java/src/com/android/intentresolver/ImagePreviewImageLoader.kt

/*
 * Copyright (C) 2022 The Android Open Source Project
 *
 * 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 com.android.intentresolver

import android.content.Context
import android.graphics.Bitmap
import android.net.Uri
import android.util.Size
import androidx.annotation.GuardedBy
import androidx.annotation.VisibleForTesting
import androidx.collection.LruCache
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.coroutineScope
import kotlinx.coroutines.CompletableDeferred
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.isActive
import kotlinx.coroutines.launch
import java.util.function.Consumer

@VisibleForTesting
class ImagePreviewImageLoader @JvmOverloads constructor(
    private val context: Context,
    private val lifecycle: Lifecycle,
    cacheSize: Int,
    private val dispatcher: CoroutineDispatcher = Dispatchers.IO
) : ImageLoader {

    private val thumbnailSize: Size =
        context.resources.getDimensionPixelSize(R.dimen.chooser_preview_image_max_dimen).let {
            Size(it, it)
        }

    @GuardedBy("self")
    private val cache = LruCache<Uri, CompletableDeferred<Bitmap?>>(cacheSize)

    override suspend fun invoke(uri: Uri): Bitmap? = loadImageAsync(uri)

    override fun loadImage(uri: Uri, callback: Consumer<Bitmap?>) {
        lifecycle.coroutineScope.launch {
            val image = loadImageAsync(uri)
            if (isActive) {
                callback.accept(image)
            }
        }
    }

    override fun prePopulate(uris: List<Uri>) {
        uris.asSequence().take(cache.maxSize()).forEach { uri ->
            lifecycle.coroutineScope.launch {
                loadImageAsync(uri)
            }
        }
    }

    private suspend fun loadImageAsync(uri: Uri): Bitmap? {
        return synchronized(cache) {
            cache.get(uri) ?: CompletableDeferred<Bitmap?>().also { result ->
                cache.put(uri, result)
                lifecycle.coroutineScope.launch(dispatcher) {
                    result.loadBitmap(uri)
                }
            }
        }.await()
    }

    private fun CompletableDeferred<Bitmap?>.loadBitmap(uri: Uri) {
        val bitmap = runCatching {
            context.contentResolver.loadThumbnail(uri,  thumbnailSize, null)
        }.getOrNull()
        complete(bitmap)
    }
}