//   ▄████████▄      +        ███ +  ▄█████████ ███     +
//  ███▀    ▀███ +         +  ███    ███▀  +    ███ +       +
//  ███  +   ███ ███   ███ █████████ ███        ███  ███   ███
//  ███     +███ ███   ███    ███    ███▐██████ ███  ███   ███
//  ███ +    ███ ███+  ███   +███    ███     +  ███  ███ + ███
//  ███▄    ▄███ ███▄  ███    ███ +  ███  +     ███  ███▄  ███
//   ▀████████▀ + ▀███████    ███▄   ███▄       ▀████ ▀███████
//       +                  +                +             ███
//  +   ▀████████████████████████████████████████████████████▀
//
// This module populates the world with stars and asteroids.

use crate::prelude::*;
use bevy::math::I64Vec3;
use bevy::prelude::*;
use bevy::render::mesh::Indices;
use bevy::scene::{InstanceId, SceneInstance};
use bevy_xpbd_3d::prelude::*;
use fastrand;
use std::collections::HashMap;

const ASTEROID_UPDATE_INTERVAL: f32 = 0.1; // seconds
const ASTEROID_SIZE_FACTOR: f32 = 10.0;
const RING_THICKNESS: f64 = 8.0e6;
const STARS_MAX_MAGNITUDE: f32 = 5.5; // max 7.0, see generate_starchart.py

const SKYBOX: bool = false;

const ASTEROID_SPAWN_STEP: f64 = 1000.0;
const ASTEROID_VIEW_RADIUS: f64 = 3000.0;

const ASSET_NAME_ASTEROID1: &str = "asteroid1";
const ASSET_NAME_ASTEROID2: &str = "asteroid2";

pub struct WorldPlugin;
impl Plugin for WorldPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, setup);
        app.add_systems(PostUpdate, handle_despawn);
        app.add_systems(Update, spawn_despawn_asteroids);
        app.add_systems(Update, handle_respawn.run_if(on_event::<RespawnEvent>()));
        app.add_plugins(PhysicsPlugins::default());
        //app.add_plugins(PhysicsDebugPlugin::default());
        app.insert_resource(Gravity(DVec3::splat(0.0)));
        app.insert_resource(AsteroidUpdateTimer(Timer::from_seconds(
            ASTEROID_UPDATE_INTERVAL,
            TimerMode::Repeating,
        )));
        app.insert_resource(ActiveAsteroids(HashMap::new()));
        app.add_event::<DespawnAsteroidEvent>();
        app.add_event::<RespawnEvent>();
    }
}

#[derive(Resource)]
struct AsteroidUpdateTimer(Timer);
#[derive(Resource)]
pub struct ActiveAsteroids(pub HashMap<I64Vec3, AsteroidData>);
#[derive(Component)]
struct Asteroid;
#[derive(Component)]
pub struct Star;
#[derive(Component)]
pub struct DespawnOnPlayerDeath;
#[derive(Event)]
pub struct RespawnEvent;

pub struct AsteroidData {
    entity: Entity,
    //viewdistance: f64,
}

#[derive(Event)]
pub struct DespawnAsteroidEvent {
    entity: Entity,
    sceneinstance: InstanceId,
    origin: I64Vec3,
}

pub fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    mut materials_skybox: ResMut<Assets<load::SkyBox>>,
) {
    // Generate starmap
    let sphere_handle = meshes.add(Sphere::new(1.0).mesh().uv(16, 16));
    let mut starcount = 0;
    for (index, star) in nature::STARS.iter().enumerate() {
        let (x, y, z, mag, _absmag, color_index, name) = *star;
        if mag > STARS_MAX_MAGNITUDE {
            continue;
        }

        let (r, g, b) = nature::star_color_index_to_rgb(color_index);
        let mut pos = DVec3::new(x as f64, z as f64, -y as f64) * nature::PARSEC2METER;
        if pos.length() > 1e21 {
            pos *= 0.002;
        }
        let pos_render = pos * 1.0;
        let scale_factor = 1e-4 * pos_render.length() as f32; // from experimentation

        let mag = mag.min(6.0);
        let scale_size =
            { |mag: f32| scale_factor * (0.230299 * mag * mag - 3.09013 * mag + 15.1782) };
        let scale = scale_size(mag);

        let scale_color =
            { |color: f32| 1.2 * color * (0.0659663 * mag * mag - 1.09862 * mag + 4.3) };
        //let scale = translation.length().powf(0.84);
        //pos_render.length().powf(0.64)
        //(radius as f64 * nature::SOL_RADIUS).powf(0.02) as f32 *

