content: /*
   * 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 com.google.android.exoplayer2.text.subrip;
  
  import android.text.Html;
  import android.text.Spanned;
  import android.text.TextUtils;
  import androidx.annotation.Nullable;
  import com.google.android.exoplayer2.text.Cue;
  import com.google.android.exoplayer2.text.SimpleSubtitleDecoder;
  import com.google.android.exoplayer2.text.Subtitle;
  import com.google.android.exoplayer2.util.Assertions;
  import com.google.android.exoplayer2.util.Log;
  import com.google.android.exoplayer2.util.LongArray;
  import com.google.android.exoplayer2.util.ParsableByteArray;
  import com.google.common.base.Charsets;
  import java.nio.charset.Charset;
  import java.util.ArrayList;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /** A {@link SimpleSubtitleDecoder} for SubRip. */
  public final class SubripDecoder extends SimpleSubtitleDecoder {
  
    // Fractional positions for use when alignment tags are present.
    private static final float START_FRACTION = 0.08f;
    private static final float END_FRACTION = 1 - START_FRACTION;
    private static final float MID_FRACTION = 0.5f;
  
    private static final String TAG = "SubripDecoder";
  
    // Some SRT files don't include hours or milliseconds in the timecode, so we use optional groups.
    private static final String SUBRIP_TIMECODE = "(?:(\\d+):)?(\\d+):(\\d+)(?:,(\\d+))?";
    private static final Pattern SUBRIP_TIMING_LINE =
        Pattern.compile("\\s*(" + SUBRIP_TIMECODE + ")\\s*-->\\s*(" + SUBRIP_TIMECODE + ")\\s*");
  
    // NOTE: Android Studio's suggestion to simplify '\\}' is incorrect [internal: b/144480183].
    private static final Pattern SUBRIP_TAG_PATTERN = Pattern.compile("\\{\\\\.*?\\}");
    private static final String SUBRIP_ALIGNMENT_TAG = "\\{\\\\an[1-9]\\}";
  
    // Alignment tags for SSA V4+.
    private static final String ALIGN_BOTTOM_LEFT = "{\\an1}";
    private static final String ALIGN_BOTTOM_MID = "{\\an2}";
    private static final String ALIGN_BOTTOM_RIGHT = "{\\an3}";
    private static final String ALIGN_MID_LEFT = "{\\an4}";
    private static final String ALIGN_MID_MID = "{\\an5}";
    private static final String ALIGN_MID_RIGHT = "{\\an6}";
    private static final String ALIGN_TOP_LEFT = "{\\an7}";
    private static final String ALIGN_TOP_MID = "{\\an8}";
    private static final String ALIGN_TOP_RIGHT = "{\\an9}";
  
    private final StringBuilder textBuilder;
    private final ArrayList<String> tags;
  
    public SubripDecoder() {
      super("SubripDecoder");
      textBuilder = new StringBuilder();
      tags = new ArrayList<>();
    }
  
    @Override
    protected Subtitle decode(byte[] data, int length, boolean reset) {
      ArrayList<Cue> cues = new ArrayList<>();
      LongArray cueTimesUs = new LongArray();
      ParsableByteArray subripData = new ParsableByteArray(data, length);
      Charset charset = detectUtfCharset(subripData);
  
      @Nullable String currentLine;
      while ((currentLine = subripData.readLine(charset)) != null) {
        if (currentLine.length() == 0) {
          // Skip blank lines.
          continue;
        }
  
        // Parse and check the index line.
        try {
          Integer.parseInt(currentLine);
        } catch (NumberFormatException e) {
          Log.w(TAG, "Skipping invalid index: " + currentLine);
          continue;
        }
  
        // Read and parse the timing line.
        currentLine = subripData.readLine(charset);
        if (currentLine == null) {
          Log.w(TAG, "Unexpected end");
          break;
        }
  
        Matcher matcher = SUBRIP_TIMING_LINE.matcher(currentLine);
        if (matcher.matches()) {
          cueTimesUs.add(parseTimecode(matcher, /* groupOffset= */ 1));
          cueTimesUs.add(parseTimecode(matcher, /* groupOffset= */ 6));
        } else {
          Log.w(TAG, "Skipping invalid timing: " + currentLine);
          continue;
        }
  
        // Read and parse the text and tags.
        textBuilder.setLength(0);
        tags.clear();
        currentLine = subripData.readLine(charset);
        while (!TextUtils.isEmpty(currentLine)) {
          if (textBuilder.length() > 0) {
            textBuilder.append("<br>");
          }
          textBuilder.append(processLine(currentLine, tags));
          currentLine = subripData.readLine(charset);
        }
  
        Spanned text = Html.fromHtml(textBuilder.toString());
  
        @Nullable String alignmentTag = null;
        for (int i = 0; i < tags.size(); i++) {
          String tag = tags.get(i);
          if (tag.matches(SUBRIP_ALIGNMENT_TAG)) {
            alignmentTag = tag;
            // Subsequent alignment tags should be ignored.
            break;
          }
        }
        cues.add(buildCue(text, alignmentTag));
        cues.add(Cue.EMPTY);
      }
  
