asteroids game

main.rs

/* Cargo.toml
[package]
name = "asteroids"
version = "0.1.0"
authors = ["me <my_email@gmail.com>"]
edition = "2018"

[dependencies]
rand = "0.5"

[dependencies.sdl2]
version = "0.31"
default-features = false
features = ["gfx"]
*/

extern crate rand;
extern crate sdl2;
// std
use std::time::{Duration, Instant};
// sdl2
use sdl2::event::Event;
//use sdl2::rect::Rect;
use sdl2::keyboard::Keycode;
use sdl2::keyboard::Scancode;
use sdl2::pixels::Color;
use sdl2::render::{Canvas, RenderTarget};
use sdl2::EventPump;
// gfx
use sdl2::gfx::primitives::DrawRenderer;
// rand
use rand::Rng;

const UPDATE_RATE: u32 = 30;
const UPDATE_LENGTH_NS: u32 = 1_000_000_000 / UPDATE_RATE;
const UPDATE_MAX_SKIP: u32 = 10;
const UPDATE_DT: f32 = 1.0 / (UPDATE_RATE as f32);
const TWO_PI: f32 = std::f32::consts::PI * 2.0;
const BULLET_RADIUS: f32 = 5.0;
const ASTEROID_STAGES: [(f32, f32); 4] = [(120.0, 15.0), (70.0, 30.0), (50.0, 50.0), (20.0, 80.0)];
const ASTEROID_STAGES_DEAD: usize = 1234;

struct Ship {
    x: f32,
    y: f32,
    radius: f32,
    angle: f32,
    speed_x: f32,
    speed_y: f32,
}

struct Bullet {
    x: f32,
    y: f32,
    angle: f32,
    time_left: f32,
}

struct Asteroid {
    x: f32,
    y: f32,
    angle: f32,
    stage: usize,
}

struct Game<'a> {
    rng: &'a mut rand::ThreadRng,
    name: &'static str,
    arena_w: f32,
    arena_h: f32,
    ship: Ship,
    key_right: bool,
    key_left: bool,
    key_up: bool,
    key_fire: bool,
    bullets: Vec<Bullet>,
    bullet_timer: f32,
    asteroids: Vec<Asteroid>,
}

fn draw_strings<T: RenderTarget>(canvas: &mut Canvas<T>, lines: &[&str]) {
    let mut string_y = 0;
    for &line in lines.iter() {
        let _ = canvas.string(0, string_y, line, Color::RGB(255, 255, 255));
        string_y += 8;
    }
}

fn are_circles_intersecting(
    a_x: f32,
    a_y: f32,
    a_radius: f32,
    b_x: f32,
    b_y: f32,
    b_radius: f32,
) -> bool {
    (a_x - b_x).powi(2) + (a_y - b_y).powi(2) <= (a_radius + b_radius).powi(2)
}

fn wrap_val<T>(val: T, limit: T) -> T
where
    T: Copy,
    T: std::ops::Add<Output = T> + std::ops::Rem<Output = T>,
{
    (limit + val) % limit
}

impl<'a> Game<'a> {
    fn new(arena_w: u32, arena_h: u32, rng: &'a mut rand::ThreadRng) -> Game<'a> {
        let mut g = Game {
            rng,
            name: "Asteroids",
            arena_w: arena_w as f32,
            arena_h: arena_h as f32,
            ship: Ship {
                x: 0.0,
                y: 0.0,
                radius: 30.0,
                angle: 0.0,
                speed_x: 0.0,
                speed_y: 0.0,
            },
            key_right: false,
            key_left: false,
            key_up: false,
            key_fire: false,
            bullets: vec![],
            bullet_timer: 0.0,
            asteroids: vec![],
        };
        g.reset();
        g
    }

    fn reset(&mut self) {
        self.ship.x = self.arena_w / 2.0;
        self.ship.y = self.arena_h / 2.0;
        self.ship.angle = 0.0;
        self.ship.speed_x = 0.0;
        self.ship.speed_y = 0.0;

        self.bullets.clear();
        self.bullet_timer = 0.5;

