/*
 * Copyright (C) 2016 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 org.mozilla.thirdparty.com.google.android.exoplayer2.source.hls;

import android.net.Uri;
import androidx.annotation.Nullable;
import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
import org.mozilla.thirdparty.com.google.android.exoplayer2.Format;
import org.mozilla.thirdparty.com.google.android.exoplayer2.drm.DrmInitData;
import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.DefaultExtractorInput;
import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.Extractor;
import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ExtractorInput;
import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.PositionHolder;
import org.mozilla.thirdparty.com.google.android.exoplayer2.metadata.Metadata;
import org.mozilla.thirdparty.com.google.android.exoplayer2.metadata.id3.Id3Decoder;
import org.mozilla.thirdparty.com.google.android.exoplayer2.metadata.id3.PrivFrame;
import org.mozilla.thirdparty.com.google.android.exoplayer2.source.chunk.MediaChunk;
import org.mozilla.thirdparty.com.google.android.exoplayer2.source.hls.playlist.HlsMediaPlaylist;
import org.mozilla.thirdparty.com.google.android.exoplayer2.upstream.DataSource;
import org.mozilla.thirdparty.com.google.android.exoplayer2.upstream.DataSpec;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Assertions;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableByteArray;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.TimestampAdjuster;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.UriUtil;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Util;
import java.io.EOFException;
import java.io.IOException;
import java.math.BigInteger;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
import org.checkerframework.checker.nullness.qual.RequiresNonNull;

/**
 * An HLS {@link MediaChunk}.
 */
/* package */ final class HlsMediaChunk extends MediaChunk {

  /**
   * Creates a new instance.
   *
   * @param extractorFactory A {@link HlsExtractorFactory} from which the HLS media chunk extractor
   *     is obtained.
   * @param dataSource The source from which the data should be loaded.
   * @param format The chunk format.
   * @param startOfPlaylistInPeriodUs The position of the playlist in the period in microseconds.
   * @param mediaPlaylist The media playlist from which this chunk was obtained.
   * @param playlistUrl The url of the playlist from which this chunk was obtained.
   * @param muxedCaptionFormats List of muxed caption {@link Format}s. Null if no closed caption
   *     information is available in the master playlist.
   * @param trackSelectionReason See {@link #trackSelectionReason}.
   * @param trackSelectionData See {@link #trackSelectionData}.
   * @param isMasterTimestampSource True if the chunk can initialize the timestamp adjuster.
   * @param timestampAdjusterProvider The provider from which to obtain the {@link
   *     TimestampAdjuster}.
   * @param previousChunk The {@link HlsMediaChunk} that preceded this one. May be null.
   * @param mediaSegmentKey The media segment decryption key, if fully encrypted. Null otherwise.
   * @param initSegmentKey The initialization segment decryption key, if fully encrypted. Null
   *     otherwise.
   */
  public static HlsMediaChunk createInstance(
      HlsExtractorFactory extractorFactory,
      DataSource dataSource,
      Format format,
      long startOfPlaylistInPeriodUs,
      HlsMediaPlaylist mediaPlaylist,
      int segmentIndexInPlaylist,
      Uri playlistUrl,
      @Nullable List<Format> muxedCaptionFormats,
      int trackSelectionReason,
      @Nullable Object trackSelectionData,
      boolean isMasterTimestampSource,
      TimestampAdjusterProvider timestampAdjusterProvider,
      @Nullable HlsMediaChunk previousChunk,
      @Nullable byte[] mediaSegmentKey,
      @Nullable byte[] initSegmentKey) {
    // Media segment.
    HlsMediaPlaylist.Segment mediaSegment = mediaPlaylist.segments.get(segmentIndexInPlaylist);
    DataSpec dataSpec =
        new DataSpec(
            UriUtil.resolveToUri(mediaPlaylist.baseUri, mediaSegment.url),
            mediaSegment.byterangeOffset,
            mediaSegment.byterangeLength,
            /* key= */ null);
    boolean mediaSegmentEncrypted = mediaSegmentKey != null;
    byte[] mediaSegmentIv =
        mediaSegmentEncrypted
            ? getEncryptionIvArray(Assertions.checkNotNull(mediaSegment.encryptionIV))
            : null;
    DataSource mediaDataSource = buildDataSource(dataSource, mediaSegmentKey, mediaSegmentIv);

