/*
 * Copyright (C) 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 com.google.android.exoplayer2.source.ads;

import android.net.Uri;
import android.os.Handler;
import android.os.Looper;
import androidx.annotation.IntDef;
import androidx.annotation.Nullable;
import android.view.ViewGroup;
import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.Timeline;
import com.google.android.exoplayer2.source.CompositeMediaSource;
import com.google.android.exoplayer2.source.DeferredMediaPeriod;
import com.google.android.exoplayer2.source.ExtractorMediaSource;
import com.google.android.exoplayer2.source.MediaPeriod;
import com.google.android.exoplayer2.source.MediaSource;
import com.google.android.exoplayer2.source.MediaSource.MediaPeriodId;
import com.google.android.exoplayer2.source.MediaSourceEventListener;
import com.google.android.exoplayer2.source.MediaSourceEventListener.LoadEventInfo;
import com.google.android.exoplayer2.source.MediaSourceEventListener.MediaLoadData;
import com.google.android.exoplayer2.upstream.Allocator;
import com.google.android.exoplayer2.upstream.DataSource;
import com.google.android.exoplayer2.upstream.DataSpec;
import com.google.android.exoplayer2.upstream.TransferListener;
import com.google.android.exoplayer2.util.Assertions;
import java.io.IOException;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * A {@link MediaSource} that inserts ads linearly with a provided content media source. This source
 * cannot be used as a child source in a composition. It must be the top-level source used to
 * prepare the player.
 */
public final class AdsMediaSource extends CompositeMediaSource<MediaPeriodId> {

  /** Factory for creating {@link MediaSource}s to play ad media. */
  public interface MediaSourceFactory {

    /**
     * Creates a new {@link MediaSource} for loading the ad media with the specified {@code uri}.
     *
     * @param uri The URI of the media or manifest to play.
     * @return The new media source.
     */
    MediaSource createMediaSource(Uri uri);

    /**
     * Returns the content types supported by media sources created by this factory. Each element
     * should be one of {@link C#TYPE_DASH}, {@link C#TYPE_SS}, {@link C#TYPE_HLS} or {@link
     * C#TYPE_OTHER}.
     *
     * @return The content types supported by media sources created by this factory.
     */
    int[] getSupportedTypes();
  }

  /**
   * Wrapper for exceptions that occur while loading ads, which are notified via {@link
   * MediaSourceEventListener#onLoadError(int, MediaPeriodId, LoadEventInfo, MediaLoadData,
   * IOException, boolean)}.
   */
  public static final class AdLoadException extends IOException {

    /**
     * Types of ad load exceptions. One of {@link #TYPE_AD}, {@link #TYPE_AD_GROUP}, {@link
     * #TYPE_ALL_ADS} or {@link #TYPE_UNEXPECTED}.
     */
    @Documented
    @Retention(RetentionPolicy.SOURCE)
    @IntDef({TYPE_AD, TYPE_AD_GROUP, TYPE_ALL_ADS, TYPE_UNEXPECTED})
    public @interface Type {}
    /** Type for when an ad failed to load. The ad will be skipped. */
    public static final int TYPE_AD = 0;
    /** Type for when an ad group failed to load. The ad group will be skipped. */
    public static final int TYPE_AD_GROUP = 1;
    /** Type for when all ad groups failed to load. All ads will be skipped. */
    public static final int TYPE_ALL_ADS = 2;
    /** Type for when an unexpected error occurred while loading ads. All ads will be skipped. */
    public static final int TYPE_UNEXPECTED = 3;

    /** Returns a new ad load exception of {@link #TYPE_AD}. */
    public static AdLoadException createForAd(Exception error) {
      return new AdLoadException(TYPE_AD, error);
    }

    /** Returns a new ad load exception of {@link #TYPE_AD_GROUP}. */
    public static AdLoadException createForAdGroup(Exception error, int adGroupIndex) {
      return new AdLoadException(
          TYPE_AD_GROUP, new IOException("Failed to load ad group " + adGroupIndex, error));
    }

