[MediaProjection] Create MediaProjectionSessionIdGenerator

/*

 * 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.server.media.projection;

import android.content.Context;

import android.content.SharedPreferences;

import android.os.Environment;

import com.android.internal.annotations.GuardedBy;

import com.android.internal.annotations.VisibleForTesting;

import java.io.File;

public class MediaProjectionSessionIdGenerator {

    private static final String PREFERENCES_FILE_NAME = "media_projection_session_id";

    private static final String SESSION_ID_PREF_KEY = "media_projection_session_id_key";

    private static final int SESSION_ID_DEFAULT_VALUE = 0;

    private static final Object sInstanceLock = new Object();

    @GuardedBy("sInstanceLock")

    private static MediaProjectionSessionIdGenerator sInstance;

    private final Object mSessionIdLock = new Object();

    @GuardedBy("mSessionIdLock")

    private final SharedPreferences mSharedPreferences;

    /** Creates or returns an existing instance of {@link MediaProjectionSessionIdGenerator}. */

    public static MediaProjectionSessionIdGenerator getInstance(Context context) {

        synchronized (sInstanceLock) {

            if (sInstance == null) {

                File preferencesFile =

                        new File(Environment.getDataSystemDirectory(), PREFERENCES_FILE_NAME);

                SharedPreferences preferences =

                        context.getSharedPreferences(preferencesFile, Context.MODE_PRIVATE);

                sInstance = new MediaProjectionSessionIdGenerator(preferences);

            }

            return sInstance;

        }

    }

    @VisibleForTesting

    public MediaProjectionSessionIdGenerator(SharedPreferences sharedPreferences) {

        this.mSharedPreferences = sharedPreferences;

    }

    /** Returns the current session ID. This value is persisted across reboots. */

    public int getCurrentSessionId() {

        synchronized (mSessionIdLock) {

            return getCurrentSessionIdInternal();

        }

    }

    /**

     * Creates and returns a new session ID. This value will be persisted as the new current session

     * ID, and will be persisted across reboots.

     */

    public int createAndGetNewSessionId() {

        synchronized (mSessionIdLock) {

            int newSessionId = getCurrentSessionId() + 1;

            setSessionIdInternal(newSessionId);

            return newSessionId;

        }

    }

    @GuardedBy("mSessionIdLock")

    private void setSessionIdInternal(int value) {

        mSharedPreferences.edit().putInt(SESSION_ID_PREF_KEY, value).apply();

    }

    @GuardedBy("mSessionIdLock")

    private int getCurrentSessionIdInternal() {

        return mSharedPreferences.getInt(SESSION_ID_PREF_KEY, SESSION_ID_DEFAULT_VALUE);

    }

}

/*

 * 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.server.media.projection;

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

import android.content.Context;

import android.content.SharedPreferences;

import android.platform.test.annotations.Presubmit;

import androidx.test.ext.junit.runners.AndroidJUnit4;

import androidx.test.filters.SmallTest;

import androidx.test.platform.app.InstrumentationRegistry;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

import org.junit.runner.RunWith;

import java.io.File;

/**

 * Tests for the {@link MediaProjectionSessionIdGenerator} class.

 *

 * <p>Build/Install/Run: atest FrameworksServicesTests:MediaProjectionSessionIdGeneratorTest

 */

@SmallTest

@Presubmit

@RunWith(AndroidJUnit4.class)

public class MediaProjectionSessionIdGeneratorTest {

    private static final String TEST_PREFS_FILE = "media-projection-session-id-test";

    private final Context mContext =

            InstrumentationRegistry.getInstrumentation().getTargetContext();

    private final File mSharedPreferencesFile = new File(mContext.getCacheDir(), TEST_PREFS_FILE);

    private final SharedPreferences mSharedPreferences = createSharePreferences();

    private final MediaProjectionSessionIdGenerator mGenerator =

            createGenerator(mSharedPreferences);

    @Before

    public void setUp() {

        mSharedPreferences.edit().clear().commit();

    }

    @After

    public void tearDown() {

        mSharedPreferences.edit().clear().commit();

        mSharedPreferencesFile.delete();

    }

    @Test

    public void getCurrentSessionId_byDefault_returns0() {

        assertThat(mGenerator.getCurrentSessionId()).isEqualTo(0);

    }

    @Test

    public void getCurrentSessionId_multipleTimes_returnsSameValue() {

        assertThat(mGenerator.getCurrentSessionId()).isEqualTo(0);

        assertThat(mGenerator.getCurrentSessionId()).isEqualTo(0);

        assertThat(mGenerator.getCurrentSessionId()).isEqualTo(0);

    }

    @Test

    public void createAndGetNewSessionId_returnsIncrementedId() {

        int previousValue = mGenerator.getCurrentSessionId();

        int newValue = mGenerator.createAndGetNewSessionId();

        assertThat(newValue).isEqualTo(previousValue + 1);

    }

    @Test

    public void createAndGetNewSessionId_persistsNewValue() {

        int newValue = mGenerator.createAndGetNewSessionId();

        MediaProjectionSessionIdGenerator newInstance = createGenerator(createSharePreferences());

        assertThat(newInstance.getCurrentSessionId()).isEqualTo(newValue);

    }

    private SharedPreferences createSharePreferences() {

        return mContext.getSharedPreferences(mSharedPreferencesFile, Context.MODE_PRIVATE);

    }

    private MediaProjectionSessionIdGenerator createGenerator(SharedPreferences sharedPreferences) {

        return new MediaProjectionSessionIdGenerator(sharedPreferences);

    }

}