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//*********************************************************************
//*********************************************************************
//							Space Invaders
//					Written by Scarface 
//					 in C++ using Dark Basic GDK
//						  16th January 2009
//*********************************************************************
//*********************************************************************

#include <DarkGDK.h>

// boundry constants ( setup for 800x600 resolution )
const int LEFT_BOUNDRY = 20;
const int RIGHT_BOUNDRY = 495;

// game speed constants
const float SPEED_ALIEN = 1.2;
const float SPEED_BULLET = 4.0;
const float SPEED_SHIP = 5.0;

// function declarations
void move_ship( );
bool move_aliens( int xdir );
void move_bullet ( );

// main
void DarkGDK( void )
{
	// display setup
	dbSyncOn( );
	dbSyncRate( 60 );
	dbSetWindowSize( 800, 600 );

	// initialize variables
	int x = 260;	
	int y = 380;
	int x_dir = 0;

	// load sound effects
	dbLoadSound( "lazer.wav", 1 );
	dbLoadSound( "explode.wav", 2 );

	// create background
	dbLoadImage ( "backdrop.bmp", 1 );
	dbSprite ( 1, 0, 0, 1 );

	// create player controlled ship
	dbCreateAnimatedSprite( 2, "ship.png", 1, 1, 2);
	dbSprite( 2, x, y, 2 );

	// create the aliens and position them
	for ( int obj = 3; obj <= 11; obj ++ )
	{
		switch ( obj )
		{
			// positions
			case 1: x = 20;		y = 20;		break;
			case 2: x = 180;	y = 20;		break;
			case 3: x = 340;	y = 20;		break;
			case 4: x = 20;		y = 90;		break;
			case 5: x = 180;	y = 90;		break;
			case 6: x = 340;	y = 90;		break;
			case 7: x = 20;		y = 160;	break;
			case 8: x = 180;	y = 160;	break;
			case 9: x = 340;	y = 160;	break;
		}
		dbCreateAnimatedSprite( obj, "alien.png", 1, 1, obj );
		dbSprite( obj, x, y, obj );	
	}
	 
	// main loop
	while( LoopGDK( ) )
	{
		// function calls
		x_dir = move_aliens( x_dir );
		move_ship( );
		move_bullet( );

		// sync display
		dbSync( );

		// if esc is press, exit loop
		if ( dbEscapeKey ( ) )
			break;
	}

	// cleanup memory
	for ( int obj = 1; obj <= 12; obj ++ )
		dbDeleteSprite( obj );

	// end program
	return;
}

// function to move the player controlled ship
void move_ship( )
{
	// setup vars for ship movement
	int x = dbSpriteX( 2 );
	int y = dbSpriteY( 2 );

	// left key is being pressed
	if ( dbLeftKey( ) )
	{
		// if the ship has neeed exceeded the allowed boundry, then move ship to the left
		if ( x > LEFT_BOUNDRY )
			dbSprite( 2, x - SPEED_SHIP, y, 2 );  		
	}
	else if ( dbRightKey( ) ) // right key is being pressed
	{
		// if the ship has neeed exceeded the allowed boundry, then move ship to the right
		if ( x < RIGHT_BOUNDRY )
			dbSprite( 2, x + SPEED_SHIP, y, 2 );
	}
}

// this function will move the aliens
// returns the current movement direction: 0 = right, 1 = left
bool move_aliens( int x_dir )
{
	// initialize variables
	int x = 0;
	int y = 0;
	int x_offset = 320;
	int move_y = false;

    // if alien is moving left
	if ( x_dir == 1 )
	{
		// loop through and reposition aliens
		for ( int obj = 3; obj <= 11; obj ++ )
		{
			// get alien position
			x = dbSpriteX( obj );
			y = dbSpriteY( obj );

			// alien is at boundry
			if ( obj = 3 && x <= LEFT_BOUNDRY )
			{
				x = LEFT_BOUNDRY;
				move_y = true;
				
			}
			// alien should be moved along down it's y xoordinates
			if ( move_y )
			{
				y += SPEED_ALIEN * 4;
				x_dir = 0;
			}
			else // move alien along x coordinate
			{
				x -= SPEED_ALIEN;
			}

			// redraw alien
			dbSprite( obj, x, y, obj );
		}
	}
	else if ( x_dir == 0 ) // if alien is moving right
	{
		// loop through and reposition aliens
		for ( int obj = 3; obj <= 11; obj ++ )
		{
			// get alien position
			x = dbSpriteX( obj );
			y = dbSpriteY( obj );

			// alien is at boundry
			if ( obj = 3 && x >= RIGHT_BOUNDRY - x_offset )
			{
				x = RIGHT_BOUNDRY - x_offset;
				move_y = true;
			}
			// alien is to be moved down the y coordinate
			if ( move_y )
			{
				y += SPEED_ALIEN * 4;
				x_dir = 0;
			}
			else // move alien along x coordinate
			{
				x += SPEED_ALIEN;
			}

			// redraw alien
			dbSprite( obj, x, y, obj );
		}
	}
	return x_dir;
}

void move_bullet ( )
{
	// initialize vars
	int x = 0;
	int y = 0;
	int x_offset = 46;
	
	// bullet already exists ( only 1 bullet at a time ^^ )
	if ( dbSpriteExist( 12 ) && dbSpriteVisible ( 12 ) )
	{
		// define vars for bullet movement
		x = dbSpriteX( 12 );
		y = dbSpriteY( 12 ) - SPEED_BULLET;
		
		// if the bullet has gone out of boundries, hide it and put it into void position
		if ( y < 20 )
		{
			dbHideSprite( 12 );
			y = 450;
		}
		// loop through aliens and see if one was hit
		for ( int obj = 3; obj <= 11; obj ++ )
		{
			// if an active alien is hit
			if ( dbSpriteCollision( 12, obj ) && dbSpriteVisible ( obj ) )
			{
				// hide the bullet & the hit alien
				dbHideSprite( 12 );
				dbHideSprite( obj );
				dbPlaySound( 2 );
				y = 450;
			}
		}
	}
	else if ( dbSpaceKey( ) ) // new bullet fired!
	{
		// set bullet's starting y position
		y = 380;

		// check if the bullet has already been created
		if ( dbSpriteExist( 12 ) )
		{
			// bullet already exists, just make it visible
			dbShowSprite( 12 );
		}
		else
		{
			// create the bullet
			dbCreateAnimatedSprite( 12, "bullet.png", 1, 1, 12 );
			
			// declare position vars
			x = dbSpriteX( 2 ) + x_offset;
			y = dbSpriteY( 2 );
		}
		
		// sound effects
		dbPlaySound( 1 );
	}
	else
		return; // nothing, end function
	
	// set bullet's position
	dbSprite( 12, x, y, 12 );
}

// function declarations
void move_ship( );
bool move_aliens( int xdir );
void move_bullet ( );