/*
 * Copyright 2017 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.work.impl;

import android.arch.core.util.Function;
import android.arch.lifecycle.LiveData;
import android.content.Context;
import android.os.Looper;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.annotation.RestrictTo;
import android.support.annotation.WorkerThread;

import androidx.work.Configuration;
import androidx.work.ExistingPeriodicWorkPolicy;
import androidx.work.ExistingWorkPolicy;
import androidx.work.OneTimeWorkRequest;
import androidx.work.PeriodicWorkRequest;
import androidx.work.R;
import androidx.work.SynchronousWorkManager;
import androidx.work.WorkContinuation;
import androidx.work.WorkManager;
import androidx.work.WorkRequest;
import androidx.work.WorkStatus;
import androidx.work.impl.background.greedy.GreedyScheduler;
import androidx.work.impl.model.WorkSpec;
import androidx.work.impl.model.WorkSpecDao;
import androidx.work.impl.utils.CancelWorkRunnable;
import androidx.work.impl.utils.ForceStopRunnable;
import androidx.work.impl.utils.LiveDataUtils;
import androidx.work.impl.utils.Preferences;
import androidx.work.impl.utils.PruneWorkRunnable;
import androidx.work.impl.utils.StartWorkRunnable;
import androidx.work.impl.utils.StopWorkRunnable;
import androidx.work.impl.utils.taskexecutor.TaskExecutor;
import androidx.work.impl.utils.taskexecutor.WorkManagerTaskExecutor;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.UUID;

/**
 * A concrete implementation of {@link WorkManager}.
 *
 * @hide
 */
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public class WorkManagerImpl extends WorkManager implements SynchronousWorkManager {

    public static final int MAX_PRE_JOB_SCHEDULER_API_LEVEL = 22;
    public static final int MIN_JOB_SCHEDULER_API_LEVEL = 23;

    private Context mContext;
    private Configuration mConfiguration;
    private WorkDatabase mWorkDatabase;
    private TaskExecutor mTaskExecutor;
    private List<Scheduler> mSchedulers;
    private Processor mProcessor;
    private Preferences mPreferences;

    private static WorkManagerImpl sDelegatedInstance = null;
    private static WorkManagerImpl sDefaultInstance = null;
    private static final Object sLock = new Object();


    /**
     * @param delegate The delegate for {@link WorkManagerImpl} for testing; {@code null} to use the
     *                 default instance
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public static void setDelegate(WorkManagerImpl delegate) {
        synchronized (sLock) {
            sDelegatedInstance = delegate;
        }
    }

    /**
     * Retrieves the singleton instance of {@link WorkManagerImpl}.
     *
     * @return The singleton instance of {@link WorkManagerImpl}
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public static WorkManagerImpl getInstance() {
        synchronized (sLock) {
            if (sDelegatedInstance != null) {
                return sDelegatedInstance;
            }

            return sDefaultInstance;
        }
    }

    /**
     * Initializes the singleton instance of {@link WorkManagerImpl}.
     *
     * @param context A {@link Context} object for configuration purposes. Internally, this class
     *                will call {@link Context#getApplicationContext()}, so you may safely pass in
     *                any Context without risking a memory leak.
     * @param configuration The {@link Configuration} for used to set up WorkManager.
     *
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public static void initialize(@NonNull Context context, @NonNull Configuration configuration) {
        synchronized (sLock) {
            if (sDelegatedInstance == null) {
                context = context.getApplicationContext();
                if (sDefaultInstance == null) {
                    sDefaultInstance = new WorkManagerImpl(context, configuration);
                }
                sDelegatedInstance = sDefaultInstance;
            }
        }
    }

    /**
     * Create an instance of {@link WorkManagerImpl}.
     *
     * @param context       The application {@link Context}
     * @param configuration The {@link Configuration} configuration.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public WorkManagerImpl(
            @NonNull Context context,
            @NonNull Configuration configuration) {
        this(context,
                configuration,
                context.getResources().getBoolean(R.bool.workmanager_test_configuration));
    }

