/* WASAPI backend for audio playback
 *
 * Based on mmozeiko's WASAPI examples
 * https://gist.github.com/mmozeiko/5a5b168e61aff4c1eaec0381da62808f#file-win32_wasapi-h
 */

PB_WSP_SharedState PB_WSP_shared_state = ZI;

////////////////////////////////
//~ Startup

void  PB_StartupCore(void)
{
    __prof;
    PB_WSP_SharedState *g = &PB_WSP_shared_state;
    PB_WSP_InitializeWasapi();
    /* Start playback job */
    RunJob(1, PB_WSP_PlaybackJob, JobPool_Audio, JobPriority_High, &g->PB_WSP_PlaybackJob_counter, 0);
    OnExit(&PB_WSP_Shutdown);
}

ExitFuncDef(PB_WSP_Shutdown)
{
    __prof;
    PB_WSP_SharedState *g = &PB_WSP_shared_state;
    Atomic32FetchSet(&g->shutdown, 1);
    YieldOnCounter(&g->PB_WSP_PlaybackJob_counter);
}

void PB_WSP_InitializeWasapi(void)
{
    PB_WSP_SharedState *g = &PB_WSP_shared_state;
    u64 sample_rate = PB_SampleRate;
    u64 channel_count = 2;
    u32 channel_mask = SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT;

    /* Create enumerator to get audio device */
    IMMDeviceEnumerator *enumerator;
    CoCreateInstance(&CLSID_MMDeviceEnumerator, 0, CLSCTX_ALL, &IID_IMMDeviceEnumerator, (LPVOID *)&enumerator);

    /* Get default playback device */
    IMMDevice *device;
    IMMDeviceEnumerator_GetDefaultAudioEndpoint(enumerator, eRender, eConsole, &device);
    IMMDeviceEnumerator_Release(enumerator);

    /* Create audio client for device */
    IMMDevice_Activate(device, &IID_IAudioClient, CLSCTX_ALL, 0, (LPVOID *)&g->client);
    IMMDevice_Release(device);

    WAVEFORMATEXTENSIBLE format_ex = {
        .Format = {
            .wFormatTag = WAVE_FORMAT_EXTENSIBLE,
            .nChannels = (WORD)channel_count,
            .nSamplesPerSec = (WORD)sample_rate,
            .nAvgBytesPerSec = (DWORD)(sample_rate * channel_count * sizeof(f32)),
            .nBlockAlign = (WORD)(channel_count * sizeof(f32)),
            .wBitsPerSample = (WORD)(8 * sizeof(f32)),
            .cbSize = sizeof(format_ex) - sizeof(format_ex.Format),
        },
        .Samples.wValidBitsPerSample = 8 * sizeof(f32),
        .dwChannelMask = channel_mask,
        .SubFormat = MEDIASUBTYPE_IEEE_FLOAT,
    };
    WAVEFORMATEX *wfx = &format_ex.Format;

#if 0
    b32 client_initialized = 0;
    IAudioClient3 *client3;
    if (SUCCEEDED(IAudioClient_QueryInterface(g->client, &IID_IAudioClient3, (LPVOID *)&client3)))
    {
        /* From Martins: Minimum buffer size will typically be 480 samples (10msec @ 48khz)
         * but it can be 128 samples (2.66 msec @ 48khz) if driver is properly installed
         * see bullet-point instructions here: https://learn.microsoft.com/en-us/windows-hardware/drivers/audio/low-latency-audio#measurement-tools
         */
        UINT32 default_period_samples, fundamental_period_samples, min_period_samples, max_period_samples;
        IAudioClient3_GetSharedModeEnginePeriod(client3, wfx, &default_period_samples, &fundamental_period_samples, &min_period_samples, &max_period_samples);

        const DWORD flags = AUDCLNT_STREAMFLAGS_EVENTCALLBACK;
        if (SUCCEEDED(IAudioClient3_InitializeSharedAudioStream(client3, flags, min_period_samples, wfx, 0)))
        {
            client_initialized = 1;
        }

        IAudioClient3_Release(client3);
    }
#else
    b32 client_initialized = 0;
#endif

    if (!client_initialized)
    {
        /* Get duration for shared-mode streams, this will typically be 480 samples (10msec @ 48khz) */
        REFERENCE_TIME duration;
        IAudioClient_GetDevicePeriod(g->client, &duration, 0);

