using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace PS7_Q2
{	//
	// Problem Set 7, Question 2
	// Written by Paul Hudak
	// November 5, 2006
	// 
	// A Simple Calculator
	// -------------------
	/* The specification:
	 * The width and height of the window form should be 225 and 320, respectively.
	 * The text for the top-level form is "Calculator".  There is a label component (size 175, 35)
	 * at the top (with white background color, text aligned to the right, size 16 regular font).
	 * There are 15 buttons (each size 48x23, size 14 bold font): ten of these are for digits;
	 * three are for the addition, subtraction, and multiplication buttons; the "C" button clears
	 * the text in the label to zero; and the "=" button prints out the result.  
	 */

	// create two new button types by inheriting from Button

	// numeric button (0-9)
	public class NumButton : Button
	{	// the value associated with a numeric button
		public int Value;
	}
	// operator button (+,-,*)
	public class OpButton : Button
	{	// the binary operator (delegate) associated with an operator button
		public BinOp Op;
	}

	// delegate to capture the binary operator
	public delegate int BinOp(int i, int j);

	// the main calculator Form
	public class Form1 : System.Windows.Forms.Form
	{	// create widgets
		
		// array of numeric buttons
		private NumButton[] buts = {new NumButton(), new NumButton(), new NumButton(), 
									new NumButton(), new NumButton(), new NumButton(),
									new NumButton(), new NumButton(), new NumButton(),
									new NumButton() };
		private Label display  = new Label();		// display area
		private OpButton add   = new OpButton();	// add button
		private OpButton sub   = new OpButton();	// substract button
		private OpButton mul   = new OpButton();	// multiply button
		private Button clear   = new Button();		// clear button
		private Button enter   = new Button();		// enter button

		// instance variables for calculator state
		private int num       = 0;					// the current number in display
		private int hidden    = 0;					// the hidden number
		private	bool flag	  = false;				// hidden number not valid
		private BinOp selectD = new BinOp(SelectD);	// a binop that selects the Display
		private BinOp binOp;						// the current binary operator
		private int lastBut   = 0;					// last button (0=Clear, 1=Number,
													//				2=Op, 3=Enter)

		private System.ComponentModel.Container components = null;

		public Form1()
		{
			// Required for Windows Form Designer support
			InitializeComponent();

			// set form properties
			Size = new Size(225,320);
			Text = "Calculator";
			
			// create two fonts
			Font f1 = new Font("Comic Sans MS", 16, FontStyle.Bold);
			Font f2 = new Font("Comic Sans MS", 14, FontStyle.Bold);

			// set all properties for each of the 10 numeric buttons
			for (int i=0; i<10; i=i+1)
			{
				buts[i].Font     = f2;
				buts[i].Text     = i.ToString();
				buts[i].Value    = i;
				buts[i].Location = new Point(20+(i%3)*68,75+(i/3)*43);
				buts[i].Size     = new Size(48,23);
				buts[i].Click   += new EventHandler(NumberClick);
				Controls.Add(buts[i]);
			}

			// set display properties
			display.TextAlign   = ContentAlignment.MiddleRight;  // System.Drawing.ContentAlignment
			display.BorderStyle = BorderStyle.Fixed3D;
			display.BackColor   = Color.White;

			// set fonts
			display.Font = f1;
			add.Font     = f2;
			sub.Font     = f2;
			mul.Font     = f2;
			clear.Font   = f2;
			enter.Font   = f2;

			// set text properties
			display.Text = "0";
			add.Text     = "+";
			sub.Text     = "-";
			mul.Text     = "*";
            clear.Text   = "C";
			enter.Text   = "=";

			// set size properties
            display.Size = new Size(175,35);
			add.Size     = new Size(48,23);
			sub.Size     = new Size(48,23);
			mul.Size     = new Size(48,23);
			clear.Size   = new Size(48,23);
			enter.Size   = new Size(48,23);

			// set location properties
			display.Location = new Point(20,20);
			add.Location     = new Point( 88,75+3*43);
			sub.Location     = new Point(156,75+3*43);
			mul.Location     = new Point( 20,75+4*43);
			clear.Location   = new Point( 88,75+4*43);
			enter.Location   = new Point(156,75+4*43);

			// set Op property in each operator button to appropriate delegate
			add.Op = new BinOp(AddOp);
			sub.Op = new BinOp(SubOp);
			mul.Op = new BinOp(MulOp);
			// set default binOp
			binOp  = selectD;

