// File: game.cxx
// Plays an interactive snake game
#include <cstdlib>
#include <ctime>
#include <graphics.h>
using namespace std;

// When steve gets this much money, the big gnat always moves toward him!
const int FULL = 28; 
const int MANY_GNATS = 30;

class sprite
{
public:
    // The first sprite constructor sets it to a small black circle;
    // The second sprite constructor sets the properties to specfied
    // values; both set the sprite to a random location.
    sprite( );
    sprite(int c, int r, char s);
    // The following member functions can change the properties
    // or location of a sprite:
    void set_properties(int c, int r, char s);
    void set_location(double x, double y);
    void set_random_location( );
    void relative_move(double delta_x, double delta_y);
    void move_randomly( );
    void move_toward
         (double target_x, double target_y, double amount);
    void move_toward(sprite target, double amount);
    void move_toward_mouse(double amount);
    // These functions don't change a sprite, but they give some
    // information or do some output with the sprite:
    bool has_hit(sprite other) const;
    bool has_hit(sprite others[], int n) const;
    void draw( ) const;
    sprite operator *(double multiplier) const;
    void operator ++( );    
private:
    // This is the information that every sprite contains:
    int color;
    int radius;
    char shape; // 'C' for circle or 'S' square
    double x;
    double y;
};

sprite sprite::operator *(double multiplier) const
{
    sprite answer(color, int(multiplier*radius), shape);
    return answer;
}

void sprite::operator ++( )
{
    radius++;
}

sprite::sprite( )
{
    set_properties(1 + rand() % 15, 2, 'C');
    set_random_location( );
}

sprite::sprite(int c, int r, char s)
{
    set_properties(c, r, s);
    set_random_location( );
}

void sprite::set_properties(int c, int r, char s)
{
    color = c;
    radius = r;
    shape = s;
}

bool sprite::has_hit(sprite other) const
{
    double distance, delta_x, delta_y;
    
    delta_x = x - other.x;
    delta_y = y - other.y;
    distance = sqrt(delta_x*delta_x + delta_y*delta_y);
    return (distance < (radius + other.radius));
}

bool sprite::has_hit(sprite others[], int n) const
{
    int i;

    for (i = 0; i < n; ++i)
    {
	if (has_hit(others[i]))
	    return true;
    }
    return false;
}

void sprite::relative_move(double delta_x, double delta_y)
{
    set_location(x+delta_x, y+delta_y);
}

void sprite::move_randomly( )
{
    move_toward(x+ (rand() % 3) - 1, y+ (rand()%3) - 1, 1);
}

void sprite::move_toward
(double target_x, double target_y, double amount)
{
    double d_x = target_x - x;
    double d_y = target_y - y;
    double d = sqrt(d_x*d_x + d_y*d_y);

    if (d > amount)
       relative_move((d_x/d)*amount, (d_y/d)*amount);
    else
       set_location(target_x, target_y);
}

void sprite::move_toward(sprite target, double amount)
{
    move_toward(target.x, target.y, amount);
}

void sprite::move_toward_mouse(double amount)
{
    move_toward(mousex(), mousey(), amount);    
}

void sprite::set_location(double x, double y)
{
    this->x = x;
    this->y = y;
}

void sprite::set_random_location( )
{
    set_location(rand( ) % (getmaxx( )+1), rand( ) % (getmaxy( )+1));
}


void sprite::draw( ) const
{
    setfillstyle(SOLID_FILL, color);
    switch (shape)
    {
    case 'C':
     fillellipse((int)x, (int)y, radius, radius);
     break;
    case 'S':
     bar((int)x-radius, (int)y-radius, (int)x+radius, (int)y+radius);
     break;
    }
}

int main( )
{
    // Initialize the graphics and random numbers:
    srand(time(NULL));
    initwindow(300, 300, "Steve vs the Gnats!", 0, 0, true);

    // Variable declarations and big gnat initialization:
    int i; 
    int stash = 0;
    sprite steve(YELLOW, 5, 'S');
    sprite money (GREEN, 5, 'C');
    sprite door(MAGENTA, 7, 'S');
    sprite gnats[MANY_GNATS];
    gnats[0].set_properties(RED, 15, 'C');

    gnats[1] = gnats[0]*0.1;
    while (!steve.has_hit(gnats, MANY_GNATS) && !steve.has_hit(door))
    {
        // Mess around with the sprites:
	steve.move_toward_mouse(2.5);
        if (steve.has_hit(money))
	{
	    stash++;
	    money.set_random_location( );
            ++gnats[0];
	}
	if (rand( ) % FULL < stash)
	    gnats[0].move_toward(steve, 2.5);
        for (i = 0; i < MANY_GNATS; i++)
	    gnats[i].move_randomly( );

	// Draw the sprites and the money bar:
	clearviewport( );
	steve.draw( );
	money.draw( );
	door.draw( );
        for (i = 0; i < MANY_GNATS; i++)
	    gnats[i].draw( );
	setfillstyle(SOLID_FILL, GREEN);
	bar(0, getmaxy()-10, stash*getmaxx()/FULL, getmaxy( ));
	swapbuffers( );
	
        // Sleep for a bit:
	delay(100);
    }

    // Print a message and wait for a key press:
    if (steve.has_hit(door))
	bgiout << "Steve escaped with $" << stash << "!";
    else
	bgiout << "Steve got et!";
    outstreamxy(10, 10);
    getch( );
    
    return 0;
}