    /** Returns a new ad load exception of {@link #TYPE_ALL_ADS}. */
    public static AdLoadException createForAllAds(Exception error) {
      return new AdLoadException(TYPE_ALL_ADS, error);
    }

    /** Returns a new ad load exception of {@link #TYPE_UNEXPECTED}. */
    public static AdLoadException createForUnexpected(RuntimeException error) {
      return new AdLoadException(TYPE_UNEXPECTED, error);
    }

    /** The {@link Type} of the ad load exception. */
    public final @Type int type;

    private AdLoadException(@Type int type, Exception cause) {
      super(cause);
      this.type = type;
    }

    /**
     * Returns the {@link RuntimeException} that caused the exception if its type is {@link
     * #TYPE_UNEXPECTED}.
     */
    public RuntimeException getRuntimeExceptionForUnexpected() {
      Assertions.checkState(type == TYPE_UNEXPECTED);
      return (RuntimeException) getCause();
    }
  }

  /**
   * Listener for ads media source events.
   *
   * @deprecated To listen for ad load error events, add a listener via {@link
   *     #addEventListener(Handler, MediaSourceEventListener)} and check for {@link
   *     AdLoadException}s in {@link MediaSourceEventListener#onLoadError(int, MediaPeriodId,
   *     LoadEventInfo, MediaLoadData, IOException, boolean)}. Individual ads loader implementations
   *     should expose ad interaction events, if applicable.
   */
  @Deprecated
  public interface EventListener {

    /**
     * Called if there was an error loading one or more ads. The loader will skip the problematic
     * ad(s).
     *
     * @param error The error.
     */
    void onAdLoadError(IOException error);

    /**
     * Called when an unexpected internal error is encountered while loading ads. The loader will
     * skip all remaining ads, as the error is not recoverable.
     *
     * @param error The error.
     */
    void onInternalAdLoadError(RuntimeException error);

    /**
     * Called when the user clicks through an ad (for example, following a 'learn more' link).
     */
    void onAdClicked();

    /**
     * Called when the user taps a non-clickthrough part of an ad.
     */
    void onAdTapped();

  }

  // Used to identify the content "child" source for CompositeMediaSource.
  private static final MediaPeriodId DUMMY_CONTENT_MEDIA_PERIOD_ID =
      new MediaPeriodId(/* periodUid= */ new Object());

  private final MediaSource contentMediaSource;
  private final MediaSourceFactory adMediaSourceFactory;
  private final AdsLoader adsLoader;
  private final ViewGroup adUiViewGroup;
  @Nullable private final Handler eventHandler;
  @Nullable private final EventListener eventListener;
  private final Handler mainHandler;
  private final Map<MediaSource, List<DeferredMediaPeriod>> deferredMediaPeriodByAdMediaSource;
  private final Timeline.Period period;

  // Accessed on the player thread.
  private ComponentListener componentListener;
  private Timeline contentTimeline;
  private Object contentManifest;
  private AdPlaybackState adPlaybackState;
  private MediaSource[][] adGroupMediaSources;
  private Timeline[][] adGroupTimelines;

  /**
   * Constructs a new source that inserts ads linearly with the content specified by {@code
   * contentMediaSource}. Ad media is loaded using {@link ExtractorMediaSource}.
   *
   * @param contentMediaSource The {@link MediaSource} providing the content to play.
   * @param dataSourceFactory Factory for data sources used to load ad media.
   * @param adsLoader The loader for ads.
   * @param adUiViewGroup A {@link ViewGroup} on top of the player that will show any ad UI.
   */
  public AdsMediaSource(
      MediaSource contentMediaSource,
      DataSource.Factory dataSourceFactory,
      AdsLoader adsLoader,
      ViewGroup adUiViewGroup) {
    this(
        contentMediaSource,
        new ExtractorMediaSource.Factory(dataSourceFactory),
        adsLoader,
        adUiViewGroup,
        /* eventHandler= */ null,
        /* eventListener= */ null);
  }

