use crate::{actor, nature, settings, hud};
use bevy::prelude::*;
use bevy::render::render_resource::{AsBindGroup, ShaderRef};
use bevy::math::{DVec3, I64Vec3};
use bevy_xpbd_3d::prelude::*;
use bevy_xpbd_3d::plugins::sync::SyncConfig;
use std::collections::HashMap;
use std::f32::consts::PI;
use fastrand;

const ASTEROID_UPDATE_INTERVAL: f32 = 0.1; // seconds
const ASTEROID_SIZE_FACTOR: f32 = 3.0;
const STARS_MAX_MAGNITUDE: f32 = 5.5;

const CENTER_WORLD_ON_PLAYER: bool = true;

const ASTEROID_SPAWN_STEP: f64 = 500.0;
const ASTEROID_VIEW_RADIUS: f64 = 3000.0;

const ASSET_ASTEROID1: &str = "models/asteroid.glb#Scene0";
const ASSET_ASTEROID2: &str = "models/asteroid2.glb#Scene0";
pub fn asset_name_to_path(name: &str) -> &'static str {
    match name {
        "suit" => "models/suit.glb#Scene0",
        "asteroid1" => ASSET_ASTEROID1,
        "asteroid2" => ASSET_ASTEROID2,
        "moonlet" => "models/moonlet.glb#Scene0",
        "monolith" => "models/monolith_neon.glb#Scene0",
        "lightorb" => "models/lightorb.glb#Scene0",
        "MeteorAceGT" => "models/MeteorAceGT.glb#Scene0",
        "pizzeria" => "models/pizzeria2.glb#Scene0",
        "pizzasign" => "models/pizzasign.glb#Scene0",
        _ => "models/error.glb#Scene0",
    }
}

pub struct WorldPlugin;
impl Plugin for WorldPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, setup);
        app.add_systems(Update, handle_cheats);
        app.add_systems(PostUpdate, handle_despawn);
        app.add_systems(Update, spawn_despawn_asteroids);
        app.add_plugins(PhysicsPlugins::default());
        app.add_plugins(MaterialPlugin::<RingMaterial>::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(AsteroidDatabase(Vec::new()));
        app.insert_resource(ActiveAsteroids(HashMap::new()));
        app.add_event::<DespawnEvent>();

        if CENTER_WORLD_ON_PLAYER {
            // Disable bevy_xpbd's position->transform sync function
            app.insert_resource(SyncConfig {
                position_to_transform: false,
                transform_to_position: false,
            });
            // Add own position->transform sync function
            app.add_systems(PreUpdate, position_to_transform);
        }
    }
}

#[derive(Resource)] struct AsteroidUpdateTimer(Timer);
#[derive(Resource)] struct AsteroidDatabase(Vec<AsteroidData>);
#[derive(Resource)] struct ActiveAsteroids(HashMap<I64Vec3, AsteroidData>);

#[derive(Component)] struct Asteroid;

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

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

#[derive(Asset, TypePath, AsBindGroup, Debug, Clone)]
pub struct RingMaterial {
    alpha_mode: AlphaMode,
    #[uniform(0)]
    ring_radius: f32,
    #[uniform(1)]
    jupiter_radius: f32,
}

impl Material for RingMaterial {
    fn fragment_shader() -> ShaderRef {
        "shaders/jupiters_rings.wgsl".into()
    }
    fn alpha_mode(&self) -> AlphaMode {
        self.alpha_mode
    }
}

#[derive(Component)]
pub struct Star;

pub fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    mut materials_custom: ResMut<Assets<RingMaterial>>,
) {
    // Generate starmap
    let sphere_handle = meshes.add(Sphere::new(1.0));
    let mut starcount = 0;
    for star in nature::STARS {
        let mag = star[3];
        if mag > STARS_MAX_MAGNITUDE {
            continue;
        }
        let scale_color = {|color: f32|
            if mag < -20.0 {
                color * 13.0f32 // Sun
            } else {
                color * (0.0659663 * mag * mag - 1.09862 * mag + 4.3)
            }
        };
        let scale_size = {|mag: f32|
            if mag < -20.0 {
                40000.0f32 // Sun
            } else {
                1000.0 * (0.230299 * mag * mag - 3.09013 * mag + 15.1782)
            } * 100.0
        };
        let (r, g, b) = nature::star_color_index_to_rgb(star[4]);
        let star_color_handle = materials.add(StandardMaterial {
            base_color: Color::rgb(scale_color(r), scale_color(g), scale_color(b)),
            unlit: true,
            ..default()
        });
        let dist = 1e9;
        commands.spawn((
            Star,
            PbrBundle {
                mesh: sphere_handle.clone(),
                material: star_color_handle.clone(),
                transform: Transform::from_xyz(
                        dist * star[0],
                        dist * star[1],
                        dist * star[2],
                    )
                    .with_scale(Vec3::splat(scale_size(mag))),
                ..default()
            }
        ));
        starcount += 1;
    }
    info!("Generated {starcount} stars");

