#!/usr/bin/perl
use strict;
use warnings;

# These will allow us to use all the modules necessary to create a GUI.
# They are all parts of the Perl SDL module.
# The :: are use to seperate the name of the module and its corresponding member.
use SDL;
use SDL::Events;
use SDLx::App;
use SDLX::Rect;



# First is to set up the screen.
# The => operator is similiar to a comma.
# but it treates the word to the left as a quoted word.
# Even though there isn't any quotes.
my $app = SDLx::App->new(
    width        => 500,
    height       => 500,
    title        => 'PONG',
    dt           => 0.04,
    exit_on_quit => 1,
);
# The next step is to set up the paddles for each player.
# This is done in a hash reference.
# This is done so its possible to add information later.
# The numbers may need to be changed later to fit the paddles to the screen.
# I am not 100% sure what -> actually does.
# Other than the fact its a deference operator.
# h is a shortened reference to height
my $player1 = {
    paddle => SDLx::Rect->new( 10, $app-> height / 2, 10, 40),
};
my $player2 = {
    paddle => SDLx::Rect->new( $app-> width - 20, $app-> height / 2, 10, 40)
};

# This is to create the ball
my $ball = {
    rect => SDLx::Rect->new( $app-> width / 2, $app-> height / 2, 10, 10 ),
	v_x  => -2.3,
	v_y  => 1.5,
};
$app->add_show_handler (
    sub {
	$app->draw_rect( [ 0, 0, $app->w, $app->h ], 0x000000FF );
        $app->draw_rect( $ball->{rect}, 0xFF0000FF );
        $app->draw_rect( $player1->{paddle}, 0xFF0000FF );
        $app->draw_rect( $player2->{paddle}, 0xFF0000FF );
        $app->update;
      }
    );
	$player1 = {
    paddle => SDLx::Rect->new( 10, $app-> height / 2, 10, 40 ),
    v_y => 0,
};
$app->add_move_handler( sub {
	my ( $step, $app ) = @_;
	my $paddle = $player1->{paddle};
	my $v_y = $player1->{v_y};
	
	$paddle->y( $paddle->y ( $v_y * $step ) );
});
$player2 = {
	paddle => SDLx::Rect->new( $app->w - 20, $app-> height / 2, 10, 40),
	v_y => 0,
};
$app->add_move_handler( sub {
	my ( $step, $app ) = @_;
	my $paddle = $player2->{paddle};
	my $v_y = $player2->{v_y};
	
	if ( $ball->{rect}->y > $paddle->y ) {
		$player2->{v_y} =1.5;
		}
		else {
			$player2->{v_y} = 0;
		}
	
	$paddle->y( $paddle->y ( $v_y * $step ) );
});
$app->add_event_handler(
	sub {
		my ( $event, $app ) = @_;
		
		if ( $event->type == SDL_KEYDOWN ) {
		
			if ( $event->key_sym == SDLK_UP ) {
				$player1->{v_y} = -20;
			}
			
			elsif ( $event->key_sym == SDLK_DOWN ) {
				$player1->{v_y} = 20;
			}
		}
		
		elsif ( $event->type == SDL_KEYUP ) {
			
			if ( 
					$event->key_sym == SDLK_UP
				 or $event->key_sym == SDLK_DOWN
			) {
				$player1->{v_y} = 0;
			}
		}
	}
);
$app->add_move_handler(
	sub {
		my ( $step, $app ) = @_;
		my $ball_rect = $ball->{rect};
		$ball_rect->x( $ball_rect->x + ($ball->{v_x} * $step) );
		$ball_rect->y( $ball_rect->y + ($ball->{v_y} * $step) );
		
		if ( $ball_rect->bottom >= $app->h ) {
			$ball_rect->bottom( $app->h);
			$ball->{v_y} *= -1;
		}
		
		elsif ( $ball_rect->top <= 0 ) {
			$ball_rect->top( 0 );
			$ball->{v_y} *= -1;
		}
		elsif ( $ball_rect->right >= $app->w ) {
			$player1->{score}++;
			reset_game();
			return;
	}
		elsif ( $ball_rect->left <= 0 ) {
			$player2->{score}++;
			reset_game();
			return;
	}
		elsif ( check_collision( $ball_rect, $player1->{paddle} )) {
			$ball_rect->left( $player1->{paddle}->right );
			$ball->{v_x} *= -1;
		}
		elsif ( check_collision( $ball_rect, $player2->{paddle} )) {
			$ball->{v_x} *= -1;
			$ball_rect->right( $player2->{paddle}->left );
			}
});
sub reset_game {
	$ball->{rect}->x( $app->w / 2 );
	$ball->{rect}->y( $app->h / 2);
	}
sub check_collision {
	my ($A, $B) = @_;
	
	return if $A->bottom < $B->top;
	return if $A->top    > $B->bottom;
	return if $A->right  < $B->left;
	return of $A->left   > $B->right;
	
	return 1;
}

$app->run;