    // Init segment.
    HlsMediaPlaylist.Segment initSegment = mediaSegment.initializationSegment;
    DataSpec initDataSpec = null;
    boolean initSegmentEncrypted = false;
    DataSource initDataSource = null;
    if (initSegment != null) {
      initSegmentEncrypted = initSegmentKey != null;
      byte[] initSegmentIv =
          initSegmentEncrypted
              ? getEncryptionIvArray(Assertions.checkNotNull(initSegment.encryptionIV))
              : null;
      Uri initSegmentUri = UriUtil.resolveToUri(mediaPlaylist.baseUri, initSegment.url);
      initDataSpec =
          new DataSpec(
              initSegmentUri,
              initSegment.byterangeOffset,
              initSegment.byterangeLength,
              /* key= */ null);
      initDataSource = buildDataSource(dataSource, initSegmentKey, initSegmentIv);
    }

    long segmentStartTimeInPeriodUs = startOfPlaylistInPeriodUs + mediaSegment.relativeStartTimeUs;
    long segmentEndTimeInPeriodUs = segmentStartTimeInPeriodUs + mediaSegment.durationUs;
    int discontinuitySequenceNumber =
        mediaPlaylist.discontinuitySequence + mediaSegment.relativeDiscontinuitySequence;

    Extractor previousExtractor = null;
    Id3Decoder id3Decoder;
    ParsableByteArray scratchId3Data;
    boolean shouldSpliceIn;
    if (previousChunk != null) {
      id3Decoder = previousChunk.id3Decoder;
      scratchId3Data = previousChunk.scratchId3Data;
      shouldSpliceIn =
          !playlistUrl.equals(previousChunk.playlistUrl) || !previousChunk.loadCompleted;
      previousExtractor =
          previousChunk.isExtractorReusable
                  && previousChunk.discontinuitySequenceNumber == discontinuitySequenceNumber
                  && !shouldSpliceIn
              ? previousChunk.extractor
              : null;
    } else {
      id3Decoder = new Id3Decoder();
      scratchId3Data = new ParsableByteArray(Id3Decoder.ID3_HEADER_LENGTH);
      shouldSpliceIn = false;
    }

    return new HlsMediaChunk(
        extractorFactory,
        mediaDataSource,
        dataSpec,
        format,
        mediaSegmentEncrypted,
        initDataSource,
        initDataSpec,
        initSegmentEncrypted,
        playlistUrl,
        muxedCaptionFormats,
        trackSelectionReason,
        trackSelectionData,
        segmentStartTimeInPeriodUs,
        segmentEndTimeInPeriodUs,
        /* chunkMediaSequence= */ mediaPlaylist.mediaSequence + segmentIndexInPlaylist,
        discontinuitySequenceNumber,
        mediaSegment.hasGapTag,
        isMasterTimestampSource,
        /* timestampAdjuster= */ timestampAdjusterProvider.getAdjuster(discontinuitySequenceNumber),
        mediaSegment.drmInitData,
        previousExtractor,
        id3Decoder,
        scratchId3Data,
        shouldSpliceIn);
  }

  public static final String PRIV_TIMESTAMP_FRAME_OWNER =
      "com.apple.streaming.transportStreamTimestamp";
  private static final PositionHolder DUMMY_POSITION_HOLDER = new PositionHolder();

  private static final AtomicInteger uidSource = new AtomicInteger();

  /**
   * A unique identifier for the chunk.
   */
  public final int uid;

  /**
   * The discontinuity sequence number of the chunk.
   */
  public final int discontinuitySequenceNumber;

  /** The url of the playlist from which this chunk was obtained. */
  public final Uri playlistUrl;