    // Add shaded ring
    let ring_radius = 229_000_000.0;
    let jupiter_radius = 71_492_000.0;
    commands.spawn((
        MaterialMeshBundle {
            mesh: meshes.add(Mesh::from(Cylinder::new(ring_radius, 1.0))),
            material: materials_custom.add(RingMaterial {
                alpha_mode: AlphaMode::Blend,
                ring_radius: ring_radius,
                jupiter_radius: jupiter_radius,
            }),
            ..default()
        },
        Position::from_xyz(0.0, -10000.0, 0.0),
        //Rotation::from(Quat::IDENTITY),
        Rotation::from(Quat::from_rotation_x(-0.3f32.to_radians())),
    ));
}

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<DespawnEvent>,
    mut db: ResMut<ActiveAsteroids>,
    asset_server: Res<AssetServer>,
    mut q_asteroid: Query<(Entity, &mut Visibility), With<Asteroid>>,
    mut last_player_cell: Local<I64Vec3>,
    mut log: ResMut<hud::Log>,
) {
    if !timer.0.tick(time.delta()).just_finished()  || q_player.is_empty() {
    //if q_player.is_empty() {
        return;
    }
    let player = q_player.get_single().unwrap();
    let player_cell = I64Vec3::new(
        (player.x / ASTEROID_SPAWN_STEP).round() as i64,
        (player.y / ASTEROID_SPAWN_STEP).round() as i64,
        (player.z / ASTEROID_SPAWN_STEP).round() as i64,
    );
    if *last_player_cell == player_cell {
        return;
    }
    *last_player_cell = player_cell;

    let mut spawned = 0;
    let mut spawned_near = 0;
    let mut despawned = 0;

    // 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
        {
            let mut despawning_worked = false;
            for (ent, mut vis) in &mut q_asteroid {
                if ent == asteroid.entity {
                    *vis = Visibility::Hidden;
                    ew_despawn.send(DespawnEvent {
                        entity: asteroid.entity,
                        origin: origin.clone(),
                    });
                    despawned += 1;
                    despawning_worked = true;
                    break;
                }
            }
            if !despawning_worked {
                error!("Couldn't despawn asteroid:");
                dbg!(origin);
            }
        }
    }

    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: f32 = (rand_s + 1e-6).powf(-0.5) as f32; // -> between ~1 and 1000

                if rand_s > 0.7 {
                    let dist = player_cell.as_dvec3().distance(origin.as_dvec3());
                    if dist > 4.0 {
                        continue;
                    }
                    spawned_near += 1;
                }

                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 = 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(-PI / 3.)),
                    Position::new(pos),
                    Asteroid,
                ));
                let asset = match class {
                    0 => ASSET_ASTEROID1,
                    _ => ASSET_ASTEROID2,
                };
                entity_commands.insert(SceneBundle {
                    scene: asset_server.load(asset),
                    transform: Transform {
                        scale: Vec3::splat(ASTEROID_SIZE_FACTOR * size),
                        ..default()
                    },
                    ..default()
                });
                db.0.insert(origin, AsteroidData {
                    entity: entity_commands.id(),
                    //viewdistance: 99999999.0,
                });
                spawned += 1;
            }
        }
    }
    if spawned != 0 || despawned != 0 {
        log.notice(format!("spawned: {spawned} (near: {spawned_near}), despawned: {despawned}"));
    }
}

