use std::time::Duration;

use bevy::{asset::RenderAssetUsages, picking::PickSet, prelude::*, render::mesh::{Indices, PrimitiveTopology}};
use noise::{Fbm, MultiFractal, NoiseFn, Perlin};
use rand::{thread_rng, Rng, SeedableRng};
use voronoice::{BoundingBox, Point, VoronoiBuilder};

mod cells;
mod picking;
use picking::*;
use cells::*;
pub use cells::CellKind;

use crate::{time::GameTime, ui::CurrentAction};

pub struct Plugin;
impl bevy::prelude::Plugin for Plugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, setup)
            .add_systems(PreUpdate, picking_backend.in_set(PickSet::Backend))
            .add_systems(Update, (update_map_mesh, cells_regeneration, expand))
            .insert_resource(ClearColor(Color::srgb(0., 0., 1.)))
            .insert_resource(Seed(thread_rng().gen()));
    }
}

pub const HEIGHT: f32 = 2.;
pub const WIDTH: f32 = 2.;
pub const REAL_HEIGHT: f32 = 500.;
pub const REAL_WIDTH: f32 = 500.;
pub const CELL_AREA: f32 = REAL_HEIGHT * REAL_WIDTH / SIZE as f32;
pub const SIZE: usize = 10000;

#[derive(Resource)]
struct Seed(u32);

#[derive(Component)]
pub struct Voronoi (voronoice::Voronoi);

#[derive(Component)]
pub struct MapMarker;

#[derive(Component)]
struct MapColors (Vec<[f32; 4]>);

#[derive(Component)]
pub struct CellsEntities (Vec<Entity>);

#[derive(Component)]
pub struct MeshNeedsUpdate(bool);

fn setup(
    mut cmds: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<ColorMaterial>>,
    seed: Res<Seed>
) {
    let mut rng = rand::rngs::SmallRng::seed_from_u64(seed.0 as u64);
    let mut sites = Vec::with_capacity(SIZE);
    for _ in 0..SIZE {
        sites.push(Point { x:rng.gen_range(-WIDTH/2.0..WIDTH/2.0) as f64, y:rng.gen_range(-HEIGHT/2.0..HEIGHT/2.0) as f64 })
    }
    let voronoi = VoronoiBuilder::default()
        .set_sites(sites)
        .set_bounding_box(BoundingBox::new_centered(WIDTH as f64, HEIGHT as f64))
        .set_lloyd_relaxation_iterations(3)
        .build()
        .unwrap();
    let mut cells = Vec::with_capacity(SIZE);
    let z_noise = Fbm::<Perlin>::new(seed.0);
    let moisture_noise = Fbm::<Perlin>::new(seed.0+1)
        .set_frequency(2.);
    for i in 0..SIZE {
        let c = voronoi.cell(i);
        let site = c.site_position();
        let z = (
            0.3 // Arbitrary value
            + ((z_noise.get([site.x, site.y])+1.)/2.) // Noise + [0; 1]
            - ((site.x.powi(2)+site.y.powi(2)).sqrt()*0.5) // Distance - [0; sqrt(2)] * 0.5
        ).clamp(0., 1.);
        let m = (
            (moisture_noise.get([site.x, site.y])+1.)/2. // Noise + [0; 1]
        ).clamp(0., 1.) as f32;
        let k = if z <= 0.5 {
            CellKind::Sea
        } else if z <= 0.52 {
            CellKind::Beach
        } else if z < 0.8 {
            CellKind::Dirt
        } else {
            CellKind::Stone
        };
        cells.push(Cell {
            kind: k,
            voronoi_id: i,
            altitude: (z*255.) as u8,
            vertices: vec![]
        });
    }
    

    let mut poss = Vec::new();
    let mut indices = Vec::new();

    for (c, cd) in voronoi.iter_cells().zip(cells.iter_mut()).filter(|(_,cd)| cd.kind != CellKind::Forest) {
        let vs = c.iter_vertices().collect::<Vec<_>>();
        let i = poss.len();
        for v in vs.iter() {
            poss.push(Vec3::new(v.x as f32, v.y as f32, 0.));
        }
        for v in 1..(vs.len()-1) {
            indices.extend_from_slice(&[i as u32, (i+v) as u32, (i+v+1) as u32]);
            cd.vertices.extend_from_slice(&[i, i+v, i+v+1]);
        }
    }

