list: rework sort dialog internals

Change the sort dialog to allow the following:
1. Allow null initial sort values in the dialog.
2. Make saving only possible if the sort changed.

app/src/main/java/org/oxycblt/auxio/list/sort/SortDialog.kt

@@ -22,6 +22,7 @@ import android.os.Bundle
 import android.view.LayoutInflater
 import androidx.core.view.updatePadding
 import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.button.MaterialButtonToggleGroup
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogSortBinding
 import org.oxycblt.auxio.list.ClickableListListener
@@ -31,10 +32,12 @@ import org.oxycblt.auxio.ui.ViewBindingBottomSheetDialogFragment
 import org.oxycblt.auxio.util.systemBarInsetsCompat
 
 abstract class SortDialog :
-    ViewBindingBottomSheetDialogFragment<DialogSortBinding>(), ClickableListListener<Sort.Mode> {
+    ViewBindingBottomSheetDialogFragment<DialogSortBinding>(),
+    ClickableListListener<Sort.Mode>,
+    MaterialButtonToggleGroup.OnButtonCheckedListener {
     private val modeAdapter = SortModeAdapter(this)
 
-    abstract fun getInitialSort(): Sort
+    abstract fun getInitialSort(): Sort?
 
     abstract fun applyChosenSort(sort: Sort)
 
@@ -50,31 +53,19 @@ abstract class SortDialog :
             v.updatePadding(bottom = insets.systemBarInsetsCompat.bottom)
             insets
         }
-
         binding.sortModeRecycler.adapter = modeAdapter
-
+        binding.sortDirectionGroup.addOnButtonCheckedListener(this)
         binding.sortCancel.setOnClickListener { dismiss() }
-
         binding.sortSave.setOnClickListener {
-            val initial = getInitialSort()
+            applyChosenSort(requireNotNull(getCurrentSort()))
-            // FIXME: This won't work for the playlist sort dialog.
-            val mode = modeAdapter.currentMode ?: initial.mode
-            val direction =
-                when (binding.sortDirectionGroup.checkedButtonId) {
-                    R.id.sort_direction_asc -> Sort.Direction.ASCENDING
-                    R.id.sort_direction_dsc -> Sort.Direction.DESCENDING
-                    else -> initial.direction
-                }
-            applyChosenSort(Sort(mode, direction))
             dismiss()
         }
 
         // --- STATE SETUP ---
         val initial = getInitialSort()
-
+        if (initial != null) {
             modeAdapter.update(getModeChoices(), UpdateInstructions.Diff)
             modeAdapter.setSelected(initial.mode)
-
             val directionId =
                 when (initial.direction) {
                     Sort.Direction.ASCENDING -> R.id.sort_direction_asc
@@ -82,8 +73,41 @@ abstract class SortDialog :
                 }
             binding.sortDirectionGroup.check(directionId)
         }
+        updateButtons()
+    }
+
+    override fun onDestroyBinding(binding: DialogSortBinding) {
+        super.onDestroyBinding(binding)
+        binding.sortDirectionGroup.removeOnButtonCheckedListener(this)
+    }
 
     override fun onClick(item: Sort.Mode, viewHolder: RecyclerView.ViewHolder) {
         modeAdapter.setSelected(item)
+        updateButtons()
+    }
+
+    override fun onButtonChecked(
+        group: MaterialButtonToggleGroup?,
+        checkedId: Int,
+        isChecked: Boolean
+    ) {
+        updateButtons()
+    }
+
+    private fun updateButtons() {
+        val binding = requireBinding()
+        binding.sortSave.isEnabled = getCurrentSort() != getInitialSort()
+    }
+
+    private fun getCurrentSort(): Sort? {
+        val initial = getInitialSort()
+        val mode = modeAdapter.currentMode ?: initial?.mode ?: return null
+        val direction =
+            when (requireBinding().sortDirectionGroup.checkedButtonId) {
+                R.id.sort_direction_asc -> Sort.Direction.ASCENDING
+                R.id.sort_direction_dsc -> Sort.Direction.DESCENDING
+                else -> initial?.direction ?: return null
+            }
+        return Sort(mode, direction)
     }
 }