use crate::AppState;

use bevy::{
	ecs::world::EntityMut,
	input::{keyboard::KeyCode, Input},
	prelude::{shape::Quad, *},
	sprite::{MaterialMesh2dBundle, Mesh2dHandle},
};
use bevy_fundsp::prelude::*;
use bevy_hanabi::*;
use bevy_rapier2d::prelude::*;
use std::collections::BTreeSet;

pub struct GamePlugin;

impl Plugin for GamePlugin {
	fn build(&self, app: &mut App) {
		app.add_event::<LevelStartupEvent>()
			.init_resource::<CharacterMaterials>()
			.init_resource::<CharacterMeshes>()
			.insert_resource(CurrentLevel(None))
			.add_system_set(SystemSet::on_enter(AppState::Game).with_system(setup))
			.add_system_set(
				SystemSet::on_update(AppState::Game)
					.with_system(post_setup_level)
					.with_system(keyboard_input_system),
			)
			.add_system_to_stage(CoreStage::PostUpdate, collision_event_system);
	}
}

// Events

struct LevelStartupEvent(Entity);

// Resources

struct CurrentLevel(Option<Entity>);

struct CharacterMaterials {
	red: Handle<ColorMaterial>,
	green: Handle<ColorMaterial>,
	blue: Handle<ColorMaterial>,
	yellow: Handle<ColorMaterial>,
	magenta: Handle<ColorMaterial>,
	cyan: Handle<ColorMaterial>,
}

impl FromWorld for CharacterMaterials {
	fn from_world(world: &mut World) -> Self {
		let mut materials = world.get_resource_mut::<Assets<ColorMaterial>>().unwrap();
		Self {
			red: materials.add(ColorMaterial::from(Color::rgba(1.0, 0., 0., 1.))),
			green: materials.add(ColorMaterial::from(Color::rgba(0., 1.0, 0., 1.))),
			blue: materials.add(ColorMaterial::from(Color::rgba(0., 0., 1.0, 1.))),
			yellow: materials.add(ColorMaterial::from(Color::rgba(1.0, 1.0, 0., 1.))),
			magenta: materials.add(ColorMaterial::from(Color::rgba(1.0, 0., 1.0, 1.))),
			cyan: materials.add(ColorMaterial::from(Color::rgba(0., 1.0, 1.0, 1.))),
		}
	}
}

struct CharacterMeshes {
	square: Mesh2dHandle,
}

impl FromWorld for CharacterMeshes {
	fn from_world(world: &mut World) -> Self {
		let mut meshes = world.get_resource_mut::<Assets<Mesh>>().unwrap();
		Self {
			square: meshes
				.add(Mesh::from(Quad {
					size: Vec2 { x: 64.0, y: 64.0 },
					flip: false,
				}))
				.into(),
		}
	}
}

// Components

#[derive(Clone, Component, Copy, Eq, Hash, PartialEq)]
struct LevelId(u32);

#[derive(Clone, Component, Copy, Eq, Hash, Ord, PartialEq, PartialOrd)]
struct CharacterId(u32);

#[derive(Clone, Component, Copy, Eq, Hash, PartialEq)]
struct SelectedCharacterId(Option<CharacterId>);

#[derive(Component)]
struct CharacterIdList(BTreeSet<CharacterId>);

// Systems

fn setup(
	mut commands: Commands,
	mut current_level: ResMut<CurrentLevel>,
	mut level_startup_event: EventWriter<LevelStartupEvent>,
) {
	let level_entity = commands
		.spawn()
		.insert(LevelId(0))
		.insert(SelectedCharacterId(None))
		.insert(CharacterIdList(BTreeSet::new()))
		.id();
	current_level.0 = Some(level_entity);

	commands
		.spawn_bundle(TransformBundle::from(Transform::from_xyz(0.0, -256.0, 0.0)))
		.insert(Collider::cuboid(400., 10.));

	level_startup_event.send(LevelStartupEvent(level_entity));
}

// This is a bad design, but it's the only way I found
fn post_setup_level(
	mut commands: Commands,
	character_materials: Res<CharacterMaterials>,
	character_meshes: Res<CharacterMeshes>,
	mut effects: ResMut<Assets<EffectAsset>>,
	mut level_query: Query<(&mut SelectedCharacterId, &mut CharacterIdList)>,
	mut level_startup_event: EventReader<LevelStartupEvent>,
) {
	for LevelStartupEvent(level_entity) in level_startup_event.iter() {
		if let Ok((mut selected_character_id, mut character_id_list)) =
			level_query.get_mut(*level_entity)
		{
			spawn_character(
				&mut commands,
				&character_meshes,
				&mut effects,
				&mut selected_character_id,
				&mut character_id_list,
				character_materials.red.clone(),
				Transform::from_xyz(-128., -64., 0.),
			);
			spawn_character(
				&mut commands,
				&character_meshes,
				&mut effects,
				&mut selected_character_id,
				&mut character_id_list,
				character_materials.green.clone(),
				Transform::from_xyz(0., -64., 0.),
			);
			spawn_character(
				&mut commands,
				&character_meshes,
				&mut effects,
				&mut selected_character_id,
				&mut character_id_list,
				character_materials.blue.clone(),
				Transform::from_xyz(128., -64., 0.),
			);
		}
	}
}

fn spawn_character(
	commands: &mut Commands,
	character_meshes: &Res<CharacterMeshes>,
	effects: &mut ResMut<Assets<EffectAsset>>,
	selected_character_id: &mut Mut<SelectedCharacterId>,
	character_id_list: &mut Mut<CharacterIdList>,
	material: Handle<ColorMaterial>,
	transform: Transform,
) {
	let character_id = CharacterId(
		character_id_list
			.0
			.iter()
			.last()
			.map_or(0, |last_character_id| last_character_id.0 + 1),
	);
	character_id_list.0.insert(character_id);

