use bevy::prelude::*;

use crate::{
    sim::{SimSystems, SimTick},
    tilemap::PlantLook,
    world::{Terrain, TileChanged, WorldMap},
};

pub struct PlantsPlugin;

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

pub const GROWTH_INTERVAL_TICKS: u64 = 60;
const WILD_MIN_FERTILITY: f32 = 0.8;

pub fn fertility(terrain: Terrain) -> f32 {
    match terrain {
        Terrain::Soil => 1.0,
        Terrain::Grass => 0.8,
        Terrain::Sand => 0.4,
        Terrain::Gravel => 0.3,
        _ => 0.0,
    }
}

pub fn grow(map: &mut WorldMap, elapsed_ticks: f32, mut on_change: impl FnMut(UVec2)) {
    for pos in map.positions() {
        let p = pos.as_ivec2();
        let Some(plant) = map.plant(p) else {
            continue;
        };
        let Some(ripening) = plant.ripening_ticks() else {
            continue;
        };
        let growth = map.growth(p);
        if growth >= 1.0 {
            continue;
        }
        let soil = fertility(map.get(p).unwrap_or(Terrain::Grass));
        let soil = match plant {
            crate::world::Plant::Crop => soil,
            _ => soil.max(WILD_MIN_FERTILITY),
        };
        let grown = (growth + elapsed_ticks / ripening * soil).min(1.0);
        map.set_growth(pos, grown);
        if PlantLook::of(plant, growth) != PlantLook::of(plant, grown) {
            on_change(pos);
        }
    }
}

fn grow_plants(
    tick: Res<SimTick>,
    mut map: ResMut<WorldMap>,
    mut changed: MessageWriter<TileChanged>,
) {
    if !tick.0.is_multiple_of(GROWTH_INTERVAL_TICKS) {
        return;
    }
    grow(&mut map, GROWTH_INTERVAL_TICKS as f32, |pos| {
        changed.write(TileChanged(pos));
    });
}

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

    fn growth_after(terrain: Terrain, plant: Plant, ticks: f32) -> f32 {
        let mut map = WorldMap::filled(UVec2::splat(2), terrain);
        map.set_plant(UVec2::ZERO, Some(plant));
        grow(&mut map, ticks, |_| {});
        map.growth(IVec2::ZERO)
    }

    #[test]
    fn crops_ripen_faster_on_fertile_soil() {
        let day = 24.0 * crate::sim::TICKS_PER_HOUR as f32;
        assert!(
            growth_after(Terrain::Soil, Plant::Crop, day)
                > growth_after(Terrain::Sand, Plant::Crop, day)
        );
        assert_eq!(growth_after(Terrain::Soil, Plant::Crop, 2.0 * day), 1.0);
    }

    #[test]
    fn trees_do_not_grow_and_stage_changes_are_reported() {
        assert_eq!(growth_after(Terrain::Soil, Plant::Tree, 1e9), 0.0);
        let mut map = WorldMap::filled(UVec2::splat(2), Terrain::Soil);
        map.set_plant(UVec2::ZERO, Some(Plant::Crop));
        let mut changes = 0;
        grow(&mut map, 1e9, |_| changes += 1);
        assert_eq!(changes, 1);
    }
}