#include <stdio.h>
#include <math.h>
#include <assert.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <libgen.h>
#include <complex.h>
#include <raylib.h>
#include <rlgl.h>
#include <sys/param.h>

#include "plug.h"

#define SAMPLE_SIZE (1<<13)
#define FONT_SIZE 69
#define SMOOTHNESS 8
#define SMEARNESS 6

char circle_shader[PATH_MAX];
char smear_shader[PATH_MAX];
char font[PATH_MAX];

typedef struct {
    Music music;
    float audio_volume;
    bool error;
    Font font;
    Shader circle;
    Shader smear;
    char render_option;
} Plug;

Plug *plug = NULL;

float in_raw[SAMPLE_SIZE];
float in_win[SAMPLE_SIZE];
float complex out_raw[SAMPLE_SIZE];
float out_log[SAMPLE_SIZE];
float out_smooth[SAMPLE_SIZE];
float out_smear[SAMPLE_SIZE];

// char render_option = 'b';

char *get_asset_path(const char *asset, const char *type)
{
    char *asset_path = malloc(sizeof(char) * PATH_MAX);
    char exe_path[PATH_MAX];
    char exe_dir[PATH_MAX];
    ssize_t len = readlink("/proc/self/exe", exe_path, sizeof(exe_path));
    if (len == -1) {
        perror("readlink");
        exit(EXIT_FAILURE);
    }
    exe_path[len] = '\0';

    strncpy(exe_dir, exe_path, sizeof(exe_dir));
    exe_dir[sizeof(exe_dir) - 1] = '\0';
    char *dir = dirname(exe_dir);

    char rel_asset_base[PATH_MAX];
    snprintf(rel_asset_base, sizeof(rel_asset_base), "%s/../share/%s", dir, type);

    char asset_base[PATH_MAX];
    if (!realpath(rel_asset_base, asset_base)) {
        fprintf(stderr, "ERROR: realpath failed for asset %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }
    if ((size_t)snprintf(asset_path, PATH_MAX, "%s/%s", asset_base, asset) >= PATH_MAX) {
        fprintf(stderr, "Asset path truncated -- path too long\n");
        exit(EXIT_FAILURE);
    }
    return asset_path;
}

void fft(float in[], size_t stride, float complex out[], size_t n)
{
    assert(n > 0);

    if (n == 1) {
        out[0] = in[0];
        return;
    }

    fft(in,          stride*2, out,       n/2); // even
    fft(in + stride, stride*2, out + n/2, n/2); // odd

    // v = o*x
    // out = e + o*x e + o*x e e | e - o*x e - o*x o o
    for (size_t k = 0; k < n/2; ++k) {
        float t = (float)k/n;
        float complex v = cexp(-2*I*PI*t)*out[k + n/2];
        float complex e = out[k];
        out[k] = e + v;
        out[k + n/2] = e - v;
    }
}

float amp(float complex z)
{
    float a = cabsf(z);
    return 2*log10f(a);
}

void callback(void *bufferData, unsigned int frames)
{
    float (*fs)[2] = bufferData;

    for (size_t i = 0; i < frames; ++i) {
        memmove(in_raw, in_raw + 1, (SAMPLE_SIZE - 1)*sizeof(in_raw[0]));
        in_raw[SAMPLE_SIZE-1] = fs[i][0];
    }
}

void PausePlayMusic(void)
{
    if (IsMusicStreamPlaying(plug->music)) {
        PauseMusicStream(plug->music);
        printf("Music paused\n");
    } else {
        ResumeMusicStream(plug->music);
        printf("Music resumed\n");
    }
}

void RaiseVolume(void)
{
    plug->audio_volume += 0.02;
    if (plug->audio_volume > 1.0) {
        plug->audio_volume = 1.0;
    }
    printf("Audio Level: %f\n", plug->audio_volume);
    SetMusicVolume(plug->music, plug->audio_volume);
}

void LowerVolume(void)
{
    plug->audio_volume -= 0.02;
    if (plug->audio_volume < 0.0) {
        plug->audio_volume = 0.0;
    }
    printf("Audio Level: %f\n", plug->audio_volume);
    SetMusicVolume(plug->music, plug->audio_volume);
}

void PrepareMusicStream(void)
{
    if (IsMusicValid(plug->music)) {
        StopMusicStream(plug->music);
        UnloadMusicStream(plug->music);
    }
}

