1 files changed, 347 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/text/webvtt/CssParser.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/text/webvtt/CssParser.java
new file mode 100644
index 0000000000..3337cc3481
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/text/webvtt/CssParser.java
@@ -0,0 +1,347 @@
+/*
+ * 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.text.webvtt;
+
+import android.text.TextUtils;
+import androidx.annotation.Nullable;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ColorParser;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableByteArray;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Util;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Provides a CSS parser for STYLE blocks in Webvtt files. Supports only a subset of the CSS
+ * features.
+ */
+/* package */ final class CssParser {
+
+  private static final String PROPERTY_BGCOLOR = "background-color";
+  private static final String PROPERTY_FONT_FAMILY = "font-family";
+  private static final String PROPERTY_FONT_WEIGHT = "font-weight";
+  private static final String PROPERTY_TEXT_DECORATION = "text-decoration";
+  private static final String VALUE_BOLD = "bold";
+  private static final String VALUE_UNDERLINE = "underline";
+  private static final String RULE_START = "{";
+  private static final String RULE_END = "}";
+  private static final String PROPERTY_FONT_STYLE = "font-style";
+  private static final String VALUE_ITALIC = "italic";
+
+  private static final Pattern VOICE_NAME_PATTERN = Pattern.compile("\\[voice=\"([^\"]*)\"\\]");
+
+  // Temporary utility data structures.
+  private final ParsableByteArray styleInput;
+  private final StringBuilder stringBuilder;
+
+  public CssParser() {
+    styleInput = new ParsableByteArray();
+    stringBuilder = new StringBuilder();
+  }
+
+  /**
+   * Takes a CSS style block and consumes up to the first empty line. Attempts to parse the contents
+   * of the style block and returns a list of {@link WebvttCssStyle} instances if successful. If
+   * parsing fails, it returns a list including only the styles which have been successfully parsed
+   * up to the style rule which was malformed.
+   *
+   * @param input The input from which the style block should be read.
+   * @return A list of {@link WebvttCssStyle}s that represents the parsed block, or a list
+   *     containing the styles up to the parsing failure.
+   */
+  public List<WebvttCssStyle> parseBlock(ParsableByteArray input) {
+    stringBuilder.setLength(0);
+    int initialInputPosition = input.getPosition();
+    skipStyleBlock(input);
+    styleInput.reset(input.data, input.getPosition());
+    styleInput.setPosition(initialInputPosition);
+
+    List<WebvttCssStyle> styles = new ArrayList<>();
+    String selector;
+    while ((selector = parseSelector(styleInput, stringBuilder)) != null) {
+      if (!RULE_START.equals(parseNextToken(styleInput, stringBuilder))) {
+        return styles;
+      }
+      WebvttCssStyle style = new WebvttCssStyle();
+      applySelectorToStyle(style, selector);
+      String token = null;
+      boolean blockEndFound = false;
+      while (!blockEndFound) {
+        int position = styleInput.getPosition();
+        token = parseNextToken(styleInput, stringBuilder);
+        blockEndFound = token == null || RULE_END.equals(token);
+        if (!blockEndFound) {
+          styleInput.setPosition(position);
+          parseStyleDeclaration(styleInput, style, stringBuilder);
+        }
+      }
+      // Check that the style rule ended correctly.
+      if (RULE_END.equals(token)) {
+        styles.add(style);
+      }
+    }
+    return styles;
+  }
+
+  /**
+   * Returns a string containing the selector. The input is expected to have the form {@code
+   * ::cue(tag#id.class1.class2[voice="someone"]}, where every element is optional.
+   *
+   * @param input From which the selector is obtained.
+   * @return A string containing the target, empty string if the selector is universal (targets all
+   *     cues) or null if an error was encountered.