	let mut gradient = Gradient::new();
	gradient.add_key(0.0, Vec4::new(1.0, 0.1, 0.1, 0.0));
	gradient.add_key(0.2, Vec4::new(1.0, 0.1, 0.1, 1.0));
	gradient.add_key(1.0, Vec4::new(1.0, 0.1, 0.1, 0.0));
	commands
		.spawn_bundle(MaterialMesh2dBundle {
			mesh: character_meshes.square.clone(),
			material,
			transform,
			..default()
		})
		.insert(character_id)
		.insert(RigidBody::Dynamic)
		.insert(Collider::cuboid(32., 32.))
		.insert(ExternalForce::default())
		.insert(Friction::new(1.0))
		.insert(Damping {
			linear_damping: 0.5,
			angular_damping: 0.5,
		})
		.insert(ExternalImpulse::default())
		.insert(ActiveEvents::COLLISION_EVENTS)
		.with_children(|c| {
			c.spawn_bundle(ParticleEffectBundle {
				effect: ParticleEffect::new(
					effects.add(
						EffectAsset {
							name: "Red particles".into(),
							capacity: 4096,
							spawner: Spawner::rate(30.0.into())
								.with_active(selected_character_id.0.is_none()),
							..Default::default()
						}
						.init(PositionCircleModifier {
							radius: 30.0,
							speed: 20.0.into(),
							dimension: ShapeDimension::Surface,
							..Default::default()
						})
						.init(ParticleLifetimeModifier { lifetime: 0.8 })
						.render(SizeOverLifetimeModifier {
							gradient: Gradient::constant(Vec2::splat(4.0)),
						})
						.render(ColorOverLifetimeModifier { gradient }),
					),
				),
				transform: Transform::from_xyz(0., 0., 0.1),
				..Default::default()
			});
		});

	// If no character is selected, then select this one
	if selected_character_id.0.is_none() {
		selected_character_id.0 = Some(character_id);
	}
}

fn collision_event_system(
	mut commands: Commands,
	current_level: Res<CurrentLevel>,
	mut collision_events: EventReader<CollisionEvent>,
	mut character_query: Query<&CharacterId>,
	mut level_query: Query<(&mut SelectedCharacterId, &mut CharacterIdList)>,
) {
	if let Some(level_entity) = current_level.0 {
		for collision_event in collision_events.iter() {
			if let CollisionEvent::Started(e1, e2, flags) = collision_event {
				if flags.is_empty() {
					if let (Ok(c1_id), Ok(c2_id)) =
						(character_query.get(*e1), character_query.get(*e2))
					{
						let (mut selected_character_id, mut character_id_list) =
							level_query.get_mut(level_entity).unwrap();
						character_id_list.0.remove(c2_id);
						if selected_character_id.0 == Some(*c2_id) {
							selected_character_id.0 = Some(*c1_id);
						}
					}
				}
			}
		}
	}
}

fn keyboard_input_system(
	keyboard_input: Res<Input<KeyCode>>,
	current_level: Res<CurrentLevel>,
	mut characters: Query<(
		&CharacterId,
		&mut ExternalImpulse,
		&mut ExternalForce,
		&Children,
	)>,
	mut level_query: Query<(&mut SelectedCharacterId, &CharacterIdList)>,
	mut effect: Query<&mut ParticleEffect>,
	dsp_assets: Res<DspAssets>,
	audio: Res<Audio>,
) {
	if let Some(level_entity) = current_level.0 {
		if let Ok((mut selected_character_id, character_id_list)) =
			level_query.get_mut(level_entity)
		{
			if keyboard_input.just_pressed(KeyCode::Tab) {
				audio.play(dsp_assets.graph(&sine_wave));

				let selected = if let Some(selected_character_id) = &mut selected_character_id.0 {
					if let Some((_character_id, _impulse, _force, children)) = characters
						.iter_mut()
						.find(|(character_id, _impulse, _force, _children)| {
							*character_id == selected_character_id
						}) {
						effect
							.get_mut(children[0])
							.unwrap()
							.maybe_spawner()
							.unwrap()
							.set_active(false);
					}

					*selected_character_id = *character_id_list
						.0
						.range(*selected_character_id..)
						.nth(1)
						.unwrap_or_else(|| character_id_list.0.iter().next().unwrap());
					*selected_character_id
				} else {
					selected_character_id.0 = Some(CharacterId(0));
					CharacterId(0)
				};
				if let Some((_character_id, _impulse, _force, children)) = characters
					.iter_mut()
					.find(|(character_id, _impulse, _force, _children)| **character_id == selected)
				{
					effect
						.get_mut(children[0])
						.unwrap()
						.maybe_spawner()
						.unwrap()
						.set_active(true);
				}
			}
			if let Some(selected_character_id) = &selected_character_id.0 {
				if let Some((_character_id, mut impulse, mut force, _children)) = characters
					.iter_mut()
					.find(|(character_id, _impulse, _force, _children)| {
						*character_id == selected_character_id
					}) {
					force.force.x = 200.
						* (keyboard_input.pressed(KeyCode::Right) as i8
							- keyboard_input.pressed(KeyCode::Left) as i8) as f32;
					impulse.impulse.y =
						keyboard_input.just_pressed(KeyCode::Space) as i8 as f32 * 100.;
				}
			}
		}
	}
}

// Sounds

pub fn sine_wave() -> impl AudioUnit32 {
	sine_hz(440.0) >> split::<U2>() * 0.2
}