#include<windows.h>

// winmm.lib をリンクする
#pragma comment(lib,"winmm")

#define SRATE	8000	//標本化周波数(1秒間のサンプル数)
#define F		400		//周波数(1秒間の波形数)

LRESULT CALLBACK WindowProc(HWND hWnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
	WAVEFORMATEX wfe;
	static HWAVEOUT hWaveOut;
	static WAVEHDR whdr;
	static LPBYTE lpWave;
	int i,len;

	static DWORD befvol;
	static int add=512;
	DWORD vol;

	HDC hdc;
	PAINTSTRUCT ps;
	char str[32];

	switch(uMsg){
		case WM_CREATE:
			wfe.wFormatTag=WAVE_FORMAT_PCM;
			wfe.nChannels=2;	//ステレオ
			wfe.wBitsPerSample=8;	//量子化ビット数
			wfe.nBlockAlign=wfe.nChannels * wfe.wBitsPerSample/8;
			wfe.nSamplesPerSec=SRATE;	//標本化周波数
			wfe.nAvgBytesPerSec=wfe.nSamplesPerSec * wfe.nBlockAlign;

			waveOutOpen(&hWaveOut,WAVE_MAPPER,&wfe,(DWORD)hWnd,0,CALLBACK_WINDOW);

			lpWave=(LPBYTE)calloc(wfe.nAvgBytesPerSec,2);	//2秒分

			len=SRATE/F;	//波長
			for(i=0;i<SRATE*2;i++){		//波形データ作成
				if(i%len < len/2){
					lpWave[2*i  ]=128+64;		//左
					lpWave[2*i+1]=128+64;		//右
				}else{
					lpWave[2*i  ]=128-64;		//左
					lpWave[2*i+1]=128-64;		//右
				}
			}

			whdr.lpData=(LPSTR)lpWave;
			whdr.dwBufferLength=wfe.nAvgBytesPerSec * 2;
			whdr.dwFlags=WHDR_BEGINLOOP | WHDR_ENDLOOP;
			whdr.dwLoops=10;

			waveOutPrepareHeader(hWaveOut,&whdr,sizeof(WAVEHDR));
			waveOutWrite(hWaveOut,&whdr,sizeof(WAVEHDR));

			waveOutGetVolume(hWaveOut,&befvol);		//起動前の音量を保存
			SetTimer(hWnd,1,50,NULL);
			return 0;
		case MM_WOM_DONE:
            waveOutWrite((HWAVEOUT)wParam,(LPWAVEHDR)lParam,sizeof(WAVEHDR));
            return 0;
		case WM_TIMER:
			waveOutGetVolume(hWaveOut,&vol);
			vol=LOWORD(vol);	//左
			if((int)vol+add <= 0){
				vol=0;
				add*=-1;
			}else if((int)vol+add >= 0xffff){
				vol=0xffff;
				add*=-1;
			}else{
				vol+=add;
			}
			waveOutSetVolume(hWaveOut,MAKELONG(vol,0xffff-vol));
			InvalidateRect(hWnd,NULL,TRUE);
			return 0;
		case WM_PAINT:
			hdc=BeginPaint(hWnd,&ps);
			waveOutGetVolume(hWaveOut,&vol);
			wsprintf(str,"左 = %5d , 右 = %5d",LOWORD(vol),HIWORD(vol));
			TextOut(hdc,0,0,str,lstrlen(str));
			EndPaint(hWnd,&ps);
			return 0;
		case WM_DESTROY:
			KillTimer(hWnd,1);
			waveOutSetVolume(hWaveOut,befvol);		//起動前の音量に戻す

			waveOutReset(hWaveOut);
			waveOutUnprepareHeader(hWaveOut,&whdr,sizeof(WAVEHDR));
			waveOutClose(hWaveOut);
			free(lpWave);
			PostQuitMessage(0);
			return 0;
	}
	return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

int WINAPI WinMain(
	HINSTANCE hInstance,HINSTANCE hPrevInstance,PSTR lpCmdLine,int nCmdShow)
{
	WNDCLASS wc;
	MSG msg;

	wc.style		 = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc	 = WindowProc;
	wc.cbClsExtra	 = 0;
	wc.cbWndExtra	 = 0;
	wc.hInstance	 = hInstance;
	wc.hIcon		 = LoadIcon(NULL,IDI_APPLICATION);
	wc.hCursor		 = LoadCursor(NULL,IDC_ARROW);
	wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wc.lpszMenuName	 = NULL;
	wc.lpszClassName = __FILE__;
	if(!RegisterClass(&wc)) return 0;

	HWND hWnd=CreateWindow(
		__FILE__,"音量の左右個別設定",
		WS_OVERLAPPEDWINDOW | WS_VISIBLE,
		CW_USEDEFAULT,CW_USEDEFAULT,
		CW_USEDEFAULT,CW_USEDEFAULT, 
		NULL,NULL,hInstance,NULL);
	if(hWnd==NULL) return 0;

	BOOL bRet;
	while((bRet=GetMessage(&msg,NULL,0,0))!=0){
		if(bRet==-1) break;
		DispatchMessage(&msg);
	}

	return (int)msg.wParam;
}