			// add controls to form
			Controls.Add(display);
			Controls.Add(add);
			Controls.Add(sub);
			Controls.Add(mul);
			Controls.Add(clear);
			Controls.Add(enter);

			// register event handlers
			enter.Click += new EventHandler(EnterClick);
			clear.Click += new EventHandler(ClearClick);
			add.Click   += new EventHandler(OpClick);
			sub.Click   += new EventHandler(OpClick);
			mul.Click   += new EventHandler(OpClick);
		}

		/* The logic for the operation of the calculator is more complex than it first appears.
		 * We need to account for all possible transitions of key presses.  I believe that the
		 * following captures the behavior of the Windows XP Calculator.
		 * 
		 * Let D be the display number, H the hidden number, Op the current operation, and
		 * F the boolean flag saying whether or not the hidden number is valid.
		 * Initial state: D=0, H=0, F=false, Op=selectD, where selectD(D,H) = D
		 * 
		 * Clear behaves the same regardless of when it is pressed -- it returns the
		 * calculator to its initial state -- and thus it's not shown below.  For the other
		 * three categories of keys, we consider the previous key in each case, and also
		 * whether or not a hidden number is active.
		 /* 
		 *			  |		Previous key press:
		 * Key-press  |		Clear(0)	Number(1)			Op(2)				Enter(3)
		 * ---------------------------------------------------------------------------------------------
		 * Number	  |		upd D		upd D				D=0, upd D			H=0, D=0, F=false, upd D
		 * Op		  |		upd Op		F:  upd Op, Swap,	upd Op				H=D, upd Op
		 *            |						D=Op(D,H)
		 *			  |					!F: upd Op, H=D,
		 *			  |						F=true
		 * Enter	  |		noop		F:  Swap,D=Op(D,H)	H=D, D=Op(D,H)		D=Op(D,H)
		 *			  |					!F: H=D, F=true
		 */

		protected void ClearClick(Object sender, EventArgs e)
		{	// reset all instance variables and clear display
			num    = 0;
			hidden = 0;
			binOp  = selectD;
			flag   = false;
			display.Text = num.ToString();
			lastBut = 0;
		}

		protected void NumberClick(Object sender, EventArgs e)
		{	// follows logic in chart above
			switch (lastBut)
			{
				case 2:
					num = 0;
					break;
				case 3:
					hidden = 0;
					num = 0;
					flag = false;
					break;
			}
			// update num by multiplying by 10 and adding current key press
            num = 10*num + ((NumButton)sender).Value;
			display.Text = num.ToString();
			lastBut = 1;
		}

		protected void OpClick(Object sender, EventArgs e)
		{	// follows logic in chart above
			binOp = ((OpButton)sender).Op;
			switch (lastBut)
			{
				case 1:
					if (flag)
					{	Swap(); Compute();
					}
					else
					{	hidden = num; flag = true;
					}
					break;
				case 3:
					hidden = num;
					break;
			}
            lastBut = 2;
		}

		protected void EnterClick(Object sender, EventArgs e)
		{	// follows logic in chart above
			switch (lastBut)
			{
				case 0:		// last button was Clear
					break;
				case 1:		// last button was Number
					if (flag)
					{	Swap();	Compute();
					}
					else
					{	hidden = num; flag = true;
					}
					break;
				case 2:		// last button was Op
					hidden = num;	// duplicate num
					Compute();
					break;
				case 3:		// last button was Enter
					Compute();
					break;
			}
			lastBut = 3;
		}

		private void Swap()
		{	// swaps display num with hidden num
			int tmp = hidden;
			hidden = num;
			num = tmp;
		}

		private void Compute()
		{	// use delegate to do computation
			num = binOp(num,hidden);
			// update display
			display.Text = num.ToString();
		}

		// define these because I don't know how to
		// reference C#'s binary operators as values
		private static int AddOp(int i, int j)
		{	return (i+j);
		}
		private static int SubOp(int i, int j)
		{	return (i-j);
		}
		private static int MulOp(int i, int j)
		{	return (i*j);
		}
		private static int SelectD(int d, int h)
		{	return (h);
		}

		// Clean up any resources being used.
		protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
				if (components != null) 
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}

		#region Windows Form Designer generated code
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
			this.components = new System.ComponentModel.Container();
			this.Size = new System.Drawing.Size(300,300);
			this.Text = "Form1";
		}
		#endregion

		// The main entry point for the application.
		[STAThread]
		static void Main() 
		{
			Application.Run(new Form1());
		}
	}
}