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

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

use crate::{
    core::{Angle, Coordinates, Player, PointLike},
    log::Log,
    map::{ITileType, Map, MapConfig},
};

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

#[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 visible: HashSet<(i32, i32)>,
    pub range: u32,
}

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

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

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

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

fn add_visibility_indices(
    mut commands: Commands,
    query: Query<
        (Entity, &Map),
        (
            Added<Map>,
            Without<VisibilityBlocked>,
            Without<VisibleTiles>,
            Without<RevealedTiles>,
        ),
    >,
    map_config: Res<MapConfig>,
) {
    for (entity, map) in query.iter() {
        let mut v = vec![];
        for tile in &map.base.tiles {
            v.push(tile.blocks_visibility());
        }
        commands.entity(entity).insert(VisibilityBlocked(v));
        let count = map.count();
        commands
            .entity(entity)
            .insert(VisibleTiles(vec![false; count]));
        commands
            .entity(entity)
            .insert(RevealedTiles(vec![map_config.start_revealed; count]));
    }
}

pub(crate) fn set_visibility_blocked(
    map: &Map,
    index: usize,
    visibility_blockers: &Query<&BlocksVisibility>,
    visibility_blocked: &mut VisibilityBlocked,
) {
    let mut new_visibility_blocked = map.base.tiles[index].blocks_visibility();
    if !new_visibility_blocked {
        for e in &map.entities[index] {
            if visibility_blockers.get(*e).is_ok() {
                new_visibility_blocked = true;
                break;
            }
        }
    }
    visibility_blocked[index] = new_visibility_blocked;
}

#[derive(Default, Deref, DerefMut)]
struct PrevIndex(HashMap<Entity, usize>);

fn map_visibility_indexing(
    mut map: Query<(&Map, &mut VisibilityBlocked)>,
    mut prev_index: ResMut<PrevIndex>,
    query: Query<
        (Entity, &Coordinates),
        (
            With<BlocksVisibility>,
            Or<(Changed<Coordinates>, Changed<BlocksVisibility>)>,
        ),
    >,
    visibility_blockers: Query<&BlocksVisibility>,
) {
    for (entity, coordinates) in query.iter() {
        for (map, mut visibility_blocked) in map.iter_mut() {
            let idx = coordinates.to_index(map.width());
            if let Some(prev_idx) = prev_index.get(&entity) {
                if *prev_idx == idx {
                    continue;
                }
                set_visibility_blocked(
                    &map,
                    *prev_idx,
                    &visibility_blockers,
                    &mut visibility_blocked,
                );
            }
            visibility_blocked[idx] = true;
            prev_index.insert(entity, idx);
        }
    }
}

fn remove_blocks_visibility(
    mut prev_index: ResMut<PrevIndex>,
    mut map: Query<(&Map, &mut VisibilityBlocked)>,
    removed: RemovedComponents<BlocksVisibility>,
    coordinates: Query<&Coordinates>,
    blocks_visibility: Query<&BlocksVisibility>,
) {
    for entity in removed.iter() {
        for (map, mut visibility_blocked) in map.iter_mut() {
            let prev = prev_index.get(&entity).cloned();
            if let Some(prev) = prev {
                prev_index.remove(&entity);
                set_visibility_blocked(&map, prev, &blocks_visibility, &mut visibility_blocked);
            }
            if let Ok(coordinates) = coordinates.get_component::<Coordinates>(entity) {
                let idx = coordinates.to_index(map.width());
                set_visibility_blocked(&map, idx, &blocks_visibility, &mut visibility_blocked);
            }
        }
    }
}

struct VisibilityGrid(Map, VisibilityBlocked);

impl InputGrid for VisibilityGrid {
    type Grid = VisibilityGrid;