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

fn handle_cheats(
    key_input: Res<ButtonInput<KeyCode>>,
    mut q_player: Query<(&Transform, &mut Position, &mut LinearVelocity), With<actor::PlayerCamera>>,
    mut q_life: Query<(&mut actor::LifeForm, ), With<actor::Player>>,
    settings: ResMut<settings::Settings>,
) {
    if !settings.dev_mode || q_player.is_empty() || q_life.is_empty() {
        return;
    }
    let (trans, mut pos, mut v) = q_player.get_single_mut().unwrap();
    let (mut lifeform, ) = q_life.get_single_mut().unwrap();
    let boost = if key_input.pressed(KeyCode::ShiftLeft) {
        1e6
    } else {
        1e3
    };
    if key_input.just_pressed(settings.key_cheat_pizza) {
        pos.0 = DVec3::new(-303370.0, 0.0, -500000.0);
    }
    if key_input.just_pressed(settings.key_cheat_farview1) {
        pos.0 = DVec3::new(-1000.0e6, 1000.0e6, -500.0e6);
    }
    if key_input.just_pressed(settings.key_cheat_farview2) {
        pos.0 = DVec3::new(1000.0e6, 1000.0e6, -500.0e6);
    }
    if key_input.just_pressed(settings.key_cheat_stop) {
        v.0 = DVec3::ZERO;
    }
    if key_input.pressed(settings.key_cheat_speed) {
        v.0 += DVec3::from(trans.rotation * Vec3::new(0.0, 0.0, boost));
    }
    if key_input.pressed(settings.key_cheat_speed_backward) {
        v.0 += DVec3::from(trans.rotation * Vec3::new(0.0, 0.0, -boost));
    }
    if key_input.pressed(settings.key_cheat_adrenaline_zero) {
        lifeform.adrenaline = 0.0;
    }
    if key_input.pressed(settings.key_cheat_adrenaline_mid) {
        lifeform.adrenaline = 0.5;
    }
    if key_input.pressed(settings.key_cheat_adrenaline_max) {
        lifeform.adrenaline = 1.0;
    }
}

// A variant of bevy_xpbd_3d::plugins::position_to_transform that adjusts
// the rendering position to center entities at the player camera.
// This avoids rendering glitches when very far away from the origin.
pub fn position_to_transform(
    q_player: Query<&Position, With<actor::PlayerCamera>>,
    mut q_trans: Query<(&'static mut Transform, &'static Position, &'static Rotation, Option<&'static Parent>)>,
    parents: Query<(&'static GlobalTransform, Option<&'static Position>, Option<&'static Rotation>), With<Children>>,
) {
    if let Ok(player_pos) = q_player.get_single() {
        for (mut transform, pos, rot, parent) in &mut q_trans {
            if let Some(parent) = parent {
                if let Ok((parent_transform, parent_pos, parent_rot)) = parents.get(**parent) {
                    // Compute the global transform of the parent using its Position and Rotation
                    let parent_transform = parent_transform.compute_transform();
                    let parent_pos = parent_pos.map_or(parent_transform.translation, |pos| {
                        pos.as_vec3()
                            // NOTE: I commented out this because it turns a vec3 to a vec4,
                            // and I don't understand why bevy_xpbd would do that.
                            //.extend(parent_transform.translation.z)
                    });
                    let parent_rot = parent_rot.map_or(parent_transform.rotation, |rot| {
                        rot.as_quat()
                    });
                    let parent_scale = parent_transform.scale;
                    let parent_transform = Transform::from_translation(parent_pos)
                        .with_rotation(parent_rot)
                        .with_scale(parent_scale);

                    // The new local transform of the child body,
                    // computed from the its global transform and its parents global transform
                    let new_transform = GlobalTransform::from(
                        Transform::from_translation(
                            pos.as_vec3()
                                // NOTE: I commented out this because it turns a vec3 to a vec4,
                                // and I don't understand why bevy_xpbd would do that.
                                //.extend(parent_pos.z + transform.translation.z * parent_scale.z),
                        )
                        .with_rotation(rot.as_quat()),
                    )
                    .reparented_to(&GlobalTransform::from(parent_transform));

                    transform.translation = new_transform.translation;
                    transform.rotation = new_transform.rotation;
                }
            } else {
                transform.translation = Vec3::new(
                    (pos.x - player_pos.x) as f32,
                    (pos.y - player_pos.y) as f32,
                    (pos.z - player_pos.z) as f32,
                );
                transform.rotation = rot.as_quat();
            }
        }
    }
}