  /**
   * Constructs a new source that inserts ads linearly with the content specified by {@code
   * contentMediaSource}.
   *
   * @param contentMediaSource The {@link MediaSource} providing the content to play.
   * @param adMediaSourceFactory Factory for media sources used to load ad media.
   * @param adsLoader The loader for ads.
   * @param adUiViewGroup A {@link ViewGroup} on top of the player that will show any ad UI.
   */
  public AdsMediaSource(
      MediaSource contentMediaSource,
      MediaSourceFactory adMediaSourceFactory,
      AdsLoader adsLoader,
      ViewGroup adUiViewGroup) {
    this(
        contentMediaSource,
        adMediaSourceFactory,
        adsLoader,
        adUiViewGroup,
        /* eventHandler= */ null,
        /* eventListener= */ null);
  }

  /**
   * Constructs a new source that inserts ads linearly with the content specified by {@code
   * contentMediaSource}. Ad media is loaded using {@link ExtractorMediaSource}.
   *
   * @param contentMediaSource The {@link MediaSource} providing the content to play.
   * @param dataSourceFactory Factory for data sources used to load ad media.
   * @param adsLoader The loader for ads.
   * @param adUiViewGroup A {@link ViewGroup} on top of the player that will show any ad UI.
   * @param eventHandler A handler for events. May be null if delivery of events is not required.
   * @param eventListener A listener of events. May be null if delivery of events is not required.
   * @deprecated To listen for ad load error events, add a listener via {@link
   *     #addEventListener(Handler, MediaSourceEventListener)} and check for {@link
   *     AdLoadException}s in {@link MediaSourceEventListener#onLoadError(int, MediaPeriodId,
   *     LoadEventInfo, MediaLoadData, IOException, boolean)}. Individual ads loader implementations
   *     should expose ad interaction events, if applicable.
   */
  @Deprecated
  public AdsMediaSource(
      MediaSource contentMediaSource,
      DataSource.Factory dataSourceFactory,
      AdsLoader adsLoader,
      ViewGroup adUiViewGroup,
      @Nullable Handler eventHandler,
      @Nullable EventListener eventListener) {
    this(
        contentMediaSource,
        new ExtractorMediaSource.Factory(dataSourceFactory),
        adsLoader,
        adUiViewGroup,
        eventHandler,
        eventListener);
  }

  /**
   * Constructs a new source that inserts ads linearly with the content specified by {@code
   * contentMediaSource}.
   *
   * @param contentMediaSource The {@link MediaSource} providing the content to play.
   * @param adMediaSourceFactory Factory for media sources used to load ad media.
   * @param adsLoader The loader for ads.
   * @param adUiViewGroup A {@link ViewGroup} on top of the player that will show any ad UI.
   * @param eventHandler A handler for events. May be null if delivery of events is not required.
   * @param eventListener A listener of events. May be null if delivery of events is not required.
   * @deprecated To listen for ad load error events, add a listener via {@link
   *     #addEventListener(Handler, MediaSourceEventListener)} and check for {@link
   *     AdLoadException}s in {@link MediaSourceEventListener#onLoadError(int, MediaPeriodId,
   *     LoadEventInfo, MediaLoadData, IOException, boolean)}. Individual ads loader implementations
   *     should expose ad interaction events, if applicable.
   */
  @Deprecated
  public AdsMediaSource(
      MediaSource contentMediaSource,
      MediaSourceFactory adMediaSourceFactory,
      AdsLoader adsLoader,
      ViewGroup adUiViewGroup,
      @Nullable Handler eventHandler,
      @Nullable EventListener eventListener) {
    this.contentMediaSource = contentMediaSource;
    this.adMediaSourceFactory = adMediaSourceFactory;
    this.adsLoader = adsLoader;
    this.adUiViewGroup = adUiViewGroup;
    this.eventHandler = eventHandler;
    this.eventListener = eventListener;
    mainHandler = new Handler(Looper.getMainLooper());
    deferredMediaPeriodByAdMediaSource = new HashMap<>();
    period = new Timeline.Period();
    adGroupMediaSources = new MediaSource[0][];
    adGroupTimelines = new Timeline[0][];
    adsLoader.setSupportedContentTypes(adMediaSourceFactory.getSupportedTypes());
  }

