use std::{
    cell::RefCell,
    collections::{HashMap, HashSet},
};

use bevy::prelude::*;
use bevy_rapier2d::{na, na::UnitComplex};
use coord_2d::{Coord, Size};
use derive_more::{Deref, DerefMut};
use shadowcast::{vision_distance, Context, InputGrid};

use crate::{
    bevy_rapier2d::prelude::*,
    core::{Angle, Coordinates, Player, PointLike},
    log::Log,
    map::{ITileType, Map, MapConfig},
    utils::target_and_other,
};

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

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

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Viewshed {
    pub range: u32,
    pub visible_points: HashSet<(i32, i32)>,
}

impl Default for Viewshed {
    fn default() -> Self {
        Self {
            range: 15,
            visible_points: HashSet::new(),
        }
    }
}

impl Viewshed {
    pub fn is_point_visible(&self, point: &dyn PointLike) -> bool {
        self.visible_points.contains(&point.into())
    }
}

#[derive(Clone, Copy, Debug, Deref, DerefMut, Reflect)]
#[reflect(Component)]
pub struct Visible(pub u8);

impl Default for Visible {
    fn default() -> Self {
        Self::opaque()
    }
}

impl Visible {
    pub fn transparent() -> Self {
        Self(0)
    }

    pub fn opaque() -> Self {
        Self(u8::MAX)
    }
}
#[derive(Clone, Debug, Default, Deref, DerefMut)]
pub struct VisibleEntities(HashSet<Entity>);

#[derive(Bundle, Default)]
pub struct ViewshedBundle {
    pub viewshed: Viewshed,
    pub visible_entities: VisibleEntities,
}

impl ViewshedBundle {
    pub fn new(range: u32) -> Self {
        Self {
            viewshed: Viewshed {
                range,
                ..Default::default()
            },
            ..Default::default()
        }
    }
}

pub enum VisibilityChanged {
    Gained { viewer: Entity, viewed: Entity },
    Lost { viewer: Entity, viewed: Entity },
}

impl PointLike for Coord {
    fn x(&self) -> f32 {
        self.x as f32
    }

    fn y(&self) -> f32 {
        self.y as f32
    }
}

fn add_visibility_indices(
    mut commands: Commands,
    query: Query<(Entity, &Map), (Added<Map>, Without<RevealedTiles>)>,
    map_config: Res<MapConfig>,
) {
    for (entity, map) in query.iter() {
        let count = map.width * map.height;
        commands
            .entity(entity)
            .insert(RevealedTiles(vec![map_config.start_revealed; count]));
    }
}

fn viewshed_removed(
    query: RemovedComponents<Viewshed>,
    visible_entities: Query<&VisibleEntities>,
    mut events: EventWriter<VisibilityChanged>,
) {
    for entity in query.iter() {
        if let Ok(visible) = visible_entities.get(entity) {
            for e in visible.iter() {
                events.send(VisibilityChanged::Lost {
                    viewer: entity,
                    viewed: *e,
                })
            }
        }
    }
}

pub struct VisibilityGrid<'a, F>(pub &'a Map, pub RefCell<Box<F>>);

impl<'a, F> InputGrid for VisibilityGrid<'a, F>
where
    F: FnMut(Coord) -> u8,
{
    type Grid = VisibilityGrid<'a, F>;

    type Opacity = u8;

    fn size(&self, grid: &Self::Grid) -> Size {
        Size::new(grid.0.width as u32, grid.0.height as u32)
    }

    fn get_opacity(&self, _grid: &Self::Grid, coord: Coord) -> Self::Opacity {
        (self.1.borrow_mut())(coord)
    }
}

