use bevy::{
    ecs::entity::Entities,
    prelude::*,
    tasks::{prelude::*, Task},
};
use bevy_rapier2d::{
    na::{Isometry2, Vector2},
    prelude::*,
    rapier::prelude::{ColliderHandle, ColliderSet, QueryPipeline, RigidBodySet},
};
use futures_lite::future;

use pathfinding::prelude::*;

use crate::{
    commands::RunIfExistsExt,
    core::PointLike,
    map::{Map, MapObstruction},
    navigation::{RotationSpeed, Speed},
};

#[derive(Component, Debug, Deref, DerefMut)]
struct Calculating(Task<Option<Path>>);

#[derive(Component, Clone, Copy, Debug, Default, Deref, DerefMut, Eq, Hash, PartialEq, Reflect)]
#[reflect(Component)]
pub struct Destination(pub (i32, i32));

impl_pointlike_for_tuple_component!(Destination);
impl_pointlike_for_tuple_component!(&Destination);

#[derive(Component, Clone, Debug, Default, Reflect)]
#[reflect(Component)]
pub struct NoPath;

#[derive(Component, Clone, Debug, Default, Deref, DerefMut, Reflect)]
#[reflect(Component)]
pub struct Path(pub Vec<(i32, i32)>);

#[derive(Component, Clone, Debug, Default, Reflect)]
#[reflect(Component)]
pub struct CostMap {
    width: usize,
    costs: Vec<f32>,
}

impl CostMap {
    pub fn new(width: usize, height: usize) -> Self {
        let count = width * height;
        Self {
            width,
            costs: vec![1.; count],
        }
    }

    pub fn modifier(&self, x: i32, y: i32) -> Option<&f32> {
        let idx = (y as usize) * self.width + (x as usize);
        self.costs.get(idx)
    }

    pub fn set_modifier(&mut self, x: usize, y: usize, cost: f32) {
        let idx = (y as usize) * self.width + (x as usize);
        self.costs[idx] = cost;
    }
}

pub fn find_path<D: 'static + Clone + Default + Send + Sync>(
    start: &dyn PointLike,
    destination: &dyn PointLike,
    map: &Map<D>,
    cost_map: &Option<CostMap>,
) -> Option<(Vec<(i32, i32)>, u32)> {
    astar(
        &start.into(),
        |p| {
            let mut successors: Vec<((i32, i32), u32)> = vec![];
            if let Some(tile) = map.at(p.0 as usize, p.1 as usize) {
                if tile.is_walkable() {
                    for tile in map.get_available_exits(p.0 as usize, p.1 as usize) {
                        let mut cost = tile.2 * 100.;
                        if let Some(cost_map) = cost_map {
                            if let Some(modifier) = cost_map.modifier(tile.0 as i32, tile.1 as i32)
                            {
                                cost *= modifier;
                            }
                        }
                        successors.push(((tile.0 as i32, tile.1 as i32), cost as u32));
                    }
                }
            }
            successors
        },
        |p| (p.distance_squared(destination) * 100.) as u32,
        |p| *p == destination.into(),
    )
}

fn find_path_for_shape(
    initiator: ColliderHandle,
    start: Transform,
    destination: Destination,
    cost_map: &Option<CostMap>,
    query_pipeline: QueryPipeline,
    collider_set: ColliderSet,
    rigid_body_set: RigidBodySet,
    shape: Collider,
) -> Option<Path> {
    let path = astar(
        &start.i32(),
        |p| {
            let mut successors: Vec<((i32, i32), u32)> = vec![];
            let x = p.0 as i32;
            let y = p.1 as i32;
            let exits = vec![
                ((x - 1, y), 1.),
                ((x + 1, y), 1.),
                ((x, y - 1), 1.),
                ((x, y + 1), 1.),
                ((x - 1, y - 1), 1.5),
                ((x + 1, y - 1), 1.5),
                ((x - 1, y + 1), 1.5),
                ((x + 1, y + 1), 1.5),
            ];
            for exit in &exits {
                let mut should_push = true;
                let shape_pos =
                    Isometry2::new(Vector2::new(exit.0 .0 as f32, exit.0 .1 as f32), 0.);
                query_pipeline.intersections_with_shape(
                    &rigid_body_set,
                    &collider_set,
                    &shape_pos,
                    &*shape.raw,
                    bevy_rapier2d::rapier::pipeline::QueryFilter::new()
                        .predicate(&|h, _c| h != initiator),
                    |_handle| {
                        should_push = false;
                        false
                    },
                );
                if should_push {
                    let mut cost = exit.1 * 100.;
                    if let Some(cost_map) = cost_map {
                        if let Some(modifier) = cost_map.modifier(exit.0 .0, exit.0 .1) {
                            cost *= modifier;
                        }
                    }
                    successors.push((exit.0, cost as u32));
                }
            }
            successors
        },
        |p| (p.distance_squared(&destination) * 100.) as u32,
        |p| *p == destination.i32(),
    );
    if let Some(path) = path {
        Some(Path(path.0))
    } else {
        None
    }
}

