/*
 * 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 androidx.media3.exoplayer.hls;

import static androidx.media3.common.util.Assertions.checkNotNull;

import android.annotation.SuppressLint;
import android.net.Uri;
import android.text.TextUtils;
import androidx.annotation.Nullable;
import androidx.media3.common.FileTypes;
import androidx.media3.common.Format;
import androidx.media3.common.Metadata;
import androidx.media3.common.MimeTypes;
import androidx.media3.common.util.TimestampAdjuster;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.exoplayer.analytics.PlayerId;
import androidx.media3.extractor.Extractor;
import androidx.media3.extractor.ExtractorInput;
import androidx.media3.extractor.mp3.Mp3Extractor;
import androidx.media3.extractor.mp4.FragmentedMp4Extractor;
import androidx.media3.extractor.ts.Ac3Extractor;
import androidx.media3.extractor.ts.Ac4Extractor;
import androidx.media3.extractor.ts.AdtsExtractor;
import androidx.media3.extractor.ts.DefaultTsPayloadReaderFactory;
import androidx.media3.extractor.ts.TsExtractor;
import com.google.common.primitives.Ints;
import java.io.EOFException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

/** Default {@link HlsExtractorFactory} implementation. */
@UnstableApi
public final class DefaultHlsExtractorFactory implements HlsExtractorFactory {

  // Extractors order is optimized according to
  // https://docs.google.com/document/d/1w2mKaWMxfz2Ei8-LdxqbPs1VLe_oudB-eryXXw9OvQQ.
  private static final int[] DEFAULT_EXTRACTOR_ORDER =
      new int[] {
        FileTypes.MP4,
        FileTypes.WEBVTT,
        FileTypes.TS,
        FileTypes.ADTS,
        FileTypes.AC3,
        FileTypes.AC4,
        FileTypes.MP3,
      };

  private final @DefaultTsPayloadReaderFactory.Flags int payloadReaderFactoryFlags;
  private final boolean exposeCea608WhenMissingDeclarations;

  /**
   * Equivalent to {@link #DefaultHlsExtractorFactory(int, boolean) new
   * DefaultHlsExtractorFactory(payloadReaderFactoryFlags = 0, exposeCea608WhenMissingDeclarations =
   * true)}
   */
  public DefaultHlsExtractorFactory() {
    this(/* payloadReaderFactoryFlags= */ 0, /* exposeCea608WhenMissingDeclarations */ true);
  }

  /**
   * Creates a factory for HLS segment extractors.
   *
   * @param payloadReaderFactoryFlags Flags to add when constructing any {@link
   *     DefaultTsPayloadReaderFactory} instances. Other flags may be added on top of {@code
   *     payloadReaderFactoryFlags} when creating {@link DefaultTsPayloadReaderFactory}.
   * @param exposeCea608WhenMissingDeclarations Whether created {@link TsExtractor} instances should
   *     expose a CEA-608 track should the multivariant playlist contain no Closed Captions
   *     declarations. If the multivariant playlist contains any Closed Captions declarations, this
   *     flag is ignored.
   */
  public DefaultHlsExtractorFactory(
      int payloadReaderFactoryFlags, boolean exposeCea608WhenMissingDeclarations) {
    this.payloadReaderFactoryFlags = payloadReaderFactoryFlags;
    this.exposeCea608WhenMissingDeclarations = exposeCea608WhenMissingDeclarations;
  }

  @Override
  public BundledHlsMediaChunkExtractor createExtractor(
      Uri uri,
      Format format,
      @Nullable List<Format> muxedCaptionFormats,
      TimestampAdjuster timestampAdjuster,
      Map<String, List<String>> responseHeaders,
      ExtractorInput sniffingExtractorInput,
      PlayerId playerId)
      throws IOException {
    @FileTypes.Type
    int formatInferredFileType = FileTypes.inferFileTypeFromMimeType(format.sampleMimeType);
    @FileTypes.Type
    int responseHeadersInferredFileType =
        FileTypes.inferFileTypeFromResponseHeaders(responseHeaders);
    @FileTypes.Type int uriInferredFileType = FileTypes.inferFileTypeFromUri(uri);

    // Defines the order in which to try the extractors.
    List<Integer> fileTypeOrder =
        new ArrayList<>(/* initialCapacity= */ DEFAULT_EXTRACTOR_ORDER.length);
    addFileTypeIfValidAndNotPresent(formatInferredFileType, fileTypeOrder);
    addFileTypeIfValidAndNotPresent(responseHeadersInferredFileType, fileTypeOrder);
    addFileTypeIfValidAndNotPresent(uriInferredFileType, fileTypeOrder);
    for (int fileType : DEFAULT_EXTRACTOR_ORDER) {
      addFileTypeIfValidAndNotPresent(fileType, fileTypeOrder);
    }

    // Extractor to be used if the type is not recognized.
    @Nullable Extractor fallBackExtractor = null;
    sniffingExtractorInput.resetPeekPosition();
    for (int i = 0; i < fileTypeOrder.size(); i++) {
      int fileType = fileTypeOrder.get(i);
      Extractor extractor =
          checkNotNull(
              createExtractorByFileType(fileType, format, muxedCaptionFormats, timestampAdjuster));
      if (sniffQuietly(extractor, sniffingExtractorInput)) {
        return new BundledHlsMediaChunkExtractor(extractor, format, timestampAdjuster);
      }
      if (fallBackExtractor == null
          && (fileType == formatInferredFileType
              || fileType == responseHeadersInferredFileType
              || fileType == uriInferredFileType
              || fileType == FileTypes.TS)) {
        // If sniffing fails, fallback to the file types inferred from context. If all else fails,
        // fallback to Transport Stream. See https://github.com/google/ExoPlayer/issues/8219.
        fallBackExtractor = extractor;
      }
    }

    return new BundledHlsMediaChunkExtractor(
        checkNotNull(fallBackExtractor), format, timestampAdjuster);
  }

  private static void addFileTypeIfValidAndNotPresent(
      @FileTypes.Type int fileType, List<Integer> fileTypes) {
    if (Ints.indexOf(DEFAULT_EXTRACTOR_ORDER, fileType) == -1 || fileTypes.contains(fileType)) {
      return;
    }
    fileTypes.add(fileType);
  }

