/* ===========================================================

 * 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.]

 *

 * ----------

 * Month.java

 * ----------

 * (C) Copyright 2001-2003, by Object Refinery Limited.

 *

 * Original Author:  David Gilbert (for Object Refinery Limited);

 * Contributor(s):   -;

 *

 * $Id: Month.java,v 1.1 2004/08/31 15:34:17 mungady Exp $

 *

 * Changes

 * -------

 * 11-Oct-2001 : Version 1 (DG);

 * 14-Nov-2001 : Added method to get year as primitive (DG);

 *               Override for toString() method (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 parseMonth(...) method (DG);

 * 14-Feb-2002 : Fixed bugs in the Month constructors (DG);

 * 26-Feb-2002 : Changed getStart(), getMiddle() and getEnd() methods to evaluate with reference

 *               to a particular time zone (DG);

 * 19-Mar-2002 : Changed API for TimePeriod classes (DG);

 * 10-Sep-2002 : Added getSerialIndex() method (DG);

 * 04-Oct-2002 : Fixed errors reported by Checkstyle (DG);

 * 10-Jan-2003 : Changed base class and method names (DG);

 * 13-Mar-2003 : Moved to com.jrefinery.data.time package, and implemented Serializable (DG);

 * 21-Oct-2003 : Added hashCode() method (DG);

 *

 */



package org.jfree.data.time;



import java.io.Serializable;

import java.util.Calendar;

import java.util.Date;

import java.util.TimeZone;



import org.jfree.date.SerialDate;



/**

 * Represents a single month.

 * <P>

 * This class is immutable, which is a requirement for all {@link RegularTimePeriod} subclasses.

 *

 */

public class Month extends RegularTimePeriod implements Serializable {



    /** The month (1-12). */

    private int month;



    /** The year in which the month falls. */

    private Year year;



    /**

     * Constructs a new Month, based on the current system time.

     */

    public Month() {



        this(new Date());



    }



    /**

     * Constructs a new month instance.

     *

     * @param month  the month (in the range 1 to 12).

     * @param year  the year.

     */

    public Month(final int month, final int year) {



        this(month, new Year(year));



    }



    /**

     * Constructs a new month instance.

     *

     * @param month  the month (in the range 1 to 12).

     * @param year  the year.

     */

    public Month(final int month, final Year year) {



        if ((month < 1) && (month > 12)) {

            throw new IllegalArgumentException("Month(...): month outside valid range.");

        }



        this.month = month;

        this.year = year;



    }



    /**

     * Constructs a Month, based on a date/time and the default time zone.

     *

     * @param time  the date/time.

     */

    public Month(final Date time) {



        this(time, RegularTimePeriod.DEFAULT_TIME_ZONE);



    }



    /**

     * Constructs a Month, based on a date/time and a time zone.

     *

     * @param time  the date/time.

     * @param zone  the time zone.

     */

    public Month(final Date time, final TimeZone zone) {



        final Calendar calendar = Calendar.getInstance(zone);

        calendar.setTime(time);

        this.month = calendar.get(Calendar.MONTH) + 1;

        this.year = new Year(calendar.get(Calendar.YEAR));



    }



    /**

     * Returns the year in which the month falls.

     *

     * @return the year in which the month falls (as a Year object).

     */

    public Year getYear() {

        return this.year;

    }



    /**

     * Returns the year in which the month falls.

     *

     * @return the year in which the monht falls (as an int).

     */

    public int getYearValue() {

        return this.year.getYear();

    }



    /**

     * Returns the month.

     *

     * Note that 1=JAN, 2=FEB, ...

     *

     * @return the month.

     */

    public int getMonth() {

        return this.month;

    }



    /**

     * Returns the month preceding this one.

     *

     * @return the month preceding this one.

     */

    public RegularTimePeriod previous() {



        final Month result;

        if (this.month != SerialDate.JANUARY) {

            result = new Month(this.month - 1, this.year);

        }

        else {

            final Year prevYear = (Year) this.year.previous();

            if (prevYear != null) {

                result = new Month(SerialDate.DECEMBER, prevYear);

            }

            else {

                result = null;

            }

        }

        return result;



    }



    /**

     * Returns the month following this one.

     *

     * @return the month following this one.

     */

    public RegularTimePeriod next() {

        final Month result;

        if (this.month != SerialDate.DECEMBER) {

            result = new Month(this.month + 1, this.year);

        }

        else {

            final Year nextYear = (Year) this.year.next();

            if (nextYear != null) {

                result = new Month(SerialDate.JANUARY, nextYear);

            }

            else {

                result = null;

            }

        }

        return result;

    }



    /**

     * Returns a serial index number for the month.