        let star_color_handle = materials.add(StandardMaterial {
            base_color: Color::rgb(scale_color(r), scale_color(g), scale_color(b)),
            unlit: true,
            ..default()
        });
        let name = if name.is_empty() {
            format!("Uncharted Star #{index}")
        } else {
            name.to_string()
        };
        let distance = if pos.length() > 1e21 {
            None
        } else {
            Some(pos.length())
        };

        commands.spawn((
            Star,
            hud::IsClickable {
                name: Some(name),
                distance,
                ..default()
            },
            PbrBundle {
                mesh: sphere_handle.clone(),
                material: star_color_handle,
                transform: Transform {
                    translation: pos_render.as_vec3(),
                    scale: Vec3::splat(scale as f32),
                    ..default()
                },
                ..default()
            },
            Position::from(pos_render),
            Rotation::from(Quat::IDENTITY),
        ));
        starcount += 1;
    }
    info!("Generated {starcount} stars");

    // Add shaded skybox
    if SKYBOX {
        let mut mesh = Mesh::from(Sphere::new(1e10).mesh().uv(5, 5));
        //let mut mesh = Mesh::from(Cuboid::from_size(Vec3::splat(2e10)));
        if let Some(Indices::U32(indices)) = mesh.indices_mut() {
            // Reverse the order of each triangle to avoid backface culling
            for slice in indices.chunks_mut(3) {
                slice.reverse();
            }
        }
        commands.spawn(MaterialMeshBundle {
            mesh: meshes.add(mesh),
            material: materials_skybox.add(load::SkyBox {}),
            transform: Transform::from_translation(Vec3::new(0.0, 0.0, 0.0)),
            ..default()
        });
    }
}

fn spawn_despawn_asteroids(
    time: Res<Time>,
    mut timer: ResMut<AsteroidUpdateTimer>,
    mut commands: Commands,
    q_player: Query<&Position, With<actor::PlayerCamera>>,
    mut ew_despawn: EventWriter<DespawnAsteroidEvent>,
    mut db: ResMut<ActiveAsteroids>,
    q_asteroid: Query<(&Position, &SceneInstance), With<Asteroid>>,
    mut last_player_cell: Local<I64Vec3>,
    id2pos: Res<game::Id2Pos>,
    asset_server: Res<AssetServer>,
) {
    if !timer.0.tick(time.delta()).just_finished() || q_player.is_empty() {
        //if q_player.is_empty() {
        return;
    }
    let jupiter_pos = if let Some(jupiter_pos) = id2pos.0.get(&"jupiter".to_string()) {
        *jupiter_pos
    } else {
        error!("Can't spawn asteroids because Jupiter's position can not be determined");
        return;
    };
    let player = q_player.get_single().unwrap();
    let fromjupiter = player.0 - jupiter_pos;
    let player_cell = I64Vec3::new(
        (fromjupiter.x / ASTEROID_SPAWN_STEP).round() as i64,
        (fromjupiter.y / ASTEROID_SPAWN_STEP).round() as i64,
        (fromjupiter.z / ASTEROID_SPAWN_STEP).round() as i64,
    );
    if *last_player_cell == player_cell {
        return;
    }
    *last_player_cell = player_cell;

    // Parameters
    let view_radius: f64 = ASTEROID_VIEW_RADIUS;
    let step: f64 = ASTEROID_SPAWN_STEP;
    let stepmax: i64 = (view_radius / step) as i64;

    // Despawn far asteroids
    let x_min = player_cell.x - stepmax;
    let x_max = player_cell.x + stepmax;
    let y_min = player_cell.y - stepmax;
    let y_max = player_cell.y + stepmax;
    let z_min = player_cell.z - stepmax;
    let z_max = player_cell.z + stepmax;
    for (origin, asteroid) in db.0.iter() {
        if origin.x < x_min
            || origin.x > x_max
            || origin.y < y_min
            || origin.y > y_max
            || origin.z < z_min
            || origin.z > z_max
        {
            if let Ok((pos, sceneinstance)) = q_asteroid.get(asteroid.entity) {
                if pos.0.distance(player.0) > 1000.0 {
                    ew_despawn.send(DespawnAsteroidEvent {
                        entity: asteroid.entity,
                        sceneinstance: **sceneinstance,
                        origin: origin.clone(),
                    });
                }
            } else {
                error!("Couldn't despawn asteroid:");
                dbg!(origin);
            }
        }
    }

