/*

Calculator Program Revisited

June 7th, 2006

*/

#include <windows.h>

#include <cstring>

using namespace std;    //already include <stdlib.h> when using namespace std;

                        //Data conversion routine is atof() function convert strings to

                        //floating-point numbers. The syntax for the atof() function is

                        //variable = atof(string);

void setNumbers(char szCurNum[10]);

void runCalculation();

char cOperation = '0';

char szFirstNum[10];

double dFirstNum = 0;

char szSecondNum[10];

double dSecondNum = 0;

LRESULT CALLBACK WINAPI MainWndProc (HWND, UINT, WPARAM, LPARAM);

HWND hWnd; HWND hwndEdit; HWND hwndButtonPlus;

HWND hwndButtonMinus; HWND hwndButtonMultiply;

HWND hwndButtonDivide; HWND hwndButton9;

HWND hwndButton8; HWND hwndButton7;

HWND hwndButton6; HWND hwndButton5;

HWND hwndButton4; HWND hwndButton3;

HWND hwndButton2; HWND hwndButton1;

HWND hwndButton0; HWND hwndButtonPoint;

HWND hwndButtonEquals; HWND hwndButtonClear;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)

{

    WNDCLASS wc;

    wc.lpszClassName = "CalculatorClass";

    wc.lpfnWndProc = MainWndProc;

    wc.style = CS_OWNDC | CS_VREDRAW | CS_HREDRAW;

    wc.hInstance = hInstance;

    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);

    wc.hCursor = LoadCursor(NULL, IDC_ARROW);

    wc.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);

    wc.lpszMenuName = "";

    wc.cbClsExtra = 0;

    wc.cbWndExtra = 0;

    RegisterClass(&wc);

    hWnd = CreateWindow("CalculatorClass", "Calculator", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 185, 265, NULL, NULL, hInstance, NULL);

    hwndEdit = CreateWindow("EDIT", NULL, WS_VISIBLE | WS_CHILD | WS_BORDER | ES_LEFT, 10, 10, 155, 20, hWnd, NULL, hInstance, NULL);

    hwndButtonPlus = CreateWindow( "BUTTON", "+", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 10, 40, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButtonMinus = CreateWindow( "BUTTON", "-", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 50, 40, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButtonMultiply = CreateWindow( "BUTTON", "*", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 90, 40, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButtonDivide = CreateWindow( "BUTTON", "/", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 130, 40, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton6 = CreateWindow( "BUTTON", "6", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 10, 80, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton7 = CreateWindow( "BUTTON", "7", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 50, 80, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton8 = CreateWindow( "BUTTON", "8", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 90, 80, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton9 = CreateWindow( "BUTTON", "9", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 130, 80, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton2 = CreateWindow( "BUTTON", "2", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 10, 120, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton3 = CreateWindow( "BUTTON", "3", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 50, 120, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton4 = CreateWindow( "BUTTON", "4", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 90, 120, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton5 = CreateWindow( "BUTTON", "5", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 130, 120, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton0 = CreateWindow( "BUTTON", "0", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 10, 160, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButton1 = CreateWindow( "BUTTON", "1", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 50, 160, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButtonPoint = CreateWindow( "BUTTON", ".", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 90, 160, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButtonEquals = CreateWindow( "BUTTON", "=", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 130, 160, 35, 35, hWnd, NULL, hInstance, NULL);

    hwndButtonClear = CreateWindow( "BUTTON", "Clear", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, 10, 200, 155, 25, hWnd, NULL, hInstance, NULL);

    ShowWindow (hWnd, nCmdShow);

    MSG msg;

    BOOL bRet;

    while ((bRet = GetMessage ( &msg, NULL, 0, 0)) !=0)

    {

        if (bRet == -1)

        {

            //handle this error and probably exit

            break;

        }

        else

        {

            TranslateMessage (&msg);

            DispatchMessage (&msg);

        }

    }

    return (int) msg.wParam;

}

LRESULT CALLBACK WINAPI MainWndProc (HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)

{

    HWND hwndCtl = (HWND) lParam;

    switch (msg)

    {

    case WM_COMMAND:

            switch (wParam)

            {

                case BN_CLICKED:

                    if (hwndCtl == hwndButton1)

                        setNumbers("1");

                    else if (hwndCtl == hwndButton2)

                        setNumbers("2");

                    else if (hwndCtl == hwndButton3)

                        setNumbers("3");

                    else if (hwndCtl == hwndButton4)

                        setNumbers("4");

                    else if (hwndCtl == hwndButton5)

                        setNumbers("5");

                    else if (hwndCtl == hwndButton6)

                        setNumbers("6");

                    else if (hwndCtl == hwndButton7)

                        setNumbers("7");

                    else if (hwndCtl == hwndButton8)

                        setNumbers("8");

                    else if (hwndCtl == hwndButton9)

                        setNumbers("9");

                    else if (hwndCtl == hwndButton0)

                        setNumbers("0");

                    else if (hwndCtl == hwndButtonPoint)

                        setNumbers(".");

                    else if (hwndCtl == hwndButtonPlus)

                    {

                        cOperation = '+';

                        dFirstNum = atof(szFirstNum);

                    }

                    else if (hwndCtl == hwndButtonMinus)

                    {

                        cOperation = '-';

                        dFirstNum = atof(szFirstNum);

                    }

                    else if (hwndCtl == hwndButtonMultiply)

                    {

                        cOperation = '*';

                        dFirstNum = atof(szFirstNum);

                    }

                    else if (hwndCtl == hwndButtonDivide)

                    {

                        cOperation = '/';

                        dFirstNum = atof(szFirstNum);

                    }

                    else if (hwndCtl == hwndButtonEquals)

                    {

                        dSecondNum = atof(szSecondNum);

                        runCalculation();

                    }

                    else if (hwndCtl == hwndButtonClear)

                    {

                        cOperation = '0';

                        strcpy(szFirstNum, "");

                        dFirstNum = 0;

                        strcpy(szSecondNum, "");

                        dSecondNum = 0;

                        SetWindowText(hwndEdit, "");

                    }

            }

            break;

    case WM_DESTROY:

            PostQuitMessage(0);

            return 0;

        default:

            return DefWindowProc(hWnd, msg, wParam, lParam);

    }

    return 0;

}

void setNumbers(char szCurNum[10])

{

    if (cOperation == '0')

    {

        strcat(szFirstNum, szCurNum);

        SetWindowText(hwndEdit, szFirstNum);

    }

    else

    {

        strcat(szSecondNum, szCurNum);

        SetWindowText(hwndEdit, szSecondNum);

    }

}

void runCalculation()

{

    double dResult = 0;

    char szResult[25];

    if (cOperation == '+')

    {

        dResult = dFirstNum + dSecondNum;

    }

    else if (cOperation == '-')

    {

        dResult = dFirstNum - dSecondNum;

    }

    else if (cOperation == '*')

    {

        dResult = dFirstNum * dSecondNum;

    }

    else if (cOperation == '/')

    {

        dResult = dFirstNum / dSecondNum;

    }

    _gcvt(dResult, 10, szResult);

    SetWindowText(hwndEdit, szResult);

    cOperation = '0';

    strcpy(szFirstNum, szResult);

    dFirstNum = 0;

    strcpy(szSecondNum, "");

    dSecondNum = 0;

}