fn update_viewshed(
    viewer_entity: &Entity,
    viewshed: &mut Viewshed,
    visible_entities: &mut VisibleEntities,
    start: &dyn PointLike,
    query_pipeline: &QueryPipeline,
    collider_query: &QueryPipelineColliderComponentsQuery,
    map: &Map,
    visible_query: &Query<&Visible>,
    events: &mut EventWriter<VisibilityChanged>,
) {
    let mut context: Context<u8> = Context::default();
    let vision_distance = vision_distance::Circle::new(viewshed.range);
    let coord = Coord::new(start.x_i32(), start.y_i32());
    let collider_set = QueryPipelineColliderComponentsSet(&collider_query);
    let origin = point!(start.x(), start.y());
    let mut new_visible_entities = HashSet::<Entity>::new();
    let visibility_grid = VisibilityGrid(
        map,
        RefCell::new(Box::new(|coord: Coord| {
            let dest = point!(coord.x as f32 + 0.5, coord.y as f32 + 0.5);
            if na::distance(&origin, &dest) >= viewshed.range as f32 {
                return u8::MAX;
            }
            let direction = (dest - origin).normalize();
            let ray = Ray::new(origin, direction);
            let max_toi = na::distance(&origin, &dest);
            let mut opacity = 0;
            query_pipeline.intersections_with_ray(
                &collider_set,
                &ray,
                max_toi,
                true,
                InteractionGroups::all(),
                Some(&|v| v.entity() != *viewer_entity && visible_query.get(v.entity()).is_ok()),
                |handle, _intersection| {
                    let entity = handle.entity();
                    new_visible_entities.insert(entity);
                    if let Ok(visible) = visible_query.get(entity) {
                        opacity = **visible;
                    }
                    opacity != u8::MAX
                },
            );
            opacity
        })),
    );
    let mut new_visible = HashSet::new();
    context.for_each_visible(
        coord,
        &visibility_grid,
        &visibility_grid,
        vision_distance,
        255,
        |coord, _directions, _visibility| {
            new_visible.insert((coord.x, coord.y));
        },
    );
    if viewshed.visible_points != new_visible {
        viewshed.visible_points = new_visible;
    }
    if new_visible_entities != **visible_entities {
        for lost in visible_entities.difference(&new_visible_entities) {
            events.send(VisibilityChanged::Lost {
                viewer: *viewer_entity,
                viewed: *lost,
            });
        }
        for gained in new_visible_entities.difference(visible_entities) {
            events.send(VisibilityChanged::Gained {
                viewer: *viewer_entity,
                viewed: *gained,
            });
        }
        **visible_entities = new_visible_entities;
    }
}

fn update_viewshed_for_coordinates(
    config: Res<RapierConfiguration>,
    visible: Query<(Entity, &Coordinates), (Changed<Coordinates>, With<Visible>)>,
    mut viewers: Query<(Entity, &mut Viewshed, &mut VisibleEntities, &Coordinates)>,
    map: Query<&Map>,
    query_pipeline: Res<QueryPipeline>,
    collider_query: QueryPipelineColliderComponentsQuery,
    visible_query: Query<&Visible>,
    mut changed: EventWriter<VisibilityChanged>,
) {
    if !config.query_pipeline_active {
        return;
    }
    for (visible_entity, coordinates) in visible.iter() {
        for (viewer_entity, mut viewshed, mut visible_entities, start) in viewers.iter_mut() {
            if viewer_entity == visible_entity
                || coordinates.distance(start) > viewshed.range as f32
            {
                continue;
            }
            if let Ok(map) = map.single() {
                update_viewshed(
                    &viewer_entity,
                    &mut viewshed,
                    &mut visible_entities,
                    start,
                    &*query_pipeline,
                    &collider_query,
                    map,
                    &visible_query,
                    &mut changed,
                );
            }
        }
    }
}

fn update_viewshed_for_start(
    config: Res<RapierConfiguration>,
    mut viewers: Query<
        (Entity, &mut Viewshed, &mut VisibleEntities, &Coordinates),
        Changed<Coordinates>,
    >,
    map: Query<&Map>,
    query_pipeline: Res<QueryPipeline>,
    collider_query: QueryPipelineColliderComponentsQuery,
    visible: Query<&Visible>,
    mut changed: EventWriter<VisibilityChanged>,
) {
    if !config.query_pipeline_active {
        return;
    }
    for (viewer_entity, mut viewshed, mut visible_entities, start) in viewers.iter_mut() {
        if let Ok(map) = map.single() {
            update_viewshed(
                &viewer_entity,
                &mut viewshed,
                &mut visible_entities,
                start,
                &*query_pipeline,
                &collider_query,
                map,
                &visible,
                &mut changed,
            );
        }
    }
}

