use crate::{actor, nature, settings, hud};
use bevy::prelude::*;
use bevy::render::render_resource::{AsBindGroup, ShaderRef};
use bevy::math::DVec3;
use bevy_xpbd_3d::prelude::*;
use bevy_xpbd_3d::plugins::sync::SyncConfig;
use std::f32::consts::PI;
use std::f64::consts::PI as PI64;

const ASTEROID_UPDATE_INTERVAL: f32 = 1.0; // seconds
const ASTEROID_SIZE: f32 = 5000.0;
const STARS_MAX_MAGNITUDE: f32 = 5.5;

const CENTER_WORLD_ON_PLAYER: bool = true;
const ASTEROIDS_ARE_SPHERES: bool = false;

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(Startup, generate_asteroids);
        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.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(Component)] struct Asteroid;

struct AsteroidData {
    entity: Option<Entity>,
    is_spawned: bool,
    class: u8,
    size: f32,
    pos: DVec3,
}

#[derive(Event)]
pub struct DespawnEvent(Entity);

#[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 generate_asteroids(
    mut db: ResMut<AsteroidDatabase>,
) {
    let phase_steps: i16 = 600;
    let radius_steps: i16 = 1000;
    let max_height_step: i16 = 6; // this one is inclusive for symmetry
    let min_height_step: i16 = -max_height_step;

    let min_radius: f64 = 92e6;
    let max_radius: f64 = 229e6;
    let ring_thickness: f64 = 2.0e6;

    let height_step_factor: f64 = ring_thickness / 2.0 / (max_height_step as f64);
    let max_phase_step_factor: f64 = 2.0 * PI64 / (phase_steps as f64);
    let max_radius_factor: f64 = (max_radius - min_radius) / (radius_steps as f64);
    let wobble: f64 = (ASTEROID_SIZE * 50.0).into();
    let mut count = 0;
    for phase_step in 0..phase_steps {
        let phase = max_phase_step_factor * phase_step as f64;
        for radius_step in 0..radius_steps {
            let radius = max_radius_factor * radius_step as f64 + min_radius;
            for height_step in min_height_step..=max_height_step {
                let height = height_step_factor * height_step as f64;

                let rand1 = (phase+radius).sin() + (height+radius).cos();
                let rand2 = (phase+height).sin() + (phase+radius).cos();
                let rand3 = (radius+height).sin() + (phase+height).cos();

                let x = phase.sin() * radius + wobble * rand1;
                let y = height + wobble * rand2;
                let z = phase.cos() * radius + wobble * rand3;

                db.0.push(AsteroidData {
                    entity: None,
                    is_spawned: false,
                    pos: DVec3::new(x, y, z),
                    size: ASTEROID_SIZE,
                    class: ((phase_step+radius_step+height_step) % 2) as u8,
                });
                count += 1;
            }
        }
    }
    info!("Generated {count} asteroids");
}

fn spawn_despawn_asteroids(
    time: Res<Time>,
    mut timer: ResMut<AsteroidUpdateTimer>,
    mut db: ResMut<AsteroidDatabase>,
    mut commands: Commands,
    q_player: Query<&Position, With<actor::PlayerCamera>>,
    mut meshes: ResMut<Assets<Mesh>>,
    mut q_asteroid: Query<(Entity, &mut Visibility), With<Asteroid>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    asset_server: Res<AssetServer>,
    mut log: ResMut<hud::Log>,
    mut ew_despawn: EventWriter<DespawnEvent>,
) {
    if !timer.0.tick(time.delta()).just_finished()  || q_player.is_empty() {
        return;
    }
    let player = q_player.get_single().unwrap();

    let mut spawned = 0;
    let mut despawned = 0;
    for asteroid in &mut db.0 {
        let dist = player.distance(asteroid.pos);
        let should_spawn = dist < 2000.0e3;
        if should_spawn == asteroid.is_spawned {
            continue;  // Nothing to do
        }
        if !should_spawn {
            // Despawn
            if let Some(entity) = asteroid.entity {
                for (ent, mut vis) in &mut q_asteroid {
                    if ent == entity {
                        *vis = Visibility::Hidden;
                        asteroid.entity = None;
                        asteroid.is_spawned = false;
                        despawned += 1;
                        ew_despawn.send(DespawnEvent(entity));
                        break;
                    }
                }
            }
            continue;
        }

        // 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(asteroid.pos),
            Asteroid,
        ));
        if ASTEROIDS_ARE_SPHERES {
            let sphere_handle = meshes.add(Sphere::default());
            let sphere_material_handle = materials.add(StandardMaterial {
                base_color: Color::rgb(0.4, 0.4, 0.4),
                perceptual_roughness: 1.0,
                metallic: 0.0,
                ..default()
            });
            entity_commands.insert(PbrBundle {
                mesh: sphere_handle,
                material: sphere_material_handle,
                transform: Transform {
                    scale: Vec3::splat(asteroid.size),
                    ..default()
                },
                ..default()
            });
        }
        else {
            let asset = match asteroid.class {
                0 => ASSET_ASTEROID1,
                _ => ASSET_ASTEROID2,
            };
            entity_commands.insert(SceneBundle {
                scene: asset_server.load(asset),
                transform: Transform {
                    scale: Vec3::splat(asteroid.size),
                    ..default()
                },
                ..default()
            });
        }
        asteroid.entity = Some(entity_commands.id());
        spawned += 1;
        asteroid.is_spawned = true;
    }
    if spawned != 0 || despawned != 0 {
        log.notice(format!("spawned: {spawned}, despawned: {despawned}"));
    }
}

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

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();
            }
        }
    }
}