+   */
+  @Nullable
+  private static String parseSelector(ParsableByteArray input, StringBuilder stringBuilder) {
+    skipWhitespaceAndComments(input);
+    if (input.bytesLeft() < 5) {
+      return null;
+    }
+    String cueSelector = input.readString(5);
+    if (!"::cue".equals(cueSelector)) {
+      return null;
+    }
+    int position = input.getPosition();
+    String token = parseNextToken(input, stringBuilder);
+    if (token == null) {
+      return null;
+    }
+    if (RULE_START.equals(token)) {
+      input.setPosition(position);
+      return "";
+    }
+    String target = null;
+    if ("(".equals(token)) {
+      target = readCueTarget(input);
+    }
+    token = parseNextToken(input, stringBuilder);
+    if (!")".equals(token)) {
+      return null;
+    }
+    return target;
+  }
+
+  /**
+   * Reads the contents of ::cue() and returns it as a string.
+   */
+  private static String readCueTarget(ParsableByteArray input) {
+    int position = input.getPosition();
+    int limit = input.limit();
+    boolean cueTargetEndFound = false;
+    while (position < limit && !cueTargetEndFound) {
+      char c = (char) input.data[position++];
+      cueTargetEndFound = c == ')';
+    }
+    return input.readString(--position - input.getPosition()).trim();
+    // --offset to return ')' to the input.
+  }
+
+  private static void parseStyleDeclaration(ParsableByteArray input, WebvttCssStyle style,
+      StringBuilder stringBuilder) {
+    skipWhitespaceAndComments(input);
+    String property = parseIdentifier(input, stringBuilder);
+    if ("".equals(property)) {
+      return;
+    }
+    if (!":".equals(parseNextToken(input, stringBuilder))) {
+      return;
+    }
+    skipWhitespaceAndComments(input);
+    String value = parsePropertyValue(input, stringBuilder);
+    if (value == null || "".equals(value)) {
+      return;
+    }
+    int position = input.getPosition();
+    String token = parseNextToken(input, stringBuilder);
+    if (";".equals(token)) {
+      // The style declaration is well formed.
+    } else if (RULE_END.equals(token)) {
+      // The style declaration is well formed and we can go on, but the closing bracket had to be
+      // fed back.
+      input.setPosition(position);
+    } else {
+      // The style declaration is not well formed.
+      return;
+    }
+    // At this point we have a presumably valid declaration, we need to parse it and fill the style.
+    if ("color".equals(property)) {
+      style.setFontColor(ColorParser.parseCssColor(value));
+    } else if (PROPERTY_BGCOLOR.equals(property)) {
+      style.setBackgroundColor(ColorParser.parseCssColor(value));
+    } else if (PROPERTY_TEXT_DECORATION.equals(property)) {
+      if (VALUE_UNDERLINE.equals(value)) {
+        style.setUnderline(true);
+      }
+    } else if (PROPERTY_FONT_FAMILY.equals(property)) {
+      style.setFontFamily(value);
+    } else if (PROPERTY_FONT_WEIGHT.equals(property)) {
+      if (VALUE_BOLD.equals(value)) {
+        style.setBold(true);
+      }
+    } else if (PROPERTY_FONT_STYLE.equals(property)) {
+      if (VALUE_ITALIC.equals(value)) {
+        style.setItalic(true);
+      }
+    }
+    // TODO: Fill remaining supported styles.
+  }
+
+  // Visible for testing.
+  /* package */ static void skipWhitespaceAndComments(ParsableByteArray input) {
+    boolean skipping = true;
+    while (input.bytesLeft() > 0 && skipping) {
+      skipping = maybeSkipWhitespace(input) || maybeSkipComment(input);
+    }
+  }
+
+  // Visible for testing.
+  @Nullable
+  /* package */ static String parseNextToken(ParsableByteArray input, StringBuilder stringBuilder) {
+    skipWhitespaceAndComments(input);
+    if (input.bytesLeft() == 0) {
+      return null;
+    }
+    String identifier = parseIdentifier(input, stringBuilder);
+    if (!"".equals(identifier)) {
+      return identifier;
+    }
+    // We found a delimiter.
+    return "" + (char) input.readUnsignedByte();
+  }
+
+  private static boolean maybeSkipWhitespace(ParsableByteArray input) {
+    switch(peekCharAtPosition(input, input.getPosition())) {
+      case '\t':
+      case '\r':
+      case '\n':
+      case '\f':
+      case ' ':
+        input.skipBytes(1);
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  // Visible for testing.