    /**
     * Create an instance of {@link WorkManagerImpl}.
     *
     * @param context         The application {@link Context}
     * @param configuration   The {@link Configuration} configuration.
     * @param useTestDatabase {@code true} If using an in-memory test database.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public WorkManagerImpl(
            @NonNull Context context,
            @NonNull Configuration configuration,
            boolean useTestDatabase) {

        context = context.getApplicationContext();
        mContext = context;
        mConfiguration = configuration;
        mWorkDatabase = WorkDatabase.create(context, useTestDatabase);
        mTaskExecutor = WorkManagerTaskExecutor.getInstance();
        mProcessor = new Processor(
                context,
                mConfiguration,
                mWorkDatabase,
                getSchedulers(),
                configuration.getExecutor());
        mPreferences = new Preferences(mContext);

        // Checks for app force stops.
        mTaskExecutor.executeOnBackgroundThread(new ForceStopRunnable(context, this));
    }

    /**
     * @return The application {@link Context} associated with this WorkManager.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public Context getApplicationContext() {
        return mContext;
    }

    /**
     * @return The {@link WorkDatabase} instance associated with this WorkManager.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public WorkDatabase getWorkDatabase() {
        return mWorkDatabase;
    }

    /**
     * @return The {@link Configuration} instance associated with this WorkManager.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    @NonNull
    public Configuration getConfiguration() {
        return mConfiguration;
    }

    /**
     * @return The {@link Scheduler}s associated with this WorkManager based on the device's
     * capabilities, SDK version, etc.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public @NonNull List<Scheduler> getSchedulers() {
        // Initialized at construction time. So no need to synchronize.
        if (mSchedulers == null) {
            mSchedulers = Arrays.asList(
                    Schedulers.createBestAvailableBackgroundScheduler(mContext, this),
                    new GreedyScheduler(mContext, this));
        }
        return mSchedulers;
    }

    /**
     * @return The {@link Processor} used to process background work.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public @NonNull Processor getProcessor() {
        return mProcessor;
    }

    /**
     * @return the {@link TaskExecutor} used by the instance of {@link WorkManager}.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public @NonNull TaskExecutor getTaskExecutor() {
        return mTaskExecutor;
    }

    /**
     * @return the {@link Preferences} used by the instance of {@link WorkManager}.
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public @NonNull Preferences getPreferences() {
        return mPreferences;
    }

    @Override
    public void enqueue(@NonNull List<? extends WorkRequest> workRequests) {
        new WorkContinuationImpl(this, workRequests).enqueue();
    }

    @Override
    public void enqueueSync(@NonNull WorkRequest... workRequest) {
        enqueueSync(Arrays.asList(workRequest));
    }

    @Override
    public void enqueueSync(@NonNull List<? extends WorkRequest> workRequest) {
        assertBackgroundThread("Cannot enqueueSync on main thread!");
        new WorkContinuationImpl(this, workRequest).enqueueSync();
    }

    @Override
    public WorkContinuation beginWith(@NonNull List<OneTimeWorkRequest> work) {
        return new WorkContinuationImpl(this, work);
    }

    @Override
    public WorkContinuation beginUniqueWork(
            @NonNull String uniqueWorkName,
            @NonNull ExistingWorkPolicy existingWorkPolicy,
            @NonNull List<OneTimeWorkRequest> work) {
        return new WorkContinuationImpl(this, uniqueWorkName, existingWorkPolicy, work);
    }

    @Override
    public void enqueueUniquePeriodicWork(
            @NonNull String uniqueWorkName,
            @NonNull ExistingPeriodicWorkPolicy existingPeriodicWorkPolicy,
            @NonNull PeriodicWorkRequest periodicWork) {
        createWorkContinuationForUniquePeriodicWork(
                uniqueWorkName,
                existingPeriodicWorkPolicy,
                periodicWork)
                .enqueue();
    }

    @Override
    public void enqueueUniquePeriodicWorkSync(
            @NonNull String uniqueWorkName,
            @NonNull ExistingPeriodicWorkPolicy existingPeriodicWorkPolicy,
            @NonNull PeriodicWorkRequest periodicWork) {
        assertBackgroundThread("Cannot enqueueUniquePeriodicWorkSync on main thread!");
        createWorkContinuationForUniquePeriodicWork(
                uniqueWorkName,
                existingPeriodicWorkPolicy,
                periodicWork)
                .enqueueSync();
    }

    private WorkContinuationImpl createWorkContinuationForUniquePeriodicWork(
            @NonNull String uniqueWorkName,
            @NonNull ExistingPeriodicWorkPolicy existingPeriodicWorkPolicy,
            @NonNull PeriodicWorkRequest periodicWork) {
        ExistingWorkPolicy existingWorkPolicy;
        if (existingPeriodicWorkPolicy == ExistingPeriodicWorkPolicy.KEEP) {
            existingWorkPolicy = ExistingWorkPolicy.KEEP;
        } else {
            existingWorkPolicy = ExistingWorkPolicy.REPLACE;
        }
        return new WorkContinuationImpl(
                this,
                uniqueWorkName,
                existingWorkPolicy,
                Collections.singletonList(periodicWork));
    }

