wenaglia/src/sys/physics.rs

use crate::com::{Blocking, Collision, Velocity, Position};
use crate::game::MyGame;

use specs::{Join,RunNow};

struct Intersection;

impl<'a> specs::System<'a> for Intersection {
    type SystemData = (
        specs::Entities<'a>,
        specs::ReadStorage<'a, Position>,
        specs::ReadStorage<'a, Velocity>,
        specs::ReadStorage<'a, Blocking>,
        specs::WriteStorage<'a, Collision>,
    );

    fn run(&mut self, (entity, position, velocity, blocking, mut collision): Self::SystemData) {
        let mut spacemap = std::collections::HashMap::new();
        for (e, pos, _) in (&entity, &position, &blocking).join() {
            spacemap.insert(pos.to_grid(), e);
        }

        for (pos, vel, col) in (&position, &velocity, &mut collision).join() {
            if let Some(_) = spacemap.get(&pos.moved(vel).to_grid()) {
                col.has_collision = true;
            }
        }
    }
}

struct Physics;

impl <'a> specs::System<'a> for Physics {
    type SystemData = (
        specs::ReadStorage<'a, Velocity>,
        specs::ReadStorage<'a, Collision>,
        specs::WriteStorage<'a, Position>,
    );

    fn run(&mut self, (velocity, collision, mut position): Self::SystemData) {
        for (vel, col, pos) in (&velocity, &collision, &mut position).join() {
            if !col.has_collision {
                pos.x += vel.dx;
                pos.y += vel.dy;
            }
        }
    }
}

struct ResetCollision;

impl<'a> specs::System<'a> for ResetCollision {
    type SystemData =
        specs::WriteStorage<'a, Collision>;

    fn run(&mut self, mut collision: Self::SystemData) {
        for mut e in (&mut collision).join() {
            e.has_collision = false;
        }
    }
}

pub fn systems(game: &mut MyGame) {
    Intersection.run_now(&game.world.res);
    Physics.run_now(&game.world.res);
    ResetCollision.run_now(&game.world.res);
}