  @SuppressLint("SwitchIntDef") // HLS only supports a small subset of the defined file types.
  @Nullable
  private Extractor createExtractorByFileType(
      @FileTypes.Type int fileType,
      Format format,
      @Nullable List<Format> muxedCaptionFormats,
      TimestampAdjuster timestampAdjuster) {
    switch (fileType) {
      case FileTypes.WEBVTT:
        return new WebvttExtractor(format.language, timestampAdjuster);
      case FileTypes.ADTS:
        return new AdtsExtractor();
      case FileTypes.AC3:
        return new Ac3Extractor();
      case FileTypes.AC4:
        return new Ac4Extractor();
      case FileTypes.MP3:
        return new Mp3Extractor(/* flags= */ 0, /* forcedFirstSampleTimestampUs= */ 0);
      case FileTypes.MP4:
        return createFragmentedMp4Extractor(timestampAdjuster, format, muxedCaptionFormats);
      case FileTypes.TS:
        return createTsExtractor(
            payloadReaderFactoryFlags,
            exposeCea608WhenMissingDeclarations,
            format,
            muxedCaptionFormats,
            timestampAdjuster);
      default:
        return null;
    }
  }

  private static TsExtractor createTsExtractor(
      @DefaultTsPayloadReaderFactory.Flags int userProvidedPayloadReaderFactoryFlags,
      boolean exposeCea608WhenMissingDeclarations,
      Format format,
      @Nullable List<Format> muxedCaptionFormats,
      TimestampAdjuster timestampAdjuster) {
    @DefaultTsPayloadReaderFactory.Flags
    int payloadReaderFactoryFlags =
        DefaultTsPayloadReaderFactory.FLAG_IGNORE_SPLICE_INFO_STREAM
            | userProvidedPayloadReaderFactoryFlags;
    if (muxedCaptionFormats != null) {
      // The playlist declares closed caption renditions, we should ignore descriptors.
      payloadReaderFactoryFlags |= DefaultTsPayloadReaderFactory.FLAG_OVERRIDE_CAPTION_DESCRIPTORS;
    } else if (exposeCea608WhenMissingDeclarations) {
      // The playlist does not provide any closed caption information. We preemptively declare a
      // closed caption track on channel 0.
      muxedCaptionFormats =
          Collections.singletonList(
              new Format.Builder().setSampleMimeType(MimeTypes.APPLICATION_CEA608).build());
    } else {
      muxedCaptionFormats = Collections.emptyList();
    }
    @Nullable String codecs = format.codecs;
    if (!TextUtils.isEmpty(codecs)) {
      // Sometimes AAC and H264 streams are declared in TS chunks even though they don't really
      // exist. If we know from the codec attribute that they don't exist, then we can
      // explicitly ignore them even if they're declared.
      if (!MimeTypes.containsCodecsCorrespondingToMimeType(codecs, MimeTypes.AUDIO_AAC)) {
        payloadReaderFactoryFlags |= DefaultTsPayloadReaderFactory.FLAG_IGNORE_AAC_STREAM;
      }
      if (!MimeTypes.containsCodecsCorrespondingToMimeType(codecs, MimeTypes.VIDEO_H264)) {
        payloadReaderFactoryFlags |= DefaultTsPayloadReaderFactory.FLAG_IGNORE_H264_STREAM;
      }
    }

    return new TsExtractor(
        TsExtractor.MODE_HLS,
        timestampAdjuster,
        new DefaultTsPayloadReaderFactory(payloadReaderFactoryFlags, muxedCaptionFormats));
  }

  private static FragmentedMp4Extractor createFragmentedMp4Extractor(
      TimestampAdjuster timestampAdjuster,
      Format format,
      @Nullable List<Format> muxedCaptionFormats) {
    // Only enable the EMSG TrackOutput if this is the 'variant' track (i.e. the main one) to avoid
    // creating a separate EMSG track for every audio track in a video stream.
    return new FragmentedMp4Extractor(
        /* flags= */ isFmp4Variant(format) ? FragmentedMp4Extractor.FLAG_ENABLE_EMSG_TRACK : 0,
        timestampAdjuster,
        /* sideloadedTrack= */ null,
        muxedCaptionFormats != null ? muxedCaptionFormats : Collections.emptyList());
  }

  /** Returns true if this {@code format} represents a 'variant' track (i.e. the main one). */
  private static boolean isFmp4Variant(Format format) {
    Metadata metadata = format.metadata;
    if (metadata == null) {
      return false;
    }
    for (int i = 0; i < metadata.length(); i++) {
      Metadata.Entry entry = metadata.get(i);
      if (entry instanceof HlsTrackMetadataEntry) {
        return !((HlsTrackMetadataEntry) entry).variantInfos.isEmpty();
      }
    }
    return false;
  }

  private static boolean sniffQuietly(Extractor extractor, ExtractorInput input)
      throws IOException {
    boolean result = false;
    try {
      result = extractor.sniff(input);
    } catch (EOFException e) {
      // Do nothing.
    } finally {
      input.resetPeekPosition();
    }
    return result;
  }
}