  @Override
  @Nullable
  public Object getTag() {
    return contentMediaSource.getTag();
  }

  @Override
  public void prepareSourceInternal(@Nullable TransferListener mediaTransferListener) {
    super.prepareSourceInternal(mediaTransferListener);
    ComponentListener componentListener = new ComponentListener();
    this.componentListener = componentListener;
    prepareChildSource(DUMMY_CONTENT_MEDIA_PERIOD_ID, contentMediaSource);
    mainHandler.post(() -> adsLoader.start(componentListener, adUiViewGroup));
  }

  @Override
  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
    if (adPlaybackState.adGroupCount > 0 && id.isAd()) {
      int adGroupIndex = id.adGroupIndex;
      int adIndexInAdGroup = id.adIndexInAdGroup;
      Uri adUri = adPlaybackState.adGroups[adGroupIndex].uris[adIndexInAdGroup];
      if (adGroupMediaSources[adGroupIndex].length <= adIndexInAdGroup) {
        MediaSource adMediaSource = adMediaSourceFactory.createMediaSource(adUri);
        int oldAdCount = adGroupMediaSources[adGroupIndex].length;
        if (adIndexInAdGroup >= oldAdCount) {
          int adCount = adIndexInAdGroup + 1;
          adGroupMediaSources[adGroupIndex] =
              Arrays.copyOf(adGroupMediaSources[adGroupIndex], adCount);
          adGroupTimelines[adGroupIndex] = Arrays.copyOf(adGroupTimelines[adGroupIndex], adCount);
        }
        adGroupMediaSources[adGroupIndex][adIndexInAdGroup] = adMediaSource;
        deferredMediaPeriodByAdMediaSource.put(adMediaSource, new ArrayList<>());
        prepareChildSource(id, adMediaSource);
      }
      MediaSource mediaSource = adGroupMediaSources[adGroupIndex][adIndexInAdGroup];
      DeferredMediaPeriod deferredMediaPeriod =
          new DeferredMediaPeriod(mediaSource, id, allocator, startPositionUs);
      deferredMediaPeriod.setPrepareErrorListener(
          new AdPrepareErrorListener(adUri, adGroupIndex, adIndexInAdGroup));
      List<DeferredMediaPeriod> mediaPeriods = deferredMediaPeriodByAdMediaSource.get(mediaSource);
      if (mediaPeriods == null) {
        Object periodUid =
            adGroupTimelines[adGroupIndex][adIndexInAdGroup].getUidOfPeriod(/* periodIndex= */ 0);
        MediaPeriodId adSourceMediaPeriodId = new MediaPeriodId(periodUid, id.windowSequenceNumber);
        deferredMediaPeriod.createPeriod(adSourceMediaPeriodId);
      } else {
        // Keep track of the deferred media period so it can be populated with the real media period
        // when the source's info becomes available.
        mediaPeriods.add(deferredMediaPeriod);
      }
      return deferredMediaPeriod;
    } else {
      DeferredMediaPeriod mediaPeriod =
          new DeferredMediaPeriod(contentMediaSource, id, allocator, startPositionUs);
      mediaPeriod.createPeriod(id);
      return mediaPeriod;
    }
  }

  @Override
  public void releasePeriod(MediaPeriod mediaPeriod) {
    DeferredMediaPeriod deferredMediaPeriod = (DeferredMediaPeriod) mediaPeriod;
    List<DeferredMediaPeriod> mediaPeriods =
        deferredMediaPeriodByAdMediaSource.get(deferredMediaPeriod.mediaSource);
    if (mediaPeriods != null) {
      mediaPeriods.remove(deferredMediaPeriod);
    }
    deferredMediaPeriod.releasePeriod();
  }

