/* GCW Zero audio timing benchmark
 *
 * Copyright (C) 2014, Nebuleon Fumika <nebuleon@gcw-zero.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "SDL.h"

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <time.h>
#include <string.h>
#include <inttypes.h>

#define SAMPLE_RATE 44100
#define RESULTS_FILE "benchaudiotiming.txt"

uint32_t SamplesRemaining;
uint8_t AlmostDone;
volatile bool SecondDone;
struct timespec EndTime;

uint64_t Results[32]; /* nanoseconds to output SamplesEmitted[i] samples */
uint32_t SamplesEmitted[32];

uint8_t TestCount()
{
    uint8_t i;

    for (i = 0; i < 32; i++)
        if ((UINT32_C(1) << i) >= SAMPLE_RATE)
            return i;
    return 31;
}

static inline int64_t NanosBetween(const struct timespec* Past, const struct timespec* Present)
{
    return (Present->tv_sec  - Past->tv_sec) * INT64_C(1000000000)
         + (Present->tv_nsec - Past->tv_nsec);
}

void BenchmarkCallback(void* userdata, Uint8* stream, int len)
{
    SDL_AudioSpec* spec = (SDL_AudioSpec*) userdata;
    uint32_t SamplesWritten = len / (spec->size / spec->samples);
    memset(stream, spec->silence, len);
    if (SecondDone)
        ; /* Don't update anything anymore! */
    else if (AlmostDone) {
        if (--AlmostDone == 0) {
            clock_gettime(CLOCK_MONOTONIC, &EndTime);
            SecondDone = true;
        }
    } else if (SamplesWritten >= SamplesRemaining) {
        SamplesRemaining = 0;
        /* We are almost done, but we must wait for SDL to request 3 more
         * buffers via this callback, because only then will we know that
         * everything has actually played.
         * HACK - On the GCW Zero, SDL 1.2 uses 3 internal buffers for
         * audio, and plays the front buffer while one of the back buffers
         * is being requested. SDL does not provide a function to query
         * this detail, which has been reverse-engineered. */
        AlmostDone = 3;
    } else {
        SamplesRemaining -= SamplesWritten;
    }
}

uint32_t Benchmark(struct timespec* StartTime, uint32_t RequestedSize)
{
    uint32_t RetVal;

    SecondDone = false;
    AlmostDone = 0;

    /* Open the audio device with a certain buffer size, in samples. */
    SDL_AudioSpec Requested, Actual;
    Requested.freq = SAMPLE_RATE;
    Requested.format = AUDIO_S16SYS;
    Requested.samples = RequestedSize;
    Requested.channels = 1; /* mono */
    Requested.callback = BenchmarkCallback;
    Requested.userdata = &Actual;

    if (SDL_OpenAudio(&Requested, &Actual) == -1) {
        fprintf(stderr, "Failed to open SDL audio: %s\n", SDL_GetError());
        return 0;
    }

    /* Now that we know how many samples the hardware wants us to write,
     * set the number of samples to be written during the next second. */
    SamplesRemaining = RetVal = (Actual.freq + Actual.samples - 1) / Actual.samples * Actual.samples;

    if (clock_gettime(CLOCK_MONOTONIC, StartTime) == -1) {
        fprintf(stderr, "\nclock_gettime failed: %s\n", strerror(errno));
        return 0;
    }

    SDL_PauseAudio(SDL_DISABLE);

    while (!SecondDone) {
        SDL_Delay(1000); /* one whole second, to minimise OS interference */
    }

    SDL_CloseAudio();

    /* EndTime was updated by the callback in the SDL audio thread. Return. */
    return RetVal;
}

int main(int argc, char** argv)
{
    bool Error = false;
    uint8_t Test;
    char* ResultsPath = NULL;
    FILE* ResultsFile = NULL;

    if (SDL_Init(SDL_INIT_AUDIO) == -1) {
        fprintf(stderr, "SDL initialisation failed: %s\n", SDL_GetError());
        Error = true;
        goto end;
    }

    const char* Home = getenv("HOME");
    if (!Home) {
        fprintf(stderr, "HOME environment variable not set\n");
        Error = true;
        goto end;
    }
    ResultsPath = (char *) malloc(strlen(Home) + strlen(RESULTS_FILE) + 2);
    sprintf(ResultsPath, "%s/%s", Home, RESULTS_FILE);

    for (Test = 0; Test < TestCount(); Test++) {
        uint32_t Emitted;
        fprintf(stderr, "\rRunning tests, %2d/%2d", Test, TestCount());
        struct timespec StartTime;
        Emitted = Benchmark(&StartTime, UINT32_C(1) << Test);
        int64_t Duration = NanosBetween(&StartTime, &EndTime);

        Results[Test] = Duration;
        SamplesEmitted[Test] = Emitted;
        if (Emitted == 0) {
            Error = true;
            goto end;
        }
    }

    fprintf(stderr, "\rRunning tests, done.\n");

    SDL_QuitSubSystem(SDL_INIT_AUDIO);

    fprintf(stderr, "Dumping results to ~/%s", RESULTS_FILE);
    ResultsFile = fopen(ResultsPath, "wb");
    if (ResultsFile) {
        fprintf(ResultsFile, "Requested buffer samples,Samples output,Time taken to output (ns),Hz\n");
        for (Test = 0; Test < TestCount(); Test++) {
            fprintf(ResultsFile, "%" PRIu32 ",%" PRIu32 ",%" PRIu64 ",%f\n",
                UINT32_C(1) << Test,
                SamplesEmitted[Test],
                Results[Test],
                1000000000.0f / ((float) Results[Test] / SamplesEmitted[Test]));
        }
        fclose(ResultsFile);
        fprintf(stderr, ", done.\n");
    } else {
        fprintf(stderr, "\nFile could not be written: %s\n", strerror(errno));
    }

end:
    free(ResultsPath);
    SDL_Quit();

    fprintf(stderr, "Press Enter (Start) to exit.\n");
    char Dummy[2];
    fgets(Dummy, 2, stdin);

    return Error ? 1 : 0;
}