    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 {
        let point = (coord.x, coord.y);
        let index = point.to_index(grid.0.width());
        if grid.1 .0[index] {
            255
        } else {
            0
        }
    }
}

fn update_viewshed(
    viewshed: &mut Viewshed,
    start: &Coordinates,
    map: &Map,
    visibility_blocked: &VisibilityBlocked,
) {
    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());
    viewshed.visible.clear();
    let visibility_grid = VisibilityGrid(map.clone(), visibility_blocked.clone());
    context.for_each_visible(
        coord,
        &visibility_grid,
        &visibility_grid,
        vision_distance,
        255,
        |coord, _directions, _visibility| {
            viewshed.visible.insert((coord.x, coord.y));
        },
    );
}

fn update_viewshed_for_coordinates(
    mut viewers: Query<(&mut Viewshed, &Coordinates), Changed<Coordinates>>,
    map: Query<(&Map, &VisibilityBlocked)>,
) {
    for (mut viewshed, start) in viewers.iter_mut() {
        for (map, visibility_blocked) in map.iter() {
            update_viewshed(&mut viewshed, start, &map, &visibility_blocked);
        }
    }
}

#[derive(Clone, Debug, Default, Deref, DerefMut)]
struct PrevVisibilityBlocked(Vec<bool>);

fn visibility_blocked_added(
    mut prev_visibility_blocked: ResMut<PrevVisibilityBlocked>,
    added: Query<&VisibilityBlocked, Added<VisibilityBlocked>>,
) {
    for visibility_blocked in added.iter() {
        **prev_visibility_blocked = visibility_blocked.to_vec();
    }
}

fn visibility_blocked_removed(
    mut prev_visibility_blocked: ResMut<PrevVisibilityBlocked>,
    removed: RemovedComponents<VisibilityBlocked>,
) {
    for _ in removed.iter() {
        prev_visibility_blocked.clear();
    }
}

fn update_viewshed_for_visibility_blocked(
    mut prev_visibility_blocked: ResMut<PrevVisibilityBlocked>,
    map: Query<(&Map, &VisibilityBlocked), Changed<VisibilityBlocked>>,
    mut queryset: QuerySet<(
        Query<(Entity, &Viewshed)>,
        Query<(&mut Viewshed, &Coordinates)>,
    )>,
) {
    for (map, visibility_blocked) in map.iter() {
        let mut to_check = vec![];
        for (index, new) in visibility_blocked.iter().enumerate() {
            let changed = if let Some(prev) = prev_visibility_blocked.get(index) {
                prev != new
            } else {
                true
            };
            if changed {
                let coords = (index % map.width(), index / map.width());
                for (entity, viewshed) in queryset.q0().iter() {
                    if viewshed.is_visible(&coords) {
                        to_check.push(entity);
                    }
                }
            }
        }
        to_check.dedup();
        for entity in to_check {
            if let Ok((mut viewshed, coordinates)) = queryset.q1_mut().get_mut(entity) {
                update_viewshed(&mut viewshed, coordinates, &map, &visibility_blocked);
            }
        }
        **prev_visibility_blocked = visibility_blocked.to_vec();
    }
}

fn update_visible_and_revealed_tiles(
    mut map: Query<
        (&Map, &mut RevealedTiles, &mut VisibleTiles),
        (
            With<VisibilityBlocked>,
            Or<(Changed<Map>, Changed<VisibilityBlocked>)>,
        ),
    >,
    viewers: Query<&Viewshed, With<Player>>,
) {
    for (map, mut revealed_tiles, mut visible_tiles) in map.iter_mut() {
        for viewshed in viewers.iter() {
            for t in visible_tiles.iter_mut() {
                *t = false
            }
            for v in viewshed.visible.iter() {
                let idx = v.to_index(map.width());
                revealed_tiles[idx] = true;
                visible_tiles[idx] = true;
            }
        }
    }
}