        self.asteroids.clear();
        self.asteroids.push(Asteroid {
            x: 100.0,
            y: 100.0,
            angle: self.rng.gen_range(0.0, 1.0),
            stage: ASTEROID_STAGES.len() - 1,
        });
        self.asteroids.push(Asteroid {
            x: self.arena_w - 100.0,
            y: 100.0,
            angle: self.rng.gen_range(0.0, 1.0),
            stage: ASTEROID_STAGES.len() - 1,
        });
        self.asteroids.push(Asteroid {
            x: self.arena_w / 2.0,
            y: self.arena_h - 100.0,
            angle: self.rng.gen_range(0.0, 1.0),
            stage: ASTEROID_STAGES.len() - 1,
        });
    }

    fn input(&mut self, event_source: &mut EventPump) -> bool {
        // process evetns
        for event in event_source.poll_iter() {
            match event {
                Event::Quit { .. }
                | Event::KeyDown {
                    keycode: Some(Keycode::Escape),
                    ..
                } => return false,
                _ => {}
            }
        }
        // update keyboard state
        let keys = event_source.keyboard_state();
        self.key_right = keys.is_scancode_pressed(Scancode::Right);
        self.key_left = keys.is_scancode_pressed(Scancode::Left);
        self.key_up = keys.is_scancode_pressed(Scancode::Up);
        self.key_fire = keys.is_scancode_pressed(Scancode::S);
        // continue
        return true;
    }

    fn update(&mut self) {
        // move ship
        if self.key_right {
            self.ship.angle = wrap_val(self.ship.angle + 10.0 * UPDATE_DT, TWO_PI);
        }
        if self.key_left {
            self.ship.angle = wrap_val(self.ship.angle - 10.0 * UPDATE_DT, TWO_PI);
        }
        if self.key_up {
            let ship_speed = 100.0;
            self.ship.speed_x = self.ship.speed_x + self.ship.angle.cos() * ship_speed * UPDATE_DT;
            self.ship.speed_y = self.ship.speed_y + self.ship.angle.sin() * ship_speed * UPDATE_DT;
        }
        self.ship.x = wrap_val(self.ship.x + self.ship.speed_x * UPDATE_DT, self.arena_w);
        self.ship.y = wrap_val(self.ship.y + self.ship.speed_y * UPDATE_DT, self.arena_h);

        // shoot
        self.bullet_timer += UPDATE_DT;
        if self.key_fire {
            if self.bullet_timer >= 0.5 {
                self.bullet_timer = 0.0;
                self.bullets.push(Bullet {
                    x: self.ship.x + self.ship.angle.cos() * self.ship.radius,
                    y: self.ship.y + self.ship.angle.sin() * self.ship.radius,
                    angle: self.ship.angle,
                    time_left: 4.0,
                });
            }
        }

        // bullets
        let mut new_asteroids: Vec<Asteroid> = vec![];
        for (_idx, b) in self.bullets.iter_mut().enumerate() {
            let bullet_speed = 500.0;
            b.x = wrap_val(b.x + b.angle.cos() * bullet_speed * UPDATE_DT, self.arena_w);
            b.y = wrap_val(b.y + b.angle.sin() * bullet_speed * UPDATE_DT, self.arena_h);
            b.time_left -= UPDATE_DT;

            // collide with asteroid
            for (_idx, a) in self.asteroids.iter_mut().enumerate() {
                if are_circles_intersecting(
                    b.x,
                    b.y,
                    BULLET_RADIUS,
                    a.x,
                    a.y,
                    ASTEROID_STAGES[a.stage].1,
                ) {
                    // kill bullet and asteroid
                    b.time_left = 0.0;
                    // add 2 new asteroids
                    if a.stage > 1 {
                        new_asteroids.push(Asteroid {
                            x: a.x,
                            y: a.y,
                            angle: TWO_PI * self.rng.gen_range(0.0, 1.0),
                            stage: a.stage - 1,
                        });
                        new_asteroids.push(Asteroid {
                            x: a.x,
                            y: a.y,
                            angle: wrap_val(
                                new_asteroids.last().unwrap().angle - std::f32::consts::PI,
                                TWO_PI,
                            ),
                            stage: a.stage - 1,
                        });
                    }
                    a.stage = ASTEROID_STAGES_DEAD;
                }
            }
            self.asteroids.retain(|a| a.stage < ASTEROID_STAGES_DEAD);
        }
        self.bullets.retain(|b| b.time_left > 0.0);
        self.asteroids.append(&mut new_asteroids);

        if self.asteroids.is_empty() {
            self.reset();
            return;
        }