      Cue[] cuesArray = cues.toArray(new Cue[0]);
      long[] cueTimesUsArray = cueTimesUs.toArray();
      return new SubripSubtitle(cuesArray, cueTimesUsArray);
    }
  
    /**
     * Determine UTF encoding of the byte array from a byte order mark (BOM), defaulting to UTF-8 if
     * no BOM is found.
     */
    private Charset detectUtfCharset(ParsableByteArray data) {
      @Nullable Charset charset = data.readUtfCharsetFromBom();
      return charset != null ? charset : Charsets.UTF_8;
    }
  
    /**
     * Trims and removes tags from the given line. The removed tags are added to {@code tags}.
     *
     * @param line The line to process.
     * @param tags A list to which removed tags will be added.
     * @return The processed line.
     */
    private String processLine(String line, ArrayList<String> tags) {
      line = line.trim();
  
      int removedCharacterCount = 0;
      StringBuilder processedLine = new StringBuilder(line);
      Matcher matcher = SUBRIP_TAG_PATTERN.matcher(line);
      while (matcher.find()) {
        String tag = matcher.group();
        tags.add(tag);
        int start = matcher.start() - removedCharacterCount;
        int tagLength = tag.length();
        processedLine.replace(start, /* end= */ start + tagLength, /* str= */ "");
        removedCharacterCount += tagLength;
      }
  
      return processedLine.toString();
    }
  
    /**
     * Build a {@link Cue} based on the given text and alignment tag.
     *
     * @param text The text.
     * @param alignmentTag The alignment tag, or {@code null} if no alignment tag is available.
     * @return Built cue
     */
    private Cue buildCue(Spanned text, @Nullable String alignmentTag) {
      Cue.Builder cue = new Cue.Builder().setText(text);
      if (alignmentTag == null) {
        return cue.build();
      }
  
      // Horizontal alignment.
      switch (alignmentTag) {
        case ALIGN_BOTTOM_LEFT:
        case ALIGN_MID_LEFT:
        case ALIGN_TOP_LEFT:
          cue.setPositionAnchor(Cue.ANCHOR_TYPE_START);
          break;
        case ALIGN_BOTTOM_RIGHT:
        case ALIGN_MID_RIGHT:
        case ALIGN_TOP_RIGHT:
          cue.setPositionAnchor(Cue.ANCHOR_TYPE_END);
          break;
        case ALIGN_BOTTOM_MID:
        case ALIGN_MID_MID:
        case ALIGN_TOP_MID:
        default:
          cue.setPositionAnchor(Cue.ANCHOR_TYPE_MIDDLE);
          break;
      }
  
      // Vertical alignment.
      switch (alignmentTag) {
        case ALIGN_BOTTOM_LEFT:
        case ALIGN_BOTTOM_MID:
        case ALIGN_BOTTOM_RIGHT:
          cue.setLineAnchor(Cue.ANCHOR_TYPE_END);
          break;
        case ALIGN_TOP_LEFT:
        case ALIGN_TOP_MID:
        case ALIGN_TOP_RIGHT:
          cue.setLineAnchor(Cue.ANCHOR_TYPE_START);
          break;
        case ALIGN_MID_LEFT:
        case ALIGN_MID_MID:
        case ALIGN_MID_RIGHT:
        default:
          cue.setLineAnchor(Cue.ANCHOR_TYPE_MIDDLE);
          break;
      }
  
      return cue.setPosition(getFractionalPositionForAnchorType(cue.getPositionAnchor()))
          .setLine(getFractionalPositionForAnchorType(cue.getLineAnchor()), Cue.LINE_TYPE_FRACTION)
          .build();
    }
  
    private static long parseTimecode(Matcher matcher, int groupOffset) {
      @Nullable String hours = matcher.group(groupOffset + 1);
      long timestampMs = hours != null ? Long.parseLong(hours) * 60 * 60 * 1000 : 0;
      timestampMs +=
          Long.parseLong(Assertions.checkNotNull(matcher.group(groupOffset + 2))) * 60 * 1000;
      timestampMs += Long.parseLong(Assertions.checkNotNull(matcher.group(groupOffset + 3))) * 1000;
      @Nullable String millis = matcher.group(groupOffset + 4);
      if (millis != null) {
        timestampMs += Long.parseLong(millis);
      }
      return timestampMs * 1000;
    }
  
    /* package */ static float getFractionalPositionForAnchorType(@Cue.AnchorType int anchorType) {
      switch (anchorType) {
        case Cue.ANCHOR_TYPE_START:
          return SubripDecoder.START_FRACTION;
        case Cue.ANCHOR_TYPE_MIDDLE:
          return SubripDecoder.MID_FRACTION;
        case Cue.ANCHOR_TYPE_END:
          return SubripDecoder.END_FRACTION;
        case Cue.TYPE_UNSET:
        default:
          // Should never happen.
          throw new IllegalArgumentException();
      }
    }
  }
  