game_of_life.rs

use notan::draw::*;
use notan::prelude::*;
use std::convert::TryInto;

const WIDTH: usize = 100;
const HEIGHT: usize = 100;
const BYTES_LENGTH: usize = WIDTH * HEIGHT * 4;

#[derive(AppState)]
struct State {
    texture: Texture,
    current_bytes: [u8; BYTES_LENGTH],
    previous_bytes: [u8; BYTES_LENGTH],
    count: f32,
    dirty: bool,
}

impl State {
    fn is_alive(&self, x: usize, y: usize) -> bool {
        let neighbors = get_neighbors(x as _, y as _);
        let count = neighbors.iter().fold(0, |sum, (x, y)| {
            let idx = index(*x, *y);
            match idx {
                Some(idx) => {
                    let is_red =
                        is_red_color(&self.previous_bytes[idx..idx + 4].try_into().unwrap());
                    if is_red {
                        sum + 1
                    } else {
                        sum
                    }
                }
                _ => sum,
            }
        });

        let was_alive = match index(x as _, y as _) {
            Some(idx) => is_red_color(&self.previous_bytes[idx..idx + 4].try_into().unwrap()),
            _ => false,
        };

        if was_alive {
            count == 2 || count == 3
        } else {
            count == 3
        }
    }

    fn swap_data(&mut self) {
        std::mem::swap(&mut self.current_bytes, &mut self.previous_bytes);
        self.dirty = true;
    }

    fn set_color(&mut self, color: Color, x: usize, y: usize) {
        if let Some(idx) = index(x as _, y as _) {
            self.current_bytes[idx..idx + 4].copy_from_slice(&color.rgba_u8());
        }
    }
}

#[notan_main]
fn main() -> Result<(), String> {
    let width = WIDTH * 4;
    let height = HEIGHT * 4;

    let win_config = WindowConfig::new().set_size(width as _, height as _);

    notan::init_with(setup)
        .initialize(init)
        .add_config(win_config)
        .add_config(DrawConfig)
        .update(update)
        .draw(draw)
        .build()
}

fn setup(gfx: &mut Graphics) -> State {
    let current_bytes = [255; BYTES_LENGTH];
    let previous_bytes = current_bytes;

    let texture = gfx
        .create_texture()
        .from_bytes(&current_bytes, WIDTH as _, HEIGHT as _)
        .build()
        .unwrap();

    State {
        texture,
        current_bytes,
        previous_bytes,
        count: 0.0,
        dirty: false,
    }
}

fn init(state: &mut State) {
    let mut rng = Random::default();
    for _ in 0..500 {
        let x = rng.gen_range(0..WIDTH);
        let y = rng.gen_range(0..HEIGHT);

        let neighbors = get_neighbors(x as _, y as _);
        neighbors.iter().for_each(|(x, y)| {
            let valid_coords = index(*x, *y).is_some();
            if valid_coords {
                state.set_color(Color::RED, *x as _, *y as _);
            }
        });
    }

    state.swap_data();
}

fn update(app: &mut App, state: &mut State) {
    state.count += app.timer.delta_f32();

    // update each 300ms
    if state.count >= 0.3 {
        state.count = 0.0;

        for y in 0..HEIGHT {
            for x in 0..WIDTH {
                let color = if state.is_alive(x, y) {
                    Color::RED
                } else {
                    Color::WHITE
                };

                state.set_color(color, x, y);
            }
        }

        state.swap_data();
    }
}

fn draw(gfx: &mut Graphics, state: &mut State) {
    // Update the texture with the new data
    if state.dirty {
        gfx.update_texture(&mut state.texture)
            .with_data(&state.current_bytes)
            .update()
            .unwrap();

        state.dirty = false;
    }

    // Draw the texture using the draw 2d API for convenience
    let mut draw = gfx.create_draw();
    draw.clear(Color::BLACK);
    draw.image(&state.texture).scale(4.0, 4.0);
    gfx.render(&draw);
}

fn index(x: isize, y: isize) -> Option<usize> {
    if x < 0 || y < 0 {
        return None;
    }

    let x = x as usize;
    let y = y as usize;
    let index = ((y * WIDTH) + x) * 4;
    if index >= BYTES_LENGTH {
        None
    } else {
        Some(index)
    }
}

#[inline]
fn is_red_color(bytes: &[u8; 4]) -> bool {
    bytes == &[255, 0, 0, 255]
}

#[rustfmt::skip]
fn get_neighbors(ix: isize, iy: isize) -> [(isize, isize); 8] {
    [
        (ix - 1, iy - 1), (ix, iy - 1), (ix + 1, iy - 1),
        (ix - 1, iy),                   (ix + 1, iy),
        (ix - 1, iy + 1), (ix, iy + 1), (ix + 1, iy + 1),
    ]
}