package biweekly.util;

import java.text.DateFormat;
import java.text.FieldPosition;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
import java.util.regex.Pattern;

/*
 Copyright (c) 2013-2015, Michael Angstadt
 All rights reserved.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met: 

 1. Redistributions of source code must retain the above copyright notice, this
 list of conditions and the following disclaimer. 
 2. Redistributions in binary form must reproduce the above copyright notice,
 this list of conditions and the following disclaimer in the documentation
 and/or other materials provided with the distribution. 

 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * Defines all of the date formats that are used in iCalendar objects, and also
 * parses/formats iCalendar dates. These date formats are defined in the ISO8601
 * specification.
 * @author Michael Angstadt
 */
public enum ICalDateFormat {
        //@formatter:off
        /**
         * Example: 20120701
         */
        DATE_BASIC(
        "\\d{8}",
        "yyyyMMdd"),
        
        /**
         * Example: 2012-07-01
         */
        DATE_EXTENDED(
        "\\d{4}-\\d{2}-\\d{2}",
        "yyyy-MM-dd"),
        
        /**
         * Example: 20120701T142110-0500
         */
        DATE_TIME_BASIC(
        "\\d{8}T\\d{6}[-\\+]\\d{4}",
        "yyyyMMdd'T'HHmmssZ"),
        
        /**
         * Example: 20120701T142110
         */
        DATE_TIME_BASIC_WITHOUT_TZ(
        "\\d{8}T\\d{6}",
        "yyyyMMdd'T'HHmmss"),
        
        /**
         * Example: 2012-07-01T14:21:10-05:00
         */
        DATE_TIME_EXTENDED(
        "\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}[-\\+]\\d{2}:\\d{2}",
        "yyyy-MM-dd'T'HH:mm:ssZ"){
                @SuppressWarnings("serial")
                @Override
                public DateFormat getDateFormat(TimeZone timezone) {
                        DateFormat df = new SimpleDateFormat(formatStr){
                                @Override
                                public Date parse(String str) throws ParseException {
                                        //remove the colon from the timezone offset
                                        //SimpleDateFormat doesn't recognize timezone offsets that have colons
                                        int index = str.lastIndexOf(':');
                                        str = str.substring(0, index) + str.substring(index+1);

                                        return super.parse(str);
                                }
                                
                                @Override
                                public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition){
                                        StringBuffer sb = super.format(date, toAppendTo, fieldPosition);
                                        
                                        //add a colon between the hour and minute offsets
                                        sb.insert(sb.length()-2, ':');
                                        
                                        return sb;
                                }
                        };
                        
                        if (timezone != null){
                                df.setTimeZone(timezone);
                        }
                        
                        return df;
                }
        },
        
        /**
         * Example: 2012-07-01T14:21:10
         */
        DATE_TIME_EXTENDED_WITHOUT_TZ(
        "\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}",
        "yyyy-MM-dd'T'HH:mm:ss"),
        
        /**
         * Example: 20120701T192110Z
         */
        UTC_TIME_BASIC(
        "\\d{8}T\\d{6}Z",
        "yyyyMMdd'T'HHmmss'Z'"){
                @Override
                public DateFormat getDateFormat(TimeZone timezone) {
                        //always use the UTC timezone
                        timezone = TimeZone.getTimeZone("UTC");
                        return super.getDateFormat(timezone);
                }
        },
        
        /**
         * Example: 2012-07-01T19:21:10Z
         */
        UTC_TIME_EXTENDED(
        "\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}Z",
        "yyyy-MM-dd'T'HH:mm:ss'Z'"){
                @Override
                public DateFormat getDateFormat(TimeZone timezone) {
                        //always use the UTC timezone
                        timezone = TimeZone.getTimeZone("UTC");
                        return super.getDateFormat(timezone);
                }
        };
        //@formatter:on

        /**
         * The regular expression pattern for the date format.
         */
        private final Pattern pattern;

        /**
         * The {@link SimpleDateFormat} format string used for parsing dates.
         */
        protected final String formatStr;

        /**
         * @param regex the regular expression for the date format
         * @param formatStr the {@link SimpleDateFormat} format string used for
         * parsing dates.
         */
        private ICalDateFormat(String regex, String formatStr) {
                pattern = Pattern.compile(regex);
                this.formatStr = formatStr;
        }

        /**
         * Determines whether a date string is in this ISO format.
         * @param dateStr the date string
         * @return true if it matches the date format, false if not
         */
        public boolean matches(String dateStr) {
                return pattern.matcher(dateStr).matches();
        }

