#include <stdio.h>

#include "SDL.h"
#include "SDL_audio.h"
#include "SDL_error.h"
#include "SDL_events.h"
#include "SDL_mouse.h"

#define KB(x) (1024 * (x))

static SDL_Window *window = NULL;
static SDL_Renderer *renderer = NULL;
static SDL_AudioDeviceID audio_device = 0;
static SDL_AudioStream *stream = NULL;
static float volume_slider_value = 1.0f;

#if defined(__clang__) || defined(__GNUC__)
static void panic_and_abort(const char *title, const char *text) __attribute__((noreturn));
#endif
static void panic_and_abort(const char *title, const char *text) {
    fprintf(stderr, "PANIC: %s ... %s\n", title, text);
    SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, title, text, window);
    SDL_Quit();
    exit(1);
}

// TODO: Refactor this nonsense into a struct
static Uint8 *wavbuf = NULL;
static Uint32 wavlen = 0;
static Uint32 wavpos = 0;
static SDL_AudioSpec wavspec;

static SDL_bool open_audio_file(const char *fname) {
    SDL_FreeAudioStream(stream);
    stream = NULL;
    SDL_FreeWAV(wavbuf);
    wavbuf = NULL;
    wavlen = 0;
    wavpos = 0;

    if (SDL_LoadWAV(fname, &wavspec, &wavbuf, &wavlen) == NULL) {
        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't load wav file!", SDL_GetError(), window);
        return SDL_FALSE;
    }

    stream = SDL_NewAudioStream(wavspec.format, wavspec.channels, wavspec.freq, AUDIO_F32, 2, 48000);
    if (!stream) {
        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create audiostream!", SDL_GetError(), window);
        SDL_FreeWAV(wavbuf);
        wavbuf = NULL;
        wavlen = 0;
        wavpos = 0;
        return SDL_FALSE;
    }

    if (SDL_AudioStreamPut(stream, wavbuf, wavlen) == -1) { // FIXME: graceful handling
        panic_and_abort("Audio stream put failed", SDL_GetError());
    }

    SDL_AudioStreamFlush(stream); // FIXME: error handling

    return SDL_TRUE;
}

int main(int argc, char **argv) {
    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO) != 0) {
        panic_and_abort("SDL_Init failed", SDL_GetError());
    }

    window = SDL_CreateWindow("sdlamp", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 1024, 768, 0);
    if (!window) {
        panic_and_abort("SDL_CreateWindow failed", SDL_GetError());
    }

    renderer = SDL_CreateRenderer(window, 0, SDL_RENDERER_PRESENTVSYNC);
    if (!renderer) {
        panic_and_abort("SDL_CreateRenderer failed", SDL_GetError());
    }

    SDL_AudioSpec desired;
    SDL_zero(desired);
    desired.freq = 48000;
    desired.format = AUDIO_F32;
    desired.channels = 2;
    desired.samples = 4096;
    desired.callback = NULL;

    audio_device = SDL_OpenAudioDevice(NULL, 0, &desired, NULL, 0);
    if (audio_device == 0) {
        panic_and_abort("Couldn't load audio device!", SDL_GetError());
    }

    // Enable events
    SDL_EventState(SDL_DROPFILE, SDL_ENABLE);
    SDL_EventState(SDL_MOUSEMOTION, SDL_ENABLE);

    // TODO: Remove temp load
    open_audio_file("CantinaBand60.wav");

    const SDL_Rect rewind_rect = {(1024 - 100) / 3, 100, 100, 100};
    const SDL_Rect pause_rect = {((1024 - 100) / 3) * 2 , 100, 100, 100};
    const SDL_Rect volume_rect = {(1024 - 500) / 2, 400, 500, 20};
    SDL_Rect volume_knob = {
        (volume_rect.x + volume_rect.w) - volume_knob.w,
        volume_rect.y,
        20,
        volume_rect.h
    };

    SDL_bool paused = SDL_TRUE;
    SDL_bool quit = SDL_FALSE;
    while (!quit) {
        SDL_Event e;
        while (SDL_PollEvent(&e)) {
            switch (e.type) {
                case SDL_QUIT:
                    quit = SDL_TRUE;
                    break;

                case SDL_MOUSEBUTTONDOWN: {
                    SDL_Point pt = { e.button.x, e.button.y };
                    if (SDL_PointInRect(&pt, &rewind_rect)) { // Pressed the "rewind" button
                        SDL_ClearQueuedAudio(audio_device);
                        SDL_AudioStreamClear(stream);
                        if (SDL_AudioStreamPut(stream, wavbuf, wavlen) == -1) { // FIXME: graceful handling
                            panic_and_abort("Audio stream put failed", SDL_GetError());
                        }
                        SDL_AudioStreamFlush(stream);
                    } else if (SDL_PointInRect(&pt, &pause_rect)) { // Pressed the "pause" button
                        paused = paused ? SDL_FALSE : SDL_TRUE;
                        SDL_PauseAudioDevice(audio_device, paused);
                    }
                    break;
                }

                case SDL_MOUSEMOTION: {
                    SDL_Point pt = { e.motion.x, e.motion.y };
                    if (SDL_PointInRect(&pt, &volume_rect) && (e.motion.state & SDL_BUTTON_LMASK)) { // left mouse pressed inside the "volume" slider
                        const float fx = (float)(pt.x - volume_rect.x);
                        volume_slider_value = (fx / (float)volume_rect.w);
                        volume_knob.x = pt.x - (volume_knob.w / 2);
                        volume_knob.x = SDL_max(volume_knob.x, volume_rect.x);
                        volume_knob.x = SDL_min(volume_knob.x, (volume_rect.x + volume_rect.w) - volume_knob.w);
                    }
                    break;
                }

                case SDL_DROPFILE: {
                    open_audio_file(e.drop.file);
                    SDL_free(e.drop.file);
                    break;
                }
            }
        }

        if (SDL_GetQueuedAudioSize(audio_device) < KB(8)) {
            const int bytes_remaining = SDL_AudioStreamAvailable(stream);
            if (bytes_remaining > 0) {
                const int new_bytes = SDL_min(bytes_remaining, KB(32));
                static Uint8 converted_buffer[KB(32)];
                SDL_AudioStreamGet(stream, converted_buffer, new_bytes); // FIXME: Error checking
                const int num_samples = (new_bytes / sizeof(float));
                float *samples = (float*)converted_buffer;
                for (size_t i = 0; i < num_samples; ++i) {
                    samples[i] *= volume_slider_value;
                }
                SDL_QueueAudio(audio_device, converted_buffer, new_bytes);
            }
        }

        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
        SDL_RenderClear(renderer);

        SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
        SDL_RenderFillRect(renderer, &rewind_rect);
        SDL_RenderFillRect(renderer, &pause_rect);
        SDL_RenderFillRect(renderer, &volume_rect);

        SDL_SetRenderDrawColor(renderer, 0, 0, 255, 255);
        SDL_RenderFillRect(renderer, &volume_knob);

        SDL_RenderPresent(renderer);
    }

    SDL_FreeWAV(wavbuf);
    SDL_CloseAudioDevice(audio_device);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}