//******************************************************************************
// Calendar.java:	Applet
//
//******************************************************************************
import java.applet.*;
import java.awt.*;
import java.util.*;

//==============================================================================
// Main Class for applet Calendar
//
//==============================================================================
public class Calendar extends Applet {
	Date datum;
	int m_monat, m_jahr;
	int[][] m_ausgabeMonat;
	CalendarMatrix calendarOutput;

	Font schrift;
	Label labelForMonth, labelForYear;
	Button incMonth, decMonth, incYear, decYear;

	public Calendar() {}

	public void init() {
		String param;
		datum = new Date();

		// month: Uebergabe Monat
		//----------------------------------------------------------------------
		param = getParameter("month");
		if (param != null)
			m_monat = Integer.parseInt(param);
		else m_monat = datum.getMonth()+1;

		// year: Uebergabe Jahr
		//----------------------------------------------------------------------
		param = getParameter("year");
		if (param != null)
			m_jahr = Integer.parseInt(param);
		else m_jahr = datum.getYear()+1900;

	    //Ausgabematrix erzeugen
		//----------------------------------------------------------------------
		calendarOutput = new CalendarMatrix(m_monat,m_jahr);

 	    //Dialogelemente erstellen und einblenden
		//----------------------------------------------------------------------
		schrift=new Font("Helvetica",Font.BOLD,14);
		
	        labelForYear=new Label(String.valueOf(m_jahr));
		labelForYear.setAlignment(Label.CENTER);
		labelForYear.setFont(schrift);
		labelForYear.resize(64,32);
		labelForMonth=new Label(" "+String.valueOf(m_monat)+" ");
		labelForMonth.setAlignment(Label.CENTER);
		labelForMonth.setFont(schrift);
		labelForMonth.resize(64,32);

		decMonth=new Button("<");
                decMonth.reshape(5,5,20,20);
 	        decMonth.setBackground(Color.lightGray);
	        incMonth=new Button(">");
	        incMonth.resize(32,32);
	        incMonth.setBackground(Color.lightGray);
	        decYear=new Button("<");
 	        decYear.resize(32,32);
	        decYear.setBackground(Color.lightGray);
	        incYear=new Button(">");
 	        incYear.resize(32,32);
	        incYear.setBackground(Color.lightGray);

	        this.add(decMonth,-1);
		this.add(labelForMonth,-1);
 	  	this.add(incMonth,-1);
  		this.add(decYear,-1);
		this.add(labelForYear,-1);
     		this.add(incYear,-1);

        	resize(256,256);

	}

	public void destroy() {}

	// Calendar Paint Handler
	//--------------------------------------------------------------------------
	public void paint(Graphics g) {

		//Liniengrafik erstellen und ausgeben
  		//----------------------------------------------------------------------
   	 	g.setColor(Color.black);

    		for (int i=1; i<9; i++) {
			g.drawLine(0,i*32-1,255,i*32-1);
 	   	} 

  	  	g.drawRect(0,0,255,255);
		g.drawLine(42,32,42,255);
 	   	g.drawLine(44,32,44,255);

		schrift=new Font("Helvetica",Font.ITALIC,12);
		g.setFont(schrift);

		g.drawString("Mo",10, 52);
		g.drawString("Di",10, 84);
		g.drawString("Mi",10,116);
		g.drawString("Do",10,148);
		g.drawString("Fr",10,180);
		g.drawString("Sa",10,212);
		g.drawString("So",10,244);

 	   	//Speziellen Monatskalender ausgeben
  		//----------------------------------------------------------------------
		schrift=new Font("Helvetica",Font.PLAIN,12);
		g.setFont(schrift);
		calendarOutput.outCalendarMatrix(g);
	}

