Introduce DisplayRepository

/*

 * Copyright (C) 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 com.android.systemui.display.data.repository

import android.hardware.display.DisplayManager

import android.hardware.display.DisplayManager.DisplayListener

import android.hardware.display.DisplayManager.EVENT_FLAG_DISPLAY_ADDED

import android.hardware.display.DisplayManager.EVENT_FLAG_DISPLAY_CHANGED

import android.hardware.display.DisplayManager.EVENT_FLAG_DISPLAY_REMOVED

import android.os.Handler

import android.view.Display

import com.android.systemui.common.coroutine.ConflatedCallbackFlow.conflatedCallbackFlow

import com.android.systemui.dagger.SysUISingleton

import com.android.systemui.dagger.qualifiers.Application

import com.android.systemui.dagger.qualifiers.Background

import com.android.systemui.util.traceSection

import javax.inject.Inject

import kotlinx.coroutines.CoroutineDispatcher

import kotlinx.coroutines.CoroutineScope

import kotlinx.coroutines.channels.awaitClose

import kotlinx.coroutines.flow.Flow

import kotlinx.coroutines.flow.SharingStarted

import kotlinx.coroutines.flow.flowOn

import kotlinx.coroutines.flow.stateIn

/** Provides a [Flow] of [Display] as returned by [DisplayManager]. */

interface DisplayRepository {

    /** Provides a nullable set of displays. */

    val displays: Flow<Set<Display>>

}

@SysUISingleton

class DisplayRepositoryImpl

@Inject

constructor(

    private val displayManager: DisplayManager,

    @Background backgroundHandler: Handler,

    @Application applicationScope: CoroutineScope,

    @Background backgroundCoroutineDispatcher: CoroutineDispatcher

) : DisplayRepository {

    override val displays: Flow<Set<Display>> =

        conflatedCallbackFlow {

                val callback =

                    object : DisplayListener {

                        override fun onDisplayAdded(displayId: Int) {

                            trySend(getDisplays())

                        }

                        override fun onDisplayRemoved(displayId: Int) {

                            trySend(getDisplays())

                        }

                        override fun onDisplayChanged(displayId: Int) {

                            trySend(getDisplays())

                        }

                    }

                displayManager.registerDisplayListener(

                    callback,

                    backgroundHandler,

                    EVENT_FLAG_DISPLAY_ADDED or

                        EVENT_FLAG_DISPLAY_CHANGED or

                        EVENT_FLAG_DISPLAY_REMOVED,

                )

                awaitClose { displayManager.unregisterDisplayListener(callback) }

            }

            .flowOn(backgroundCoroutineDispatcher)

            .stateIn(

                applicationScope,

                started = SharingStarted.WhileSubscribed(),

                initialValue = getDisplays()

            )

    fun getDisplays(): Set<Display> =

        traceSection("DisplayRepository#getDisplays()") {

            displayManager.displays?.toSet() ?: emptySet()

        }

}

/*

 * Copyright (C) 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 com.android.systemui.display.data.repository

import android.hardware.display.DisplayManager

import android.os.Looper

import android.testing.AndroidTestingRunner

import android.testing.TestableLooper

import android.view.Display

import androidx.test.filters.SmallTest

import com.android.systemui.SysuiTestCase

import com.android.systemui.coroutines.FlowValue

import com.android.systemui.coroutines.collectLastValue

import com.android.systemui.util.mockito.eq

import com.android.systemui.util.mockito.kotlinArgumentCaptor

import com.android.systemui.util.mockito.mock

import com.android.systemui.util.mockito.whenever

import com.android.systemui.utils.os.FakeHandler

import com.google.common.truth.Truth.assertThat

import kotlinx.coroutines.ExperimentalCoroutinesApi

import kotlinx.coroutines.test.TestScope

import kotlinx.coroutines.test.UnconfinedTestDispatcher

import kotlinx.coroutines.test.runTest

import org.junit.Before

import org.junit.Test

import org.junit.runner.RunWith

import org.mockito.ArgumentMatchers.any

import org.mockito.ArgumentMatchers.anyLong

import org.mockito.Mockito.never

import org.mockito.Mockito.times

import org.mockito.Mockito.verify

@RunWith(AndroidTestingRunner::class)

@TestableLooper.RunWithLooper

@OptIn(ExperimentalCoroutinesApi::class)

