/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you 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 play.core.cookie.encoding;

import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * This DateFormat decodes 3 formats of {@link Date}, but only encodes the one, the first:
 *
 * <ul>
 *   <li>Sun, 06 Nov 1994 08:49:37 GMT: standard specification, the only one with valid generation
 *   <li>Sun, 06 Nov 1994 08:49:37 GMT: obsolete specification
 *   <li>Sun Nov 6 08:49:37 1994: obsolete specification
 * </ul>
 */
final class HttpHeaderDateFormat extends SimpleDateFormat {
  private static final long serialVersionUID = -925286159755905325L;

  private final SimpleDateFormat format1 = new HttpHeaderDateFormatObsolete1();
  private final SimpleDateFormat format2 = new HttpHeaderDateFormatObsolete2();

  private static final ThreadLocal<HttpHeaderDateFormat> FORMAT_THREAD_LOCAL =
      new ThreadLocal<HttpHeaderDateFormat>() {
        @Override
        protected HttpHeaderDateFormat initialValue() {
          return new HttpHeaderDateFormat();
        }
      };

  public static HttpHeaderDateFormat get() {
    return FORMAT_THREAD_LOCAL.get();
  }

  /** Standard date format */
  private HttpHeaderDateFormat() {
    super("E, dd MMM yyyy HH:mm:ss z", Locale.ENGLISH);
    setTimeZone(TimeZone.getTimeZone("GMT"));
  }

  @Override
  public Date parse(String text, ParsePosition pos) {
    Date date = super.parse(text, pos);
    if (date == null) {
      date = format1.parse(text, pos);
    }
    if (date == null) {
      date = format2.parse(text, pos);
    }
    return date;
  }

  /** First obsolete format */
  private static final class HttpHeaderDateFormatObsolete1 extends SimpleDateFormat {
    private static final long serialVersionUID = -3178072504225114298L;

    HttpHeaderDateFormatObsolete1() {
      super("E, dd-MMM-yy HH:mm:ss z", Locale.ENGLISH);
      setTimeZone(TimeZone.getTimeZone("GMT"));
    }
  }

  /** Second obsolete format */
  private static final class HttpHeaderDateFormatObsolete2 extends SimpleDateFormat {
    private static final long serialVersionUID = 3010674519968303714L;

    HttpHeaderDateFormatObsolete2() {
      super("E MMM d HH:mm:ss yyyy", Locale.ENGLISH);
      setTimeZone(TimeZone.getTimeZone("GMT"));
    }
  }
}
