/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2004, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * This library is free software; you can redistribute it and/or modify it under the terms
 * of the GNU Lesser General Public License as published by the Free Software Foundation;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ---------
 * Week.java
 * ---------
 * (C) Copyright 2001-2004, by Object Refinery Limited and Contributors.
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   Aimin Han;
 *
 * $Id: Week.java,v 1.5 2004/11/04 11:21:54 mungady Exp $
 *
 * Changes
 * -------
 * 11-Oct-2001 : Version 1 (DG);
 * 18-Dec-2001 : Changed order of parameters in constructor (DG);
 * 19-Dec-2001 : Added a new constructor as suggested by Paul English (DG);
 * 29-Jan-2002 : Worked on the parseWeek(...) method (DG);
 * 13-Feb-2002 : Fixed bug in Week(Date) constructor (DG);
 * 26-Feb-2002 : Changed getStart(), getMiddle() and getEnd() methods to evaluate with reference
 *               to a particular time zone (DG);
 * 05-Apr-2002 : Reinstated this class to the JCommon library (DG);
 * 24-Jun-2002 : Removed unnecessary main method (DG);
 * 10-Sep-2002 : Added getSerialIndex() method (DG);
 * 06-Oct-2002 : Fixed errors reported by Checkstyle (DG);
 * 18-Oct-2002 : Changed to observe 52 or 53 weeks per year, consistent with GregorianCalendar.
 *               Thanks to Aimin Han for the code (DG);
 * 02-Jan-2003 : Removed debug code (DG);
 * 13-Mar-2003 : Moved to com.jrefinery.data.time package, and implemented Serializable (DG);
 * 21-Oct-2003 : Added hashCode() method (DG);
 * 24-May-2004 : Modified getFirstMillisecond() and getLastMillisecond() to take account of
 *               firstDayOfWeek setting in Java's Calendar class (DG);
 * 30-Sep-2004 : Replaced getTime().getTime() with getTimeInMillis() (DG);
 * 04-Nov-2004 : Reverted change of 30-Sep-2004, because it won't work for JDK 1.3 (DG);
 *
 */

package org.jfree.data.time;

import java.io.Serializable;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;

/**
 * A calendar week.  All years are considered to have 53 weeks, numbered from 1 to
 * 53, although in many cases the 53rd week is empty.  Most of the time, the 1st week
 * of the year *begins* in the previous calendar year, but it always finishes in the current
 * year (this behaviour matches the workings of the <code>GregorianCalendar</code> class).
 * <P>
 * This class is immutable, which is a requirement for all {@link RegularTimePeriod} subclasses.
 */
public class Week extends RegularTimePeriod implements Serializable {

    /** Constant for the first week in the year. */
    public static final int FIRST_WEEK_IN_YEAR = 1;

    /** Constant for the last week in the year. */
    public static final int LAST_WEEK_IN_YEAR = 53;

    /** The year in which the week falls. */
    private Year year;

    /** The week (1-53). */
    private int week;

    /**
     * Creates a new time period for the week in which the current system date/time falls.
     */
    public Week() {
        this(new Date());
    }

    /**
     * Creates a time period representing the week in the specified year.
     *
     * @param week  the week (1 to 53).
     * @param year  the year (1900 to 9999).
     */
    public Week(int week, int year) {
        this(week, new Year(year));
    }

    /**
     * Creates a time period representing the week in the specified year.
     *
     * @param week  the week (1 to 53).
     * @param year  the year (1900 to 9999).
     */
    public Week(int week, Year year) {
        if ((week < FIRST_WEEK_IN_YEAR) && (week > LAST_WEEK_IN_YEAR)) {
            throw new IllegalArgumentException("The 'week' argument must be in the range 1 - 53.");
        }
        this.week = week;
        this.year = year;
    }

    /**
     * Creates a time period for the week in which the specified date/time falls.
     *
     * @param time  the time (<code>null</code> not permitted).
     */
    public Week(Date time) {
        // defer argument checking...
        this(time, RegularTimePeriod.DEFAULT_TIME_ZONE);
    }

    /**
     * Creates a time period for the week in which the specified date/time falls, calculated
     * relative to the specified time zone.
     *
     * @param time  the date/time (<code>null</code> not permitted).
     * @param zone  the time zone (<code>null</code> not permitted).
     */
    public Week(Date time, TimeZone zone) {
        if (time == null) {
            throw new IllegalArgumentException("Null 'time' argument.");   
        }
        if (zone == null) {
            throw new IllegalArgumentException("Null 'zone' argument.");   
        }
        Calendar calendar = Calendar.getInstance(zone);
        calendar.setTime(time);