	// Calendar Eventhandler
	//---------------------------------------------------------------------------
	public boolean action(Event e,Object arj) {
		if (e.target==decMonth) {
			m_monat=calendarOutput.decMonth();
			labelForMonth.setText(String.valueOf(m_monat));
			this.repaint();
			return true;
		}
		if (e.target==incMonth) {
			m_monat=calendarOutput.incMonth();
			labelForMonth.setText(String.valueOf(m_monat));
			this.repaint();
			return true;
		}
		if (e.target==decYear) {
			m_jahr=calendarOutput.decYear();
		        labelForYear.setText(String.valueOf(m_jahr));
			this.repaint();
			return true;
		}
		if (e.target==incYear) {
			m_jahr=calendarOutput.incYear();
            		labelForYear.setText(String.valueOf(m_jahr));
			this.repaint();
			return true;
		}
		else return false;
	}

    	public Color getBackground() {
		return Color.white;
    	}

}


//******************************************************************************
// CalendarMatrix.class
//
//******************************************************************************
class CalendarMatrix {

	private int calx, caly, caldayspace;  
	private int month, year;
        private int calmatrix[][];

	// Konstruktor der Klasse CalendarMatrix


	public CalendarMatrix(int calmonth, int calyear) { 
		calmatrix = new int[6][7];
		month=calmonth;
		year=calyear;
		caldayspace=32;
		calx=64;
		caly=52;				
	}

		 
	
	// Interne Methoden

    //
    // Berechnung des Wochentages: Notwendig, da die Standard Java Methode Date.getDay()
    // entgegen der Java-Spezifikation von Sun !kein! Datum vor 1970 und nach 2037 berechnet
    // 
	private int getWeekday(int i_year, int i_month, int i_day) {
	      if (i_month<3) {
 	        i_month+=10;
	        i_year-=1;
	      } else {
	        i_month-=2;
 	      } 
	      int y1 = i_year / 100;
 	      int y2 = i_year % 100;
	      Double y3 = new Double(2.6 * i_month - 0.1);
	      int dow = (i_day + y3.intValue() + y2 + (y2 / 4) + (y1 / 4) - (2 * y1) + 49) % 7;
		  if (dow == 0) dow=7;

 	      return dow;
  	}

	//
	//	Besetzt die Elemente der Matrix mit den zum Monat passenden Daten
	//
	private void setCalMatrix(Graphics g) {
		int maxday=0;
		int day=1;
		int weekday=1;
	
		// Wieviele Tage besitzt der Monat?
		switch (month) {
		case 1  : maxday=31; break;
		case 2  : maxday=31; 
			   if ((double)year/4 == year/4) maxday=29; 
			   	else maxday=28; 
		 	   break;
		case 3  : maxday=31; break;
		case 4  : maxday=30; break;
		case 5  : maxday=31; break;
		case 6  : maxday=30; break;
		case 7  : maxday=31; break;
		case 8  : maxday=31; break;
		case 9  : maxday=30; break;
		case 10 : maxday=31; break;
		case 11 : maxday=30; break;
		case 12 : maxday=31; break;
		}

		// Matrix wird mit den zum Monat gehörenden Werten belegt
		weekday = getWeekday(year,month,1);
		for (int x=0; x<6; x++) {
			for (int y=0; y<7; y++) {
				if ((x==0) && (weekday-1>y)) calmatrix[x][y]=0;
					else if (day>maxday) calmatrix[x][y]=0;
							else { calmatrix[x][y]=day;
						           day = day+1; 
							}
			}			
		}		
	}


	// Öffentliche Methoden


	//
	// Gibt den Inhalt der Matrix formatiert aus
	//
	public void outCalendarMatrix(Graphics g) {
		setCalMatrix(g);
		for (int x=0; x<6; x++) {
			for (int y=0; y<7; y++) {
				if (calmatrix[x][y]>9) 
					g.drawString((new Integer(calmatrix[x][y]).toString()), (caldayspace*x)+calx, (caldayspace*y)+caly);
				else if (calmatrix[x][y]>0)
					g.drawString((new Integer(calmatrix[x][y]).toString()), (caldayspace*x)+calx+6, (caldayspace*y)+caly);
				
			}
		}
	}


	//
	// Die folgenden Methoden In- bzw. Dekrementieren den Monat bzw das Jahr
	// unter Berücksichtigung der Grenzen 1-12 für den Monat bzw 1901-2099 für das Jahr
	//
	public int incMonth() {
		if (month<12) month = month+1;
		return(month);
	}

	
	public int decMonth() {
		if (month>1) month = month-1;
		return(month);
	}


	public int incYear() {
		if (year<2099) year = year+1;
		return(year);
	
	}

	
	public int decYear() {
		if (year>1901) year = year-1;
		return(year);
	}

}