/*
    * Copyright (C) 2012 The Guava Authors
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package java.nio.charset;
  
  import java.util.Collections;
  import java.util.SortedMap;
  import java.util.TreeMap;
  
  /**
   * A minimal GWT emulation of {@link Charset}.
   *
   * @author Gregory Kick
   */
  public abstract class Charset implements Comparable<Charset> {
    private static final Charset UTF_8 = new Charset("UTF-8") {};
  
    private static final SortedMap<String, Charset> AVAILABLE_CHARSETS =
        new TreeMap<String, Charset>();
    static {
      AVAILABLE_CHARSETS.put(UTF_8.name(), UTF_8);
    }
  
    public static SortedMap<String, Charset> availableCharsets() {
      return Collections.unmodifiableSortedMap(AVAILABLE_CHARSETS);
    }
  
    public static Charset forName(String charsetName) {
      if (charsetName == null) {
        throw new IllegalArgumentException("Null charset name");
      }
      int length = charsetName.length();
      if (length == 0) {
        throw new IllegalCharsetNameException(charsetName);
      }
      for (int i = 0; i < length; i++) {
        char c = charsetName.charAt(i);
        if ((c >= 'A' && c <= 'Z')
            || (c >= 'a' && c <= 'z')
            || (c >= '0' && c <= '9')
            || (c == '-' && i != 0)
            || (c == ':' && i != 0)
            || (c == '_' && i != 0)
            || (c == '.' && i != 0)) {
          continue;
        }
        throw new IllegalCharsetNameException(charsetName);
      }
      Charset charset = AVAILABLE_CHARSETS.get(charsetName.toUpperCase());
      if (charset != null) {
        return charset;
      }
      throw new UnsupportedCharsetException(charsetName);
    }
  
    private final String name;
  
    private Charset(String name) {
      this.name = name;
    }
  
    public final String name() {
      return name;
    }
  
    public final int compareTo(Charset that) {
      return this.name.compareToIgnoreCase(that.name);
    }
  
    public final int hashCode() {
      return name.hashCode();
    }
  
    public final boolean equals(Object o) {
      if (o == this) {
        return true;
      } else if (o instanceof Charset) {
        Charset that = (Charset) o;
        return this.name.equals(that.name);
      } else {
        return false;
      }
    }
  
    public final String toString() {
      return name;
   }
 }