#include <windows.h>
#include <time.h>
#include <math.h>
#include <string.h>
#include <stdio.h>
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);

char szClassName[ ] = "WindowsApp";
HWND hwnd;
HWND hbutton1;
HWND hEditA1;
HWND hbutton2;
HWND hEditA2;
HWND hbutton3;

char filename_1[1000];
char filename_2[1000];
int WINAPI WinMain (HINSTANCE hThisInstance,
                    HINSTANCE hPrevInstance,
                    LPSTR lpszArgument,
                    int nFunsterStil)

{
MSG messages;
WNDCLASSEX wincl;

wincl.hInstance = hThisInstance;
wincl.lpszClassName = szClassName;
wincl.lpfnWndProc = WindowProcedure;
wincl.style = CS_DBLCLKS;
wincl.cbSize = sizeof (WNDCLASSEX);

wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
wincl.lpszMenuName = NULL;
wincl.cbClsExtra = 0;
wincl.cbWndExtra = 0;

wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

if (!RegisterClassEx (&wincl))
return 0;

hwnd = CreateWindowEx (
0,
szClassName,
"files",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,
CW_USEDEFAULT,
700,
700,
HWND_DESKTOP,
NULL,
hThisInstance,
NULL
);

HWND hbutton1 = CreateWindow(TEXT("button"),
TEXT("Открыть файл"),
WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON ,
0, 0, 150, 25,
hwnd, (HMENU)10000, hThisInstance, NULL);

hEditA1=CreateWindow(TEXT("Edit"), 
 TEXT(""), 
WS_CHILD | WS_VISIBLE | WS_BORDER, 
 150, 0, 500, 25, 
hwnd, NULL, NULL, NULL);

HWND hbutton2 = CreateWindow(TEXT("button"),
TEXT("Открыть файл"),
WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON ,
0, 100, 150, 25,
hwnd, (HMENU)10001, hThisInstance, NULL);

hEditA2=CreateWindow(TEXT("Edit"), 
 TEXT(""), 
WS_CHILD | WS_VISIBLE | WS_BORDER, 
 150, 100, 500, 25, 
hwnd, NULL, NULL, NULL);

HWND hbutton3 = CreateWindow(TEXT("button"),
TEXT("Сравнить файлы"),
WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON ,
0, 200, 150, 25,
hwnd, (HMENU)10002, hThisInstance, NULL);
 

ShowWindow (hwnd, nFunsterStil);

while (GetMessage (&messages, NULL, 0, 0))
{
TranslateMessage(&messages);
DispatchMessage(&messages);
}

return messages.wParam;
}

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{

case WM_COMMAND:
{
if (LOWORD(wParam)==10000)
{

 char filename[ MAX_PATH ];

  OPENFILENAME ofn;
    ZeroMemory( &filename, sizeof( filename ) );
    ZeroMemory( &ofn,      sizeof( ofn ) );
    ofn.lStructSize  = sizeof( ofn );
    ofn.hwndOwner    = NULL; 
    ofn.lpstrFilter  = "Any File\0*.*\0";
    ofn.lpstrFile    = filename;
    ofn.nMaxFile     = MAX_PATH;
    ofn.lpstrTitle   = "Выбери файл";
    ofn.Flags        = OFN_DONTADDTORECENT | OFN_FILEMUSTEXIST;

GetOpenFileNameA( &ofn );

SetWindowText(hEditA1,filename);
strcpy(filename_1,filename);

}

if (LOWORD(wParam)==10001)
{
 char filename[ MAX_PATH ];

  OPENFILENAME ofn;
    ZeroMemory( &filename, sizeof( filename ) );
    ZeroMemory( &ofn,      sizeof( ofn ) );
    ofn.lStructSize  = sizeof( ofn );
    ofn.hwndOwner    = NULL; 
    ofn.lpstrFilter  = "Any File\0*.*\0";
    ofn.lpstrFile    = filename;
    ofn.nMaxFile     = MAX_PATH;
    ofn.lpstrTitle   = "Выбери файл";
    ofn.Flags        = OFN_DONTADDTORECENT | OFN_FILEMUSTEXIST;

GetOpenFileNameA( &ofn );

SetWindowText(hEditA2,filename);

strcpy(filename_2,filename);

}

if (LOWORD(wParam)==10002)
{

FILE *pFile1 = fopen(filename_1,"r");
FILE *pFile2 = fopen(filename_2,"r");

fseek( pFile1, 0, SEEK_END );

int Size1 = ftell( pFile1 );

fseek( pFile2, 0, SEEK_END );

int Size2 = ftell( pFile2 );

if (Size1 != Size2)
{
MessageBox(hwnd,(LPSTR)"Файлы не равны", "Сообщение", MB_OK);
break;
}
rewind( pFile1 );
rewind( pFile2 );

int found = 0;
while (1)
{
int ch1 = fgetc(pFile1);
int ch2 = fgetc(pFile2);

if (ch1 == EOF) break;
if (ch1 == ch2) {
found = 1;
}
else
{
found = 2;
}
}    

if (found == 1)
{
MessageBox(hwnd,(LPSTR)"Файлы равны", "Сообщение", MB_OK);
}

if (found == 2)
{
MessageBox(hwnd,(LPSTR)"Файлы не равны", "Info", MB_OK);
}

}

}

break;

case WM_DESTROY:
PostQuitMessage (0);
break;
default:
return DefWindowProc (hwnd, message, wParam, lParam);
}

return 0;
}