#include "allegro.h"

//create some colors
#define WHITE makecol(255,255,255)
#define BLACK makecol(0,0,0)
#define RED makecol(255,0,0)
#define GREEN makecol(0,255,0)
#define BLUE makecol(0,0,255)
#define SMOKE makecol(140,130,120)

//point structure used to draw lines
typedef struct POINT
{
    int x,y;
}POINT;

//points array holds do_line points for drawing a line
POINT points[2000];
int curpoint,totalpoints;

//bitmap images
BITMAP *buffer;
BITMAP *crosshair;
BITMAP *city;

//misc variables
int x1,y1,x2,y2;
int done=0;
int destroyed=1;
int n;
int mx,my,mb;
int score = -1;

void updatescore()
{
    //update and display the score
    score++;
    textprintf_right(buffer,font,SCREEN_W-5,1,WHITE, 
        "SCORE: %d  ", score);
}
    
void explosion(BITMAP *bmp, int x,int y,int finalcolor)
{
    int color,size;

    for (n=0; n<20; n++)
    {
        //generate a random color
        color = makecol(rand()%255,rand()%255,rand()%255);
        //random explosion size
        size = 20+rand()%20;
        //draw the random filled circle
        circlefill(bmp, x, y, size, color);
        //short pause
        rest(2);
    }
    //missile tracker looks for this explosion color
    circlefill(bmp, x, y, 40, finalcolor);
}


void doline(BITMAP *bmp, int x, int y, int d)
{
    //line callback function...fills the points array
    points[totalpoints].x = x;
    points[totalpoints].y = y;
    totalpoints++;
}

void firenewmissile()
{
    //activate the new missile
    destroyed=0;
    totalpoints = 0;
    curpoint = 0;

    //random starting location
    x1 = rand() % (SCREEN_W-1);
    y1 = 20;
    
    //random ending location
    x2 = rand() % (SCREEN_W-1);
    y2 = SCREEN_H-50;
        
    //construct the line point-by-point
    do_line(buffer,x1,y1,x2,y2,0,&doline);
}

void movemissile()
{
    //grab a local copy of the current point
    int x = points[curpoint].x;
    int y = points[curpoint].y;
    
    //hide mouse pointer
    scare_mouse();

    //erase missile
    rectfill(buffer,x-6,y-3,x+6,y+1,BLACK);

    //see if missile was hit by defense weapon
    if (getpixel(screen,x,y) == GREEN)
    {
        //missile destroyed! score a point
        destroyed++;
        updatescore();
    }
    else
    //no hit, just draw the missile and smoke trail
    {
        //draw the smoke trail
        putpixel(buffer,x,y-3,SMOKE);
        //draw the missile
        circlefill(buffer,x,y,2,BLUE);
    }
    
    //show mouse pointer
    unscare_mouse();

    //did the missile hit a city?
    curpoint++;
    if (curpoint >= totalpoints)
    {
        //destroy the missile
        destroyed++;
        //animate explosion directly on screen
        explosion(screen, x, y, BLACK);
        //show the damage on the backbuffer
        circlefill(buffer, x, y, 40, BLACK);
    }
}

void main(void)
{
    //initialize program    
    allegro_init();
    set_color_depth(16);
    set_gfx_mode(GFX_AUTODETECT_WINDOWED, 640, 480, 0, 0);
    install_keyboard();
    install_mouse();
    install_timer();
    srand(time(NULL));

    //create a secondary screen buffer
    buffer = create_bitmap(640,480);

    //display title
    textout(buffer,font,"Strategic Defense (ESC to quit)",0,1,WHITE);
    
    //display score
    updatescore();
    
    //draw border around screen
    rect(buffer, 0, 12, SCREEN_W-2, SCREEN_H-2, RED);
    
    //load and draw the city images
    city = load_bitmap("city.bmp", NULL);
    for (n = 0; n < 5; n++)
        masked_blit(city, buffer, 0, 0, 50+n*120, 
            SCREEN_H-city->h-2, city->w, city->h);

    //load the mouse cursor
    crosshair = load_bitmap("crosshair.bmp", NULL); 
    set_mouse_sprite(crosshair);
    set_mouse_sprite_focus(15,15);
    show_mouse(buffer);

    readkey();
    
    //main loop
    while (!key[KEY_ESC])
    {
        //grab the current mouse values
        mx = mouse_x;
        my = mouse_y;
        mb = (mouse_b & 1);

        //fire another missile if needed
        if (destroyed)
            firenewmissile();

        //left mouse button, fire the defense weapon
        if (mb)
            explosion(screen,mx,my,GREEN);

        //update enemy missile position
        movemissile();

        //update screen       
        blit(buffer,screen,0,0,0,0,640,480);
        
        //pause
        rest(10);
    }
    
    set_mouse_sprite(NULL);
    destroy_bitmap(city);
    destroy_bitmap(crosshair);
    allegro_exit();

}
END_OF_MAIN();