use std::collections::HashSet;

use bevy::prelude::*;

use crate::{
    colonist::{Colonist, Path},
    items::Item,
    jobs::{CurrentJob, Job, Reservations, Target, Task},
    pathfinding::nearest_tile,
    sim::{SimSystems, TICKS_PER_HOUR},
    structures::{Structure, StructureKind},
    world::{TILE_SIZE, TilePos, WorldMap},
    zones::{Zones, can_zone},
};

pub struct NeedsPlugin;

impl Plugin for NeedsPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(FixedUpdate, update_rest.in_set(SimSystems::Act))
            .add_systems(Update, show_sleep_markers);
    }
}

pub const REST_DRAIN_PER_TICK: f32 = 1.0 / (24.0 * TICKS_PER_HOUR as f32);
pub const REST_RECOVERY_PER_TICK: f32 = 1.0 / (7.0 * TICKS_PER_HOUR as f32);
pub const BED_REST_RECOVERY_PER_TICK: f32 = 1.0 / (5.0 * TICKS_PER_HOUR as f32);
pub const BEDTIME_REST: f32 = 0.9;
pub const NAP_REST: f32 = 0.3;
pub const EXHAUSTED_REST: f32 = 0.1;
const SLEEP_SPOT_SEARCH_TILES: usize = 3000;

#[derive(Component, Debug, Clone, Copy, PartialEq)]
pub struct Rest(pub f32);

impl Default for Rest {
    fn default() -> Self {
        Self(1.0)
    }
}

pub fn is_night(hour: f32) -> bool {
    !(6.0..21.0).contains(&hour)
}

pub fn wants_sleep(rest: f32, hour: f32) -> bool {
    rest < NAP_REST || (is_night(hour) && rest < BEDTIME_REST)
}

pub fn done_sleeping(rest: f32, hour: f32) -> bool {
    rest >= 1.0 && !is_night(hour)
}

pub fn is_sleeping(job: &CurrentJob, tile: &TilePos, path: &Path) -> bool {
    matches!(
        job.0,
        Some(Job {
            task: Task::Sleep { spot },
            ..
        }) if spot == tile.0 && path.0.is_empty()
    )
}

pub fn update_rest(
    structures: Query<(&TilePos, &Structure), Without<Colonist>>,
    mut colonists: Query<(&mut Rest, &CurrentJob, &TilePos, &Path), With<Colonist>>,
) {
    let beds: HashSet<UVec2> = structures
        .iter()
        .filter(|(_, s)| s.kind == StructureKind::Bed)
        .map(|(pos, _)| pos.0)
        .collect();
    for (mut rest, job, tile, path) in &mut colonists {
        let change = match (is_sleeping(job, tile, path), beds.contains(&tile.0)) {
            (true, true) => BED_REST_RECOVERY_PER_TICK,
            (true, false) => REST_RECOVERY_PER_TICK,
            (false, _) => -REST_DRAIN_PER_TICK,
        };
        rest.0 = (rest.0 + change).clamp(0.0, 1.0);
    }
}

pub struct SleepContext<'a> {
    pub map: &'a WorldMap,
    pub zones: &'a Zones,
    pub reservations: &'a Reservations,
    pub items: &'a [(Item, TilePos)],
    pub structures: &'a [(UVec2, StructureKind, u32)],
}

impl SleepContext<'_> {
    fn free(&self, tile: UVec2) -> bool {
        can_zone(self.map, tile.as_ivec2())
            && self.map.plant(tile.as_ivec2()).is_none()
            && !self.zones.is_stockpile(tile)
            && !self.structures.iter().any(|(pos, ..)| *pos == tile)
            && !self.items.iter().any(|(_, pos)| pos.0 == tile)
            && self.reservations.is_free(Target::SleepSpot(tile))
    }

    fn nearest(&self, kind: StructureKind, from: UVec2) -> Option<UVec2> {
        self.structures
            .iter()
            .filter(|(pos, k, _)| {
                *k == kind
                    && (kind != StructureKind::Bed
                        || self.reservations.is_free(Target::SleepSpot(*pos)))
            })
            .map(|(pos, ..)| *pos)
            .min_by(|a, b| {
                a.as_vec2()
                    .distance_squared(from.as_vec2())
                    .total_cmp(&b.as_vec2().distance_squared(from.as_vec2()))
            })
    }

    pub fn spot(&self, from: UVec2) -> UVec2 {
        if let Some(bed) = self.nearest(StructureKind::Bed, from) {
            return bed;
        }
        let anchor = self
            .nearest(StructureKind::Campfire, from)
            .unwrap_or_else(|| self.zones.home(from));
        nearest_tile(self.map, anchor, SLEEP_SPOT_SEARCH_TILES, |p| self.free(p)).unwrap_or(from)
    }
}