        // sometimes the last few days of the year are considered to fall in the *first* week of
        // the following year.  Refer to the Javadocs for GregorianCalendar.
        int tempWeek = calendar.get(Calendar.WEEK_OF_YEAR);
        if (tempWeek == 1 && calendar.get(Calendar.MONTH) == Calendar.DECEMBER) {
            this.week = 1;
            this.year =  new Year(calendar.get(Calendar.YEAR) + 1);
        }
        else {
            this.week = Math.min(tempWeek, LAST_WEEK_IN_YEAR);
            this.year = new Year(calendar.get(Calendar.YEAR));
        }

    }

    /**
     * Returns the year in which the week falls.
     *
     * @return The year (never <code>null</code>).
     */
    public Year getYear() {
        return this.year;
    }

    /**
     * Returns the year in which the week falls, as an integer value.
     *
     * @return The year.
     */
    public int getYearValue() {
        return this.year.getYear();
    }

    /**
     * Returns the week.
     *
     * @return The week.
     */
    public int getWeek() {
        return this.week;
    }

    /**
     * Returns the week preceding this one.  This method will return <code>null</code> for some
     * lower limit on the range of weeks (currently week 1, 1900).  For week 1 of any year, the 
     * previous week is always week 53, but week 53 may not contain any days (you should 
     * check for this).
     *
     * @return The preceding week (possibly <code>null</code>).
     */
    public RegularTimePeriod previous() {

        Week result;
        if (this.week != FIRST_WEEK_IN_YEAR) {
            result = new Week(this.week - 1, this.year);
        }
        else {
            // we need to work out if the previous year has 52 or 53 weeks...
            Year prevYear = (Year) this.year.previous();
            if (prevYear != null) {
                int yy = prevYear.getYear();
                Calendar prevYearCalendar = Calendar.getInstance();
                prevYearCalendar.set(yy, Calendar.DECEMBER, 31);
                result = new Week(
                    prevYearCalendar.getActualMaximum(Calendar.WEEK_OF_YEAR), prevYear
                );
            }
            else {
                result = null;
            }
        }
        return result;

    }

    /**
     * Returns the week following this one.  This method will return <code>null</code> for some
     * upper limit on the range of weeks (currently week 53, 9999).  For week 52 of any year,
     * the following week is always week 53, but week 53 may not contain any days (you should
     * check for this).
     *
     * @return The following week (possibly <code>null</code>).
     */
    public RegularTimePeriod next() {

        Week result;
        if (this.week < 52) {
            result = new Week(this.week + 1, this.year);
        }
        else {
            Calendar calendar = Calendar.getInstance();
            calendar.set(this.year.getYear(), Calendar.DECEMBER, 31);
            int actualMaxWeek = calendar.getActualMaximum(Calendar.WEEK_OF_YEAR);
            if (this.week != actualMaxWeek) {
                result = new Week(this.week + 1, this.year);
            }
            else {
                Year nextYear = (Year) this.year.next();
                if (nextYear != null) {
                    result = new Week(FIRST_WEEK_IN_YEAR, nextYear);
                }
                else {
                    result = null;
                }
            }
        }
        return result;

    }

    /**
     * Returns a serial index number for the week.
     *
     * @return The serial index number.
     */
    public long getSerialIndex() {
        return this.year.getYear() * 53L + this.week;
    }

    /**
     * Returns the first millisecond of the week, evaluated using the supplied
     * calendar (which determines the time zone).
     *
     * @param calendar  the calendar.
     *
     * @return The first millisecond of the week.
     */
    public long getFirstMillisecond(Calendar calendar) {
        Calendar c = (Calendar) calendar.clone();
        c.clear();
        c.set(Calendar.YEAR, this.year.getYear());
        c.set(Calendar.WEEK_OF_YEAR, this.week);
        c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek());
        c.set(Calendar.HOUR, 0);
        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);
        c.set(Calendar.MILLISECOND, 0);
        //return c.getTimeInMillis();  // this won't work for JDK 1.3
        return c.getTime().getTime();
    }

    /**
     * Returns the last millisecond of the week, evaluated using the supplied
     * calendar (which determines the time zone).
     *
     * @param calendar  the calendar.
     *
     * @return The last millisecond of the week.
     */
    public long getLastMillisecond(Calendar calendar) {
        RegularTimePeriod next = next();
        return next.getFirstMillisecond(calendar) - 1;
    }

    /**
     * Returns a string representing the week (e.g. "Week 9, 2002").
     *
     * TODO: look at internationalisation.
     *
     * @return A string representing the week.
     */
    public String toString() {
        return "Week " + this.week + ", " + this.year;
    }

    /**
     * Tests the equality of this Week object to an arbitrary object.  Returns
     * true if the target is a Week instance representing the same week as this
     * object.  In all other cases, returns false.
     * @param obj The object.
     *
     * @return <code>true</code> if week and year of this and object are the same.
     */
    public boolean equals(Object obj) {

        if (obj == this) {
            return true;
        }
        if (!(obj instanceof Week)) {
            return false;
        }
        Week that = (Week) obj;
        if (this.week != that.week) {
            return false;
        }
        if (!this.year.equals(that.year)) {
            return false;
        }
        return true;

