use crate::{config::planet::{Planet, PlanetBundle, PlanetConfigCollection}, ecs::PlanetSensor, world_config::WorldConfigResource};
use bevy::{asset::Handle, math::DVec3};
use crate::prelude::*;
use bevy_replicon::prelude::Replicated;
use crate::config::planet::{PlanetSpring, PlanetSpringJoint};

pub fn planets_plugin(app: &mut App) {
    app.init_resource::<PlanetConfigResource>()
        .add_systems(Startup, start_loading_planets)
        .add_systems(Update, update_planets);
}

#[derive(Resource, Default)]
pub struct PlanetConfigResource {
    handle: Option<Handle<PlanetConfigCollection>>,
}

fn start_loading_planets(assets: Res<AssetServer>, mut planets: ResMut<PlanetConfigResource>) {
    planets.handle = Some(assets.load("config/planets.pc.toml"));
}

pub fn update_planets(
    mut commands: Commands,
    mut ev_config: MessageReader<AssetEvent<PlanetConfigCollection>>,
    assets: ResMut<Assets<PlanetConfigCollection>>,
    planets: ResMut<PlanetConfigResource>,
    mut q_planets: Query<(
        Entity,
        &mut Planet,
        &mut Transform,
        &mut Mass,
    )>,
    mut planet_joint_springs: Query<(&PlanetSpringJoint, &mut FixedJoint)>,
    world_config: Res<WorldConfigResource>,
) {
    let Some(ref world_config) = world_config.config else {
        return;
    };
    let Some(handle) = planets.handle.as_ref() else {
        return;
    };

    let waiting_for_asset_id = handle.id();

    for ev in ev_config.read() {
        match ev {
            AssetEvent::Added { id } => {
                if *id == waiting_for_asset_id {
                    debug!("planet config loaded - creating planets");
                    let planet_config = assets.get(*id).unwrap();
                    for planet in &planet_config.planets {
                        let planet_position = vec3(planet.default_transform[0], planet.default_transform[1], planet.default_transform[2]);
                        let mut planet_entity = commands
                            .spawn((PlanetBundle {
                                planet: planet.clone(),
                                transform: Transform::from_xyz(
                                    planet.default_transform[0],
                                    planet.default_transform[1],
                                    planet.default_transform[2],
                                ),
                                collider: Collider::circle(planet.radius),
                                mass: Mass(planet.mass)
                            },
                            SleepingDisabled
                        ));
                        planet_entity.with_child((
                            Collider::circle(planet.radius+2.0),
                            Sensor,
                            PlanetSensor(planet.name.clone()),
                            CollisionEventsEnabled,
                        ));
                        let planet_entity_id = planet_entity.id();
                        if let Some(orbit) = &planet.orbit {
                            let Some(parent_planet) = planet_config.planets.iter().find(|u| orbit.orbiting == u.name) else { continue };
                            let parent_planet_position = vec3(parent_planet.default_transform[0],
                                parent_planet.default_transform[1], parent_planet.default_transform[2]);
                            let r = (planet_position - parent_planet_position).as_dvec3();
                            let g = world_config.world.gravity * parent_planet.mass as f64
                                / r.length_squared();
                            // tangential velocity
                            let v = (g*r.length() as f64).sqrt();
                            let v_dir = DVec3::Z.cross(r).truncate().normalize();
                            let v = v_dir * v;
                            planet_entity.insert(LinearVelocity(v));

                            let spring = commands.spawn((
                                PlanetSpring {
                                    name: planet.name.clone()
                                },
                                Transform::from_xyz(
                                    planet.default_transform[0],
                                    planet.default_transform[1],
                                    planet.default_transform[2],
                                ),
                                RigidBody::Kinematic,
                            )).id();
                            commands.spawn((
                                PlanetSpringJoint {
                                    name: planet.name.clone()
                                },
                                FixedJoint::new(planet_entity_id, spring).with_point_compliance(planet_config.orbit.planet_spring_compliance),
                                JointDamping {
                                    linear: planet_config.orbit.planet_spring_damping,
                                    angular: 1.0,
                                },
                            ));
                        }

                        trace!(?planet, "new planet spawned");
                    }
                }
            }
            AssetEvent::Modified { id } => {
                if *id == waiting_for_asset_id {
                    trace!("planet config modified - reloading planets");
                    let planet_config = assets.get(*id).unwrap();

                    info!("updating compliance on all planet spring joints");
                    planet_joint_springs.iter_mut().for_each(|mut u| u.1.point_compliance = planet_config.orbit.planet_spring_compliance);

                    for planet in &planet_config.planets {
                        let existing_planet = q_planets
                            .iter_mut()
                            .find(|(_, p, _, _)| p.name == planet.name);

                        if let Some((existing, mut e_planet, mut e_transform, mut e_mass)) =
                            existing_planet
                        {
                            commands
                                .entity(existing)
                                .remove::<Collider>()
                                .insert(Collider::circle(planet.radius));
                            *e_planet = planet.clone();
                            *e_mass = Mass(planet.mass);
                            trace!(?planet, "planet hot-reloaded");
                        } else {
                            let planet_entity = commands
                                .spawn(PlanetBundle {
                                    planet: planet.clone(),
                                    transform: Transform::from_xyz(
                                        planet.default_transform[0],
                                        planet.default_transform[1],
                                        planet.default_transform[2],
                                    ),
                                    collider: Collider::circle(planet.radius),
                                    mass: Mass(
                                        planet.mass,
                                    ),
                                }).id();

                            if planet.orbit.is_some() {
                                let spring =commands.spawn((
                                    PlanetSpring {
                                        name: planet.name.clone()
                                    },
                                    Transform::from_xyz(
                                        planet.default_transform[0],
                                        planet.default_transform[1],
                                        planet.default_transform[2],
                                    )
                                )).id();
                                commands.spawn((
                                    PlanetSpringJoint {
                                        name: planet.name.clone()
                                    },
                                    FixedJoint::new(planet_entity, spring).with_point_compliance(planet_config.orbit.planet_spring_compliance)
                                ));
                            }
                            trace!(?planet, "new planet spawned");
                        }
                    }
                }
            }
            _ => {}
        }
    }
}