use bevy::*;
use bevy::{render::*, asset::{Asset, AssetStorage, Handle}, math::{Mat4, Vec3}, Schedulable};
use rand::{rngs::StdRng, Rng, SeedableRng, random};
use std::collections::VecDeque;

struct Person;

struct Velocity {
    pub value: math::Vec3,
}

struct NavigationPoint {
    pub target: math::Vec3,
}

struct Wander {
    pub duration_bounds: math::Vec2,
    pub distance_bounds: math::Vec2,
    pub duration: f32,
    pub elapsed: f32,
}

fn main() {
    AppBuilder::new()
        .add_defaults()
        .setup(&setup)
        .run();
}

fn setup(world: &mut World, scheduler: &mut SystemScheduler<AppStage>) {
    let cube = Mesh::load(MeshType::Cube);
    let cube_handle = {
        let mut mesh_storage = world.resources.get_mut::<AssetStorage<Mesh, MeshType>>().unwrap();
        mesh_storage.add(cube, "cube")
    };

    let transform_system_bundle = transform_system_bundle::build(world);
    scheduler.add_systems(AppStage::Update, transform_system_bundle);
    scheduler.add_system(AppStage::Update, build_wander_system());
    scheduler.add_system(AppStage::Update, build_navigate_system());
    scheduler.add_system(AppStage::Update, build_move_system());
    scheduler.add_system(AppStage::Update, build_print_status_system());

    world.insert((), vec![
        // lights
        (
            Light {
                color: wgpu::Color {
                    r: 0.8,
                    g: 0.8,
                    b: 0.5,
                    a: 1.0,
                },
                fov: f32::to_radians(60.0),
                depth: 0.1 .. 50.0,
                target_view: None,
            },
            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0)),
            LocalToWorld::identity(),
            Translation::new(4.0, -4.0, 5.0),
            Rotation::from_euler_angles(0.0, 0.0, 0.0)
        ),
    ]);

    world.insert((), vec![
        // camera
        (
            Camera::new(CameraType::Projection {
                fov: std::f32::consts::PI / 4.0,
                near: 1.0,
                far: 1000.0,
                aspect_ratio: 1.0,
            }),
            ActiveCamera,
            LocalToWorld(Mat4::look_at_rh(
                Vec3::new(6.0, -40.0, 20.0),
                Vec3::new(0.0, 0.0, 0.0),
                Vec3::new(0.0, 0.0, 1.0),)),
        )
    ]);

    let mut rng = StdRng::from_entropy();
    for _ in 0 .. 70000 {
        create_person(world, cube_handle.clone(),
            Translation::new(rng.gen_range(-50.0, 50.0), 0.0, rng.gen_range(-50.0, 50.0)));
    }
}

fn build_wander_system() -> Box<dyn Schedulable> {
    let mut rng = StdRng::from_entropy();
    
    SystemBuilder::new("Wander")
        .read_resource::<Time>()
        .with_query(<(
            Read<Person>,
            Read<Translation>,
            Write<Wander>,
            Write<NavigationPoint>,
        )>::query())
        .build(move |
            _, world,
            time ,
            person_query| {
            for (_, translation, mut wander, mut navigation_point) in person_query.iter(world) {
                wander.elapsed += time.delta_seconds;
                if wander.elapsed >= wander.duration {
                    let direction = math::vec3(
                        rng.gen_range(-1.0, 1.0),
                        rng.gen_range(-1.0, 1.0),
                        rng.gen_range(0.0, 0.001),
                    ).normalize();
                    let distance = rng.gen_range(wander.distance_bounds.x(), wander.distance_bounds.y());
                    navigation_point.target = translation.0 + direction * distance;
                    wander.elapsed = 0.0;
                    wander.duration = rng.gen_range(wander.duration_bounds.x(), wander.duration_bounds.y());
                }
            }
        })
}

fn build_navigate_system() -> Box<dyn Schedulable> {
    SystemBuilder::new("Navigate")
        .with_query(<(
            Read<Person>,
            Write<Translation>,
            Write<Velocity>,
            Write<NavigationPoint>,
        )>::query())
        .build(move |
            _, world,
            _, person_query| {
            for (_, translation, mut velocity, navigation_point) in person_query.iter(world) {
                let distance = navigation_point.target - translation.0;
                if distance.length() > 0.01 {
                    let direction = distance.normalize();
                    velocity.value = direction * 2.0;
                } else {
                    velocity.value = math::vec3(0.0, 0.0, 0.0);
                }
            }
        })
}

fn build_move_system() -> Box<dyn Schedulable> {
    SystemBuilder::new("Move")
        .read_resource::<Time>()
        .with_query(<(
            Write<Translation>,
            Read<Velocity>,
        )>::query())
        .build(move |_, world, time , person_query| {
            for (mut translation, velocity) in person_query.iter(world) {
                translation.0 += velocity.value * time.delta_seconds;
            }
        })
}

fn build_print_status_system() -> Box<dyn Schedulable> {
    let mut elapsed = 0.0;
    let mut frame_time_total = 0.0;
    let mut frame_time_count = 0;
    let frame_time_max = 10;
    let mut frame_time_values = VecDeque::new();
    SystemBuilder::new("PrintStatus")
        .read_resource::<Time>()
        .with_query(<(
            Read<Person>,
        )>::query())
        .build(move |_, world, time , person_query| {
            elapsed += time.delta_seconds;
            frame_time_values.push_front(time.delta_seconds);
            frame_time_total += time.delta_seconds;
            frame_time_count += 1;
            if frame_time_count > frame_time_max {
                frame_time_count = frame_time_max;
                frame_time_total -= frame_time_values.pop_back().unwrap();
            }
            if elapsed > 1.0 {
                // println!("fps: {}", if time.delta_seconds == 0.0 { 0.0 } else { 1.0 / time.delta_seconds });
                if frame_time_count > 0 && frame_time_total > 0.0  {
                    println!("fps: {}", 1.0 / (frame_time_total / frame_time_count as f32))
                }
                println!("peeps: {}", person_query.iter(world).count());
                elapsed = 0.0;
            }
        })
}

fn create_person(world: &mut World, mesh_handle: Handle<Mesh>, translation: Translation) {
    world.insert((), vec![
        (
            Person{},
            Wander {
                duration_bounds: math::vec2(3.0, 10.0),
                distance_bounds: math::vec2(-50.0, 50.0),
                elapsed: 0.0,
                duration: 0.0,
            },
            NavigationPoint {
                target: math::vec3(0.0, 0.0, 0.0),
            },
            Velocity {
                value: math::vec3(0.0, 0.0, 0.0),
            },
            Instanced,
            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0) * random::<f32>()),
            mesh_handle,
            LocalToWorld::identity(),
            translation
        ),
    ]);
}