/*
 * 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;
  }
}