mod camera;
mod config;
mod renderer;
mod sim;

use futures::executor;
use fxhash::FxHashMap;
use rand::random_range;
use std::{collections::VecDeque, sync::Arc, time::Instant};
use winit::{
    application::ApplicationHandler,
    event::{
        ElementState, KeyEvent, MouseButton,
        WindowEvent::{self},
    },
    event_loop::{ActiveEventLoop, ControlFlow, EventLoop},
    keyboard::{KeyCode, PhysicalKey},
    window::Window,
};

use crate::{
    camera::Camera,
    config::{PHYSICS_DELTA_TIME, PHYSICS_FPS, SIM_FPS, WINDOW_TITLE},
    renderer::RendererState,
    sim::{
        cell::{cell::Cell, materials::MaterialId},
        cell_sim::{sim::sim_tick, world::World},
        rb_sim::RbSimManager,
        write_rb_entity_to_world,
    },
};

pub type Error = Box<dyn std::error::Error>;
pub type Result<T> = std::result::Result<T, Error>;

struct Config {
    brush_radius: f32,
    brush_material: MaterialId,
    dropper_material: MaterialId,
    use_threading: bool,
}

struct Input {
    last_mouse_pos_on_screen: Option<(f32, f32)>,
    last_mouse_world_pos: Option<(f32, f32)>,
    is_lmb_pressed: bool,
    trigger_test_1: bool,

    // keybindings
    is_up_pressed: bool,
    is_left_pressed: bool,
    is_down_pressed: bool,
    is_right_pressed: bool,
}

struct Diagnostics {
    frame_times: VecDeque<f32>,
    fps: f32,
}

struct App {
    window: Option<Arc<Window>>,
    renderer_state: Option<RendererState>,

    input: Input,

    camera: Option<Camera>,

    // grid
    world: Option<World>,

    // physics
    rb_sim_manager: Option<RbSimManager>,

    // sim state
    // the last/current (not yet completed) seqno
    sim_seqno: u64,
    sim_paused: bool,
    ignore_pause_next_tick: bool,
    last_sim_update: Instant,
    sim_updates_due: f32,

    // physics state
    last_physics_update: Instant,
    physics_updates_due: f32,

    last_render: Instant,

    config: Config,
    diagnostics: Diagnostics,
}

impl App {
    // called as often as possible
    // delta time is the real seconds elapsed since the last time this was called
    fn update(&mut self, delta_time: f32) {
        // apply inputs
        if let Some(camera) = &mut self.camera {
            camera.handle_camera_input(&self.input, delta_time)
        }

        // --TEST SPAWNING--
        if self.input.trigger_test_1
            && let Some(lm) = self.input.last_mouse_world_pos
            && let Some(rbsm) = &mut self.rb_sim_manager
        {
            self.input.trigger_test_1 = false;
            rbsm.test_spawn_box(lm.0, lm.1, self.config.dropper_material);
        }

        // --TEST DRAWING--
        if self.input.is_lmb_pressed
            && let Some(lm) = self.input.last_mouse_world_pos
        {
            // start with the bounding box of the drawing brush circle + some margin
            // clamp the bounding box to the board sie
            let bb_xl = (lm.0 - self.config.brush_radius).round() as i32;
            let bb_xu = (lm.0 + self.config.brush_radius).round() as i32;
            let bb_yl = (lm.1 - self.config.brush_radius).round() as i32;
            let bb_yu = (lm.1 + self.config.brush_radius).round() as i32;

            // for each point, check if the distance is less than the brush size and write the pixel
            for x in bb_xl..bb_xu {
                for y in bb_yl..bb_yu {
                    let r = random_range(0.0..1.0);
                    if ((x - lm.0.round() as i32).pow(2) + (y - lm.1.round() as i32).pow(2))
                        < (self.config.brush_radius as i32).pow(2)
                        && r > 0.9
                    {
                        let mut cell = Cell::from_material(self.config.brush_material);
                        cell.match_parity(self.sim_seqno);
                        // ensure we simulate on the first tick
                        if let Some(world) = &mut self.world {
                            world.set_cell_from_game_position(
                                x, y, cell, false, // wake the chunk
                            )
                        }
                    }
                }
            }
        }
    }
    // called SIM_FPS times per second
    // will be called before the render and before the physics update(s)
    // may be called multiple times if the sim time is behind
    fn sim_update(&mut self) {
        if let Some(world) = &mut self.world
            && let Some(rbsm) = &mut self.rb_sim_manager
        {
            // before we tick, write all the rb entities into the sim world
            // TODO optimize
            let entity_ids: Vec<u32> = rbsm.rb_entities.keys().copied().collect();
            let mut cells_written_by_entity: Vec<(u32, Vec<(u8, u8, i32, i32)>)> = Vec::new();

            for entity_id in entity_ids {
                let cells_written =
                    write_rb_entity_to_world(world, rbsm, entity_id, self.sim_seqno);
                cells_written_by_entity.push((entity_id, cells_written));
            }

            sim_tick(world, self.sim_seqno, self.config.use_threading);
            self.sim_seqno += 1;

