/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package ch.boye.httpclientandroidlib.impl.cookie;

import java.lang.ref.SoftReference;
import java.text.DateFormat;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
import java.util.TimeZone;

import android.os.Build;

import ch.boye.httpclientandroidlib.annotation.Immutable;

/**
 * A utility class for parsing and formatting HTTP dates as used in cookies and other headers. This class handles dates as defined by RFC 2616 section 3.3.1 as
 * well as some other common non-standard formats.
 * 
 * 
 * @since 4.0
 */
@Immutable
public final class DateUtils {

	/**
	 * Date format pattern used to parse HTTP date headers in RFC 1123 format.
	 */
	public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";

	/**
	 * Date format pattern used to parse HTTP date headers in RFC 1036 format.
	 */
	public static final String PATTERN_RFC1036 = "EEE, dd-MMM-yy HH:mm:ss zzz";

	/**
	 * Date format pattern used to parse HTTP date headers in ANSI C <code>asctime()</code> format.
	 */
	public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";

	private static final String[] DEFAULT_PATTERNS = new String[] { PATTERN_RFC1123, PATTERN_RFC1036, PATTERN_ASCTIME };

	private static final Date DEFAULT_TWO_DIGIT_YEAR_START;

	public static final TimeZone GMT = TimeZone.getTimeZone("GMT");

	private static boolean mICS;

	static {
		Calendar calendar = Calendar.getInstance();
		calendar.setTimeZone(GMT);
		calendar.set(2000, Calendar.JANUARY, 1, 0, 0, 0);
		calendar.set(Calendar.MILLISECOND, 0);
		DEFAULT_TWO_DIGIT_YEAR_START = calendar.getTime();

		mICS = Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH;
	}

	/**
	 * Parses a date value. The formats used for parsing the date value are retrieved from the default http params.
	 * 
	 * @param dateValue
	 *            the date value to parse
	 * 
	 * @return the parsed date
	 * 
	 * @throws DateParseException
	 *             if the value could not be parsed using any of the supported date formats
	 */
	public static Date parseDate(String dateValue) throws DateParseException {
		return parseDate(dateValue, null, null);
	}

	/**
	 * Parses the date value using the given date formats.
	 * 
	 * @param dateValue
	 *            the date value to parse
	 * @param dateFormats
	 *            the date formats to use
	 * 
	 * @return the parsed date
	 * 
	 * @throws DateParseException
	 *             if none of the dataFormats could parse the dateValue
	 */
	public static Date parseDate(final String dateValue, String[] dateFormats) throws DateParseException {
		return parseDate(dateValue, dateFormats, null);
	}

	/**
	 * Parses the date value using the given date formats.
	 * 
	 * @param dateValue
	 *            the date value to parse
	 * @param dateFormats
	 *            the date formats to use
	 * @param startDate
	 *            During parsing, two digit years will be placed in the range <code>startDate</code> to <code>startDate + 100 years</code>. This value may be
	 *            <code>null</code>. When <code>null</code> is given as a parameter, year <code>2000</code> will be used.
	 * 
	 * @return the parsed date
	 * 
	 * @throws DateParseException
	 *             if none of the dataFormats could parse the dateValue
	 */
	public static Date parseDate(String dateValue, String[] dateFormats, Date startDate) throws DateParseException {

		if (dateValue == null) {
			throw new IllegalArgumentException("dateValue is null");
		}
		if (dateFormats == null) {
			dateFormats = DEFAULT_PATTERNS;
		}
		if (startDate == null) {
			startDate = DEFAULT_TWO_DIGIT_YEAR_START;
		}
		// trim single quotes around date if present
		// see issue #5279
		if (dateValue.length() > 1 && dateValue.startsWith("'") && dateValue.endsWith("'")) {
			dateValue = dateValue.substring(1, dateValue.length() - 1);
		}

		// don't use ThreadLocal in versions < ICS as time zone loading takes forever
		if (!mICS) {
			for (String dateFormat : dateFormats) {
				SimpleDateFormat dateParser = DateFormatHolderSync.formatFor(dateFormat);
				synchronized (dateParser) {
					dateParser.set2DigitYearStart(startDate);
					ParsePosition pos = new ParsePosition(0);

					Date result = dateParser.parse(dateValue, pos);

					if (pos.getIndex() != 0)
						return result;
				}
			}
		}
		else {
			for (String dateFormat : dateFormats) {
				SimpleDateFormat dateParser = DateFormatHolder.formatFor(dateFormat);
				dateParser.set2DigitYearStart(startDate);
				ParsePosition pos = new ParsePosition(0);
				Date result = dateParser.parse(dateValue, pos);
				if (pos.getIndex() != 0)
					return result;
			}
		}

		// we were unable to parse the date
		throw new DateParseException("Unable to parse the date " + dateValue);
	}