    let colors = vec![[0.; 4]; poss.len()];
    let mesh = Mesh::new(PrimitiveTopology::TriangleList, RenderAssetUsages::default())
        // Add 4 vertices, each with its own position attribute (coordinate in
        // 3D space), for each of the corners of the parallelogram.
        .with_inserted_attribute(
            Mesh::ATTRIBUTE_POSITION,
            poss
        )
        .with_inserted_attribute(
            Mesh::ATTRIBUTE_COLOR,
            colors.clone()
        )
        .with_inserted_indices(Indices::U32(indices));

    let mut cells_entities = Vec::with_capacity(cells.len());
    cmds.spawn((
        Mesh2d(meshes.add(mesh)),
        MeshMaterial2d(materials.add(ColorMaterial::default())),
        Transform::default(),
        Voronoi(voronoi),
        MapColors(colors),
        MeshNeedsUpdate(true),
        MapMarker
    )).with_children(|parent| {
        for cell in cells {
            let kind = cell.kind;
            let mut cmd = parent.spawn(cell);
            match kind {
                CellKind::Grass | CellKind::Forest => {
                    cmd.insert((Wealth(0), Regeneration {
                        last_update: Duration::ZERO,
                        full_growth_duration: kind.regen_full_growth_duration()
                    }));
                },
                _ => {}
            }
            cmd.observe(|
                    trigger: Trigger<Pointer<Click>>,
                    mut cells: Query<&mut Cell>,
                    mut map_needs_update: Query<&mut MeshNeedsUpdate, With<MapMarker>>,
                    mut cmds: Commands,
                    ca: Res<CurrentAction>,
                    gt: Res<GameTime>,
                | {
                if trigger.duration > Duration::from_millis(200) {
                    return
                }
                match *ca {
                    CurrentAction::ChangeCell(ck) => {
                        let mut cell = cells.get_mut(trigger.target).unwrap();
                        match ck {
                            CellKind::Forest => match cell.kind {
                                CellKind::Dirt | CellKind::Grass => {
                                    cmds.entity(trigger.target).insert((Wealth(0), Regeneration {
                                        last_update: gt.current,
                                        full_growth_duration: CellKind::Forest.regen_full_growth_duration()
                                    }));
                                    cell.kind = CellKind::Forest;
                                    map_needs_update.single_mut().0 = true;
                                },
                                _ => {}
                            },
                            CellKind::Grass => match cell.kind {
                                CellKind::Dirt => {
                                    cmds.entity(trigger.target).insert((Wealth(0), Regeneration {
                                        last_update: gt.current,
                                        full_growth_duration: CellKind::Grass.regen_full_growth_duration()
                                    }));
                                    cell.kind = CellKind::Grass;
                                    map_needs_update.single_mut().0 = true;
                                },
                                _ => {}
                            }
                            _ => {}
                        }
                    }
                    _ => {}
                }
                
            });
            cells_entities.push(cmd.id());
        }
    }).insert(CellsEntities(cells_entities));

}

fn update_map_mesh(
    cells: Query<(&Cell, Option<&Wealth>)>,
    mut map: Query<(&Mesh2d, &mut MapColors, &mut MeshNeedsUpdate), With<MapMarker>>,
    mut meshes: ResMut<Assets<Mesh>>
) {
    let (mesh, mut cols, mut needs_update) = map.single_mut();
    if needs_update.0 {
        if let Some(mesh) = meshes.get_mut(mesh) {
            let mut modified = false;
            for (cell, wealth) in cells.iter() {
                let col = cell.color(wealth.map(|w| w.0).unwrap_or_default());
                for id in cell.vertices.iter() {
                    modified = modified || cols.0[*id] != col;
                    cols.0[*id] = col.clone();
                }
            }
            if modified {
                mesh.insert_attribute(Mesh::ATTRIBUTE_COLOR, cols.0.clone());
            }
        }
        needs_update.0 = false;
    }
}