  @Nullable private final DataSource initDataSource;
  @Nullable private final DataSpec initDataSpec;
  @Nullable private final Extractor previousExtractor;

  private final boolean isMasterTimestampSource;
  private final boolean hasGapTag;
  private final TimestampAdjuster timestampAdjuster;
  private final boolean shouldSpliceIn;
  private final HlsExtractorFactory extractorFactory;
  @Nullable private final List<Format> muxedCaptionFormats;
  @Nullable private final DrmInitData drmInitData;
  private final Id3Decoder id3Decoder;
  private final ParsableByteArray scratchId3Data;
  private final boolean mediaSegmentEncrypted;
  private final boolean initSegmentEncrypted;

  @MonotonicNonNull private Extractor extractor;
  private boolean isExtractorReusable;
  @MonotonicNonNull private HlsSampleStreamWrapper output;
  // nextLoadPosition refers to the init segment if initDataLoadRequired is true.
  // Otherwise, nextLoadPosition refers to the media segment.
  private int nextLoadPosition;
  private boolean initDataLoadRequired;
  private volatile boolean loadCanceled;
  private boolean loadCompleted;

  private HlsMediaChunk(
      HlsExtractorFactory extractorFactory,
      DataSource mediaDataSource,
      DataSpec dataSpec,
      Format format,
      boolean mediaSegmentEncrypted,
      @Nullable DataSource initDataSource,
      @Nullable DataSpec initDataSpec,
      boolean initSegmentEncrypted,
      Uri playlistUrl,
      @Nullable List<Format> muxedCaptionFormats,
      int trackSelectionReason,
      @Nullable Object trackSelectionData,
      long startTimeUs,
      long endTimeUs,
      long chunkMediaSequence,
      int discontinuitySequenceNumber,
      boolean hasGapTag,
      boolean isMasterTimestampSource,
      TimestampAdjuster timestampAdjuster,
      @Nullable DrmInitData drmInitData,
      @Nullable Extractor previousExtractor,
      Id3Decoder id3Decoder,
      ParsableByteArray scratchId3Data,
      boolean shouldSpliceIn) {
    super(
        mediaDataSource,
        dataSpec,
        format,
        trackSelectionReason,
        trackSelectionData,
        startTimeUs,
        endTimeUs,
        chunkMediaSequence);
    this.mediaSegmentEncrypted = mediaSegmentEncrypted;
    this.discontinuitySequenceNumber = discontinuitySequenceNumber;
    this.initDataSpec = initDataSpec;
    this.initDataSource = initDataSource;
    this.initDataLoadRequired = initDataSpec != null;
    this.initSegmentEncrypted = initSegmentEncrypted;
    this.playlistUrl = playlistUrl;
    this.isMasterTimestampSource = isMasterTimestampSource;
    this.timestampAdjuster = timestampAdjuster;
    this.hasGapTag = hasGapTag;
    this.extractorFactory = extractorFactory;
    this.muxedCaptionFormats = muxedCaptionFormats;
    this.drmInitData = drmInitData;
    this.previousExtractor = previousExtractor;
    this.id3Decoder = id3Decoder;
    this.scratchId3Data = scratchId3Data;
    this.shouldSpliceIn = shouldSpliceIn;
    uid = uidSource.getAndIncrement();
  }

  /**
   * Initializes the chunk for loading, setting the {@link HlsSampleStreamWrapper} that will receive
   * samples as they are loaded.
   *
   * @param output The output that will receive the loaded samples.
   */
  public void init(HlsSampleStreamWrapper output) {
    this.output = output;
    output.init(uid, shouldSpliceIn);
  }

  @Override
  public boolean isLoadCompleted() {
    return loadCompleted;
  }

  // Loadable implementation

  @Override
  public void cancelLoad() {
    loadCanceled = true;
  }

  @Override
  public void load() throws IOException, InterruptedException {
    // output == null means init() hasn't been called.
    Assertions.checkNotNull(output);
    if (extractor == null && previousExtractor != null) {
      extractor = previousExtractor;
      isExtractorReusable = true;
      initDataLoadRequired = false;
    }
    maybeLoadInitData();
    if (!loadCanceled) {
      if (!hasGapTag) {
        loadMedia();
      }
      loadCompleted = true;
    }
  }

  // Internal methods.