  @Override
  public void releaseSourceInternal() {
    super.releaseSourceInternal();
    componentListener.release();
    componentListener = null;
    deferredMediaPeriodByAdMediaSource.clear();
    contentTimeline = null;
    contentManifest = null;
    adPlaybackState = null;
    adGroupMediaSources = new MediaSource[0][];
    adGroupTimelines = new Timeline[0][];
    mainHandler.post(adsLoader::stop);
  }

  @Override
  protected void onChildSourceInfoRefreshed(
      MediaPeriodId mediaPeriodId,
      MediaSource mediaSource,
      Timeline timeline,
      @Nullable Object manifest) {
    if (mediaPeriodId.isAd()) {
      int adGroupIndex = mediaPeriodId.adGroupIndex;
      int adIndexInAdGroup = mediaPeriodId.adIndexInAdGroup;
      onAdSourceInfoRefreshed(mediaSource, adGroupIndex, adIndexInAdGroup, timeline);
    } else {
      onContentSourceInfoRefreshed(timeline, manifest);
    }
  }

  @Override
  protected @Nullable MediaPeriodId getMediaPeriodIdForChildMediaPeriodId(
      MediaPeriodId childId, MediaPeriodId mediaPeriodId) {
    // The child id for the content period is just DUMMY_CONTENT_MEDIA_PERIOD_ID. That's why we need
    // to forward the reported mediaPeriodId in this case.
    return childId.isAd() ? childId : mediaPeriodId;
  }

  // Internal methods.

  private void onAdPlaybackState(AdPlaybackState adPlaybackState) {
    if (this.adPlaybackState == null) {
      adGroupMediaSources = new MediaSource[adPlaybackState.adGroupCount][];
      Arrays.fill(adGroupMediaSources, new MediaSource[0]);
      adGroupTimelines = new Timeline[adPlaybackState.adGroupCount][];
      Arrays.fill(adGroupTimelines, new Timeline[0]);
    }
    this.adPlaybackState = adPlaybackState;
    maybeUpdateSourceInfo();
  }

  private void onContentSourceInfoRefreshed(Timeline timeline, Object manifest) {
    Assertions.checkArgument(timeline.getPeriodCount() == 1);
    contentTimeline = timeline;
    contentManifest = manifest;
    maybeUpdateSourceInfo();
  }

  private void onAdSourceInfoRefreshed(MediaSource mediaSource, int adGroupIndex,
      int adIndexInAdGroup, Timeline timeline) {
    Assertions.checkArgument(timeline.getPeriodCount() == 1);
    adGroupTimelines[adGroupIndex][adIndexInAdGroup] = timeline;
    List<DeferredMediaPeriod> mediaPeriods = deferredMediaPeriodByAdMediaSource.remove(mediaSource);
    if (mediaPeriods != null) {
      Object periodUid = timeline.getUidOfPeriod(/* periodIndex= */ 0);
      for (int i = 0; i < mediaPeriods.size(); i++) {
        DeferredMediaPeriod mediaPeriod = mediaPeriods.get(i);
        MediaPeriodId adSourceMediaPeriodId =
            new MediaPeriodId(periodUid, mediaPeriod.id.windowSequenceNumber);
        mediaPeriod.createPeriod(adSourceMediaPeriodId);
      }
    }
    maybeUpdateSourceInfo();
  }

  private void maybeUpdateSourceInfo() {
    if (adPlaybackState != null && contentTimeline != null) {
      adPlaybackState = adPlaybackState.withAdDurationsUs(getAdDurations(adGroupTimelines, period));
      Timeline timeline =
          adPlaybackState.adGroupCount == 0
              ? contentTimeline
              : new SinglePeriodAdTimeline(contentTimeline, adPlaybackState);
      refreshSourceInfo(timeline, contentManifest);
    }
  }

  private static long[][] getAdDurations(Timeline[][] adTimelines, Timeline.Period period) {
    long[][] adDurations = new long[adTimelines.length][];
    for (int i = 0; i < adTimelines.length; i++) {
      adDurations[i] = new long[adTimelines[i].length];
      for (int j = 0; j < adTimelines[i].length; j++) {
        adDurations[i][j] =
            adTimelines[i][j] == null
                ? C.TIME_UNSET
                : adTimelines[i][j].getPeriod(/* periodIndex= */ 0, period).getDurationUs();
      }
    }
    return adDurations;
  }

