/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2013, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core.pattern.util;

/**
 * This implementation is intended for use in PatternLayout.
 * 
 * @author Ceki G&uuml;lc&uuml;
 */
public class RegularEscapeUtil implements IEscapeUtil {

  public void escape(String escapeChars, StringBuffer buf, char next,
      int pointer) {
    if (escapeChars.indexOf(next) >= 0) {
      buf.append(next);
    } else
      switch (next) {
      case '_':
        // the \_ sequence is swallowed
        break;
      case '\\':
        buf.append(next);
        break;
      case 't':
        buf.append('\t');
        break;
      case 'r':
        buf.append('\r');
        break;
      case 'n':
        buf.append('\n');
        break;
      default:
        String commaSeperatedEscapeChars = formatEscapeCharsForListing(escapeChars);
        throw new IllegalArgumentException("Illegal char '" + next + " at column "
            + pointer + ". Only \\\\, \\_" + commaSeperatedEscapeChars
            + ", \\t, \\n, \\r combinations are allowed as escape characters.");
      }
  }

  String formatEscapeCharsForListing(String escapeChars) {
    StringBuilder commaSeperatedEscapeChars = new StringBuilder();
    for (int i = 0; i < escapeChars.length(); i++) {
      commaSeperatedEscapeChars.append(", \\").append(escapeChars.charAt(i));
    }
    return commaSeperatedEscapeChars.toString();
  }

  public static String basicEscape(String s) {
    char c;
    int len = s.length();
    StringBuilder sbuf = new StringBuilder(len);

    int i = 0;
    while (i < len) {
      c = s.charAt(i++);
      if (c == '\\') {
        c = s.charAt(i++);
        if (c == 'n') {
          c = '\n';
        } else if (c == 'r') {
          c = '\r';
        } else if (c == 't') {
          c = '\t';
        } else if (c == 'f') {
          c = '\f';
        } else if (c == '\b') {
          c = '\b';
        } else if (c == '\"') {
          c = '\"';
        } else if (c == '\'') {
          c = '\'';
        } else if (c == '\\') {
          c = '\\';
        }
      }
      sbuf.append(c);
    }
    return sbuf.toString();
  }
}