  @RequiresNonNull("output")
  private void maybeLoadInitData() throws IOException, InterruptedException {
    if (!initDataLoadRequired) {
      return;
    }
    // initDataLoadRequired =>  initDataSource != null && initDataSpec != null
    Assertions.checkNotNull(initDataSource);
    Assertions.checkNotNull(initDataSpec);
    feedDataToExtractor(initDataSource, initDataSpec, initSegmentEncrypted);
    nextLoadPosition = 0;
    initDataLoadRequired = false;
  }

  @RequiresNonNull("output")
  private void loadMedia() throws IOException, InterruptedException {
    if (!isMasterTimestampSource) {
      timestampAdjuster.waitUntilInitialized();
    } else if (timestampAdjuster.getFirstSampleTimestampUs() == TimestampAdjuster.DO_NOT_OFFSET) {
      // We're the master and we haven't set the desired first sample timestamp yet.
      timestampAdjuster.setFirstSampleTimestampUs(startTimeUs);
    }
    feedDataToExtractor(dataSource, dataSpec, mediaSegmentEncrypted);
  }

  /**
   * Attempts to feed the given {@code dataSpec} to {@code this.extractor}. Whenever the operation
   * concludes (because of a thrown exception or because the operation finishes), the number of fed
   * bytes is written to {@code nextLoadPosition}.
   */
  @RequiresNonNull("output")
  private void feedDataToExtractor(
      DataSource dataSource, DataSpec dataSpec, boolean dataIsEncrypted)
      throws IOException, InterruptedException {
    // If we previously fed part of this chunk to the extractor, we need to skip it this time. For
    // encrypted content we need to skip the data by reading it through the source, so as to ensure
    // correct decryption of the remainder of the chunk. For clear content, we can request the
    // remainder of the chunk directly.
    DataSpec loadDataSpec;
    boolean skipLoadedBytes;
    if (dataIsEncrypted) {
      loadDataSpec = dataSpec;
      skipLoadedBytes = nextLoadPosition != 0;
    } else {
      loadDataSpec = dataSpec.subrange(nextLoadPosition);
      skipLoadedBytes = false;
    }
    try {
      ExtractorInput input = prepareExtraction(dataSource, loadDataSpec);
      if (skipLoadedBytes) {
        input.skipFully(nextLoadPosition);
      }
      try {
        int result = Extractor.RESULT_CONTINUE;
        while (result == Extractor.RESULT_CONTINUE && !loadCanceled) {
          result = extractor.read(input, DUMMY_POSITION_HOLDER);
        }
      } finally {
        nextLoadPosition = (int) (input.getPosition() - dataSpec.absoluteStreamPosition);
      }
    } finally {
      Util.closeQuietly(dataSource);
    }
  }

  @RequiresNonNull("output")
  @EnsuresNonNull("extractor")
  private DefaultExtractorInput prepareExtraction(DataSource dataSource, DataSpec dataSpec)
      throws IOException, InterruptedException {
    long bytesToRead = dataSource.open(dataSpec);
    DefaultExtractorInput extractorInput =
        new DefaultExtractorInput(dataSource, dataSpec.absoluteStreamPosition, bytesToRead);

    if (extractor == null) {
      long id3Timestamp = peekId3PrivTimestamp(extractorInput);
      extractorInput.resetPeekPosition();

      HlsExtractorFactory.Result result =
          extractorFactory.createExtractor(
              previousExtractor,
              dataSpec.uri,
              trackFormat,
              muxedCaptionFormats,
              timestampAdjuster,
              dataSource.getResponseHeaders(),
              extractorInput);
      extractor = result.extractor;
      isExtractorReusable = result.isReusable;
      if (result.isPackedAudioExtractor) {
        output.setSampleOffsetUs(
            id3Timestamp != C.TIME_UNSET
                ? timestampAdjuster.adjustTsTimestamp(id3Timestamp)
                : startTimeUs);
      } else {
        // In case the container format changes mid-stream to non-packed-audio, we need to reset
        // the timestamp offset.
        output.setSampleOffsetUs(/* sampleOffsetUs= */ 0L);
      }
      output.onNewExtractor();
      extractor.init(output);
    }
    output.setDrmInitData(drmInitData);
    return extractorInput;
  }