	/**
	 * Formats the given date according to the RFC 1123 pattern.
	 * 
	 * @param date
	 *            The date to format.
	 * @return An RFC 1123 formatted date string.
	 * 
	 * @see #PATTERN_RFC1123
	 */
	public static String formatDate(Date date) {
		return formatDate(date, PATTERN_RFC1123);
	}

	/**
	 * Formats the given date according to the specified pattern. The pattern must conform to that used by the {@link SimpleDateFormat simple date format}
	 * class.
	 * 
	 * @param date
	 *            The date to format.
	 * @param pattern
	 *            The pattern to use for formatting the date.
	 * @return A formatted date string.
	 * 
	 * @throws IllegalArgumentException
	 *             If the given date pattern is invalid.
	 * 
	 * @see SimpleDateFormat
	 */
	public static String formatDate(Date date, String pattern) {
		if (date == null)
			throw new IllegalArgumentException("date is null");
		if (pattern == null)
			throw new IllegalArgumentException("pattern is null");

		

		if (!mICS) {
			SimpleDateFormat formatter = DateFormatHolderSync.formatFor(pattern);
			synchronized (formatter) {
				return formatter.format(date);
			}
		}
		else {
			SimpleDateFormat formatter = DateFormatHolder.formatFor(pattern);
			return formatter.format(date);
		}
	}

	/**
	 * Clears thread-local variable containing {@link DateFormat} cache.
	 */
	public static void clearThreadLocal() {
		DateFormatHolder.clearThreadLocal();
	}

	/** This class should not be instantiated. */
	private DateUtils() {
	}

	/**
	 * A factory for {@link SimpleDateFormat}s. The instances are stored in a threadlocal way because SimpleDateFormat is not threadsafe as noted in
	 * {@link SimpleDateFormat its javadoc}.
	 * 
	 */
	final static class DateFormatHolderSync {

		private static Map<String, SimpleDateFormat> mFormats;

		/**
		 * creates a {@link SimpleDateFormat} for the requested format string.
		 * 
		 * @param pattern
		 *            a non-<code>null</code> format String according to {@link SimpleDateFormat}. The format is not checked against <code>null</code> since all
		 *            paths go through {@link DateUtils}.
		 * @return the requested format. This simple dateformat should not be used to {@link SimpleDateFormat#applyPattern(String) apply} to a different
		 *         pattern.
		 */
		public synchronized static SimpleDateFormat formatFor(String pattern) {

			if (mFormats == null) {
				mFormats = new HashMap<String, SimpleDateFormat>();

			}

			SimpleDateFormat format = mFormats.get(pattern);
			if (format == null) {
				format = new SimpleDateFormat(pattern, Locale.US);
				format.setTimeZone(TimeZone.getTimeZone("GMT"));
				mFormats.put(pattern, format);
			}

			return format;
		}

	

	}
	
	 /**
     * A factory for {@link SimpleDateFormat}s. The instances are stored in a
     * threadlocal way because SimpleDateFormat is not threadsafe as noted in
     * {@link SimpleDateFormat its javadoc}.
     *
     */
    final static class DateFormatHolder {

        private static final ThreadLocal<SoftReference<Map<String, SimpleDateFormat>>>
            THREADLOCAL_FORMATS = new ThreadLocal<SoftReference<Map<String, SimpleDateFormat>>>() {

            @Override
            protected SoftReference<Map<String, SimpleDateFormat>> initialValue() {
                return new SoftReference<Map<String, SimpleDateFormat>>(
                        new HashMap<String, SimpleDateFormat>());
            }

        };

        /**
         * creates a {@link SimpleDateFormat} for the requested format string.
         *
         * @param pattern
         *            a non-<code>null</code> format String according to
         *            {@link SimpleDateFormat}. The format is not checked against
         *            <code>null</code> since all paths go through
         *            {@link DateUtils}.
         * @return the requested format. This simple dateformat should not be used
         *         to {@link SimpleDateFormat#applyPattern(String) apply} to a
         *         different pattern.
         */
        public static SimpleDateFormat formatFor(String pattern) {
            SoftReference<Map<String, SimpleDateFormat>> ref = THREADLOCAL_FORMATS.get();
            Map<String, SimpleDateFormat> formats = ref.get();
            if (formats == null) {
                formats = new HashMap<String, SimpleDateFormat>();
                THREADLOCAL_FORMATS.set(
                        new SoftReference<Map<String, SimpleDateFormat>>(formats));
            }

            SimpleDateFormat format = formats.get(pattern);
            if (format == null) {
                format = new SimpleDateFormat(pattern, Locale.US);
                format.setTimeZone(TimeZone.getTimeZone("GMT"));
                formats.put(pattern, format);
            }

            return format;
        }

        public static void clearThreadLocal() {
            THREADLOCAL_FORMATS.remove();
        }

    }


}
