third_party/WebKit/Source/core/css/parser/CSSSupportsParser.cpp

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "core/css/parser/CSSSupportsParser.h"

#include "core/css/parser/CSSParserImpl.h"

namespace blink {

CSSSupportsParser::SupportsResult CSSSupportsParser::supportsCondition(
    CSSParserTokenRange range,
    CSSParserImpl& parser) {
  // TODO(timloh): The spec allows leading whitespace in @supports but not
  // CSS.supports, but major browser vendors allow it in CSS.supports also.
  range.consumeWhitespace();
  return CSSSupportsParser(parser).consumeCondition(range);
}

enum ClauseType { Unresolved, Conjunction, Disjunction };

CSSSupportsParser::SupportsResult CSSSupportsParser::consumeCondition(
    CSSParserTokenRange range) {
  if (range.peek().type() == IdentToken)
    return consumeNegation(range);

  bool result;
  ClauseType clauseType = Unresolved;

  while (true) {
    SupportsResult nextResult = consumeConditionInParenthesis(range);
    if (nextResult == Invalid)
      return Invalid;
    bool nextSupported = nextResult;
    if (clauseType == Unresolved)
      result = nextSupported;
    else if (clauseType == Conjunction)
      result &= nextSupported;
    else
      result |= nextSupported;

    if (range.atEnd())
      break;
    if (range.consumeIncludingWhitespace().type() != WhitespaceToken)
      return Invalid;
    if (range.atEnd())
      break;

    const CSSParserToken& token = range.consume();
    if (token.type() != IdentToken)
      return Invalid;
    if (clauseType == Unresolved)
      clauseType = token.value().length() == 3 ? Conjunction : Disjunction;
    if ((clauseType == Conjunction &&
         !equalIgnoringASCIICase(token.value(), "and")) ||
        (clauseType == Disjunction &&
         !equalIgnoringASCIICase(token.value(), "or")))
      return Invalid;

    if (range.consumeIncludingWhitespace().type() != WhitespaceToken)
      return Invalid;
  }
  return result ? Supported : Unsupported;
}

CSSSupportsParser::SupportsResult CSSSupportsParser::consumeNegation(
    CSSParserTokenRange range) {
  ASSERT(range.peek().type() == IdentToken);
  if (!equalIgnoringASCIICase(range.consume().value(), "not"))
    return Invalid;
  if (range.consumeIncludingWhitespace().type() != WhitespaceToken)
    return Invalid;
  SupportsResult result = consumeConditionInParenthesis(range);
  range.consumeWhitespace();
  if (!range.atEnd() || result == Invalid)
    return Invalid;
  return result ? Unsupported : Supported;
}

CSSSupportsParser::SupportsResult
CSSSupportsParser::consumeConditionInParenthesis(CSSParserTokenRange& range) {
  if (range.peek().type() == FunctionToken) {
    range.consumeComponentValue();
    return Unsupported;
  }
  if (range.peek().type() != LeftParenthesisToken)
    return Invalid;
  CSSParserTokenRange innerRange = range.consumeBlock();
  innerRange.consumeWhitespace();
  SupportsResult result = consumeCondition(innerRange);
  if (result != Invalid)
    return result;
  return innerRange.peek().type() == IdentToken &&
                 m_parser.supportsDeclaration(innerRange)
             ? Supported
             : Unsupported;
}

}  // namespace blink