#define _POSIX_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <time.h>

#define KEY_UP    65
#define KEY_DOWN  66
#define KEY_LEFT  68
#define KEY_RIGHT 67
#define KEY_SPACE 32

#define MAX_BULLETS 20
#define STEP_B 2500
#define MAX_ENEMIES 204
#define STEP_E 8000

typedef struct
{
    int x; int y;
    char  image ;
} Entity;

void checkcollision();
void shoot();
void movebullets();
void moveenemies();
void moveentity(Entity* entity, int addx, int addy);
void end();
void draw();
void drawentity(Entity* entity);
void clrscr();
void gotoxy(int x, int y);
int  getkey();

Entity player;
Entity* bullets[MAX_BULLETS];
int bullet_count = 0;
int step_b = 0;
Entity* enemies[MAX_ENEMIES];
int enemies_count = 0;
int need_draw = 1;
int step_e = 0;
int direction = 1;

int main()
{
    int key;

    player.x = 40; player.y = 24; player.image = '#';

    int initial_x = 1;
    int initial_y = 1;
    for(int i = 0; i < MAX_ENEMIES; i++)
    {
        enemies[i] = malloc(sizeof(Entity));
        enemies[i]->x = initial_x % 40;
        enemies[i]->y = initial_y;
        enemies[i]->image = '@';
        enemies_count++;
        initial_x += 2;
        if (initial_x % 41 == 0) { initial_y++; }
    }

    while(1)
    {
        key = getkey();
        if (key == KEY_RIGHT) { moveentity(&player,  1,  0); } // derecha
        if (key == KEY_LEFT)  { moveentity(&player,  -1, 0); } // izquierda
        if (key == KEY_SPACE) { shoot(); }

        if (enemies_count <= 0) { end(); break; }
        moveenemies();
        movebullets();
        checkcollision();
        draw();
    }

    return 0;
}

void checkcollision()
{
    for(int i = 0; i < MAX_ENEMIES; i++)
    {
        for(int j = 0; j < MAX_BULLETS; j++)
        {
            if (enemies[i] == NULL) { continue; }
            if (bullets[j] == NULL) { continue; }
            if (bullets[j]->y < 1) { bullets[j] = NULL; bullet_count--; continue; }
            if (bullets[j]->x != enemies[i]->x) { continue; }
            if (bullets[j]->y != enemies[i]->y) { continue; }
            enemies[i] = NULL; enemies_count--;
            bullets[j] = NULL; bullet_count--;
        }
    }
}

void shoot()
{
    if (bullet_count >= MAX_BULLETS) { return; }
    bullet_count++;
    int i;
    for(int j = 0; j < bullet_count; j++) { if (bullets[j] == NULL) { i = j; } }
    bullets[i] = malloc(sizeof(Entity));
    bullets[i]->x = player.x;
    bullets[i]->y = player.y - 1;
    bullets[i]->image = '*';
}

void movebullets()
{
    if (step_b < STEP_B) { step_b++; return; }
    step_b = 0;
    for(int j = 0; j < MAX_BULLETS; j++)
    {
        if (bullets[j] != NULL)
        {
            moveentity(bullets[j], 0, -1);
        }
    }
}
void moveenemies()
{
    if (step_e < STEP_E) { step_e++; return; }
    step_e = 0;
    int move_down = 0;
    for(int i = 0; i < MAX_ENEMIES; i++)
    {
        if (enemies[i] == NULL) { continue; }
        if (direction == 1) { moveentity(enemies[i], 1, 0);  } // derecha
        if (direction == 0) { moveentity(enemies[i], -1, 0); } // izquierda
    }
    for(int i = 0; i < MAX_ENEMIES; i++)
    {
        if (enemies[i] == NULL) { continue; }
        if (enemies[i]->x > 79) { direction = 0; move_down = 1; }
        if (enemies[i]->x < 1)  { direction = 1; move_down = 1; }
    }
    if (move_down == 1)
    {
        for(int i = 0; i < MAX_ENEMIES; i++)
        {
            if (enemies[i] == NULL) { continue; }
            moveentity(enemies[i], 0, 1);
        }
    }
}

void moveentity(Entity* entity, int addx, int addy)
{
    entity->x += addx;
    entity->y += addy;
    need_draw = 1;
}

void draw()
{
    if (need_draw == 0) { return; }
    clrscr();
    drawentity(&player);
    for(int i = 0; i < MAX_ENEMIES; i++)
    {
        if (enemies[i] == NULL) { continue; }
        drawentity(enemies[i]);
    }
    for(int i = 0; i < MAX_BULLETS; i++)
    {
        if (bullets[i] == NULL) { continue; }
        drawentity(bullets[i]);
    }
    gotoxy(0, 0);
    need_draw = 0;
}

void end()
{
    clrscr();
    gotoxy(34, 11);
    printf("ENHORABUENA");
    gotoxy(35, 12);
    printf("HAS GANADO");
}

void drawentity(Entity* entity)
{
    gotoxy(entity->x, entity->y);
    printf("%c", entity->image);
}

void clrscr()
{
  printf("\033[2J");   // Borra pantalla
  printf("\033[1;1H"); // Posicionamos el cursor en la fila 1 columna 1
}

void gotoxy(int x, int y)
{
  printf("\033[%d;%dH", y, x);  // Posicionamos el cursor en X, Y
}

int getkey()
{
    int character;
    struct termios orig_term_attr;
    struct termios new_term_attr;

    /* set the terminal to raw mode */
    tcgetattr(fileno(stdin), &orig_term_attr);
    memcpy(&new_term_attr, &orig_term_attr, sizeof(struct termios));
    new_term_attr.c_lflag &= ~(ECHO|ICANON);
    new_term_attr.c_cc[VTIME] = 0;
    new_term_attr.c_cc[VMIN] = 0;
    tcsetattr(fileno(stdin), TCSANOW, &new_term_attr);

    /* read a character from the stdin stream without blocking */
    /*   returns EOF (-1) if no character is available */
    character = fgetc(stdin);

    /* restore the original terminal attributes */
    tcsetattr(fileno(stdin), TCSANOW, &orig_term_attr);

    return character;
}