@SmallTest

class DisplayRepositoryTest : SysuiTestCase() {

    private val displayManager = mock<DisplayManager>()

    private val displayListener = kotlinArgumentCaptor<DisplayManager.DisplayListener>()

    private val testHandler = FakeHandler(Looper.getMainLooper())

    private val testScope = TestScope(UnconfinedTestDispatcher())

    private lateinit var displayRepository: DisplayRepositoryImpl

    @Before

    fun setup() {

        setDisplays(emptyList())

        displayRepository =

            DisplayRepositoryImpl(

                displayManager,

                testHandler,

                TestScope(UnconfinedTestDispatcher()),

                UnconfinedTestDispatcher()

            )

        verify(displayManager, never()).registerDisplayListener(any(), any())

    }

    @Test

    fun onFlowCollection_displayListenerRegistered() =

        testScope.runTest {

            val value by latestDisplayFlowValue()

            assertThat(value).isEmpty()

            verify(displayManager).registerDisplayListener(any(), eq(testHandler), anyLong())

        }

    @Test

    fun afterFlowCollection_displayListenerUnregistered() {

        testScope.runTest {

            val value by latestDisplayFlowValue()

            assertThat(value).isEmpty()

            verify(displayManager).registerDisplayListener(any(), eq(testHandler), anyLong())

        }

        verify(displayManager).unregisterDisplayListener(any())

    }

    @Test

    fun afterFlowCollection_multipleSusbcriptions_oneRemoved_displayListenerNotUnregistered() {

        testScope.runTest {

            val firstSubscriber by latestDisplayFlowValue()

            assertThat(firstSubscriber).isEmpty()

            verify(displayManager, times(1))

                .registerDisplayListener(displayListener.capture(), eq(testHandler), anyLong())

            val innerScope = TestScope()

            innerScope.runTest {

                val secondSubscriber by latestDisplayFlowValue()

                assertThat(secondSubscriber).isEmpty()

                // No new registration, just the precedent one.

                verify(displayManager, times(1))

                    .registerDisplayListener(any(), eq(testHandler), anyLong())

            }

            // Let's make sure it has *NOT* been unregistered, as there is still a subscriber.

            setDisplays(1)

            displayListener.value.onDisplayAdded(1)

            assertThat(firstSubscriber?.ids()).containsExactly(1)

        }

        // All subscribers are done, unregister should have been called.

        verify(displayManager).unregisterDisplayListener(any())

    }

    @Test

    fun onDisplayAdded_propagated() =

        testScope.runTest {

            val value by latestDisplayFlowValue()

            setDisplays(1)

            displayListener.value.onDisplayAdded(1)

            assertThat(value?.ids()).containsExactly(1)

        }

    @Test

    fun onDisplayRemoved_propagated() =

        testScope.runTest {

            val value by latestDisplayFlowValue()

            setDisplays(1, 2, 3, 4)

            displayListener.value.onDisplayAdded(1)

            displayListener.value.onDisplayAdded(2)

            displayListener.value.onDisplayAdded(3)

            displayListener.value.onDisplayAdded(4)

            setDisplays(1, 2, 3)

            displayListener.value.onDisplayRemoved(4)

            assertThat(value?.ids()).containsExactly(1, 2, 3)

        }

    @Test

    fun onDisplayChanged_propagated() =

        testScope.runTest {

            val value by latestDisplayFlowValue()

            setDisplays(1, 2, 3, 4)

            displayListener.value.onDisplayAdded(1)

            displayListener.value.onDisplayAdded(2)

            displayListener.value.onDisplayAdded(3)

            displayListener.value.onDisplayAdded(4)

            displayListener.value.onDisplayChanged(4)

            assertThat(value?.ids()).containsExactly(1, 2, 3, 4)

        }

    private fun Iterable<Display>.ids(): List<Int> = map { it.displayId }

    // Wrapper to capture the displayListener.

    private fun TestScope.latestDisplayFlowValue(): FlowValue<Set<Display>?> {

        val flowValue = collectLastValue(displayRepository.displays)

        verify(displayManager)

            .registerDisplayListener(displayListener.capture(), eq(testHandler), anyLong())

        return flowValue

    }

    private fun setDisplays(displays: List<Display>) {

        whenever(displayManager.displays).thenReturn(displays.toTypedArray())

    }

    private fun setDisplays(vararg ids: Int) {

        setDisplays(ids.map { display(it) })

    }

    private fun display(id: Int): Display {

        return mock<Display>().also { mockDisplay ->

            whenever(mockDisplay.displayId).thenReturn(id)

        }

    }

}