void StartMusicStream(void)
{
    if (IsMusicValid(plug->music)) {
        plug->error = false;
        printf("music.frameCount = %u\n", plug->music.frameCount);
        printf("music.stream.sampleRate = %u\n", plug->music.stream.sampleRate);
        printf("music.stream.sampleSize = %u\n", plug->music.stream.sampleSize);
        printf("music.stream.channels = %u\n", plug->music.stream.channels);
        SetMusicVolume(plug->music, plug->audio_volume);
        AttachAudioStreamProcessor(plug->music.stream, callback);
        PlayMusicStream(plug->music);
    } else {
        plug->error = true;
    }
}

size_t fft_analyze(float dt)
{
    // Apply Hann Window on input - https://en.wikipedia.org/wiki/Hann_function
    for (size_t i = 0; i < SAMPLE_SIZE; ++i) {
        float t = (float)i/(SAMPLE_SIZE-1);
        float hann = 0.5 - 0.5*cosf(2*PI*t);
        in_win[i] = hann * in_raw[i];
    }

    // FFT
    fft(in_win, 1, out_raw, SAMPLE_SIZE);

    // Convert into logarithmic scale
    float step = 1.06;
    float lowf = 1.0f;
    size_t m = 0;
    float max_amp = 1.0f;
    for (float f = lowf; (size_t) f < SAMPLE_SIZE/2; f = ceilf(f*step)) {
        float f1 = ceilf(f*step);
        float a = 0.0f;
        for (size_t q = (size_t) f; q < SAMPLE_SIZE/2 && q < (size_t) f1; ++q) {
            float b = amp(out_raw[q]);
            if (b > a) a = b;
        }
        if (max_amp < a) max_amp = a;
        out_log[m++] = a;
    }

    // Normalize frequencies 0..1 range
    for (size_t i = 0; i < m; ++i) {
        out_log[i] /= max_amp;
    }

    // Interpolate frequencies
    for (size_t i = 0; i < m; ++i) {
        out_smooth[i] += (out_log[i] - out_smooth[i])*dt*SMOOTHNESS;
        out_smear[i] += (out_smooth[i] - out_smear[i])*dt*SMEARNESS;
    }
    return m;
}

void fft_render_bars(int w, int h, size_t m)
{
    // Display the frequencies
    float cell_width = (float)w/m;
    float saturation = 0.75f;
    float value = 0.9f;

    // Draw the bars
    for (size_t i = 0; i < m; ++i) {
        float t = out_smooth[i];
        float hue = (float)i/m;
        Color color = ColorFromHSV(hue*360, saturation, value);
        float thickness = (cell_width/1.8)*sqrtf(t);
        Vector2 start_pos = {
            .x = i*cell_width + cell_width/2,
            .y = h,
        };
        Vector2 end_pos = {
            .x = start_pos.x,
            .y = start_pos.y - h*2/3*t,
        };
        DrawLineEx(start_pos, end_pos, thickness, color);
    }


    // Construct a texture to be used in the shader
    // since fragTexCoord doesn't work on shapes
    Texture2D texture = { rlGetTextureIdDefault(), 1, 1, 1, PIXELFORMAT_UNCOMPRESSED_R8G8B8A8 };

    // Draw smear frames
    BeginShaderMode(plug->smear);
    for (size_t i = 0; i < m; ++i) {
        float start = out_smear[i];
        float end = out_smooth[i];
        float hue = (float)i/m;
        Color color = ColorFromHSV(hue*360, saturation, value);
        float radius = cell_width*3*sqrt(end);
        Vector2 origin = {0};
        Vector2 start_pos = {
            .x = i*cell_width + cell_width/2,
            .y = h - h*2/3*start,
        };
        Vector2 end_pos = {
            .x = i*cell_width + cell_width/2,
            .y = h - h*2/3*end,
        };
        if (end_pos.y >= start_pos.y) {
            Rectangle dest = {
                .x = start_pos.x - radius/2,
                .y = start_pos.y,
                .width = radius,
                .height = end_pos.y - start_pos.y,
            };
            Rectangle source = {0, 0, 1, 0.5};
            DrawTexturePro(texture, source, dest, origin, 0, color);
        } else {
            Rectangle dest = {
                .x = end_pos.x - radius/2,
                .y = end_pos.y,
                .width = radius,
                .height = start_pos.y - end_pos.y,
            };
            Rectangle source = {0, 0.5, 1, 0.5};
            DrawTexturePro(texture, source, dest, origin, 0, color);
        }
    }
    EndShaderMode();