#[derive(Component)]
pub struct SleepMarker;

pub fn sleep_marker() -> impl Bundle {
    (
        SleepMarker,
        Text2d::new("z"),
        TextFont::from_font_size(12.0),
        TextColor(Color::srgb(0.85, 0.9, 1.0)),
        Transform::from_xyz(TILE_SIZE * 0.35, TILE_SIZE * 0.45, 0.2),
        Visibility::Hidden,
    )
}

fn show_sleep_markers(
    colonists: Query<(&CurrentJob, &TilePos, &Path, &Children), With<Colonist>>,
    mut markers: Query<&mut Visibility, With<SleepMarker>>,
) {
    for (job, tile, path, children) in &colonists {
        let shown = if is_sleeping(job, tile, path) {
            Visibility::Inherited
        } else {
            Visibility::Hidden
        };
        for &child in children {
            if let Ok(mut visibility) = markers.get_mut(child) {
                visibility.set_if_neq(shown);
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::world::Terrain;

    #[test]
    fn colonists_sleep_at_night_and_nap_only_when_tired() {
        assert!(wants_sleep(0.8, 22.0));
        assert!(!wants_sleep(0.95, 22.0));
        assert!(!wants_sleep(0.8, 12.0));
        assert!(wants_sleep(0.2, 12.0));
    }

    // A colonist that is fully rested at 3 am keeps resting rather than wandering off into the
    // dark; the night ends sleep, a full rest bar alone does not.
    #[test]
    fn sleep_lasts_until_morning() {
        assert!(!done_sleeping(1.0, 3.0));
        assert!(done_sleeping(1.0, 7.0));
        assert!(!done_sleeping(0.7, 7.0));
    }

    #[test]
    fn rest_drains_awake_and_recovers_asleep() {
        let mut app = App::new();
        app.add_systems(Update, update_rest);
        let tile = UVec2::new(3, 3);
        let awake = app
            .world_mut()
            .spawn((
                Colonist {
                    name: "Waker".into(),
                },
                Rest(0.5),
                CurrentJob(None),
                TilePos(tile),
                Path::default(),
            ))
            .id();
        let asleep = app
            .world_mut()
            .spawn((
                Colonist {
                    name: "Sleeper".into(),
                },
                Rest(0.5),
                CurrentJob(Some(Job {
                    task: Task::Sleep { spot: tile },
                    ordered: false,
                })),
                TilePos(tile),
                Path::default(),
            ))
            .id();
        app.update();
        assert!(app.world().get::<Rest>(awake).unwrap().0 < 0.5);
        assert!(app.world().get::<Rest>(asleep).unwrap().0 > 0.5);
    }

    fn sleeper(app: &mut App, tile: UVec2) -> Entity {
        app.world_mut()
            .spawn((
                Colonist {
                    name: "Sleeper".into(),
                },
                Rest(0.2),
                CurrentJob(Some(Job {
                    task: Task::Sleep { spot: tile },
                    ordered: false,
                })),
                TilePos(tile),
                Path::default(),
            ))
            .id()
    }

    #[test]
    fn beds_restore_rest_faster_than_the_ground() {
        let mut app = App::new();
        app.add_systems(Update, update_rest);
        let bed = UVec2::new(1, 1);
        app.world_mut().spawn((
            Structure {
                kind: StructureKind::Bed,
            },
            TilePos(bed),
        ));
        let in_bed = sleeper(&mut app, bed);
        let on_ground = sleeper(&mut app, UVec2::new(5, 5));
        app.update();
        let rest = |e| app.world().get::<Rest>(e).unwrap().0;
        assert!(rest(in_bed) > rest(on_ground));
    }

    #[test]
    fn sleepers_take_a_free_bed_over_the_campfire() {
        let map = WorldMap::filled(UVec2::splat(20), Terrain::Grass);
        let zones = Zones::default();
        let mut reservations = Reservations::default();
        let structures = [
            (UVec2::new(3, 3), StructureKind::Campfire, 1000),
            (UVec2::new(15, 15), StructureKind::Bed, u32::MAX),
            (UVec2::new(16, 15), StructureKind::Bed, u32::MAX),
        ];
        reservations.reserve(Target::SleepSpot(UVec2::new(15, 15)), Entity::PLACEHOLDER);
        let ctx = SleepContext {
            map: &map,
            zones: &zones,
            reservations: &reservations,
            items: &[],
            structures: &structures,
        };
        assert_eq!(ctx.spot(UVec2::new(2, 2)), UVec2::new(16, 15));
    }

    #[test]
    fn sleepers_bed_down_by_the_campfire() {
        let map = WorldMap::filled(UVec2::splat(20), Terrain::Grass);
        let zones = Zones::default();
        let reservations = Reservations::default();
        let fires = [(UVec2::new(15, 15), StructureKind::Campfire, 1000)];
        let ctx = SleepContext {
            map: &map,
            zones: &zones,
            reservations: &reservations,
            items: &[],
            structures: &fires,
        };
        let spot = ctx.spot(UVec2::new(2, 2));
        assert!(spot.as_vec2().distance(Vec2::splat(15.0)) < 2.0);
        assert_ne!(spot, UVec2::new(15, 15));
    }
}