datastore/datastore-core/src/androidInstrumentedTest/kotlin/androidx/datastore/core/multiprocess/MultiProcessTestRule.kt

/*
 * Copyright 2023 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 androidx.datastore.core.multiprocess

import androidx.datastore.core.twoWayIpc.TwoWayIpcConnection
import androidx.datastore.core.twoWayIpc.TwoWayIpcService
import androidx.datastore.core.twoWayIpc.TwoWayIpcService2
import androidx.test.platform.app.InstrumentationRegistry
import java.util.concurrent.atomic.AtomicBoolean
import kotlin.time.Duration.Companion.seconds
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.async
import kotlinx.coroutines.awaitAll
import kotlinx.coroutines.cancel
import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.sync.Mutex
import kotlinx.coroutines.sync.withLock
import kotlinx.coroutines.withTimeout
import org.junit.rules.TestWatcher
import org.junit.runner.Description

/**
 * Used for testing multi-process cases while also maintaining resources so that services
 * are properly closed after test.
 */
class MultiProcessTestRule : TestWatcher() {
    private val didRunTest = AtomicBoolean(false)
    private val context = InstrumentationRegistry.getInstrumentation().context

    // use a real scope, it is too hard to use a TestScope when we cannot control the IPC
    val datastoreScope = CoroutineScope(
        Dispatchers.IO + Job()
    )
    private val connectionsMutex = Mutex()
    private val connections = mutableListOf<TwoWayIpcConnection>()
    private val availableServiceClasses = mutableListOf<Class<out TwoWayIpcService>>(
        TwoWayIpcService::class.java,
        TwoWayIpcService2::class.java
    )

    fun runTest(block: suspend CoroutineScope.() -> Unit) {
        // don't use datastore scope here as it will not finish by itself.
        runBlocking {
            check(didRunTest.compareAndSet(false, true)) {
                "Cannot call runTest multiple times"
            }
            try {
                withTimeout(TEST_TIMEOUT) {
                    block()
                }
            } finally {
                connections.map {
                    async { it.disconnect() }
                }.awaitAll()
            }
        }
    }

    suspend fun createConnection(): TwoWayIpcConnection {
        val connection = connectionsMutex.withLock {
            val klass = availableServiceClasses.removeFirstOrNull() ?: error(
                "Cannot create more services," +
                    "you can declare more in the manifest if needed"
            )
            TwoWayIpcConnection(context, klass).also {
                connections.add(it)
            }
        }
        connection.connect()
        return connection
    }

    override fun finished(description: Description) {
        super.finished(description)
        datastoreScope.cancel()
    }

    companion object {
        val TEST_TIMEOUT = 10.seconds
    }
}