        // asteroids
        for (_idx, a) in self.asteroids.iter_mut().enumerate() {
            let asteroid_speed = ASTEROID_STAGES[a.stage].0;
            a.x = wrap_val(
                a.x + a.angle.cos() * asteroid_speed * UPDATE_DT,
                self.arena_w,
            );
            a.y = wrap_val(
                a.y + a.angle.sin() * asteroid_speed * UPDATE_DT,
                self.arena_h,
            );

            // collosion
            if are_circles_intersecting(
                self.ship.x,
                self.ship.y,
                self.ship.radius,
                a.x,
                a.y,
                ASTEROID_STAGES[a.stage].1,
            ) {
                // restart game
                self.reset();
                return;
            }
        }
    }

    fn draw_objects<T: RenderTarget>(&self, canvas: &mut Canvas<T>, offset_x: i16, offset_y: i16) {
        // ship
        let _ = canvas.filled_circle(
            offset_x + self.ship.x as i16,
            offset_y + self.ship.y as i16,
            self.ship.radius as i16,
            Color::RGB(0, 0, 255),
        );

        // ship cockpit
        let ship_circle_distance = 20.0;
        let _ = canvas.filled_circle(
            offset_x + (self.ship.x + self.ship.angle.cos() * ship_circle_distance) as i16,
            offset_y + (self.ship.y + self.ship.angle.sin() * ship_circle_distance) as i16,
            5,
            Color::RGB(0, 255, 255),
        );

        // bullets
        for (_idx, b) in self.bullets.iter().enumerate() {
            let _ = canvas.filled_circle(
                offset_x + b.x as i16,
                offset_y + b.y as i16,
                BULLET_RADIUS as i16,
                Color::RGB(0, 255, 0),
            );
        }

        // asteroids
        for (_idx, a) in self.asteroids.iter().enumerate() {
            let _ = canvas.filled_circle(
                offset_x + a.x as i16,
                offset_y + a.y as i16,
                ASTEROID_STAGES[a.stage].1 as i16,
                Color::RGB(255, 255, 0),
            );
        }
    }

    fn draw<T: RenderTarget>(&self, canvas: &mut Canvas<T>) {
        canvas.set_draw_color(Color::RGB(0, 0, 0));
        canvas.clear();

        for y in -1..2 {
            for x in -1..2 {
                self.draw_objects(canvas, x * (self.arena_w as i16), y * (self.arena_h as i16));
            }
        }

        /*
        draw_strings(
            canvas,
            &[
                &format!("ship.angle: {}", self.ship.angle),
                &format!("ship.x: {}", self.ship.x),
                &format!("ship.y: {}", self.ship.x),
                &format!("ship.speed_x: {}", self.ship.speed_x),
                &format!("ship.speed_y: {}", self.ship.speed_x),
            ],
        );
        */
    }
}

pub fn main() {
    let arena_w = 800;
    let arena_h = 600;
    let mut rng = rand::thread_rng();
    let mut game = Game::new(arena_w, arena_h, &mut rng);

    let sdl_context = sdl2::init().unwrap();
    let video_subsystem = sdl_context.video().unwrap();

    let window = video_subsystem
        .window(game.name, arena_w, arena_h)
        .position_centered()
        .build()
        .unwrap();

    let mut canvas = window
        .into_canvas()
        .accelerated()
        .present_vsync()
        .build()
        .unwrap();

    let mut event_source = sdl_context.event_pump().unwrap();

    let update_length = Duration::new(0, UPDATE_LENGTH_NS);
    let mut next_update = Instant::now();
    'running: loop {
        let mut loop_cnt = 0;
        while (Instant::now() > next_update) && (loop_cnt < UPDATE_MAX_SKIP) {
            if !game.input(&mut event_source) {
                break 'running;
            }
            game.update();
            next_update += update_length;
            loop_cnt += 1;
        }

        game.draw(&mut canvas);
        canvas.present();
    }
}