    @Override
    public void cancelWorkById(@NonNull UUID id) {
        mTaskExecutor.executeOnBackgroundThread(CancelWorkRunnable.forId(id, this));
    }

    @Override
    @WorkerThread
    public void cancelWorkByIdSync(@NonNull UUID id) {
        assertBackgroundThread("Cannot cancelWorkByIdSync on main thread!");
        CancelWorkRunnable.forId(id, this).run();
    }

    @Override
    public void cancelAllWorkByTag(@NonNull final String tag) {
        mTaskExecutor.executeOnBackgroundThread(
                CancelWorkRunnable.forTag(tag, this));
    }

    @Override
    @WorkerThread
    public void cancelAllWorkByTagSync(@NonNull String tag) {
        assertBackgroundThread("Cannot cancelAllWorkByTagSync on main thread!");
        CancelWorkRunnable.forTag(tag, this).run();
    }

    @Override
    public void cancelUniqueWork(@NonNull String uniqueWorkName) {
        mTaskExecutor.executeOnBackgroundThread(
                CancelWorkRunnable.forName(uniqueWorkName, this));
    }

    @Override
    @WorkerThread
    public void cancelUniqueWorkSync(@NonNull String uniqueWorkName) {
        assertBackgroundThread("Cannot cancelAllWorkByNameBlocking on main thread!");
        CancelWorkRunnable.forName(uniqueWorkName, this).run();
    }

    @Override
    public void cancelAllWork() {
        mTaskExecutor.executeOnBackgroundThread(CancelWorkRunnable.forAll(this));
    }

    @Override
    @WorkerThread
    public void cancelAllWorkSync() {
        assertBackgroundThread("Cannot cancelAllWorkSync on main thread!");
        CancelWorkRunnable.forAll(this).run();
    }

    @Override
    public LiveData<Long> getLastCancelAllTimeMillis() {
        return mPreferences.getLastCancelAllTimeMillisLiveData();
    }

    @Override
    public long getLastCancelAllTimeMillisSync() {
        return mPreferences.getLastCancelAllTimeMillis();
    }

    @Override
    public void pruneWork() {
        mTaskExecutor.executeOnBackgroundThread(new PruneWorkRunnable(this));
    }

    @Override
    @WorkerThread
    public void pruneWorkSync() {
        assertBackgroundThread("Cannot pruneWork on main thread!");
        new PruneWorkRunnable(this).run();
    }

    @Override
    public LiveData<WorkStatus> getStatusById(@NonNull UUID id) {
        WorkSpecDao dao = mWorkDatabase.workSpecDao();
        LiveData<List<WorkSpec.WorkStatusPojo>> inputLiveData =
                dao.getWorkStatusPojoLiveDataForIds(Collections.singletonList(id.toString()));
        return LiveDataUtils.dedupedMappedLiveDataFor(inputLiveData,
                new Function<List<WorkSpec.WorkStatusPojo>, WorkStatus>() {
                    @Override
                    public WorkStatus apply(List<WorkSpec.WorkStatusPojo> input) {
                        WorkStatus workStatus = null;
                        if (input != null && input.size() > 0) {
                            workStatus = input.get(0).toWorkStatus();
                        }
                        return workStatus;
                    }
                });
    }

    @Override
    @WorkerThread
    public @Nullable WorkStatus getStatusByIdSync(@NonNull UUID id) {
        assertBackgroundThread("Cannot call getStatusByIdSync on main thread!");
        WorkSpec.WorkStatusPojo workStatusPojo =
                mWorkDatabase.workSpecDao().getWorkStatusPojoForId(id.toString());
        if (workStatusPojo != null) {
            return workStatusPojo.toWorkStatus();
        } else {
            return null;
        }
    }

