// coop_tone: a minimal WASAPI render process that plays a continuous sine wave on
// the default output endpoint. Used as a known audio source for the audio-mirror
// integration test (a real process actively rendering audio to capture from).
//
//   coop_tone [seconds] [frequencyHz]
//
// Default: runs ~3 s at 440 Hz. Prints "TONE_RENDERING" once audio is flowing so
// a parent can synchronize before it starts capturing.

#include <atomic>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <vector>

#include <windows.h>

#include <audioclient.h>
#include <mmdeviceapi.h>
#include <mmreg.h>

namespace
{

constexpr double kPi = 3.14159265358979323846;

template <typename T>
void release(T*& p)
{
	if (p)
	{
		p->Release();
		p = nullptr;
	}
}

} // namespace

int wmain(int argc, wchar_t** argv)
{
	const double seconds = (argc > 1) ? _wtof(argv[1]) : 3.0;
	const double freq = (argc > 2) ? _wtof(argv[2]) : 440.0;

	if (FAILED(CoInitializeEx(nullptr, COINIT_MULTITHREADED)))
	{
		std::fprintf(stderr, "CoInitializeEx failed\n");
		return 1;
	}

	IMMDeviceEnumerator* enumerator = nullptr;
	IMMDevice* endpoint = nullptr;
	IAudioClient* client = nullptr;
	IAudioRenderClient* render = nullptr;
	WAVEFORMATEX* fmt = nullptr;
	int rc = 1;

	do
	{
		if (FAILED(CoCreateInstance(__uuidof(MMDeviceEnumerator), nullptr, CLSCTX_ALL,
		                            __uuidof(IMMDeviceEnumerator), reinterpret_cast<void**>(&enumerator))))
		{
			break;
		}
		if (FAILED(enumerator->GetDefaultAudioEndpoint(eRender, eConsole, &endpoint)))
		{
			break;
		}
		if (FAILED(endpoint->Activate(__uuidof(IAudioClient), CLSCTX_ALL, nullptr,
		                              reinterpret_cast<void**>(&client))))
		{
			break;
		}
		if (FAILED(client->GetMixFormat(&fmt)))
		{
			break;
		}

		HANDLE buffer_event = CreateEventW(nullptr, FALSE, FALSE, nullptr);
		constexpr REFERENCE_TIME kBuffer = 30 * 10000; // 30 ms
		if (FAILED(client->Initialize(AUDCLNT_SHAREMODE_SHARED, AUDCLNT_STREAMFLAGS_EVENTCALLBACK, kBuffer,
		                              0, fmt, nullptr)))
		{
			break;
		}
		client->SetEventHandle(buffer_event);
		if (FAILED(client->GetService(__uuidof(IAudioRenderClient), reinterpret_cast<void**>(&render))))
		{
			break;
		}
		UINT32 buffer_frames = 0;
		client->GetBufferSize(&buffer_frames);

		const bool is_float =
		    fmt->wFormatTag == WAVE_FORMAT_IEEE_FLOAT ||
		    (fmt->wFormatTag == WAVE_FORMAT_EXTENSIBLE &&
		     reinterpret_cast<WAVEFORMATEXTENSIBLE*>(fmt)->SubFormat == KSDATAFORMAT_SUBTYPE_IEEE_FLOAT);
		const unsigned channels = fmt->nChannels;
		const double rate = fmt->nSamplesPerSec;
		const double step = 2.0 * kPi * freq / rate;

		auto write_frames = [&](UINT32 frames, double& phase) {
			BYTE* data = nullptr;
			if (FAILED(render->GetBuffer(frames, &data)))
			{
				return;
			}
			for (UINT32 i = 0; i < frames; ++i)
			{
				const double s = std::sin(phase) * 0.25; // -12 dB, gentle
				phase += step;
				if (phase > 2.0 * kPi)
				{
					phase -= 2.0 * kPi;
				}
				for (unsigned c = 0; c < channels; ++c)
				{
					if (is_float)
					{
						reinterpret_cast<float*>(data)[i * channels + c] = static_cast<float>(s);
					}
					else
					{
						reinterpret_cast<INT16*>(data)[i * channels + c] =
						    static_cast<INT16>(s * 32767.0);
					}
				}
			}
			render->ReleaseBuffer(frames, 0);
		};

		double phase = 0.0;
		write_frames(buffer_frames, phase); // pre-roll
		client->Start();
		std::printf("TONE_RENDERING pid=%lu %.0fHz %s %.0fHz %uch\n", GetCurrentProcessId(), freq,
		            is_float ? "float" : "pcm16", rate, channels);
		std::fflush(stdout);

		const DWORD end_tick = GetTickCount() + static_cast<DWORD>(seconds * 1000.0);
		while (GetTickCount() < end_tick)
		{
			if (WaitForSingleObject(buffer_event, 200) != WAIT_OBJECT_0)
			{
				continue;
			}
			UINT32 padding = 0;
			if (FAILED(client->GetCurrentPadding(&padding)))
			{
				break;
			}
			write_frames(buffer_frames - padding, phase);
		}
		client->Stop();
		CloseHandle(buffer_event);
		rc = 0;
	} while (false);

	release(render);
	release(client);
	release(endpoint);
	release(enumerator);
	if (fmt)
	{
		CoTaskMemFree(fmt);
	}
	CoUninitialize();
	return rc;
}