    }

    /**
     * Returns a hash code for this object instance.
     * <p>
     * The approach described by Joshua Bloch in "Effective Java" has been used here:
     * <p>
     * <code>http://developer.java.sun.com/developer/Books/effectivejava/Chapter3.pdf</code>
     * 
     * @return A hash code.
     */
    public int hashCode() {
        int result = 17;
        result = 37 * result + this.week;
        result = 37 * result + this.year.hashCode();
        return result;
    }

    /**
     * Returns an integer indicating the order of this Week object relative to
     * the specified object:
     *
     * negative == before, zero == same, positive == after.
     *
     * @param o1  the object to compare.
     *
     * @return negative == before, zero == same, positive == after.
     */
    public int compareTo(Object o1) {

        int result;

        // CASE 1 : Comparing to another Week object
        // --------------------------------------------
        if (o1 instanceof Week) {
            Week w = (Week) o1;
            result = this.year.getYear() - w.getYear().getYear();
            if (result == 0) {
                result = this.week - w.getWeek();
            }
        }

        // CASE 2 : Comparing to another TimePeriod object
        // -----------------------------------------------
        else if (o1 instanceof RegularTimePeriod) {
            // more difficult case - evaluate later...
            result = 0;
        }

        // CASE 3 : Comparing to a non-TimePeriod object
        // ---------------------------------------------
        else {
            // consider time periods to be ordered after general objects
            result = 1;
        }

        return result;

    }

    /**
     * Parses the string argument as a week.
     * <P>
     * This method is required to accept the format "YYYY-Wnn".  It will also
     * accept "Wnn-YYYY". Anything else, at the moment, is a bonus.
     *
     * @param s  string to parse.
     *
     * @return <code>null</code> if the string is not parseable, the week otherwise.
     */
    public static Week parseWeek(String s) {

        Week result = null;
        if (s != null) {

            // trim whitespace from either end of the string
            s = s.trim();

            int i = Week.findSeparator(s);
            if (i != -1) {
                String s1 = s.substring(0, i).trim();
                String s2 = s.substring(i + 1, s.length()).trim();

                Year y = Week.evaluateAsYear(s1);
                int w;
                if (y != null) {
                    w = Week.stringToWeek(s2);
                    if (w == -1) {
                        throw new TimePeriodFormatException(
                            "Week.parseWeek(String): can't evaluate the week.");
                    }
                    result = new Week(w, y);
                }
                else {
                    y = Week.evaluateAsYear(s2);
                    if (y != null) {
                        w = Week.stringToWeek(s1);
                        if (w == -1) {
                            throw new TimePeriodFormatException(
                                "Week.parseWeek(String): can't evaluate the week.");
                        }
                        result = new Week(w, y);
                    }
                    else {
                        throw new TimePeriodFormatException(
                            "Week.parseWeek(String): can't evaluate the year.");
                    }
                }

            }
            else {
                throw new TimePeriodFormatException(
                    "Week.parseWeek(String): could not find separator.");
            }

        }
        return result;

    }

    /**
     * Finds the first occurrence of ' ', '-', ',' or '.'
     *
     * @param s  the string to parse.
     *
     * @return <code>-1</code> if none of the characters was found, the
     *      index of the first occurrence otherwise.
     */
    private static int findSeparator(String s) {

        int result = s.indexOf('-');
        if (result == -1) {
            result = s.indexOf(',');
        }
        if (result == -1) {
            result = s.indexOf(' ');
        }
        if (result == -1) {
            result = s.indexOf('.');
        }
        return result;
    }

    /**
     * Creates a year from a string, or returns null (format exceptions
     * suppressed).
     *
     * @param s  string to parse.
     *
     * @return <code>null</code> if the string is not parseable, the year otherwise.
     */
    private static Year evaluateAsYear(String s) {

        Year result = null;
        try {
            result = Year.parseYear(s);
        }
        catch (TimePeriodFormatException e) {
            // suppress
        }
        return result;

    }

    /**
     * Converts a string to a week.
     *
     * @param s  the string to parse.
     * @return <code>-1</code> if the string does not contain a week number,
     *      the number of the week otherwise.
     */
    private static int stringToWeek(String s) {

        int result = -1;
        s = s.replace('W', ' ');
        s = s.trim();
        try {
            result = Integer.parseInt(s);
            if ((result < 1) || (result > LAST_WEEK_IN_YEAR)) {
                result = -1;
            }
        }
        catch (NumberFormatException e) {
            // suppress
        }
        return result;

    }
    
}