+  /* package */ static void skipStyleBlock(ParsableByteArray input) {
+    // The style block cannot contain empty lines, so we assume the input ends when a empty line
+    // is found.
+    String line;
+    do {
+      line = input.readLine();
+    } while (!TextUtils.isEmpty(line));
+  }
+
+  private static char peekCharAtPosition(ParsableByteArray input, int position) {
+    return (char) input.data[position];
+  }
+
+  @Nullable
+  private static String parsePropertyValue(ParsableByteArray input, StringBuilder stringBuilder) {
+    StringBuilder expressionBuilder = new StringBuilder();
+    String token;
+    int position;
+    boolean expressionEndFound = false;
+    // TODO: Add support for "Strings in quotes with spaces".
+    while (!expressionEndFound) {
+      position = input.getPosition();
+      token = parseNextToken(input, stringBuilder);
+      if (token == null) {
+        // Syntax error.
+        return null;
+      }
+      if (RULE_END.equals(token) || ";".equals(token)) {
+        input.setPosition(position);
+        expressionEndFound = true;
+      } else {
+        expressionBuilder.append(token);
+      }
+    }
+    return expressionBuilder.toString();
+  }
+
+  private static boolean maybeSkipComment(ParsableByteArray input) {
+    int position = input.getPosition();
+    int limit = input.limit();
+    byte[] data = input.data;
+    if (position + 2 <= limit && data[position++] == '/' && data[position++] == '*') {
+      while (position + 1 < limit) {
+        char skippedChar = (char) data[position++];
+        if (skippedChar == '*') {
+          if (((char) data[position]) == '/') {
+            position++;
+            limit = position;
+          }
+        }
+      }
+      input.skipBytes(limit - input.getPosition());
+      return true;
+    }
+    return false;
+  }
+
+  private static String parseIdentifier(ParsableByteArray input, StringBuilder stringBuilder) {
+    stringBuilder.setLength(0);
+    int position = input.getPosition();
+    int limit = input.limit();
+    boolean identifierEndFound = false;
+    while (position  < limit && !identifierEndFound) {
+      char c = (char) input.data[position];
+      if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || c == '#'
+          || c == '-' || c == '.' || c == '_') {
+        position++;
+        stringBuilder.append(c);
+      } else {
+        identifierEndFound = true;
+      }
+    }
+    input.skipBytes(position - input.getPosition());
+    return stringBuilder.toString();
+  }
+
+  /**
+   * Sets the target of a {@link WebvttCssStyle} by splitting a selector of the form
+   * {@code ::cue(tag#id.class1.class2[voice="someone"]}, where every element is optional.
+   */
+  private void applySelectorToStyle(WebvttCssStyle style, String selector) {
+    if ("".equals(selector)) {
+      return; // Universal selector.
+    }
+    int voiceStartIndex = selector.indexOf('[');
+    if (voiceStartIndex != -1) {
+      Matcher matcher = VOICE_NAME_PATTERN.matcher(selector.substring(voiceStartIndex));
+      if (matcher.matches()) {
+        style.setTargetVoice(matcher.group(1));
+      }
+      selector = selector.substring(0, voiceStartIndex);
+    }
+    String[] classDivision = Util.split(selector, "\\.");
+    String tagAndIdDivision = classDivision[0];
+    int idPrefixIndex = tagAndIdDivision.indexOf('#');
+    if (idPrefixIndex != -1) {
+      style.setTargetTagName(tagAndIdDivision.substring(0, idPrefixIndex));
+      style.setTargetId(tagAndIdDivision.substring(idPrefixIndex + 1)); // We discard the '#'.
+    } else {
+      style.setTargetTagName(tagAndIdDivision);
+    }
+    if (classDivision.length > 1) {
+      style.setTargetClasses(Util.nullSafeArrayCopyOfRange(classDivision, 1, classDivision.length));
+    }
+  }
+
+}