  /**
   * Peek the presentation timestamp of the first sample in the chunk from an ID3 PRIV as defined
   * in the HLS spec, version 20, Section 3.4. Returns {@link C#TIME_UNSET} if the frame is not
   * found. This method only modifies the peek position.
   *
   * @param input The {@link ExtractorInput} to obtain the PRIV frame from.
   * @return The parsed, adjusted timestamp in microseconds
   * @throws IOException If an error occurred peeking from the input.
   * @throws InterruptedException If the thread was interrupted.
   */
  private long peekId3PrivTimestamp(ExtractorInput input) throws IOException, InterruptedException {
    input.resetPeekPosition();
    try {
      input.peekFully(scratchId3Data.data, 0, Id3Decoder.ID3_HEADER_LENGTH);
    } catch (EOFException e) {
      // The input isn't long enough for there to be any ID3 data.
      return C.TIME_UNSET;
    }
    scratchId3Data.reset(Id3Decoder.ID3_HEADER_LENGTH);
    int id = scratchId3Data.readUnsignedInt24();
    if (id != Id3Decoder.ID3_TAG) {
      return C.TIME_UNSET;
    }
    scratchId3Data.skipBytes(3); // version(2), flags(1).
    int id3Size = scratchId3Data.readSynchSafeInt();
    int requiredCapacity = id3Size + Id3Decoder.ID3_HEADER_LENGTH;
    if (requiredCapacity > scratchId3Data.capacity()) {
      byte[] data = scratchId3Data.data;
      scratchId3Data.reset(requiredCapacity);
      System.arraycopy(data, 0, scratchId3Data.data, 0, Id3Decoder.ID3_HEADER_LENGTH);
    }
    input.peekFully(scratchId3Data.data, Id3Decoder.ID3_HEADER_LENGTH, id3Size);
    Metadata metadata = id3Decoder.decode(scratchId3Data.data, id3Size);
    if (metadata == null) {
      return C.TIME_UNSET;
    }
    int metadataLength = metadata.length();
    for (int i = 0; i < metadataLength; i++) {
      Metadata.Entry frame = metadata.get(i);
      if (frame instanceof PrivFrame) {
        PrivFrame privFrame = (PrivFrame) frame;
        if (PRIV_TIMESTAMP_FRAME_OWNER.equals(privFrame.owner)) {
          System.arraycopy(
              privFrame.privateData, 0, scratchId3Data.data, 0, 8 /* timestamp size */);
          scratchId3Data.reset(8);
          // The top 31 bits should be zeros, but explicitly zero them to wrap in the case that the
          // streaming provider forgot. See: https://github.com/google/ExoPlayer/pull/3495.
          return scratchId3Data.readLong() & 0x1FFFFFFFFL;
        }
      }
    }
    return C.TIME_UNSET;
  }

  // Internal methods.

  private static byte[] getEncryptionIvArray(String ivString) {
    String trimmedIv;
    if (Util.toLowerInvariant(ivString).startsWith("0x")) {
      trimmedIv = ivString.substring(2);
    } else {
      trimmedIv = ivString;
    }

    byte[] ivData = new BigInteger(trimmedIv, /* radix= */ 16).toByteArray();
    byte[] ivDataWithPadding = new byte[16];
    int offset = ivData.length > 16 ? ivData.length - 16 : 0;
    System.arraycopy(
        ivData,
        offset,
        ivDataWithPadding,
        ivDataWithPadding.length - ivData.length + offset,
        ivData.length - offset);
    return ivDataWithPadding;
  }

  /**
   * If the segment is fully encrypted, returns an {@link Aes128DataSource} that wraps the original
   * in order to decrypt the loaded data. Else returns the original.
   *
   * <p>{@code fullSegmentEncryptionKey} & {@code encryptionIv} can either both be null, or neither.
   */
  private static DataSource buildDataSource(
      DataSource dataSource,
      @Nullable byte[] fullSegmentEncryptionKey,
      @Nullable byte[] encryptionIv) {
    if (fullSegmentEncryptionKey != null) {
      Assertions.checkNotNull(encryptionIv);
      return new Aes128DataSource(dataSource, fullSegmentEncryptionKey, encryptionIv);
    }
    return dataSource;
  }

}