/**
 * Logback: the generic, reliable, fast and flexible logging framework for Java.
 * 
 * Copyright (C) 2000-2006, QOS.ch
 * 
 * This library 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.
 */
package ch.qos.logback.core.util;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Instances of this class represent the size of a file. Internally, the size is
 * stored as long.>
 * 
 * <p>The {@link #valueOf} method can convert strings such as "3 kb", "5 mb", into
 * FileSize instances. The recognized unit specifications for file size are the
 * "kb", "mb", and "gb". The unit name may be followed by an "s". Thus, "2 kbs"
 * and "2 kb" are equivalent. In the absence of a time unit specification, byte
 * is assumed.
 *  
 * @author Ceki G&uuml;lc&uuml;
 * 
 */
public class FileSize {

  private final static String LENGTH_PART = "([0-9]+)";
  private final static int DOUBLE_GROUP = 1;

  private final static String UNIT_PART = "(|kb|mb|gb)s?";
  private final static int UNIT_GROUP = 2;

  private static final Pattern FILE_SIZE_PATTERN = Pattern.compile(LENGTH_PART
      + "\\s*" + UNIT_PART, Pattern.CASE_INSENSITIVE);

  static final long KB_COEFFICIENT = 1024;
  static final long MB_COEFFICIENT = 1024 * KB_COEFFICIENT;
  static final long GB_COEFFICIENT = 1024 * MB_COEFFICIENT;

  final long size;

  FileSize(long size) {
    this.size = size;
  }

  public long getSize() {
    return size;
  }

  static public FileSize valueOf(String fileSizeStr) {
    Matcher matcher = FILE_SIZE_PATTERN.matcher(fileSizeStr);

    long coefficient;
    if (matcher.matches()) {
      String lenStr = matcher.group(DOUBLE_GROUP);
      String unitStr = matcher.group(UNIT_GROUP);

      long lenValue = Long.valueOf(lenStr);
      if (unitStr.equalsIgnoreCase("")) {
        coefficient = 1;
      } else if (unitStr.equalsIgnoreCase("kb")) {
        coefficient = KB_COEFFICIENT;
      } else if (unitStr.equalsIgnoreCase("mb")) {
        coefficient = MB_COEFFICIENT;
      } else if (unitStr.equalsIgnoreCase("gb")) {
        coefficient = GB_COEFFICIENT;
      } else {
        throw new IllegalStateException("Unexpected " + unitStr);
      }
      return new FileSize(lenValue * coefficient);
    } else {
      throw new IllegalArgumentException("String value [" + fileSizeStr
          + "] is not in the expected format.");
    }

  }
}