fn calculate_path(
    mut commands: Commands,
    rapier_context: Res<RapierContext>,
    obstructions: Query<&RapierColliderHandle, With<MapObstruction>>,
    query: Query<
        (
            Entity,
            &RapierColliderHandle,
            &Destination,
            &Transform,
            &Collider,
            Option<&CostMap>,
        ),
        Changed<Destination>,
    >,
) {
    for (entity, handle, destination, coordinates, shape, cost_map) in &query {
        if coordinates.i32() == **destination {
            commands
                .entity(entity)
                .remove::<Path>()
                .remove::<NoPath>()
                .remove::<Calculating>()
                .remove::<Destination>()
                .remove::<Speed>();
            continue;
        }
        let coordinates_clone = *coordinates;
        let destination_clone = *destination;
        let query_pipeline = rapier_context.query_pipeline.clone();
        let cost_map_clone = cost_map.cloned();
        let handle_clone = *handle;
        let mut collider_set = rapier_context.colliders.clone();
        let mut to_remove = vec![];
        for handle in collider_set.iter() {
            if !obstructions.iter().map(|v| v.0).any(|x| x == handle.0) {
                to_remove.push(handle.0);
            }
        }
        let mut bodies = rapier_context.bodies.clone();
        if !to_remove.is_empty() {
            let mut islands = rapier_context.islands.clone();
            for handle in to_remove {
                collider_set.remove(handle, &mut islands, &mut bodies, false);
            }
        }
        let shape_clone = (*shape).clone();
        trace!(
            "{:?}: path: calculating from {:?} to {:?}",
            entity,
            coordinates.i32(),
            destination
        );
        let pool = AsyncComputeTaskPool::get();
        let task = pool.spawn(async move {
            find_path_for_shape(
                handle_clone.0,
                coordinates_clone,
                destination_clone,
                &cost_map_clone,
                query_pipeline,
                collider_set,
                bodies,
                shape_clone,
            )
        });
        commands.run_if_exists(entity, |mut entity| {
            entity.insert(Calculating(task));
            entity.remove::<Path>();
            entity.remove::<NoPath>();
        });
    }
}

fn poll_tasks(mut commands: Commands, mut query: Query<(Entity, &mut Calculating)>) {
    for (entity, mut calculating) in query.iter_mut() {
        if let Some(result) = future::block_on(future::poll_once(&mut **calculating)) {
            if let Some(path) = result {
                trace!("{:?}: path: result: {:?}", entity, path);
                commands.entity(entity).insert(path);
            } else {
                trace!("{:?}: path: no path", entity);
                commands.entity(entity).insert(NoPath);
            }
            commands.entity(entity).remove::<Calculating>();
        }
    }
}

fn remove_destination(
    mut commands: Commands,
    entities: &Entities,
    removed: RemovedComponents<Destination>,
) {
    for entity in removed.iter() {
        if entities.contains(entity) {
            commands.entity(entity).remove::<Calculating>();
        }
    }
}

fn negotiate_path(
    mut commands: Commands,
    mut query: Query<(
        Entity,
        &mut Path,
        &mut Transform,
        &mut Velocity,
        &Speed,
        Option<&RotationSpeed>,
    )>,
) {
    for (entity, mut path, mut transform, mut velocity, speed, rotation_speed) in &mut query {
        let start_i32 = (transform.translation.x, transform.translation.y).i32();
        let mut cleanup = false;
        if let Some(last) = path.last() {
            if last == &start_i32 {
                trace!("{:?}: path: at destination", entity);
                cleanup = true;
            }
        }
        if !cleanup {
            if let Some(position) = path.iter().position(|v| v == &start_i32) {
                trace!("{:?}: Path contains start", entity);
                let (_, new_path) = path.split_at(position + 1);
                **path = new_path.to_vec();
            }
            if let Some(next) = path.first() {
                trace!(
                    "{:?}: path: moving from {:?} to {:?}",
                    entity,
                    start_i32,
                    next
                );
                let start = transform.translation.truncate();
                let next = Vec2::new(next.0 as f32 + 0.5, next.1 as f32 + 0.5);
                let mut direction = next - start;
                direction = direction.normalize();
                trace!("{:?}: path: direction: {:?}", entity, direction);
                direction *= **speed;
                velocity.linvel = direction;
                trace!("{:?}: path: velocity: {:?}", entity, velocity.linvel);
                if rotation_speed.is_some() {
                    let v = next - start;
                    let angle = v.y.atan2(v.x);
                    transform.rotation = Quat::from_rotation_z(angle);
                }
            } else {
                cleanup = true;
            }
        }
        if cleanup {
            commands
                .entity(entity)
                .remove::<Path>()
                .remove::<NoPath>()
                .remove::<Destination>()
                .remove::<Speed>();
        }
    }
}

pub struct PathfindingPlugin;

impl Plugin for PathfindingPlugin {
    fn build(&self, app: &mut App) {
        app.add_system(calculate_path)
            .add_system_to_stage(CoreStage::PostUpdate, remove_destination)
            .add_system(poll_tasks)
            .add_system_to_stage(CoreStage::PostUpdate, negotiate_path);
    }
}