#define _WIN32_WINNT 0x500

#include <windows.h>
#include <tchar.h>
//#define NXDEBUG
#ifdef NXDEBUG
#include <stdio.h>
#endif

TCHAR	g_prog_dir[MAX_PATH*2];
DWORD	g_prog_dir_len;
HHOOK	g_khook;
HANDLE  g_hEvent;
int mode_3s = 0;

static void
cswSetLayoutRot(HWND hWnd, int isCtrl)
{
	if (isCtrl)
		PostMessage(hWnd,WM_INPUTLANGCHANGEREQUEST,0,(LPARAM)HKL_PREV);
	else
		PostMessage(hWnd,WM_INPUTLANGCHANGEREQUEST,0,(LPARAM)HKL_NEXT);
}

static void
cswSetLayout(HWND hWnd, int isCtrl)
{
	if (!mode_3s)
		return cswSetLayoutRot(hWnd, isCtrl);
	HKL layouts[3];
	int r = GetKeyboardLayoutList(3, layouts);
	if (r != 3)
		return cswSetLayoutRot(hWnd, isCtrl);
	HKL current = GetKeyboardLayout(GetWindowThreadProcessId(hWnd, NULL));
#ifdef NXDEBUG
	char buf[1000];
	_snprintf(buf, sizeof(buf), "current=%lx, layouts[0]=%lx, layouts[1]=%lx, layouts[2]=%lx\n",
		(long)current, (long)layouts[0], (long)layouts[1], (long)layouts[2]);
	OutputDebugStringA(buf);
#endif
	if (current == layouts[0]) {
		PostMessage(hWnd, WM_INPUTLANGCHANGEREQUEST, 0, (LPARAM)(isCtrl ? layouts[2] : layouts[1]));
	} else if (current == layouts[1]) {
		PostMessage(hWnd, WM_INPUTLANGCHANGEREQUEST, 0, (LPARAM)(isCtrl ? layouts[2] : layouts[0]));
	} else {
		PostMessage(hWnd, WM_INPUTLANGCHANGEREQUEST, 0, (LPARAM)(isCtrl ? layouts[1] : layouts[0]));
	}
}

LRESULT CALLBACK KbdHook(int nCode, WPARAM wParam, LPARAM lParam) {
  if (nCode<0)
    return CallNextHookEx(g_khook, nCode, wParam, lParam);
  if (nCode==HC_ACTION) {
    KBDLLHOOKSTRUCT   *ks=(KBDLLHOOKSTRUCT*)lParam;
    if (ks->vkCode==VK_CAPITAL) {
	  int shs = 65535 & GetKeyState(VK_SHIFT);
	  int cts = 65535 & GetKeyState(VK_CONTROL);
#ifdef NXDEBUG
	  int cls = 65535 & GetKeyState(VK_CAPITAL);
	  char buf[1000];
	  sprintf(buf, "KbdHook: nCode=%d wParam=%x lParam=%lx vkCode=%d cls=%x shs=%x\n",
			nCode, (int)wParam, (long)lParam, (int)ks->vkCode, (int)cls, (int)shs);
	  OutputDebugStringA(buf);
#endif
	  if ((shs & 0x8000) != 0) {
#ifdef NXDEBUG
			OutputDebugStringA("seeing original Caps request, passing by\n");
#endif
			goto skip;
	  }
      if (wParam==WM_KEYDOWN) {
#ifdef NXDEBUG
		OutputDebugStringA("seeing Caps-as-language, sending language change request\n");
#endif
		HWND hWnd=GetForegroundWindow();
		if (hWnd) {
			cswSetLayout(hWnd, ((cts & 0x8000) != 0));
		}
	  }
      return 1;
    }
  }
skip:
  return CallNextHookEx(g_khook,nCode,wParam,lParam);
}

void  failedx(const TCHAR *msg) {
  MessageBox(NULL,msg,_T("Error"),MB_OK|MB_ICONERROR);
  ExitProcess(1);
}

void  failed(const TCHAR *msg) {
  DWORD		fm;
  TCHAR		*msg1,*msg2;
  const TCHAR	*args[2];
  
  fm=FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM|
      FORMAT_MESSAGE_IGNORE_INSERTS,
      NULL,GetLastError(),0,(LPTSTR)&msg1,0,NULL);
  if (fm==0)
    ExitProcess(1);
  args[0]=msg;
  args[1]=msg1;
  fm=FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_STRING|
      FORMAT_MESSAGE_ARGUMENT_ARRAY,
      _T("%1: %2"),0,0,(LPTSTR)&msg2,0,(va_list*)&args[0]);
  if (fm==0)
    ExitProcess(1);
  MessageBox(NULL,msg2,_T("Error"),MB_OK|MB_ICONERROR);
  ExitProcess(1);
}

void CALLBACK TimerCb(HWND hWnd,UINT uMsg,UINT_PTR idEvent,DWORD dwTime) {
  if (WaitForSingleObject(g_hEvent,0)==WAIT_OBJECT_0)
    PostQuitMessage(0);
}

int WINAPI CALLBACK WinMain(
    HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    LPSTR lpCmdLine,
    int nCmdShow
					   )
{
  MSG	  msg;
  DWORD	  sz;
  BOOL	  fQuit=FALSE;
  TCHAR	  *cmd;

  cmd=GetCommandLine();
  sz=lstrlen(cmd);
  if (sz>2 && (lstrcmp(cmd+sz-2,_T(" q"))==0) || (lstrcmp(cmd+sz-2,_T(" Q"))==0))
    fQuit=TRUE;
  if (sz>2 && (lstrcmp(cmd+sz-3,_T(" 3s"))==0) || (lstrcmp(cmd+sz-3,_T(" 3S"))==0))
    mode_3s = TRUE;
  
  g_hEvent=CreateEvent(NULL,TRUE,FALSE,_T("HaaliLSwitch"));
  if (g_hEvent==NULL)
    failed(_T("CreateEvent()"));
  if (GetLastError()==ERROR_ALREADY_EXISTS) {
    if (fQuit) {
      SetEvent(g_hEvent);
      goto quit;
    }
    failedx(_T("CPSwitch or LSwitch is already running!"));
  }

  if (fQuit)
    failedx(_T("CPSwitch or LSwitch is not running!"));

  sz=GetModuleFileName(NULL,g_prog_dir,MAX_PATH);
  if (sz==0)
    failed(_T("GetModuleFileName()"));
  if (sz==MAX_PATH)
    failedx(_T("Module file name is too long."));
  while (sz>0 && g_prog_dir[sz-1]!=_T('\\'))
    --sz;
  g_prog_dir_len=sz;
  
  if (SetTimer(NULL,0,500,TimerCb)==0)
    failed(_T("SetTimer()"));

  g_khook=SetWindowsHookEx(WH_KEYBOARD_LL,KbdHook,GetModuleHandle(0),0);
  if (g_khook==0)
    failed(_T("SetWindowsHookEx()"));

  while (GetMessage(&msg,0,0,0)) {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
  }
  
  UnhookWindowsHookEx(g_khook);
quit:
  CloseHandle(g_hEvent);

  ExitProcess(0);
}