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

// Crate
use crate::{
    comp::{phys::Pos, Agent, Control, Jumping, Attacking},
    state::Time,
};

// Basic ECS AI agent system
pub struct Sys;

impl<'a> System<'a> for Sys {
    type SystemData = (
        Read<'a, Time>,
        Entities<'a>,
        WriteStorage<'a, Agent>,
        ReadStorage<'a, Pos>,
        WriteStorage<'a, Control>,
        WriteStorage<'a, Jumping>,
        WriteStorage<'a, Attacking>,
    );

    fn run(
        &mut self,
        (time, entities, mut agents, positions, mut controls, mut jumpings, mut attackings): Self::SystemData,
    ) {
        for (entity, agent, pos, control) in
            (&entities, &mut agents, &positions, &mut controls).join()
        {
            match agent {
                Agent::Wanderer(bearing) => {
                    *bearing += Vec2::new(rand::random::<f32>() - 0.5, rand::random::<f32>() - 0.5)
                        * 0.1
                        - *bearing * 0.01
                        - pos.0 * 0.0002;

                    if bearing.magnitude_squared() != 0.0 {
                        control.move_dir = bearing.normalized();
                    }
                }
                Agent::Pet { target, offset } => {
                    // Run towards target
                    match positions.get(*target) {
                        Some(tgt_pos) => {
                            let tgt_pos = tgt_pos.0 + *offset;

                            if tgt_pos.z > pos.0.z + 1.0 {
                                jumpings.insert(entity, Jumping);
                            }

                            // Move towards the target.
                            let dist: f32 = Vec2::from(tgt_pos - pos.0).magnitude();
                            control.move_dir = if dist > 5.0 {
                                Vec2::from(tgt_pos - pos.0).normalized()
                            } else if dist < 1.5 && dist > 0.0 {
                                Vec2::from(pos.0 - tgt_pos).normalized()
                            } else {
                                Vec2::zero()
                            };
                        }
                        _ => control.move_dir = Vec2::zero(),
                    }

                    // Change offset occasionally.
                    if rand::random::<f32>() < 0.003 {
                        *offset =
                            Vec2::new(rand::random::<f32>() - 0.5, rand::random::<f32>() - 0.5)
                                * 10.0;
                    }
                },
                Agent::Enemy { target } => {
                    let choose_new = match target.map(|tgt| positions.get(tgt)).flatten() {
                        Some(tgt_pos) => {
                            let dist = Vec2::<f32>::from(tgt_pos.0 - pos.0).magnitude();
                            if dist < 2.0 {
                                control.move_dir = Vec2::zero();

                                if rand::random::<f32>() < 0.2 {
                                    attackings.insert(entity, Attacking::start());
                                }

                                false
                            } else if dist < 60.0 {
                                control.move_dir = Vec2::<f32>::from(tgt_pos.0 - pos.0).normalized() * 0.96;

                                false
                            } else {
                                true
                            }
                        },
                        None => {
                            control.move_dir = Vec2::one();
                            rand::random::<f32>().fract() < 0.25
                        },
                    };

                    if choose_new {
                        let entities = (&entities, &positions)
                            .join()
                            .filter(|(_, e_pos)| Vec2::<f32>::from(e_pos.0 - pos.0).magnitude() < 30.0)
                            .map(|(e, _)| e)
                            .collect::<Vec<_>>();

                        *target = rand::thread_rng().choose(&entities).cloned();
                    }
                },
            }
        }
    }
}