fn remove_visible(
    removed: RemovedComponents<Visible>,
    mut viewers: Query<(Entity, &mut Viewshed, &mut VisibleEntities, &Coordinates)>,
    map: Query<&Map>,
    query_pipeline: Res<QueryPipeline>,
    collider_query: QueryPipelineColliderComponentsQuery,
    visible: Query<&Visible>,
    mut changed: EventWriter<VisibilityChanged>,
) {
    for removed in removed.iter() {
        for (viewer_entity, mut viewshed, mut visible_entities, start) in viewers.iter_mut() {
            if !visible_entities.contains(&removed) {
                continue;
            }
            visible_entities.remove(&removed);
            if let Ok(map) = map.single() {
                update_viewshed(
                    &viewer_entity,
                    &mut viewshed,
                    &mut visible_entities,
                    start,
                    &*query_pipeline,
                    &collider_query,
                    map,
                    &visible,
                    &mut changed,
                );
            }
        }
    }
}

fn update_revealed_tiles(
    mut map: Query<(&Map, &mut RevealedTiles)>,
    viewers: Query<&Viewshed, With<Player>>,
) {
    for (map, mut revealed_tiles) in map.iter_mut() {
        for viewshed in viewers.iter() {
            for v in viewshed.visible_points.iter() {
                let idx = v.to_index(map.width);
                if idx >= revealed_tiles.len() {
                    continue;
                }
                revealed_tiles[idx] = true;
            }
        }
    }
}

fn log_visible(
    time: Res<Time>,
    mut recently_lost: Local<HashMap<Entity, Timer>>,
    mut events: EventReader<VisibilityChanged>,
    mut log: Query<&mut Log>,
    viewers: Query<(Entity, &Coordinates, &Transform), (With<Player>, With<Viewshed>)>,
    visible: Query<
        (&Name, Option<&RigidBodyPosition>, Option<&ColliderPosition>),
        Without<DontLogWhenVisible>,
    >,
) {
    for timer in recently_lost.values_mut() {
        timer.tick(time.delta());
    }
    recently_lost.retain(|_entity, timer| !timer.finished());
    for event in events.iter() {
        let viewer = match event {
            VisibilityChanged::Gained { viewer, .. } => viewer,
            VisibilityChanged::Lost { viewer, .. } => viewer,
        };
        if let Ok((viewer_entity, viewer_coordinates, viewer_transform)) = viewers.get(*viewer) {
            if let VisibilityChanged::Gained { viewed, .. } = event {
                if *viewed == viewer_entity || recently_lost.contains_key(viewed) {
                    continue;
                }
                if let Ok((name, body_position, collider_position)) = visible.get(*viewed) {
                    if let Ok(mut log) = log.single_mut() {
                        let viewed_coordinates = if let Some(p) = body_position {
                            (p.position.translation.x, p.position.translation.y)
                        } else if let Some(p) = collider_position {
                            (p.translation.x, p.translation.y)
                        } else {
                            (0., 0.)
                        };
                        let forward = viewer_transform.local_x();
                        let yaw = Angle::Radians(forward.y.atan2(forward.x));
                        let location = viewer_coordinates
                            .direction_and_distance(&viewed_coordinates, Some(yaw));
                        log.push(format!("{}: {}", **name, location));
                    }
                }
            } else if let VisibilityChanged::Lost { viewed, .. } = event {
                recently_lost.insert(*viewed, Timer::from_seconds(2., false));
            }
        }
    }
}

pub const LOG_VISIBLE_LABEL: &str = "LOG_VISIBLE";

pub struct VisibilityPlugin;

impl Plugin for VisibilityPlugin {
    fn build(&self, app: &mut AppBuilder) {
        app.add_event::<VisibilityChanged>()
            .add_system(add_visibility_indices.system())
            .add_system_to_stage(CoreStage::PostUpdate, viewshed_removed.system())
            .add_system(update_viewshed_for_coordinates.system())
            .add_system(update_viewshed_for_start.system())
            .add_system_to_stage(CoreStage::PostUpdate, remove_visible.system())
            .add_system_to_stage(CoreStage::PostUpdate, update_revealed_tiles.system())
            .add_system_to_stage(CoreStage::PostUpdate, log_visible.system());
    }
}