#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <sysexits.h>
#include <fcntl.h>
#include <math.h>

#include <xas/audio.h>
#include <xas/riff.h>

#define SYNTH_STATUS_ON (1 << 0)

typedef struct _synth_sine {
    int flags;
    float phase;

    size_t sample_rate,
           frequency;
} synth_sine;

static void usage(int argc, char **argv, const char *message, ...) {
    va_list args;

    va_start(args, message);

    if (message) {
        vfprintf(stderr, message, args);
        fputc('\n', stderr);
    }

    va_end(args);

    fprintf(stderr, "usage: %s output.wav\n", argv[0]);

    exit(EX_USAGE);
}

static ssize_t synth_sine_fill(synth_sine *synth,
                               int16_t *samples,
                               size_t count,
                               xas_audio_stream *stream) {
    size_t i;

    for (i=0; i<count; i++) {
        if (synth->flags & SYNTH_STATUS_ON) {
            samples[i] = (int16_t)roundf((INT16_MAX >> 2) * sinf(synth->phase));

            synth->phase += (2.0f * M_PI) / (stream->sample_rate / synth->frequency);
        } else {
            samples[i] = 0;
        }
    }

    return count;
}

int main(int argc, char **argv) {
    xas_audio_stream *stream;

    int duration_s  = 60,
        frequency   = 220,
        sample_rate = 44100;

    int i;

    if (argc != 2) {
        usage(argc, argv, "No output file provided");
    }

    if ((stream = xas_riff_file_open(argv[1],
                                       2,
                                       sample_rate,
                                       1,
                                       O_WRONLY | O_CREAT | O_TRUNC)) == NULL) {
        goto error_riff_file_open;
    }

    for (i=0; i < duration_s * frequency; i++) {
        float phase;

        for (phase = 0.0; phase < 2 * M_PI; phase += (2 * M_PI) / (sample_rate / frequency)) {
            int16_t value = (int16_t)round((INT16_MAX >> 2) * sin(phase));

            xas_audio_stream_write(stream, &value, 1);
        }
    }

    xas_audio_stream_flush(stream);
    xas_audio_stream_destroy(stream);

    return EX_OK;

error_riff_file_open:
    return EX_OSERR;
}