use bevy::{prelude::*, render::renderer};

#[derive(Component)]
#[require(Transform)]
pub struct PhysicsBody {
    pub mass: f32,
    pub force: Vec2,
    pub velocity: Vec2,
    pub drag: f32, // velocity multiplied each physics update by (1-drag)
}

impl Default for PhysicsBody {
    fn default() -> Self {
        Self {
            mass: 1.0,
            force: Vec2::ZERO,
            velocity: Vec2::ZERO,
            drag: 0.0,
        }
    }
}

pub fn integrate(mut query: Query<(&mut Transform, &mut PhysicsBody)>, time: Res<Time<Fixed>>) {
    for (mut transform, mut physicsbody) in &mut query {
        let force = physicsbody.force;
        let mass = physicsbody.mass;
        let drag = physicsbody.drag;
        let delta_secs = time.delta_secs();

        physicsbody.velocity += force * delta_secs / mass;
        // Drag because stability is good you know
        physicsbody.velocity *= 1.0 - drag;

        transform.translation.x += physicsbody.velocity.x * delta_secs;
        transform.translation.y += physicsbody.velocity.y * delta_secs;
        physicsbody.force = Vec2::ZERO;
    }
}