            // after we tick, remove the written rb cells and update the entities
            // TODO optimize
            for (entity_id, cells_written) in cells_written_by_entity {
                let rb_entity = rbsm.rb_entities.get_mut(&entity_id).unwrap();
                for (lx, ly, x, y) in cells_written {
                    // update the entity
                    // TODO we should skip cells that weren't changed?
                    let new_local_cell = world.get_cell_from_game_position(x, y).unwrap();
                    // if new_local_cell.material != MaterialId::Void && !new_local_cell.rb() {
                    //     panic!("Someone swapped into this rb's cell!");
                    // }
                    rb_entity.set_cell_at_local_position(lx, ly, new_local_cell);
                    // update the world
                    world.set_cell_from_game_position(x, y, Cell::void(), false);
                }
            }
        }
    }
    // called PHYSICS_FPS times per second
    // will be called before the render
    // may be called multiple times if the physics time is behind
    // physics_delta_time is statically 1/PHYSICS_FPS
    fn physics_update(&mut self, physics_delta_time: f32) {
        if let Some(physics_manager) = &mut self.rb_sim_manager {
            physics_manager.rb_tick(physics_delta_time);
        }
    }
}

impl Default for App {
    fn default() -> Self {
        Self {
            window: None,
            renderer_state: None,

            input: Input {
                last_mouse_pos_on_screen: None,
                last_mouse_world_pos: None,

                trigger_test_1: false,
                is_lmb_pressed: false,
                is_up_pressed: false,
                is_left_pressed: false,
                is_down_pressed: false,
                is_right_pressed: false,
            },

            camera: None,

            world: Some(World::from_default_size()),

            rb_sim_manager: Some(RbSimManager::new()),

            sim_seqno: 0,
            sim_paused: false,
            ignore_pause_next_tick: false,
            last_sim_update: Instant::now(),
            sim_updates_due: 0.0,

            last_physics_update: Instant::now(),
            physics_updates_due: 0.0,

            last_render: Instant::now(),

            config: Config {
                use_threading: true,
                brush_radius: 10.0,
                brush_material: MaterialId::Sand,
                dropper_material: MaterialId::Sand,
            },
            diagnostics: Diagnostics {
                fps: 0.0,
                frame_times: VecDeque::new(),
            },
        }
    }
}

impl ApplicationHandler for App {
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        let window = Arc::new(
            event_loop
                .create_window(Window::default_attributes().with_title(WINDOW_TITLE))
                .unwrap(),
        );

        self.window = Some(window.clone());
        self.renderer_state = Some(executor::block_on(RendererState::new(window.clone())));
        if let Some(rbsm) = &mut self.rb_sim_manager {
            rbsm.test();
        }

        let size = window.inner_size();
        self.camera = Some(Camera::new((size.width as i32, size.height as i32)));

        // let surface = SurfaceTexture::new(size.width, size.height, window_ref);

        // let mut pixels = Pixels::new(PIXEL_BUFFER_WIDTH, PIXEL_BUFFER_HEIGHT, surface).unwrap();

        // pixels.set_scaling_mode(ScalingMode::Fill);
    }

    fn window_event(
        &mut self,
        event_loop: &ActiveEventLoop,
        _: winit::window::WindowId,
        event: WindowEvent,
    ) {
        if let Some(renderer_state) = &mut self.renderer_state
            && let Some(window) = &mut self.window
        {
            let egui_response = renderer_state.egui_state.on_window_event(window, &event);
            // if egui consumed the event, it means we shouldn't treat any e.g., mouse clicks
            if egui_response.consumed {
                return;
            }
        }

        match event {
            WindowEvent::KeyboardInput {
                event:
                    KeyEvent {
                        physical_key: PhysicalKey::Code(code),
                        state,
                        repeat,
                        ..
                    },
                ..
            } => {
                let pressed = state.is_pressed();
                match code {
                    KeyCode::KeyW => self.input.is_up_pressed = pressed,
                    KeyCode::KeyA => self.input.is_left_pressed = pressed,
                    KeyCode::KeyS => self.input.is_down_pressed = pressed,
                    KeyCode::KeyD => self.input.is_right_pressed = pressed,
                    KeyCode::KeyC => self.world = Some(World::from_default_size()),
                    KeyCode::KeyV => {
                        if let Some(rbsm) = self.rb_sim_manager.as_mut() {
                            let entity_ids: Vec<u32> = rbsm.rb_entities.keys().copied().collect();
                            for entity_id in entity_ids {
                                rbsm.destroy_rb_entity(entity_id);
                            }
                        }
                    }
                    KeyCode::KeyP if pressed && !repeat => {
                        if let Some(rbsm) = self.rb_sim_manager.as_mut() {
                            for &id in rbsm.rb_entities.keys() {
                                write_rb_entity_to_world(
                                    self.world.as_mut().unwrap(),
                                    rbsm,
                                    id,
                                    self.sim_seqno,
                                );
                            }

