#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <unistd.h>
#include <SDL/SDL.h>

typedef struct
{
    double x, y;
    double tx, ty;
    int z;
} per;

int n;
per *mass;
double rad;
double ra;
double vh, vz;


void zombie_field(int k, double *fx, double *fy)
{
    int i;
    double ffx, ffy;
    double l;
    double x = mass[k].x;
    double y = mass[k].y;
    *fx = 0;
    *fy = 0;
    for (i = 0; i < n; i++)
    {
        if (mass[i].z == 1)
        {
            ffx = mass[i].x - x;
            ffy = mass[i].y - y;
            l = sqrt(ffx*ffx + ffy*ffy);
            if (l > 1e-10)
            {
                ffx /= -l;
                ffy /= -l;
            }
            *fx += ffx;
            *fy += ffy;
        }
    }
}

void human_field(int k, double *fx, double *fy)
{
    int i;
    double l;
    double ffx, ffy;
    double x = mass[k].x;
    double y = mass[k].y;
    *fx = 0;
    *fy = 0;
    for (i = 0; i < n; i++)
    {
        if (mass[i].z == 0)
        {
            ffx = mass[i].x - x;
            ffy = mass[i].y - y;
            l = sqrt(ffx*ffx + ffy*ffy);

            if (l > 1e-6)
            {
                ffx /= l*l;
                ffy /= l*l;
            }
            *fx += ffx;
            *fy += ffy;
        }
    }
}

void space_field(int k, double *fx, double *fy)
{
    int i;
    double l;
    double ffx, ffy;
    double x = mass[k].x;
    double y = mass[k].y;
    *fx = 0;
    *fy = 0;
    for (i = 0; i < n; i++)
    {
        if (mass[i].z == mass[k].z)
        {
            ffx = mass[i].x - x;
            ffy = mass[i].y - y;
            l = ffx*ffx + ffy*ffy;
            if (l > 1e-6)
            {
                ffx /= -l;
                ffy /= -l;
            }
            *fx += ffx;
            *fy += ffy;
        }
    }
}

void extra_field(int k, double *fx, double *fy)
{
    int i;
    double l;
    double ffx, ffy;
    double x = mass[k].x;
    double y = mass[k].y;

    l = sqrt(x*x+y*y);
    if (l > rad)
    {
        *fx = -x;
        *fy = -y;
    }


}

int if_victim(int k)
{
    int i;
    for (i = 0; i < n; i++)
    {
        if (mass[i].z == 1)
        {
            double x, y, zx, zy, l;
            x = mass[k].x;
            y = mass[k].y;
            zx = mass[i].x;
            zy = mass[i].y;
            l = sqrt((x-zx)*(x-zx) + (y-zy)*(y-zy));
            if (l < ra)
                return 1;
        }
    }
    return 0;
}

void go(double dt)
{
    int i;
    for (i = 0; i < n; i++)
    {
        double fx, fy, sx=0, sy=0, l;
        if (mass[i].z == 0)
        {
            zombie_field(i, &fx, &fy);
        }
        else
        {
            human_field(i, &fx, &fy);
        }

        sx += fx;
        sy += fy;

        space_field(i, &fx, &fy);

        sx += fx;
        sy += fy;

        extra_field(i, &fx, &fy);

        sx += fx;
        sy += fy;

        l = sqrt(sx*sx+sy*sy);
        if (l > 1e-6)
        {
            sx /= l;
            sy /= l;
        }

        if (mass[i].z == 0)
        {
            sx *= vh*dt;
            sy *= vh*dt;
        }
        else
        {
            sx *= vz*dt;
            sy *= vz*dt;
        }

        mass[i].tx = mass[i].x + sx;
        mass[i].ty = mass[i].y + sy;
    }
    for (i = 0; i < n; i++)
    {
        double l;
        mass[i].x = mass[i].tx;
        mass[i].y = mass[i].ty;
    }
    for (i = 0; i < n; i++)
    {
        if (mass[i].z == 0)
            mass[i].z = if_victim(i);
    }
}


Uint8 colour_h, colour_z;

void draw_pixel(int X, int Y, Uint8 color, SDL_Surface *screen)
{
    Uint8 *pixmem;
    if (X < 10)
        X = 10;
    if (Y < 10)
        Y = 10;
    if (X >= 790)
        X = 789;
    if (Y >= 790)
        Y = 789;

    pixmem = (Uint8 *)screen->pixels + Y * screen->pitch + X * screen->format->BytesPerPixel;
    *pixmem = color;
}

void draw_per(double x, double y, int z, SDL_Surface *screen)
{
    Uint8 color;
    int X, Y;
    if (z)
        color = colour_z;
    else
        color = colour_h;
    X = x/(rad*2)*400 + 400;
    Y = y/(rad*2)*400 + 400;

    draw_pixel(X-1, Y-1, color, screen);
    draw_pixel(X-1, Y, color, screen);
    draw_pixel(X-1, Y+1, color, screen);
    draw_pixel(X, Y-1, color, screen);
    draw_pixel(X, Y, color, screen);
    draw_pixel(X, Y+1, color, screen);
    draw_pixel(X+1, Y-1, color, screen);
    draw_pixel(X+1, Y, color, screen);
    draw_pixel(X+1, Y+1, color, screen);


}

int main(void)
{
    double t, t1;
    double dt = 0.1;
    int i;
    int keypress = 0;
    SDL_Surface *screen;
    SDL_Event event;

    Uint8 *pixmem;

    srand(time(NULL));

    n = 20;
    rad = 10;
    ra = 0.5;

    vh = 1;
    vz = 2;

    t1 = 10;

    SDL_Init(SDL_INIT_VIDEO);
    screen = SDL_SetVideoMode(800, 800,8,SDL_HWSURFACE|SDL_DOUBLEBUF);

    colour_h = SDL_MapRGB( screen->format, 0, 255, 0 );
    colour_z = SDL_MapRGB( screen->format, 255, 0, 0 );


    mass = malloc(sizeof(per)*n);

    for (i = 0; i < n; i++)
    {
        double l, a;

        l = (rand()%RAND_MAX)/((double)RAND_MAX)*rad;
        a = (rand()%RAND_MAX)/((double)RAND_MAX)*2*3.141;
        mass[i].x = l*cos(a);
        mass[i].y = l*sin(a);

        mass[i].z = 0;
    }

    mass[0].z = 1;


    while(!keypress)
    {
        go(dt);
            usleep(dt*1e6);
        printf("t = %lf\n", t);

        SDL_FillRect(screen, NULL, 0x000000);
        for (i = 0; i < n; i++)
        {
            draw_per(mass[i].x, mass[i].y, mass[i].z, screen);
            printf("%s %lf %lf\n", mass[i].z?"z":"h", mass[i].x, mass[i].y);
        }

        SDL_Flip(screen);

        while(SDL_PollEvent(&event))
            {
                switch (event.type)
                    {
                case SDL_QUIT:
                    keypress = 1;
                    break;
                case SDL_KEYDOWN:
                    keypress = 1;
                    break;
            }
        }
        t+= dt;
    }


    SDL_Quit();
    free(mass);
    return 0;
}