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/*
 * SonarQube JavaScript Plugin
 * Copyright (C) 2011-2022 SonarSource SA
 * mailto:info AT sonarsource DOT com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package org.sonar.plugins.javascript.css.metrics;

import com.sonar.sslr.impl.Lexer;

import static com.sonar.sslr.impl.channel.RegexpChannelBuilder.regexp;

// This is a at-best lexer.
// It is far from being entirely matching the standard definition of css/less/scss tokens nor
// following the theory of what a lexer responsibilities are but as we are only building line metrics and highlighting
// on top of it we decided to focus on simplicity over being extensive.

// Be careful to avoid/limit usage of backtracking regex. There is nearly always an alternative with a forward lookup.
// This will allow to improve performance and avoid a lof of StackOverflowException.
public final class CssLexer {

  private static final String NEW_LINE = "(?:\r\n|\r|\n|\f)";
  private static final String WHITESPACE = "[\t\n\f\r ]";
  private static final String NON_ASCII = "[^\\p{ASCII}]";
  private static final String HEX_DIGIT = "0-9a-fA-F";
  private static final String ESCAPE = "(?:\\\\[" + HEX_DIGIT + "]{1,6}" + WHITESPACE + "?)|\\[^\r\n\f" + HEX_DIGIT + "]";

  private static final String PUNCTUATOR = "[!:,;%&+#\\*-/=>\\(\\)\\[\\]\\{\\}]";

  // Use dotall mode (https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html#DOTALL) to match line return
  // while using .
  private static final String MULTI_LINE_COMMENT = "(?s)/\\*.*?\\*/";
  private static final String INLINE_COMMENT = "//[^\n\r\f]*+";

  private static final String NUMBER = "[+|-]?+(?:\\d++(?:\\.\\d++)?+|\\.\\d++)(?:[a-z]++|%)?+";

  private static final String NAME_CHAR = "[a-zA-Z0-9_-]|" + NON_ASCII + "|" + ESCAPE;
  private static final String NAME_START = "[a-zA-Z_]|" + NON_ASCII + "|" + ESCAPE;

  private static final String IDENTIFIER = "-?+(?:" + NAME_START + ")(?:" + NAME_CHAR + ")*+";
  private static final String AT_IDENTIFIER = "@++" + IDENTIFIER;
  private static final String HASH_IDENTIFIER = "#(?:" + NAME_CHAR + ")++";
  private static final String DOLLAR_IDENTIFIER = "\\$(?:" + NAME_CHAR + ")++";

  private static final String DOUBLE_QUOTE_STRING = "~?+\"(?:[^\"\\\\\r\n\f]|" + ESCAPE + "|\\\\" + NEW_LINE + ")*+\"";
  private static final String SINGLE_QUOTE_STRING = "~?+'(?:[^'\\\\\r\n\f]|" + ESCAPE + "|\\\\" + NEW_LINE + ")*+'";

  private CssLexer() {
  }

  public static Lexer create() {
    return Lexer.builder()
      .withFailIfNoChannelToConsumeOneCharacter(false)

      .withChannel(regexp(CssTokenType.COMMENT, MULTI_LINE_COMMENT))
      .withChannel(regexp(CssTokenType.COMMENT, INLINE_COMMENT))
      .withChannel(regexp(CssTokenType.STRING, DOUBLE_QUOTE_STRING))
      .withChannel(regexp(CssTokenType.STRING, SINGLE_QUOTE_STRING))
      .withChannel(regexp(CssTokenType.AT_IDENTIFIER, AT_IDENTIFIER))
      .withChannel(regexp(CssTokenType.HASH_IDENTIFIER, HASH_IDENTIFIER))
      .withChannel(regexp(CssTokenType.DOLLAR_IDENTIFIER, DOLLAR_IDENTIFIER))
      .withChannel(regexp(CssTokenType.IDENTIFIER, IDENTIFIER))
      .withChannel(regexp(CssTokenType.NUMBER, NUMBER))
      .withChannel(regexp(CssTokenType.PUNCTUATOR, PUNCTUATOR))

      .build();
  }
}