        /**
         * Builds a {@link DateFormat} object for parsing and formating dates in
         * this ISO format.
         * @return the {@link DateFormat} object
         */
        public DateFormat getDateFormat() {
                return getDateFormat(null);
        }

        /**
         * Builds a {@link DateFormat} object for parsing and formating dates in
         * this ISO format.
         * @param timezone the timezone the date is in or null for the default
         * timezone
         * @return the {@link DateFormat} object
         */
        public DateFormat getDateFormat(TimeZone timezone) {
                DateFormat df = new SimpleDateFormat(formatStr);
                if (timezone != null) {
                        df.setTimeZone(timezone);
                }
                return df;
        }

        /**
         * Formats a date in this ISO format.
         * @param date the date to format
         * @return the date string
         */
        public String format(Date date) {
                return format(date, null);
        }

        /**
         * Formats a date in this ISO format.
         * @param date the date to format
         * @param timezone the timezone to format the date in or null for the
         * default timezone
         * @return the date string
         */
        public String format(Date date, TimeZone timezone) {
                DateFormat df = getDateFormat(timezone);
                return df.format(date);
        }

        /**
         * Determines the ISO format a date string is in.
         * @param dateStr the date string (e.g. "20140322T120000Z")
         * @return the ISO format (e.g. DATETIME_BASIC) or null if not found
         */
        public static ICalDateFormat find(String dateStr) {
                for (ICalDateFormat format : values()) {
                        if (format.matches(dateStr)) {
                                return format;
                        }
                }
                return null;
        }

        /**
         * Parses an iCalendar date.
         * @param dateStr the date string to parse (e.g. "20130609T181023Z")
         * @return the parsed date
         * @throws IllegalArgumentException if the date string isn't in one of the
         * accepted ISO8601 formats
         */
        public static Date parse(String dateStr) {
                return parse(dateStr, null);
        }

        /**
         * Parses an iCalendar date.
         * @param dateStr the date string to parse (e.g. "20130609T181023Z")
         * @param timezone the timezone to parse the date as or null to use the
         * JVM's default timezone (if the date string contains its own timezone,
         * then that timezone will be used instead)
         * @return the parsed date
         * @throws IllegalArgumentException if the date string isn't in one of the
         * accepted ISO8601 formats
         */
        public static Date parse(String dateStr, TimeZone timezone) {
                //determine which ISOFormat the date is in
                ICalDateFormat format = find(dateStr);
                if (format == null) {
                        throw parseException(dateStr);
                }

                //parse the date
                DateFormat df = format.getDateFormat(timezone);
                try {
                        return df.parse(dateStr);
                } catch (ParseException e) {
                        //should never be thrown because the string is checked against a regex before being parsed
                        throw parseException(dateStr);
                }
        }

        /**
         * Determines whether a date string has a time component.
         * @param dateStr the date string (e.g. "20130601T120000")
         * @return true if it has a time component, false if not
         */
        public static boolean dateHasTime(String dateStr) {
                return dateStr.contains("T");
        }

        /**
         * Determines whether a date string is in UTC time or has a timezone offset.
         * @param dateStr the date string (e.g. "20130601T120000Z",
         * "20130601T120000-0400")
         * @return true if it has a timezone, false if not
         */
        public static boolean dateHasTimezone(String dateStr) {
                return isUTC(dateStr) || dateStr.matches(".*?[-+]\\d\\d:?\\d\\d");
        }

        /**
         * Determines if a date string is in UTC time.
         * @param dateStr the date string (e.g. "20130601T120000Z")
         * @return true if it's in UTC, false if not
         */
        public static boolean isUTC(String dateStr) {
                return dateStr.endsWith("Z");
        }

        /**
         * Gets the {@link TimeZone} object that corresponds to the given ID.
         * @param timezoneId the timezone ID (e.g. "America/New_York")
         * @return the timezone object or null if not found
         */
        public static TimeZone parseTimeZoneId(String timezoneId) {
                TimeZone timezone = TimeZone.getTimeZone(timezoneId);
                return "GMT".equals(timezone.getID()) && !"GMT".equalsIgnoreCase(timezoneId) ? null : timezone;
        }

        private static IllegalArgumentException parseException(String dateStr) {
                return new IllegalArgumentException("Date string \"" + dateStr + "\" is not in a valid ISO-8601 format.");
        }
}