element-x-android/libraries/androidutils/src/main/kotlin/io/element/android/libraries/androidutils/diff/DefaultDiffCallback.kt

/*
 * Copyright (c) 2023 New Vector Ltd
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.element.android.libraries.androidutils.diff

import androidx.recyclerview.widget.DiffUtil

/**
 *  Default implementation of [DiffUtil.Callback] that uses [areItemsTheSame] to compare items.
 */
internal class DefaultDiffCallback<T>(
    private val oldList: List<T>,
    private val newList: List<T>,
    private val areItemsTheSame: (oldItem: T?, newItem: T?) -> Boolean,
) : DiffUtil.Callback() {
    override fun getOldListSize(): Int {
        return oldList.size
    }

    override fun getNewListSize(): Int {
        return newList.size
    }

    override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
        val oldItem = oldList.getOrNull(oldItemPosition)
        val newItem = newList.getOrNull(newItemPosition)
        return areItemsTheSame(oldItem, newItem)
    }

    override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
        val oldItem = oldList.getOrNull(oldItemPosition)
        val newItem = newList.getOrNull(newItemPosition)
        return oldItem == newItem
    }
}