use std::{sync::Arc, cell::RefCell};

use async_std::{task::block_on, sync::Mutex};

use hecs::World;
use instant::Instant;
use tracing::{metadata::LevelFilter, info, debug, warn};
use tracing_subscriber::{
    layer::{Layer, SubscriberExt},
    filter::FilterFn,
    util::SubscriberInitExt,
};

use winit::{window::{WindowBuilder, Window}, event::{Event, WindowEvent, KeyboardInput, ElementState, VirtualKeyCode}, event_loop::{EventLoop, ControlFlow}};

use crate::{render::{renderer::{Renderer, BasicRenderer}, render_job::RenderJob}, input_event::InputEvent, ecs::{components::{mesh::MeshComponent, transform::TransformComponent}, SystemFnExecutor, SimpleSystem}};

struct TickCounter {
    counter: u32,
    last_second: Instant,
    changed: bool,
    tps: f32,
    /// the time (in seconds) that passes between each tick
    tick_time: f32
}

impl TickCounter {
    fn new() -> Self {
        Self {
            counter: 0,
            last_second: Instant::now(),
            tps: 0.0,
            changed: false,
            tick_time: 0.0,
        }
    }

    /// Returns true if the tps changed
    fn tick(&mut self) -> bool {
        self.counter += 1;

        if self.last_second.elapsed().as_secs() > 0 {
            self.tick_time = 1000.0 / self.counter as f32;
            self.tps = self.counter as f32;

            self.changed = true;
            self.counter = 0;
            self.last_second = Instant::now();
        }

        self.changed
    }

    /// Gets the change in ticks per second
    fn get_change(&mut self) -> Option<f32> {
        match self.changed {
            true => {
                self.changed = false;

                Some(self.tps)
            },
            false => None,
        }
    }

    /// Get the time (in seconds) between ticks
    fn get_tick_time(&self) -> f32 {
        self.tick_time
    }
}


struct GameLoop {
    window: Arc<Window>,
    renderer: Box<dyn Renderer>,
    
    world: Arc<Mutex<World>>,
    system_fn_executor: SystemFnExecutor,
    fps_counter: TickCounter,
}

impl GameLoop {
    pub async fn new(window: Arc<Window>, world: Arc<Mutex<World>>) -> GameLoop {
        Self {
            window: Arc::clone(&window),
            renderer: Box::new(BasicRenderer::create_with_window(window).await),

            world,
            system_fn_executor: SystemFnExecutor::new(),
            fps_counter: TickCounter::new(),
        }
    }

    pub async fn on_resize(&mut self, new_size: winit::dpi::PhysicalSize<u32>) {
        self.renderer.on_resize(new_size).await;
    }

    pub fn run_sync(&mut self, event: Event<()>, control_flow: &mut ControlFlow) {
        block_on(self.run_event_loop(event, control_flow))
    }

    async fn update(&mut self) {
        let mut world = self.world.lock().await;
        self.system_fn_executor.execute_mut(&mut world).unwrap(); // always returns Ok(())
    }

    async fn input_update(&mut self, event: &InputEvent) -> Option<ControlFlow> {
        match event {
            InputEvent::KeyboardInput {
                input:
                    KeyboardInput {
                        state: ElementState::Pressed,
                        virtual_keycode: Some(VirtualKeyCode::Escape),
                        ..
                    },
                ..
            } => {
                self.on_exit();

                Some(ControlFlow::Exit)
            },

            _ => {
                debug!("Got unhandled input event: \"{:?}\"", event);

                None
            }
        }
    }

    fn render_window() {
        todo!()
    }

    fn render_item() {
        todo!()
    }

    fn on_exit(&mut self) {
        info!("On exit!");
    }

    pub async fn run_event_loop(&mut self, event: Event<'_, ()>, control_flow: &mut ControlFlow) {
        *control_flow = ControlFlow::Poll;
        match event {
            Event::WindowEvent {
                ref event,
                window_id,
            } if window_id == self.window.id() => {
                // If try_from failed, that means that the WindowEvent is not an
                // input related event.
                if let Ok(input_event) = InputEvent::try_from(event) {
                    if let Some(new_control) = self.input_update(&input_event).await {
                        *control_flow = new_control;
                    }
                } else {
                    match event {
                        WindowEvent::CloseRequested => {
                            self.on_exit();

                            *control_flow = ControlFlow::Exit
                        },

                        WindowEvent::Resized(physical_size) => {
                            self.on_resize(*physical_size).await;
                        },
    
                        WindowEvent::ScaleFactorChanged { new_inner_size, .. } => {
                            self.on_resize(**new_inner_size).await;
                        },
    
                        _ => {}
                    }
                }
            },

            Event::RedrawRequested(window_id) if window_id == self.window.id() => {
                // Update the world
                self.update().await;

                /* self.fps_counter.tick();
                if let Some(fps) = self.fps_counter.get_change() {
                    debug!("FPS: {}fps, {:.2}ms/frame", fps, self.fps_counter.get_tick_time());
                } */

                let mut world = self.world.lock().await;
                self.renderer.as_mut().prepare(&mut world).await;
                drop(world);

                match self.renderer.as_mut().render().await {
                    Ok(_) => {}
                    // Reconfigure the surface if lost
                    Err(wgpu::SurfaceError::Lost) => self.on_resize(self.renderer.as_ref().surface_size()).await,
                    // The system is out of memory, we should probably quit
                    Err(wgpu::SurfaceError::OutOfMemory) => *control_flow = ControlFlow::Exit,
                    // All other errors (Outdated, Timeout) should be resolved by the next frame
                    Err(e) => eprintln!("{:?}", e),
                }
            },

            Event::MainEventsCleared => {
                self.window.request_redraw();
            },
            _ => {}
        }
    }
}

pub struct Game {
    world: Option<Arc<Mutex<World>>>,
}

impl Default for Game {
    fn default() -> Self {
        Self {
            world: None,
        }
    }
}

impl Game {
    pub async fn initialize() -> Game {
        let filter = FilterFn::new(|metadata| {
            metadata.module_path()
                .unwrap_or_else(|| metadata.target())
                .starts_with("lyra_engine") && (LevelFilter::DEBUG >= metadata.level().to_owned())
        });

        let layer = tracing_subscriber::fmt::layer();

        tracing_subscriber::registry()
            .with(layer.with_filter(filter))
            .init();

        Self::default()
    }

    pub fn with_world(&mut self, world: World) -> &mut Self {
        self.world = Some(Arc::new(Mutex::new(world)));

        self
    }

    pub fn with_world_arc(&mut self, world: Arc<Mutex<World>>) -> &mut Self {
        self.world = Some(world);

        self
    }

    pub async fn run(&mut self) {
        let world = self.world.take().expect("ECS World was never given to Game!");

        let event_loop = EventLoop::new();
        let window = Arc::new(WindowBuilder::new().build(&event_loop).unwrap());

        let mut g_loop = GameLoop::new(Arc::clone(&window), world).await;

        event_loop.run(move |event, _, control_flow| {
            g_loop.run_sync(event, control_flow);
        });
    }
}