  /** Listener for component events. All methods are called on the main thread. */
  private final class ComponentListener implements AdsLoader.EventListener {

    private final Handler playerHandler;

    private volatile boolean released;

    /**
     * Creates new listener which forwards ad playback states on the creating thread and all other
     * events on the external event listener thread.
     */
    public ComponentListener() {
      playerHandler = new Handler();
    }

    /** Releases the component listener. */
    public void release() {
      released = true;
      playerHandler.removeCallbacksAndMessages(null);
    }

    @Override
    public void onAdPlaybackState(final AdPlaybackState adPlaybackState) {
      if (released) {
        return;
      }
      playerHandler.post(
          () -> {
            if (released) {
              return;
            }
            AdsMediaSource.this.onAdPlaybackState(adPlaybackState);
          });
    }

    @Override
    public void onAdClicked() {
      if (released) {
        return;
      }
      if (eventHandler != null && eventListener != null) {
        eventHandler.post(
            () -> {
              if (!released) {
                eventListener.onAdClicked();
              }
            });
      }
    }

    @Override
    public void onAdTapped() {
      if (released) {
        return;
      }
      if (eventHandler != null && eventListener != null) {
        eventHandler.post(
            () -> {
              if (!released) {
                eventListener.onAdTapped();
              }
            });
      }
    }

    @Override
    public void onAdLoadError(final AdLoadException error, DataSpec dataSpec) {
      if (released) {
        return;
      }
      createEventDispatcher(/* mediaPeriodId= */ null)
          .loadError(
              dataSpec,
              dataSpec.uri,
              /* responseHeaders= */ Collections.emptyMap(),
              C.DATA_TYPE_AD,
              C.TRACK_TYPE_UNKNOWN,
              /* loadDurationMs= */ 0,
              /* bytesLoaded= */ 0,
              error,
              /* wasCanceled= */ true);
      if (eventHandler != null && eventListener != null) {
        eventHandler.post(
            () -> {
              if (!released) {
                if (error.type == AdLoadException.TYPE_UNEXPECTED) {
                  eventListener.onInternalAdLoadError(error.getRuntimeExceptionForUnexpected());
                } else {
                  eventListener.onAdLoadError(error);
                }
              }
            });
      }
    }
  }

  private final class AdPrepareErrorListener implements DeferredMediaPeriod.PrepareErrorListener {

    private final Uri adUri;
    private final int adGroupIndex;
    private final int adIndexInAdGroup;

    public AdPrepareErrorListener(Uri adUri, int adGroupIndex, int adIndexInAdGroup) {
      this.adUri = adUri;
      this.adGroupIndex = adGroupIndex;
      this.adIndexInAdGroup = adIndexInAdGroup;
    }

    @Override
    public void onPrepareError(MediaPeriodId mediaPeriodId, final IOException exception) {
      createEventDispatcher(mediaPeriodId)
          .loadError(
              new DataSpec(adUri),
              adUri,
              /* responseHeaders= */ Collections.emptyMap(),
              C.DATA_TYPE_AD,
              C.TRACK_TYPE_UNKNOWN,
              /* loadDurationMs= */ 0,
              /* bytesLoaded= */ 0,
              AdLoadException.createForAd(exception),
              /* wasCanceled= */ true);
      mainHandler.post(
          () -> adsLoader.handlePrepareError(adGroupIndex, adIndexInAdGroup, exception));
    }
  }
}
