDrawable(
@@ -72,10 +75,10 @@ private constructor(
     }
 
     @SuppressLint("ClickableViewAccessibility")
-    override fun bind(item: Song, listener: QueueItemListener) {
+    override fun bind(item: QueueViewModel.QueueSong, listener: QueueItemListener) {
-        binding.songAlbumCover.bind(item)
+        binding.songAlbumCover.bind(item.song)
-        binding.songName.textSafe = item.resolveName(binding.context)
+        binding.songName.textSafe = item.song.resolveName(binding.context)
-        binding.songInfo.textSafe = item.resolveIndividualArtistName(binding.context)
+        binding.songInfo.textSafe = item.song.resolveIndividualArtistName(binding.context)
 
         binding.background.isInvisible = true
 
@@ -84,6 +87,18 @@ private constructor(
 
         binding.body.setOnClickListener { listener.onClick(this) }
 
+        if (item.previous) {
+            binding.songName.alpha = 0.5f
+            binding.songInfo.alpha = 0.5f
+            binding.songAlbumCover.alpha = 0.5f
+            binding.songDragHandle.isEnabled = false
+        } else {
+            binding.songName.alpha = 1f
+            binding.songInfo.alpha = 1f
+            binding.songAlbumCover.alpha = 1f
+            binding.songDragHandle.isEnabled = true
+        }
+
         // Roll our own drag handlers as the default ones suck
         binding.songDragHandle.setOnTouchListener { _, motionEvent ->
             binding.songDragHandle.performClick()
@@ -104,6 +119,19 @@ private constructor(
                     QueueSongViewHolder(ItemQueueSongBinding.inflate(context.inflater))
             }
 
-        val DIFFER = SongViewHolder.DIFFER
+        val DIFFER =
+            object : SimpleItemCallback<QueueViewModel.QueueSong>() {
+                override fun areContentsTheSame(
+                    oldItem: QueueViewModel.QueueSong,
+                    newItem: QueueViewModel.QueueSong
+                ) =
+                    super.areContentsTheSame(oldItem, newItem) &&
+                        oldItem.previous == newItem.previous
+
+                override fun areItemsTheSame(
+                    oldItem: QueueViewModel.QueueSong,
+                    newItem: QueueViewModel.QueueSong
+                ) = oldItem.song == newItem.song && oldItem.previous == newItem.previous
+            }
     }
 }

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueDragCallback.kt

@@ -42,9 +42,16 @@ class QueueDragCallback(private val playbackModel: QueueViewModel) : ItemTouchHe
     override fun getMovementFlags(
         recyclerView: RecyclerView,
         viewHolder: RecyclerView.ViewHolder
-    ): Int =
+    ): Int {
-        makeFlag(ItemTouchHelper.ACTION_STATE_DRAG, ItemTouchHelper.UP or ItemTouchHelper.DOWN) or
+        val queueHolder = viewHolder as QueueSongViewHolder
-            makeFlag(ItemTouchHelper.ACTION_STATE_SWIPE, ItemTouchHelper.START)
+        return if (queueHolder.isEnabled) {
+            makeFlag(
+                ItemTouchHelper.ACTION_STATE_DRAG, ItemTouchHelper.UP or ItemTouchHelper.DOWN) or
+                makeFlag(ItemTouchHelper.ACTION_STATE_SWIPE, ItemTouchHelper.START)
+        } else {
+            0
+        }
+    }
 
     override fun interpolateOutOfBoundsScroll(
         recyclerView: RecyclerView,

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueFragment.kt

@@ -22,7 +22,9 @@ import android.view.LayoutInflater
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
 import androidx.recyclerview.widget.ItemTouchHelper
+import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import java.util.*
 import org.oxycblt.auxio.databinding.FragmentQueueBinding
 import org.oxycblt.auxio.ui.fragment.ViewBindingFragment
 import org.oxycblt.auxio.util.collectImmediately
@@ -64,13 +66,28 @@ class QueueFragment : ViewBindingFragment<FragmentQueueBinding>(), QueueItemList
         touchHelper.startDrag(viewHolder)
     }
 
-    private fun updateQueue(queue: QueueViewModel.QueueData) {
+    private fun updateQueue(queue: List<QueueViewModel.QueueSong>) {
-        if (queue.nonTrivial) {
+        val instructions = queueModel.instructions
-            // nonTrivial implies that using a synced submitList would be slow, replace the list
+        if (instructions != null) {
-            // instead.
+            if (instructions.replace) {
-            queueAdapter.data.replaceList(queue.queue)
+                queueAdapter.data.replaceList(queue)
+            } else {
+                queueAdapter.data.submitList(queue)
+            }
+
+            if (instructions.scrollTo != null) {
+                val binding = requireBinding()
+                val lmm = binding.queueRecycler.layoutManager as LinearLayoutManager
+                val indices =
+                    lmm.findFirstCompletelyVisibleItemPosition()..lmm
+                            .findLastCompletelyVisibleItemPosition()
+
+                if (instructions.scrollTo !in indices) {
+                    requireBinding().queueRecycler.scrollToPosition(instructions.scrollTo)
+                }
+            }
         } else {
-            queueAdapter.data.submitList(queue.queue)
+            queueAdapter.data.submitList(queue)
         }
     }
 }