     *

     * @return the serial index number.

     */

    public long getSerialIndex() {

        return this.year.getYear() * 12L + this.month;

    }



    /**

     * Returns a string representing the month (e.g. "January 2002").

     * <P>

     * To do: look at internationalisation.

     *

     * @return a string representing the month.

     */

    public String toString() {

        return SerialDate.monthCodeToString(this.month) + " " + this.year;

    }



    /**

     * Tests the equality of this Month object to an arbitrary object.

     * Returns true if the target is a Month instance representing the same

     * month as this object.  In all other cases, returns false.

     *

     * @param obj  the object.

     *

     * @return <code>true</code> if month and year of this and object are the same.

     */

    public boolean equals(final Object obj) {



        if (obj != null) {

            if (obj instanceof Month) {

                final Month target = (Month) obj;

                return ((this.month == target.getMonth()) && (this.year.equals(target.getYear())));

            }

            else {

                return false;

            }

        }

        else {

            return false;

        }



    }



    /**

     * 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.month;

        result = 37 * result + this.year.hashCode();

        return result;

    }



    /**

     * Returns an integer indicating the order of this Month 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(final Object o1) {



        int result;



        // CASE 1 : Comparing to another Month object

        // --------------------------------------------

        if (o1 instanceof Month) {

            final Month m = (Month) o1;

            result = this.year.getYear() - m.getYear().getYear();

            if (result == 0) {

                result = this.month - m.getMonth();

            }

        }



        // 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;



    }



    /**

     * Returns the first millisecond of the month, evaluated using the supplied

     * calendar (which determines the time zone).

     *

     * @param calendar  the calendar.

     *

     * @return the first millisecond of the month.

     */

    public long getFirstMillisecond(final Calendar calendar) {



        final Day first = new Day(1, this.month, this.year.getYear());

        return first.getFirstMillisecond(calendar);



    }



    /**

     * Returns the last millisecond of the month, evaluated using the supplied

     * calendar (which determines the time zone).

     *

     * @param calendar  the calendar.

     *

     * @return the last millisecond of the month.

     */

    public long getLastMillisecond(final Calendar calendar) {



        final int eom = SerialDate.lastDayOfMonth(this.month, this.year.getYear());

        final Day last = new Day(eom, this.month, this.year.getYear());

        return last.getLastMillisecond(calendar);



    }



    /**

     * Parses the string argument as a month.

     * <P>

     * This method is required to accept the format "YYYY-MM".  It will also

     * accept "MM-YYYY". Anything else, at the moment, is a bonus.

     *

     * @param s  the string to parse.

     *

     * @return <code>null</code> if the string is not parseable, the month otherwise.

     */

    public static Month parseMonth(String s) {



        Month result = null;

        if (s != null) {



            // trim whitespace from either end of the string

            s = s.trim();



            final int i = Month.findSeparator(s);

            if (i != -1) {

                final String s1 = s.substring(0, i).trim();

                final String s2 = s.substring(i + 1, s.length()).trim();



                Year year = Month.evaluateAsYear(s1);

                final int month;

                if (year != null) {

                    month = SerialDate.stringToMonthCode(s2);

                    if (month == -1) {

                        throw new TimePeriodFormatException(

                            "Month.parseMonth(String): can't evaluate the month.");

                    }

                    result = new Month(month, year);

                }

                else {

                    year = Month.evaluateAsYear(s2);

                    if (year != null) {

                        month = SerialDate.stringToMonthCode(s1);

                        if (month == -1) {

                            throw new TimePeriodFormatException(

                                "Month.parseMonth(String): can't evaluate the month.");

                        }

                        result = new Month(month, year);

                    }

                    else {

                        throw new TimePeriodFormatException(

                            "Month.parseMonth(String): can't evaluate the year.");

                    }

                }



            }

            else {

                throw new TimePeriodFormatException(

                    "Month.parseMonth(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 where found, the

     *      position of the first occurence otherwise.

     */

    private static int findSeparator(final 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  the string to parse.

     *

     * @return <code>nukl</code> if the string is not parseable, the year otherwise.

     */

    private static Year evaluateAsYear(final String s) {



        Year result = null;

        try {

            result = Year.parseYear(s);

        }

        catch (TimePeriodFormatException e) {

            // suppress

        }

        return result;



    }



}