        /* Initialize audio playback
         *
         * NOTE:
         * Passing AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM will tell WASAPI to
         * always convert to native mixing format. This may introduce latency
         * but allows for any input format.
         */
        const DWORD flags = AUDCLNT_STREAMFLAGS_EVENTCALLBACK | AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM | AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY;
        IAudioClient_Initialize(g->client, AUDCLNT_SHAREMODE_SHARED, flags, duration, 0, wfx, 0);
    }

    IAudioClient_GetMixFormat(g->client, &g->buffer_format);

    /* Set up event handler to wait on */
    g->event = CreateEventW(0, 0, 0, 0);
    IAudioClient_SetEventHandle(g->client, g->event);

    /* Get playback client */
    IAudioClient_GetService(g->client, &IID_IAudioRenderClient, (LPVOID *)&g->playback);

    /* Start the playback */
    IAudioClient_Start(g->client);

    /* Get audio buffer size in samples */
    IAudioClient_GetBufferSize(g->client, &g->buffer_frames);
}

////////////////////////////////
//~ Wasapi update

PB_WSP_Buff PB_WSP_BeginUpdate(void)
{
    __prof;
    PB_WSP_SharedState *g = &PB_WSP_shared_state;
    PB_WSP_Buff wspbuf = ZI;

    /* Get padding frames */
    u32 padding_frames;
    IAudioClient_GetCurrentPadding(g->client, &padding_frames);

    /* Get output buffer from WASAPI */
    wspbuf.frames_count = 0;
    if (padding_frames <= g->buffer_frames)
    {
        wspbuf.frames_count = g->buffer_frames - padding_frames;
    }
    IAudioRenderClient_GetBuffer(g->playback, wspbuf.frames_count, &wspbuf.frames);

    return wspbuf;
}

void PB_WSP_EndUpdate(PB_WSP_Buff *wspbuf, MIX_PcmF32 src)
{
    __prof;
    PB_WSP_SharedState *g = &PB_WSP_shared_state;
    u32 frames_in_source = src.count / 2;
    u32 frames_in_output = wspbuf->frames_count;

    u32 flags = 0;
    if (frames_in_source == frames_in_output)
    {
        /* Copy bytes to output */
        u32 bytes_per_sample = g->buffer_format->nBlockAlign / g->buffer_format->nChannels;
        u32 write_size = frames_in_source * 2 * bytes_per_sample;
        CopyBytes(wspbuf->frames, src.samples, write_size);
    }
    else
    {
        /* Submit silence if not enough samples */
        flags = AUDCLNT_BUFFERFLAGS_SILENT;

        /* This shouldn't occur, mixer should be generating samples equivilent
         * to value returned from `PB_WSP_BeginUpdate`. */
        Assert(0);
    }

#if !AUDIO_ENABLED
    flags = AUDCLNT_BUFFERFLAGS_SILENT;
#endif

    /* Submit output buffer to WASAPI */
    IAudioRenderClient_ReleaseBuffer(g->playback, frames_in_source, flags);
    __profframe("Audio");
}

////////////////////////////////
//~ Playback job

JobDef(PB_WSP_PlaybackJob, UNUSED sig, UNUSED id)
{
    __prof;
    PB_WSP_SharedState *g = &PB_WSP_shared_state;

    /* FIXME: If playback fails at any point and mixer stops advancing, we
     * need to halt mixer to prevent memory leak when sounds are played. */
     /* TODO: Signal counter that running job wiats on, rather than scheduling job manually */
    while (!Atomic32Fetch(&g->shutdown))
    {
        TempArena scratch = BeginScratchNoConflict();
        {
            __profn("Wasapi wait");
            WaitForSingleObject(g->event, INFINITE);
        }
        {
            __profn("Fill sample buffer");
            PB_WSP_Buff wspbuf = PB_WSP_BeginUpdate();
            MIX_PcmF32 pcm = MIX_MixAllTracks(scratch.arena, wspbuf.frames_count);
            PB_WSP_EndUpdate(&wspbuf, pcm);
        }
        EndScratch(scratch);
    }
}