    @Override
    public LiveData<List<WorkStatus>> getStatusesByTag(@NonNull String tag) {
        WorkSpecDao workSpecDao = mWorkDatabase.workSpecDao();
        LiveData<List<WorkSpec.WorkStatusPojo>> inputLiveData =
                workSpecDao.getWorkStatusPojoLiveDataForTag(tag);
        return LiveDataUtils.dedupedMappedLiveDataFor(inputLiveData, WorkSpec.WORK_STATUS_MAPPER);
    }

    @Override
    public List<WorkStatus> getStatusesByTagSync(@NonNull String tag) {
        assertBackgroundThread("Cannot call getStatusesByTagSync on main thread!");
        WorkSpecDao workSpecDao = mWorkDatabase.workSpecDao();
        List<WorkSpec.WorkStatusPojo> input = workSpecDao.getWorkStatusPojoForTag(tag);
        return WorkSpec.WORK_STATUS_MAPPER.apply(input);
    }

    @Override
    public LiveData<List<WorkStatus>> getStatusesForUniqueWork(@NonNull String uniqueWorkName) {
        WorkSpecDao workSpecDao = mWorkDatabase.workSpecDao();
        LiveData<List<WorkSpec.WorkStatusPojo>> inputLiveData =
                workSpecDao.getWorkStatusPojoLiveDataForName(uniqueWorkName);
        return LiveDataUtils.dedupedMappedLiveDataFor(inputLiveData, WorkSpec.WORK_STATUS_MAPPER);
    }

    @Override
    public List<WorkStatus> getStatusesForUniqueWorkSync(@NonNull String uniqueWorkName) {
        assertBackgroundThread("Cannot call getStatusesByNameBlocking on main thread!");
        WorkSpecDao workSpecDao = mWorkDatabase.workSpecDao();
        List<WorkSpec.WorkStatusPojo> input = workSpecDao.getWorkStatusPojoForName(uniqueWorkName);
        return WorkSpec.WORK_STATUS_MAPPER.apply(input);
    }

    @Override
    public SynchronousWorkManager synchronous() {
        return this;
    }

    LiveData<List<WorkStatus>> getStatusesById(@NonNull List<String> workSpecIds) {
        WorkSpecDao dao = mWorkDatabase.workSpecDao();
        LiveData<List<WorkSpec.WorkStatusPojo>> inputLiveData =
                dao.getWorkStatusPojoLiveDataForIds(workSpecIds);
        return LiveDataUtils.dedupedMappedLiveDataFor(inputLiveData, WorkSpec.WORK_STATUS_MAPPER);
    }

    List<WorkStatus> getStatusesByIdSync(@NonNull List<String> workSpecIds) {
        List<WorkSpec.WorkStatusPojo> workStatusPojos = mWorkDatabase.workSpecDao()
                .getWorkStatusPojoForIds(workSpecIds);

        return WorkSpec.WORK_STATUS_MAPPER.apply(workStatusPojos);
    }

    /**
     * @param workSpecId The {@link WorkSpec} id to start
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public void startWork(String workSpecId) {
        startWork(workSpecId, null);
    }

    /**
     * @param workSpecId The {@link WorkSpec} id to start
     * @param runtimeExtras The {@link Extras.RuntimeExtras} associated with this work
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public void startWork(String workSpecId, Extras.RuntimeExtras runtimeExtras) {
        mTaskExecutor.executeOnBackgroundThread(
                new StartWorkRunnable(this, workSpecId, runtimeExtras));
    }

    /**
     * @param workSpecId The {@link WorkSpec} id to stop
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public void stopWork(String workSpecId) {
        mTaskExecutor.executeOnBackgroundThread(new StopWorkRunnable(this, workSpecId));
    }

    /**
     * Reschedules all the eligible work. Useful for cases like, app was force stopped or
     * BOOT_COMPLETED, TIMEZONE_CHANGED and TIME_SET for AlarmManager.
     *
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public void rescheduleEligibleWork() {
        // Reset scheduled state.
        getWorkDatabase().workSpecDao().resetScheduledState();

        // Delegate to the WorkManager's schedulers.
        // Using getters here so we can use from a mocked instance
        // of WorkManagerImpl.
        Schedulers.schedule(getConfiguration(), getWorkDatabase(), getSchedulers());
    }

    private void assertBackgroundThread(String errorMessage) {
        if (Looper.getMainLooper().getThread() == Thread.currentThread()) {
            throw new IllegalStateException(errorMessage);
        }
    }
}