    // Draw the circles
    BeginShaderMode(plug->circle);
    for (size_t i = 0; i < m; ++i) {
        float t = out_smooth[i];
        float hue = (float)i/m;
        Color color = ColorFromHSV(hue*360, saturation, value);
        float radius = cell_width*4*sqrtf(t);
        Vector2 position = {
            .x = i*cell_width + cell_width/2 - radius,
            .y = h - h*2/3*t - radius,
        };
        DrawTextureEx(texture, position, 0, 2*radius, color);
    }
    EndShaderMode();
}

void fft_render_circle(int w, int h, size_t m)
{
    // Display the frequencies
    float cell_width = (float)720/m;
    float saturation = 0.75f;
    float value = 0.9f;

    // Construct a texture to be used in the shader
    // since fragTexCoord doesn't work on shapes
    Texture2D texture = { rlGetTextureIdDefault(), 1, 1, 1, PIXELFORMAT_UNCOMPRESSED_R8G8B8A8 };

    // Draw the circles
    BeginShaderMode(plug->circle);
    for (size_t i = 0; i < m; ++i) {
        float t = out_smooth[i];
        float hue = (float)i/m;
        Color color = ColorFromHSV(hue*360, saturation, value);
        float radius = cell_width*4*sqrtf(t);
        Vector2 position = {
            .x = w/2 + (h/2.1 * cos(i * cell_width)) * sqrtf(t) - radius,
            .y = h/2 + (h/2.1 * sin(i * cell_width)) * sqrtf(t) - radius,
        };
        DrawTextureEx(texture, position, 0, 2*radius, color);
    }
    EndShaderMode();
}

Plug *plug_pre_reload(void)
{
    if (IsMusicValid(plug->music)) {
        DetachAudioStreamProcessor(plug->music.stream, callback);
    }
    return plug;
}

void plug_post_reload(Plug *prev)
{
    plug = prev;
    if (IsMusicValid(plug->music)) {
        AttachAudioStreamProcessor(plug->music.stream, callback);
    }
    UnloadShader(plug->circle);
    UnloadShader(plug->smear);
    plug->circle = LoadShader(NULL, circle_shader);
    plug->smear = LoadShader(NULL, smear_shader);
}

void plug_init(void)
{
    plug = malloc(sizeof(*plug));
    assert(plug != NULL && "Not enough RAM!");
    memset(plug, 0, sizeof(*plug));

    char *font_path = get_asset_path("AlegreyaSans-Regular.ttf", "fonts");
    char *circles_path = get_asset_path("circles.fs", "shaders");
    char *smear_path = get_asset_path("smear.fs", "shaders");

    plug->font = LoadFontEx(font_path, FONT_SIZE, NULL, 0);
    plug->circle = LoadShader(NULL, circles_path);
    plug->smear = LoadShader(NULL, smear_path);
    plug->audio_volume = 0.5f;
    plug->render_option = 'b';

    free(font_path);
    free(circles_path);
    free(smear_path);
}

void plug_update(void)
{
    if (IsMusicValid(plug->music)) {
        UpdateMusicStream(plug->music);
    }

    if (IsKeyPressed(KEY_SPACE) && IsMusicValid(plug->music)) {
        PausePlayMusic();
    }

    if (IsKeyPressed(KEY_UP)) {
        RaiseVolume();
    }

    if (IsKeyPressed(KEY_DOWN)) {
        LowerVolume();
    }

    if (IsKeyPressed(KEY_N)) {
        plug->render_option = 'b';
    }

    if (IsKeyPressed(KEY_I)) {
        plug->render_option = 'c';
    }

    if (IsFileDropped()){
        FilePathList droppedFiles = LoadDroppedFiles();
        const char *file_path = droppedFiles.paths[0];

        PrepareMusicStream();
        plug->music = LoadMusicStream(file_path);
        StartMusicStream();

        UnloadDroppedFiles(droppedFiles);
    }

    float w = GetRenderWidth();
    float h = GetRenderHeight();
    float dt = GetFrameTime();

    BeginDrawing();
    ClearBackground(CLITERAL(Color) {
        0x1, 0x1, 0x1, 0xFF
    });

    if (IsMusicValid(plug->music)) {
        size_t m = fft_analyze(dt);
        switch(plug->render_option)
        {
            case 'b': fft_render_bars(w, h, m); break;
            case 'c': fft_render_circle(w, h, m); break;
            default: break;
        }

    } else {
        const char *label;
        Color color;
        if (plug->error) {
            label = "Could not load file";
            color = RED;
        } else {
            label = "Drag & Drop Music Here";
            color = WHITE;
        }
        Vector2 size = MeasureTextEx(plug->font, label, plug->font.baseSize, 0);
        Vector2 position = {
            .x = w/2 - size.x/2,
            .y = h/2 - size.y/2,
        };
        DrawTextEx(plug->font, label, position, plug->font.baseSize, 0, color);
    }
    EndDrawing();
}