enemies.c~

#include <allegro5/allegro.h>
#include <allegro5/allegro_primitives.h>
#include <allegro5/allegro_image.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define WIDTH 640
#define HEIGHT 640
//EN is the maximum enemy number
#define EN 5
//MAX_SHIPS is the maximum number of ships posible on the screen
#define MAX_ENEMIES 6

typedef struct Enemies_{
  int x;
  int y;
  int speed;
  bool live;
}Enemy;

const int FPS=30;

//main function
int main(int argc, char **argv){
  int i,j;
  int counter=0;
  
  srand(time(NULL));
  
  //initializing allegro
  if(!al_init() || !al_init_primitives_addon() || !al_init_image_addon()){
    printf("Error\n");
    return 0;
  }

  //create display
  ALLEGRO_DISPLAY* display=al_create_display(WIDTH, HEIGHT);
  if(!display){
    printf("Error\n");
    return 0;
  }

  //event handling and timer
  ALLEGRO_EVENT event;
  ALLEGRO_EVENT_QUEUE* queue=al_create_event_queue();
  if(!queue){
    printf("Error\n");
    return 0;
  }
  ALLEGRO_TIMER *timer=al_create_timer(1.0/FPS);
  if(!timer){
    printf("error\n");
    return 0;
  }

  //registering event sources
  if(!al_install_keyboard()){
    printf("Error\n");
    return 0;
  }
  al_register_event_source(queue, al_get_display_event_source(display));
  al_register_event_source(queue, al_get_timer_event_source(timer));
  al_register_event_source(queue, al_get_keyboard_event_source());

  //cresating enemy array to store enemies and initializing enemies
  Enemy enemies[MAX_ENEMIES];
  for(i=0;i<MAX_ENEMIES;i++){
    enemies[i].x=0;
    enemies[i].y=0;
    enemies[i].speed=5;
    enemies[i].live=false;
  }

  //game loop
  int ship=0;
  bool done=false;
  bool redraw=true;
  al_start_timer(timer);

  while(!done){
    al_wait_for_event(queue, &event);

    //if it is a timer event, update counter and enemy ships
    if(event.type==ALLEGRO_EVENT_TIMER){
      redraw=true;
      counter++;
      if(counter==15){
	//after two seconds, we create new ships
	counter=0;
	for(i=0;i<rand()%EN;i++){
	  if(!enemies[ship].live){
	    enemies[ship].x=rand()%640;
	    enemies[ship].y=0;
	    enemies[ship].live=true;
	    ship=(ship+1)%MAX_ENEMIES;
	  }
	}
      }
      //we update live ships positions and kill ships if position exceeds 640
      for(i=0;i<MAX_ENEMIES;i++){
	if(enemies[i].live){
	  enemies[i].y +=enemies[i].speed;
	}
	if(enemies[i].y>=640){
	  enemies[i].y=0;
	  enemies[i].live=false;
	}
      }
    }
    else if(event.type==ALLEGRO_EVENT_DISPLAY_CLOSE){
      done=false;
    }
    else if(event.type==ALLEGRO_EVENT_KEY_DOWN){
      if(event.keyboard.keycode==ALLEGRO_KEY_ESCAPE){
	done=true;
      }
    }

    //draw ships
    if(redraw && al_is_event_queue_empty(queue)){
      //if event queue is empty
      for(i=0;i<MAX_ENEMIES ;i++){
	if(enemies[i].live){
	  al_draw_filled_rectangle(enemies[i].x-10, enemies[i].y-10, enemies[i].x+10, enemies[i].y+10, al_map_rgb(255, 0, 255));
	}
      }
      
      al_flip_display();
      al_clear_to_color(al_map_rgb(0, 0, 0));

      redraw=false;
    }
  }    

  al_destroy_event_queue(queue);
  al_destroy_timer(timer);
  al_destroy_display(display);

}