#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
// https://tetra.seventeencups.net/tutorial/01-creating-a-project
use tetra::graphics::{self, Color, Rectangle, Texture};
use tetra::input::{self, Key};
use tetra::math::Vec2;
use tetra::window;
use tetra::{Context, ContextBuilder, State};

const WINDOW_WIDTH:f32 = 640.0;
const WINDOW_HEIGHT:f32 = 480.0;
const PADDLE_SPEED:f32 = 8.0;
const BALL_SPEED:f32 = 5.0;                                     
const PADDLE_SPIN: f32 = 4.0;
const BALL_ACC:f32 = 0.05;

struct Entity {
    texture: Texture,
    position: Vec2<f32>,
    velocity: Vec2<f32>,
}

impl Entity{
    fn new(texture: Texture,position: Vec2<f32>) -> Self{
        Entity::with_velocity(texture,position,Vec2::zero())
    }
    fn with_velocity(texture: Texture,position: Vec2<f32>,velocity: Vec2<f32>) -> Self {
        Entity{
            texture,
            position,
            velocity,
        }
    }
    fn centre(&self)-> Vec2<f32>{
        Vec2::new(
            self.position.x + (self.width() / 2.0),
            self.position.y + (self.height() / 2.0),
        )
    }
    fn width(&self) -> f32{
        self.texture.width() as f32
    }
    fn height(&self) -> f32{
        self.texture.height() as f32
    }
    fn bounds(&self) -> Rectangle {
        Rectangle::new(
            self.position.x,
            self.position.y,
            self.width(),
            self.height(),
        )
    }
}

struct GameState {
    player1: Entity,
    player2: Entity,
    ball: Entity,
}

impl GameState{
    fn new(ctx: &mut Context) -> tetra::Result<GameState>{
        let player1_texture:Texture = Texture::new(ctx,"./resources/player1.png")?;
        //player1_texture
        let player2_texture:Texture = Texture::new(ctx,"./resources/player2.png")?;
        let ball_texture:Texture = Texture::new(ctx,"./resources/ball.png")?;

        let player1_position = 
        Vec2::new(16.0,(WINDOW_HEIGHT - player1_texture.height() as f32) / 2.0);
        let player2_position = 
        Vec2::new(WINDOW_WIDTH - player2_texture.width() as f32 -16.0,(WINDOW_HEIGHT - player2_texture.height() as f32) / 2.0);
        let ball_position = 
        Vec2::new(WINDOW_WIDTH / 2.0 - (ball_texture.width() as f32 / 2.0) as f32,WINDOW_HEIGHT / 2.0 - (ball_texture.height() as f32 / 2.0) as f32);

        let ball_speed = Vec2::new(-BALL_SPEED,0.0);

        Ok(GameState {
            player1: Entity::new(player1_texture,player1_position),
            player2: Entity::new(player2_texture,player2_position),
            ball: Entity::with_velocity(ball_texture,ball_position,ball_speed),
        })
    }
}

impl State for GameState{
    
    fn draw(&mut self, ctx: &mut Context) -> tetra::Result {
        graphics::clear(ctx,Color::rgb(0.329,0.584,0.929));

        self.player1.texture.draw(ctx,self.player1.position);
        self.player2.texture.draw(ctx,self.player2.position);
        self.ball.texture.draw(ctx,self.ball.position);

        Ok(())
    }
    fn update(&mut self,ctx: &mut Context) -> tetra::Result{
        //Player 1 movements
        if input::is_key_down(ctx, Key::W) && self.player1.position.y as i32 > 0{
            self.player1.position.y -= PADDLE_SPEED;
        }
        if input::is_key_down(ctx, Key::S) && ((self.player1.position.y as i32 + self.player1.texture.height()) as f32) < WINDOW_HEIGHT{
            self.player1.position.y += PADDLE_SPEED;
        }
        //player 2 movements
        if input::is_key_down(ctx, Key::Up) && self.player2.position.y as i32 > 0{
            self.player2.position.y -= PADDLE_SPEED;
        }
        if input::is_key_down(ctx, Key::Down) && ((self.player2.position.y as i32 + self.player1.texture.height()) as f32) < WINDOW_HEIGHT{
            self.player2.position.y += PADDLE_SPEED;
        }

        //Collisions 

        let player1_bounds:Rectangle = self.player1.bounds();
        let player2_bounds:Rectangle = self.player2.bounds();
        let ball_bounds:Rectangle = self.ball.bounds();

        let paddle_hit = if ball_bounds.intersects(&player1_bounds) {
            Some(&self.player1)
        }else if ball_bounds.intersects(&player2_bounds){
            Some(&self.player2)
        }else{
            None
        };

        if let Some(paddle) = paddle_hit{
            //increase ball velocity before flipping it
            self.ball.velocity.x = 
            -(self.ball.velocity.x + (BALL_ACC * self.ball.velocity.x.signum()));

            //Calculate the offset between the paddle center and the ball
            let offset = (paddle.centre().y - self.ball.centre().y) / paddle.height();

            self.ball.velocity.y += PADDLE_SPIN * -offset;
        }

        self.ball.position += self.ball.velocity;

        //check borders
        if self.ball.position.y <= 0.0 || self.ball.position.y + self.ball.height() >= WINDOW_HEIGHT{
            self.ball.velocity.y = -self.ball.velocity.y;
        }
        //check winner
        if self.ball.position.x <= 0.0{
            window::quit(ctx);
            println!("Player 2 won!");
        }
        if self.ball.position.x + self.ball.width() >= WINDOW_WIDTH{
            window::quit(ctx);
            println!("Player 1 won!");
        }

        Ok(())
    }
}

fn main() -> tetra::Result{
    ContextBuilder::new("Pong",WINDOW_WIDTH as i32,WINDOW_HEIGHT as i32)
        .quit_on_escape(true)
        .build()?
        .run(GameState::new)
}