fn log_visible(
    time: Res<Time>,
    mut seen: Local<HashSet<Entity>>,
    mut recently_lost: Local<HashMap<Entity, Timer>>,
    mut log: Query<&mut Log>,
    viewers: Query<(&Viewshed, &Coordinates, &Transform), With<Player>>,
    map: Query<&Map>,
    names: Query<&Name>,
    players: Query<&Player>,
    dont_log_when_visible: Query<&DontLogWhenVisible>,
) {
    for timer in recently_lost.values_mut() {
        timer.tick(time.delta());
    }
    let recently_lost_clone = recently_lost.clone();
    for (entity, timer) in recently_lost_clone.iter() {
        if timer.finished() {
            recently_lost.remove(&entity);
        }
    }
    let mut new_seen = HashSet::new();
    if let Ok(mut log) = log.single_mut() {
        for (viewshed, coordinates, transform) in viewers.iter() {
            for viewed_coordinates in &viewshed.visible {
                for map in map.iter() {
                    let index = viewed_coordinates.to_index(map.width());
                    for entity in &map.entities[index] {
                        if recently_lost.contains_key(&entity) {
                            continue;
                        }
                        if let Ok(name) = names.get(*entity) {
                            if players.get(*entity).is_err() {
                                if !seen.contains(&*entity)
                                    && dont_log_when_visible.get(*entity).is_err()
                                {
                                    let name = name.to_string();
                                    let forward = transform.local_x();
                                    let yaw = Angle::Radians(forward.y.atan2(forward.x));
                                    let location = coordinates
                                        .direction_and_distance(viewed_coordinates, Some(yaw));
                                    log.push(format!("{}: {}", name, location));
                                }
                                new_seen.insert(*entity);
                            }
                        }
                    }
                }
            }
        }
    }
    let recently_lost_entities = seen.difference(&new_seen);
    for entity in recently_lost_entities {
        recently_lost.insert(*entity, Timer::from_seconds(2., false));
    }
    *seen = new_seen;
}

pub const LOG_VISIBLE_LABEL: &str = "LOG_VISIBLE";

pub struct VisibilityPlugin;

impl Plugin for VisibilityPlugin {
    fn build(&self, app: &mut AppBuilder) {
        const UPDATE_VISIBILITY_INDEX: &str = "UPDATE_VISIBILITY_INDEX";
        const UPDATE_VIEWSHED: &str = "UPDATE_VIEWSHED";
        const MAP_VISIBILITY: &str = "MAP_VISIBILITY";
        app.init_resource::<PrevVisibilityBlocked>()
            .init_resource::<PrevIndex>()
            .add_system(visibility_blocked_added.system())
            .add_system_to_stage(CoreStage::PostUpdate, visibility_blocked_removed.system())
            .add_system(add_visibility_indices.system())
            .add_system_to_stage(
                CoreStage::PostUpdate,
                add_visibility_indices
                    .system()
                    .before(UPDATE_VISIBILITY_INDEX),
            )
            .add_system_to_stage(
                CoreStage::PostUpdate,
                remove_blocks_visibility
                    .system()
                    .before(UPDATE_VISIBILITY_INDEX),
            )
            .add_system_to_stage(
                CoreStage::PostUpdate,
                map_visibility_indexing
                    .system()
                    .label(UPDATE_VISIBILITY_INDEX)
                    .after(crate::map::UPDATE_ENTITY_INDEX_LABEL),
            )
            .add_system_to_stage(
                CoreStage::PostUpdate,
                update_viewshed_for_coordinates
                    .system()
                    .label(UPDATE_VIEWSHED)
                    .after(UPDATE_VISIBILITY_INDEX),
            )
            .add_system_to_stage(
                CoreStage::PostUpdate,
                update_viewshed_for_visibility_blocked
                    .system()
                    .label(UPDATE_VIEWSHED)
                    .after(UPDATE_VISIBILITY_INDEX),
            )
            .add_system_to_stage(
                CoreStage::PostUpdate,
                update_visible_and_revealed_tiles
                    .system()
                    .label(MAP_VISIBILITY)
                    .after(UPDATE_VIEWSHED),
            )
            .add_system_to_stage(
                CoreStage::PostUpdate,
                log_visible
                    .system()
                    .label(LOG_VISIBLE_LABEL)
                    .after(MAP_VISIBILITY),
            );
    }
}