                            let entity_ids: Vec<u32> = rbsm.rb_entities.keys().copied().collect();
                            for entity_id in entity_ids {
                                rbsm.destroy_rb_entity(entity_id);
                            }
                        }
                    }
                    KeyCode::Space if pressed => self.sim_paused = !self.sim_paused,
                    KeyCode::KeyX if pressed => self.ignore_pause_next_tick = true,
                    KeyCode::KeyQ if pressed && !repeat => self.input.trigger_test_1 = true,
                    _ => {}
                }
            }
            WindowEvent::CursorMoved { position, .. } => {
                self.input.last_mouse_pos_on_screen = Some((position.x as f32, position.y as f32));
                self.input.last_mouse_world_pos = self.camera.as_mut().map(|camera| {
                    camera.screen_position_to_world(position.x as f32, position.y as f32)
                })
            }
            WindowEvent::MouseInput { state, button, .. } => {
                if button == MouseButton::Left {
                    self.input.is_lmb_pressed = state == ElementState::Pressed
                }
            }
            WindowEvent::Resized(size) => {
                if let Some(renderer_state) = &mut self.renderer_state
                    && let Some(camera) = &mut self.camera
                {
                    renderer_state.resize(size.width, size.height);
                    camera.resize((size.width as i32, size.height as i32));
                }
            }
            WindowEvent::CloseRequested => {
                event_loop.exit();
            }
            WindowEvent::RedrawRequested => {
                #[cfg(feature = "profiler")]
                puffin::GlobalProfiler::lock().new_frame();

                puffin::profile_scope!("redraw_requested");
                // compute FPS diagnostics
                let now = Instant::now();
                let secs_since_last_frame = (now - self.last_render).as_secs_f32();
                self.last_render = now;

                let delta_time = secs_since_last_frame / (1.0 / 60.0);

                self.diagnostics
                    .frame_times
                    .push_back(secs_since_last_frame);

                if self.diagnostics.frame_times.len() > 30 {
                    self.diagnostics.frame_times.pop_front();
                }

                let average_frame_time = self.diagnostics.frame_times.iter().sum::<f32>()
                    / self.diagnostics.frame_times.len() as f32;

                self.diagnostics.fps = 1.0 / average_frame_time;

                // UPDATE
                self.update(delta_time);

                // SIM UPDATE
                let secs_since_last_sim_update = (now - self.last_sim_update).as_secs_f32();
                let expected_secs_since_last_sim_update = 1.0 / SIM_FPS as f32;

                self.last_sim_update = now;
                if self.sim_paused && self.ignore_pause_next_tick {
                    self.sim_update();
                    self.ignore_pause_next_tick = false;
                } else if !self.sim_paused {
                    self.sim_updates_due +=
                        secs_since_last_sim_update / expected_secs_since_last_sim_update;
                    let mut updates_done = 0;
                    // don't ever update more than 3 times per frame, or else we can get a pseudo deadlock
                    while self.sim_updates_due >= 1.0 && updates_done < 3 {
                        self.sim_update();
                        self.sim_updates_due -= 1.0;
                        updates_done += 1;
                    }
                    self.sim_updates_due = self.sim_updates_due.min(3.0);
                }

                // PHYSICS UPDATE
                let secs_since_last_physics_update = (now - self.last_physics_update).as_secs_f32();
                let expected_secs_since_last_physics_update = 1.0 / PHYSICS_FPS as f32;

                self.last_physics_update = now;
                if !self.sim_paused {
                    self.physics_updates_due +=
                        secs_since_last_physics_update / expected_secs_since_last_physics_update;
                    let mut updates_done = 0;
                    // don't ever update more than 3 times per frame, or else we can get a pseudo deadlock
                    while self.physics_updates_due >= 1.0 && updates_done < 3 {
                        self.physics_update(PHYSICS_DELTA_TIME);
                        self.physics_updates_due -= 1.0;
                        updates_done += 1;
                    }
                    self.physics_updates_due = self.physics_updates_due.min(3.0);
                }

                if let Some(renderer_state) = &mut self.renderer_state
                    && let Some(world) = &mut self.world
                    && let Some(rb_sim_manager) = &mut self.rb_sim_manager
                    && let Some(camera) = &mut self.camera
                {
                    renderer_state.render(
                        world,
                        rb_sim_manager,
                        camera,
                        &mut self.config,
                        &self.diagnostics,
                        &self.input,
                    );
                }
            }
            _ => {}
        }
    }

    fn about_to_wait(&mut self, _: &ActiveEventLoop) {
        if let Some(window) = &self.window {
            window.request_redraw();
        } else {
            panic!("No window!")
        }
    }
}

#[cfg(feature = "profiler")]
fn start_profiler() {
    let _server = puffin_http::Server::new("127.0.0.1:8585").unwrap();
    puffin::set_scopes_on(true);
    std::mem::forget(_server); // keep serving for the process lifetime

    std::process::Command::new("puffin_viewer")
        .args(["--url", "127.0.0.1:8585"])
        .spawn()
        .ok(); // don't die if it isn't installed
}

fn main() -> Result<()> {
    #[cfg(feature = "profiler")]
    start_profiler();

    let event_loop = EventLoop::new()?;
    event_loop.set_control_flow(ControlFlow::Poll);

    let mut app = App::default();
    event_loop.run_app(&mut app)?;

    Ok(())
}