    // Density based on the radius alone
    let radius_plane = (fromjupiter.x * fromjupiter.x + fromjupiter.z * fromjupiter.z).sqrt();
    let density_r = nature::ring_density((radius_plane / 1e6) as f32);
    if density_r < 0.001 {
        return;
    }
    // Density based on radius and the vertical distance to the ring
    let normalized_distance = fromjupiter.y / (RING_THICKNESS / 2.0);
    let density = density_r * (-4.0 * normalized_distance.powf(2.0)).exp() as f32;
    if density < 0.001 {
        return;
    }

    let mut rng = fastrand::Rng::new();
    for x in -stepmax..=stepmax {
        for y in -stepmax..=stepmax {
            for z in -stepmax..=stepmax {
                let origin = I64Vec3::new(
                    player_cell.x + x as i64,
                    player_cell.y + y as i64,
                    player_cell.z + z as i64,
                );
                if db.0.contains_key(&origin) {
                    // already in db, nothing to do
                    continue;
                }

                // Get a seed based on all of the origin axes
                // Probably there's a faster way
                rng.seed(origin.x as u64);
                let seed = rng.u64(0..u64::MAX).wrapping_add(origin.y as u64);
                rng.seed(seed);
                let seed = rng.u64(0..u64::MAX).wrapping_add(origin.z as u64);
                rng.seed(seed);

                let rand_s = rng.f32();
                let size_raw: f32 = (rand_s + 1e-4).powf(-0.5) as f32; // -> between ~1 and 100
                let size_density = size_raw * density;

                if size_density < 0.3 {
                    continue;
                }
                if size_raw < 20.0 {
                    let dist = player_cell.as_dvec3().distance(origin.as_dvec3());
                    if dist > 6.0 {
                        continue;
                    }
                }
                let size: f32 = ASTEROID_SIZE_FACTOR * size_density;

                let rand_x = rng.f64();
                let rand_y = rng.f64();
                let rand_z = rng.f64();
                let rand_c = rng.bool();
                let class = if rand_c { 0 } else { 1 };

                //let max_viewdist = ASTEROID_VIEW_RADIUS / ASTEROID_SPAWN_STEP;
                let wobble = ASTEROID_SPAWN_STEP * 0.5;
                let pos = jupiter_pos
                    + DVec3::new(
                        origin.x as f64 * ASTEROID_SPAWN_STEP + wobble * rand_x * 2.0 - 1.0,
                        origin.y as f64 * ASTEROID_SPAWN_STEP + wobble * rand_y * 2.0 - 1.0,
                        origin.z as f64 * ASTEROID_SPAWN_STEP + wobble * rand_z * 2.0 - 1.0,
                    );

                // Spawn
                let mut entity_commands = commands.spawn((
                    actor::Actor::default(),
                    RigidBody::Dynamic,
                    AngularVelocity(DVec3::new(0.1, 0.1, 0.03)),
                    LinearVelocity(DVec3::new(0.0, 0.0, 0.35)),
                    Collider::sphere(1.0),
                    Rotation::from(Quat::from_rotation_y(-PI32 / 3.)),
                    Position::new(pos),
                    hud::IsClickable {
                        name: Some("Uncharted Rock".to_string()),
                        ..default()
                    },
                    Asteroid,
                    DespawnOnPlayerDeath,
                ));
                let model = match class {
                    0 => ASSET_NAME_ASTEROID1,
                    _ => ASSET_NAME_ASTEROID2,
                };
                entity_commands.insert(SpatialBundle {
                    transform: Transform {
                        scale: Vec3::splat(size),
                        ..default()
                    },
                    ..default()
                });
                load_asset(model, &mut entity_commands, &*asset_server);
                db.0.insert(
                    origin,
                    AsteroidData {
                        entity: entity_commands.id(),
                        //viewdistance: 99999999.0,
                    },
                );
            }
        }
    }
}

fn handle_despawn(
    mut commands: Commands,
    mut er_despawn: EventReader<DespawnAsteroidEvent>,
    mut db: ResMut<ActiveAsteroids>,
    mut scene_spawner: ResMut<SceneSpawner>,
) {
    for despawn in er_despawn.read() {
        commands.entity(despawn.entity).despawn();
        scene_spawner.despawn_instance(despawn.sceneinstance);
        db.0.remove(&despawn.origin);
    }
}

pub fn handle_respawn(
    ew_spawn: EventWriter<cmd::SpawnEvent>,
    mut achievement_tracker: ResMut<var::AchievementTracker>,
) {
    *achievement_tracker = var::AchievementTracker::default();
    cmd::load_defs(ew_spawn);
}