// Library
use specs::{Entities, Join, Read, ReadStorage, ReadExpect, System, WriteStorage};
use vek::*;

// Crate
use crate::{
    comp::{
        phys::{Dir, Pos, Vel},
        Animation, AnimationHistory, Control,
    },
    terrain::TerrainMap,
    vol::{ReadVol, Vox},
};

// Basic ECS AI agent system
pub struct Sys;

impl<'a> System<'a> for Sys {
    type SystemData = (
        ReadExpect<'a, TerrainMap>,
        Entities<'a>,
        ReadStorage<'a, Pos>,
        WriteStorage<'a, Vel>,
        WriteStorage<'a, Dir>,
        WriteStorage<'a, AnimationHistory>,
        ReadStorage<'a, Control>,
    );

    fn run(&mut self, (terrain, entities, pos, mut vels, mut dirs, mut anims, controls): Self::SystemData) {
        for (entity, pos, mut vel, mut dir, control) in
            (&entities, &pos, &mut vels, &mut dirs, &controls).join()
        {
            let on_ground = terrain
                .get((pos.0 - Vec3::unit_z() * 0.1).map(|e| e.floor() as i32))
                .map(|vox| !vox.is_empty())
                .unwrap_or(false) && vel.0.z <= 0.0;

            if on_ground {
                // TODO: Don't hard-code this
                // Apply physics to the player: acceleration and non-linear decceleration
                vel.0 += control.move_dir * 2.0 - vel.0.map(|e| e * e.abs() + e) * 0.03;

                if control.jumping {
                    vel.0.z += 16.0;
                }
            } else {
                // TODO: Don't hard-code this
                // Apply physics to the player: acceleration and non-linear decceleration
                vel.0 += control.move_dir * 0.2;
            }

            let animation = if on_ground {
                if control.move_dir.magnitude() > 0.01 {
                    dir.0 = vel.0.normalized() * Vec3::new(1.0, 1.0, 0.0);
                    Animation::Run
                } else {
                    Animation::Idle
                }
            } else {
                Animation::Jump
            };

            let last_animation = anims.get_mut(entity).map(|h| h.current);

            anims.insert(
                entity,
                AnimationHistory {
                    last: last_animation,
                    current: animation,
                },
            );
        }
    }
}