use bevy::prelude::*;

use crate::{
    colonist::{Colonist, Path},
    items::{Item, ItemKind},
    jobs::{CurrentJob, Reservations, Target},
    needs::is_sleeping,
    pathfinding::nearest_tile,
    sim::{SimSystems, TICKS_PER_HOUR},
    world::{TilePos, WorldMap},
};

pub struct FoodPlugin;

impl Plugin for FoodPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(FixedUpdate, update_hunger.in_set(SimSystems::Act));
    }
}

pub const HUNGER_PER_TICK: f32 = 1.0 / (24.0 * TICKS_PER_HOUR as f32);
pub const SLEEPING_HUNGER_FACTOR: f32 = 0.5;
pub const HUNGRY: f32 = 0.35;
pub const STARVING: f32 = 0.05;
pub const EAT_TICKS: u32 = 90;
const FOOD_SEARCH_TILES: usize = 15000;

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

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

pub fn wants_food(fed: f32) -> bool {
    fed < HUNGRY
}

pub fn portion(kind: ItemKind, fed: f32) -> u32 {
    ((1.0 - fed) / kind.nutrition()).ceil().max(1.0) as u32
}

pub fn find_food(
    map: &WorldMap,
    reservations: &Reservations,
    items: &[(Item, TilePos)],
    from: UVec2,
) -> Option<UVec2> {
    let has = |p: UVec2, accept: fn(ItemKind) -> bool| {
        reservations.is_free(Target::Pickup(p))
            && items
                .iter()
                .any(|(item, pos)| pos.0 == p && accept(item.kind))
    };
    nearest_tile(map, from, FOOD_SEARCH_TILES, |p| {
        has(p, |k| k == ItemKind::Meal)
    })
    .or_else(|| {
        nearest_tile(map, from, FOOD_SEARCH_TILES, |p| {
            has(p, ItemKind::is_raw_food)
        })
    })
}

pub fn update_hunger(
    mut colonists: Query<(&mut Hunger, &CurrentJob, &TilePos, &Path), With<Colonist>>,
) {
    for (mut hunger, job, tile, path) in &mut colonists {
        let rate = if is_sleeping(job, tile, path) {
            HUNGER_PER_TICK * SLEEPING_HUNGER_FACTOR
        } else {
            HUNGER_PER_TICK
        };
        hunger.0 = (hunger.0 - rate).max(0.0);
    }
}

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

    #[test]
    fn portions_fill_a_colonist_up() {
        assert_eq!(portion(ItemKind::Meal, 0.2), 1);
        assert_eq!(portion(ItemKind::Berries, 0.3), 7);
        assert_eq!(portion(ItemKind::Berries, 0.99), 1);
    }

    #[test]
    fn colonists_prefer_meals_over_raw_food() {
        let map = WorldMap::filled(UVec2::splat(20), Terrain::Grass);
        let reservations = Reservations::default();
        let food = |kind, x| (Item { kind, count: 5 }, TilePos(UVec2::new(x, 0)));
        let items = [
            food(ItemKind::Berries, 1),
            food(ItemKind::Meal, 15),
            food(ItemKind::Wood, 0),
        ];
        assert_eq!(
            find_food(&map, &reservations, &items, UVec2::ZERO),
            Some(UVec2::new(15, 0))
        );
        assert_eq!(
            find_food(&map, &reservations, &items[..1], UVec2::ZERO),
            Some(UVec2::new(1, 0))
        );
        assert_eq!(
            find_food(&map, &reservations, &items[2..], UVec2::ZERO),
            None
        );
    }
}