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/*
 * SonarQube Python Plugin
 * Copyright (C) 2011-2024 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 Sonar Source-Available License Version 1, as published by SonarSource SA.
 *
 * 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 Sonar Source-Available License for more details.
 *
 * You should have received a copy of the Sonar Source-Available License
 * along with this program; if not, see https://sonarsource.com/license/ssal/
 */
package org.sonar.python.lexer;

import com.sonar.sslr.api.Token;
import com.sonar.sslr.impl.Lexer;
import org.sonar.python.api.PythonTokenType;
import org.sonar.sslr.channel.Channel;
import org.sonar.sslr.channel.CodeReader;

/**
 * http://docs.python.org/reference/lexical_analysis.html#indentation
 */
public class IndentationChannel extends Channel {

  private final StringBuilder buffer = new StringBuilder();
  private final LexerState lexerState;

  public IndentationChannel(LexerState lexerState) {
    this.lexerState = lexerState;
  }

  @Override
  public boolean consume(CodeReader code, Lexer lexer) {
    if (lexerState.joined) {
      lexerState.joined = false;
      return false;
    }

    if (code.getColumnPosition() != 0) {
      return false;
    }

    int line = code.getLinePosition();
    int column = code.getColumnPosition();

    int whiteSpaceIndex = 0;
    char ch = code.charAt(whiteSpaceIndex);
    while (isWhiteSpace(ch)) {
      whiteSpaceIndex++;
      ch = code.charAt(whiteSpaceIndex);
    }

    if (isBlankLine(ch)) {
      return false;
    }

    buffer.setLength(0);
    int indentationLevel = 0;
    for (int i = 0; i < whiteSpaceIndex; i++) {
      char currentChar = (char) code.pop();
      buffer.append(currentChar);
      if (currentChar == '\t') {
        indentationLevel += countTabReplacer(indentationLevel);
      } else {
        indentationLevel++;
      }
    }

    processIndents(lexer, line, column, indentationLevel);
    return buffer.length() != 0;
  }

  private static int countTabReplacer(int indentationLevel) {
    return 8-indentationLevel%8;
  }

  private static boolean isWhiteSpace(char ch) {
    return (ch == ' ') || (ch == '\t');
  }

  private static boolean isBlankLine(char ch) {
    return (ch == '\n') || (ch == '\r') || (ch == '#') || (ch == (char) -1);
  }

  private void processIndents(Lexer lexer, int line, int column, int indentationLevel) {
    if (indentationLevel > lexerState.indentationStack.peek()) {
      lexerState.indentationStack.push(indentationLevel);
      lexer.addToken(Token.builder()
          .setType(PythonTokenType.INDENT)
          .setValueAndOriginalValue(buffer.toString())
          .setURI(lexer.getURI())
          .setLine(line)
          .setColumn(column)
          .build());
    } else if (indentationLevel < lexerState.indentationStack.peek()) {
      while (indentationLevel < lexerState.indentationStack.peek()) {
        lexerState.indentationStack.pop();
        lexer.addToken(Token.builder()
            .setType(PythonTokenType.DEDENT)
            .setValueAndOriginalValue(buffer.toString())
            .setURI(lexer.getURI())
            .setLine(line)
            .setColumn(column)
            .build());
      }
    }
  }

}