From b17db2b4627acc1f9d0e9862ccfa802cf959f1e1 Mon Sep 17 00:00:00 2001
From: t895 <clombardo169@gmail.com>
Date: Wed, 10 Jan 2024 13:04:06 -0500
Subject: [PATCH] android: Create generic single selection list adapter

---
 .../adapters/AbstractSingleSelectionList.kt   | 105 ++++++++++++++++++
 .../org/yuzu/yuzu_emu/model/SelectableItem.kt |   9 ++
 2 files changed, 114 insertions(+)
 create mode 100644 src/android/app/src/main/java/org/yuzu/yuzu_emu/adapters/AbstractSingleSelectionList.kt
 create mode 100644 src/android/app/src/main/java/org/yuzu/yuzu_emu/model/SelectableItem.kt

diff --git a/src/android/app/src/main/java/org/yuzu/yuzu_emu/adapters/AbstractSingleSelectionList.kt b/src/android/app/src/main/java/org/yuzu/yuzu_emu/adapters/AbstractSingleSelectionList.kt
new file mode 100644
index 0000000000..52163f9d78
--- /dev/null
+++ b/src/android/app/src/main/java/org/yuzu/yuzu_emu/adapters/AbstractSingleSelectionList.kt
@@ -0,0 +1,105 @@
+// SPDX-FileCopyrightText: 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package org.yuzu.yuzu_emu.adapters
+
+import org.yuzu.yuzu_emu.model.SelectableItem
+import org.yuzu.yuzu_emu.viewholder.AbstractViewHolder
+
+/**
+ * Generic list class meant to take care of single selection UI updates
+ * @param currentList The list to show initially
+ * @param defaultSelection The default selection to use if no list items are selected by
+ * [SelectableItem.selected] or if the currently selected item is removed from the list
+ */
+abstract class AbstractSingleSelectionList<
+    Model : SelectableItem,
+    Holder : AbstractViewHolder<Model>
+    >(
+    final override var currentList: List<Model>,
+    private val defaultSelection: DefaultSelection = DefaultSelection.Start
+) : AbstractListAdapter<Model, Holder>(currentList) {
+    var selectedItem = getDefaultSelection()
+
+    init {
+        findSelectedItem()
+    }
+
+    /**
+     * Changes the selection state of the [SelectableItem] that was selected and the previously selected
+     * item and notifies the underlying adapter of the change for those items. Invokes [callback] last.
+     * Does nothing if [position] is the same as the currently selected item.
+     * @param position Index of the item that was selected
+     * @param callback Lambda that's called at the end of the list changes and has the selected list
+     * position passed in as a parameter
+     */
+    fun selectItem(position: Int, callback: ((position: Int) -> Unit)? = null) {
+        if (position == selectedItem) {
+            return
+        }
+
+        val previouslySelectedItem = selectedItem
+        selectedItem = position
+        if (currentList.indices.contains(selectedItem)) {
+            currentList[selectedItem].onSelectionStateChanged(true)
+        }
+        if (currentList.indices.contains(previouslySelectedItem)) {
+            currentList[previouslySelectedItem].onSelectionStateChanged(false)
+        }
+        onItemChanged(previouslySelectedItem)
+        onItemChanged(selectedItem)
+        callback?.invoke(position)
+    }
+
+    /**
+     * Removes a given item from the list and notifies the underlying adapter of the change. If the
+     * currently selected item was the item that was removed, the item at the position provided
+     * by [defaultSelection] will be made the new selection. Invokes [callback] last.
+     * @param position Index of the item that was removed
+     * @param callback Lambda that's called at the end of the list changes and has the removed and
+     * selected list positions passed in as parameters
+     */
+    fun removeSelectableItem(
+        position: Int,
+        callback: ((removedPosition: Int, selectedPosition: Int) -> Unit)?
+    ) {
+        removeItem(position)
+        if (position == selectedItem) {
+            selectedItem = getDefaultSelection()
+            currentList[selectedItem].onSelectionStateChanged(true)
+            onItemChanged(selectedItem)
+        } else if (position < selectedItem) {
+            selectedItem--
+        }
+        callback?.invoke(position, selectedItem)
+    }
+
+    override fun addItem(item: Model, position: Int, callback: ((Int) -> Unit)?) {
+        super.addItem(item, position, callback)
+        if (position <= selectedItem && position != -1) {
+            selectedItem++
+        }
+    }
+
+    override fun replaceList(newList: List<Model>) {
+        super.replaceList(newList)
+        findSelectedItem()
+    }
+
+    private fun findSelectedItem() {
+        for (i in currentList.indices) {
+            if (currentList[i].selected) {
+                selectedItem = i
+                break
+            }
+        }
+    }
+
+    private fun getDefaultSelection(): Int =
+        when (defaultSelection) {
+            DefaultSelection.Start -> currentList.indices.first
+            DefaultSelection.End -> currentList.indices.last
+        }
+
+    enum class DefaultSelection { Start, End }
+}
diff --git a/src/android/app/src/main/java/org/yuzu/yuzu_emu/model/SelectableItem.kt b/src/android/app/src/main/java/org/yuzu/yuzu_emu/model/SelectableItem.kt
new file mode 100644
index 0000000000..11c22d3237
--- /dev/null
+++ b/src/android/app/src/main/java/org/yuzu/yuzu_emu/model/SelectableItem.kt
@@ -0,0 +1,9 @@
+// SPDX-FileCopyrightText: 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package org.yuzu.yuzu_emu.model
+
+interface SelectableItem {
+    var selected: Boolean
+    fun onSelectionStateChanged(selected: Boolean)
+}