#include "stdlib.h"
#include "SDL2/SDL.h"
#include "math.h"
#include "time.h"
#include <CL/cl.h>

const int WIDTH = 800;
const int HEIGHT = 800;
const int POLYGON_SIZE = sizeof(float) * 3 * 3;
const int POLYGONS = 10;

int is_intersecting(int a, int b, int c, int d, int p, int q, int r, int s) {
    float det, gamma, lambda;
    
    det = (c - a) * (s - q) - (r - p) * (d - b);
    
    if (det == 0) {
        return 1;
    } 
    else {
        lambda = ((s - q) * (r - a) + (p - r) * (s - b)) / det;
        gamma = ((b - d) * (r - a) + (c - a) * (s - b)) / det;
        return (0 < lambda && lambda < 1) && (0 < gamma && gamma < 1);
    }
}

void norm(float dest[2], float a[2]){
    float magnitude = sqrt((pow(a[0], 2) + pow(a[1], 2)));
    
    dest[0] = a[0] / magnitude;
    dest[1] = a[1] / magnitude;
}

void sub(float dest[2], float a[2], float b[2]){
    dest[0] = a[0] - b[0];
    dest[1] = a[1] - b[1];
}

void add(float dest[2], float a[2], float b[2]){
    dest[0] = a[0] + b[0];
    dest[1] = a[1] + b[1];
}

int main(){
    srand(time(NULL));

    float polygons[POLYGONS][3][3];

    SDL_Init(SDL_INIT_VIDEO);
    SDL_Window* window = SDL_CreateWindow("Rasterizer", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, WIDTH, HEIGHT, SDL_WINDOW_OPENGL);
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    SDL_Texture* texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_STREAMING, WIDTH, HEIGHT);

    int running = 1;

    Uint32 frame_buffer[WIDTH * HEIGHT];
    float z_buffer[WIDTH * HEIGHT];

    int frame = 0;

    Uint32 start_time, frame_time;
    float fps;

    while (running) {
        start_time = SDL_GetTicks();

        //if (frame % 1 == 0){
            for (int p = 0; p < POLYGONS; p++){
                for (int point = 0; point < 3; point++){
                    for (int i = 0; i < 3; i++){
                        polygons[p][point][i] = rand() % WIDTH + 1;
                    }
                }
            }
        //}

        for (int i = 0; i < WIDTH * HEIGHT; ++i) {
            frame_buffer[i] = 0x22222222;
        }

        memset(&z_buffer, 0, sizeof(float) * WIDTH * HEIGHT);

        SDL_Event event;
        while (SDL_PollEvent(&event)){
            switch (event.type){
                case SDL_QUIT:
                running = 0;
            }
        }
        
        for (int polygon = 0; polygon < POLYGONS; polygon++){
            float x0 = polygons[polygon][0][0];
            float y0 = polygons[polygon][0][1];
            float z0 = polygons[polygon][0][2];
            float x1 = polygons[polygon][1][0];
            float y1 = polygons[polygon][1][1];
            float z1 = polygons[polygon][1][2];
            float x2 = polygons[polygon][2][0];
            float y2 = polygons[polygon][2][1];
            float z2 = polygons[polygon][2][2];
            
            float smallest_x = x0;
            float largest_x = x0;
            float smallest_y = y0;
            float largest_y = y0;
            
            for (int point = 0; point < 3; point++){
                float x = polygons[polygon][point][0];
                float y = polygons[polygon][point][1];
                
                if (x > largest_x){
                    largest_x = x;
                }
                
                if (x < smallest_x){
                    smallest_x = x;
                }
                
                if (y > largest_y){
                    largest_y = y;
                }
                
                if (y < smallest_y){
                    smallest_y = y;
                }
            }
            
            smallest_x = fmin(smallest_x, 0);
            largest_x = fmax(largest_x, WIDTH);
            smallest_y = fmin(smallest_y, 0);
            largest_y = fmax(largest_y, HEIGHT);

            // test every pixel in a rect around the triangle. If it's inside, color it.
            for (int x = (int)smallest_x; x < largest_x; x++){
                for (int y = (int)smallest_y; y < largest_y; y++){
                    int intersections = 0;
                    
                    for (int i = 0; i < 3; i++){
                        intersections += is_intersecting(x, y, 10000, 100000, polygons[polygon][i][0], polygons[polygon][i][1], polygons[polygon][(i + 1) % 3][0], polygons[polygon][(i + 1) % 3][1]);
                    }

                    if (intersections % 2 == 0){
                        continue;
                    }

                    float denominator = (y1 - y2) * (x0 - x2) + (x2 - x1) * (y0 - y2);
                    float w0 = ((y1 - y2) * (x - x2) + (x2 - x1) * (y - y2)) / denominator;
                    float w1 = ((y2 - y0) * (x - x0) + (x0 - x2) * (y - y2)) / denominator;
                    float w2 = 1.0 - w0 - w1;

                    if (denominator < 0) {
                        w0 = -w0;
                        w1 = -w1;
                        w2 = -w2;
                        denominator = -denominator;
                    }                    

                    float z = w0 * z0 + w1 * z1 + w2 * z2;

                    
                                        if (z < 0){
                                            z *= -1;
                                        }
                //    printf("%f\n", z);

                    if (z > z_buffer[y * WIDTH + x]){
                        z_buffer[y * WIDTH + x] = z;
                    }
                    else {
                        continue;
                    }

                   frame_buffer[y * WIDTH + x] = 0xFFFFFFFF / POLYGONS * (polygon + 1);
                }
            }
        }
        
        SDL_UpdateTexture(texture, NULL, frame_buffer, WIDTH * sizeof(Uint32));
        
        SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, texture, NULL, NULL);
        SDL_RenderPresent(renderer);
        
        frame++;

        frame_time = SDL_GetTicks()-start_time;
        fps = (frame_time > 0) ? 1000.0f / frame_time : 0.0f;
        printf("%f fps\n", fps);
        printf("%d polygons\n", POLYGONS);
    }
    
    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
}