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueViewModel.kt

@@ -23,15 +23,21 @@ import kotlinx.coroutines.flow.StateFlow
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
-import org.oxycblt.auxio.util.logD
+import org.oxycblt.auxio.ui.recycler.Item
 
 class QueueViewModel : ViewModel(), PlaybackStateManager.Callback {
     private val playbackManager = PlaybackStateManager.getInstance()
 
-    data class QueueData(val queue: List<Song>, val nonTrivial: Boolean)
+    data class QueueSong(val song: Song, val previous: Boolean) : Item() {
+        override val id: Long
+            get() = song.id
+    }
 
-    private val _queue = MutableStateFlow(QueueData(listOf(), false))
+    private val _queue = MutableStateFlow(listOf<QueueSong>())
-    val queue: StateFlow<QueueData> = _queue
+    val queue: StateFlow<List<QueueSong>> = _queue
+
+    data class QueueInstructions(val replace: Boolean, val scrollTo: Int?)
+    var instructions: QueueInstructions? = null
 
     init {
         playbackManager.addCallback(this)
@@ -41,53 +47,64 @@ class QueueViewModel : ViewModel(), PlaybackStateManager.Callback {
      * Go to an item in the queue using it's recyclerview adapter index. No-ops if out of bounds.
      */
     fun goto(adapterIndex: Int) {
-        val index = adapterIndex + (playbackManager.queue.size - _queue.value.queue.size)
+        if (adapterIndex !in playbackManager.queue.indices) {
-        logD(adapterIndex)
+            return
-        logD(playbackManager.queue.size - _queue.value.queue.size)
-
-        if (index in playbackManager.queue.indices) {
-            playbackManager.goto(index)
         }
+
+        playbackManager.goto(adapterIndex)
     }
 
     /** Remove a queue item using it's recyclerview adapter index. */
     fun removeQueueDataItem(adapterIndex: Int) {
-        val index = adapterIndex + (playbackManager.queue.size - _queue.value.queue.size)
+        if (adapterIndex <= playbackManager.index ||
-        if (index in playbackManager.queue.indices) {
+            adapterIndex !in playbackManager.queue.indices) {
-            playbackManager.removeQueueItem(index)
+            return
         }
+
+        playbackManager.removeQueueItem(adapterIndex)
     }
+
     /** Move queue items using their recyclerview adapter indices. */
     fun moveQueueDataItems(adapterFrom: Int, adapterTo: Int): Boolean {
-        val delta = (playbackManager.queue.size - _queue.value.queue.size)
+        if (adapterFrom <= playbackManager.index || adapterTo <= playbackManager.index) {
-        val from = adapterFrom + delta
+            return false
-        val to = adapterTo + delta
-        if (from in playbackManager.queue.indices && to in playbackManager.queue.indices) {
-            playbackManager.moveQueueItem(from, to)
-            return true
         }
 
+        playbackManager.moveQueueItem(adapterFrom, adapterTo)
+
         return false
     }
 
+    fun finishInstructions() {
+        instructions = null
+    }
+
     override fun onIndexMoved(index: Int) {
-        _queue.value = QueueData(generateQueue(index, playbackManager.queue), false)
+        instructions = QueueInstructions(false, index + 1)
+        _queue.value = generateQueue(index, playbackManager.queue)
     }
 
     override fun onQueueChanged(queue: List<Song>) {
-        _queue.value = QueueData(generateQueue(playbackManager.index, queue), false)
+        instructions = QueueInstructions(false, null)
+        _queue.value = generateQueue(playbackManager.index, queue)
     }
 
     override fun onQueueReworked(index: Int, queue: List<Song>) {
-        _queue.value = QueueData(generateQueue(index, queue), true)
+        instructions = QueueInstructions(true, index + 1)
+        _queue.value = generateQueue(index, queue)
     }
 
     override fun onNewPlayback(index: Int, queue: List<Song>, parent: MusicParent?) {
-        _queue.value = QueueData(generateQueue(index, queue), true)
+        instructions = QueueInstructions(true, index + 1)
+        _queue.value = generateQueue(index, queue)
     }
 
-    private fun generateQueue(index: Int, queue: List<Song>) =
+    private fun generateQueue(index: Int, queue: List<Song>): List<QueueSong> {
-        queue.slice(index + 1..playbackManager.queue.lastIndex)
+        val before = queue.slice(0..index).map { QueueSong(it, true) }
+        val after =
+            queue.slice(index + 1..playbackManager.queue.lastIndex).map { QueueSong(it, false) }
+        return before + after
+    }
 
     override fun onCleared() {
         super.onCleared()