use std::{sync::Arc, collections::VecDeque, ptr::NonNull};

use async_std::task::block_on;

use lyra_ecs::{world::World, system::{System, IntoSystem}};
use tracing::{info, error, Level};
use tracing_appender::non_blocking;
use tracing_subscriber::{
    layer::SubscriberExt,
    filter,
    util::SubscriberInitExt, fmt,
};

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

use crate::{render::{renderer::{Renderer, BasicRenderer}, window::WindowOptions}, input::InputEvent, plugin::Plugin, change_tracker::Ct, EventQueue, StagedExecutor, Stage};

#[derive(Clone, Copy, Hash, Debug)]
pub enum GameStages {
    /// This stage runs before all other stages.
    First,
    /// This stage runs before `Update`.
    PreUpdate,
    /// This stage is where most game logic would be.
    Update,
    /// This stage is ran after `Update`.
    PostUpdate,
    /// This stage runs after all other stages.
    Last,
}

impl Stage for GameStages {}

pub struct Controls<'a> {
    pub world: &'a mut World,
}

#[derive(Clone, Default)]
pub struct WindowState {
    pub is_focused: bool,
    pub is_cursor_inside_window: bool,
}

impl WindowState {
    pub fn new() -> Self {
        Self::default()
    }
}

struct GameLoop {
    window: Arc<Window>,
    renderer: Box<dyn Renderer>,
    
    world: World,

    staged_exec: StagedExecutor,
}

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

            world,
            staged_exec,
        }
    }

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

    pub async fn on_init(&mut self) {
        // Create the EventQueue resource in the world
        self.world.add_resource(self.window.clone());
    }

    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 world_ptr = NonNull::from(&self.world);

        if let Err(e) = self.staged_exec.execute(world_ptr, true) {
            error!("Error when executing staged systems: '{}'", e);
        }
    }

    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 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::DeviceEvent { device_id, event: DeviceEvent::MouseMotion { delta } } => {
                //debug!("motion: {delta:?}");
                // convert a MouseMotion event to an InputEvent
                // make sure that the mouse is inside the window and the mouse has focus before reporting mouse motion
                /* let trigger = matches!(self.world.get_resource::<WindowState>(), Some(window_state)
                    if window_state.is_focused && window_state.is_cursor_inside_window); */

                let trigger = matches!(self.world.try_get_resource::<Ct<WindowOptions>>(), Some(window)
                    if window.focused && window.cursor_inside_window);

                if trigger {
                    let mut event_queue = self.world.try_get_resource_mut::<EventQueue>().unwrap();

                    let input_event = InputEvent::MouseMotion { device_id, delta, };
                    event_queue.trigger_event(input_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) {
                    // Its possible to receive multiple input events before the update event for
                    // the InputSystem is called, so we must use a queue for the events.
                    {
                        if let Some(mut event_queue) = self.world.try_get_resource_mut::<EventQueue>() {
                            event_queue.trigger_event(input_event.clone());
                        };
                    }

                    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;
                        },

                        WindowEvent::Focused(is_focused) => {
                            let mut state = self.world.get_resource_or_else(WindowState::new);
                            state.is_focused = *is_focused;
                        },
    
                        _ => {}
                    }
                }
            },

            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());
                } */

                self.renderer.as_mut().prepare(&mut self.world);
                if let Some(mut event_queue) = self.world.try_get_resource_mut::<EventQueue>() {
                    event_queue.update_events();
                }

                match self.renderer.as_mut().render() {
                    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<World>,
    plugins: VecDeque<Box<dyn Plugin>>,
    system_exec: Option<StagedExecutor>,
    startup_systems: VecDeque<Box<dyn System>>,
    
}

impl Default for Game {
    fn default() -> Self {
        let mut staged = StagedExecutor::new();
        staged.add_stage(GameStages::First);
        staged.add_stage_after(GameStages::First, GameStages::PreUpdate);
        staged.add_stage_after(GameStages::PreUpdate, GameStages::Update);
        staged.add_stage_after(GameStages::Update, GameStages::PostUpdate);
        staged.add_stage_after(GameStages::PostUpdate, GameStages::Last);

        Self {
            world: Some(World::new()),
            plugins: VecDeque::new(),
            system_exec: Some(staged),
            startup_systems: VecDeque::new(),
        }
    }
}

impl Game {
    pub async fn initialize() -> Game {
        Self::default()
    }

    /// Get the world of this game
    pub fn world(&mut self) -> &mut World {
        // world is always `Some`, so unwrapping is safe
        self.world.as_mut().unwrap()
    }

    /// Add a system to the ecs world
    pub fn with_system<S, A>(&mut self, name: &str, system: S, depends: &[&str]) -> &mut Self
    where
        S: IntoSystem<A>,
        <S as IntoSystem<A>>::System: 'static
    {
        let system_dispatcher = self.system_exec.as_mut().unwrap();
        system_dispatcher.add_system_to_stage(GameStages::Update, name, system.into_system(), depends);

        self
    }

    /// Add a stage.
    /// 
    /// This stage could run at any moment if nothing is dependent on it.
    pub fn add_stage<T: Stage>(&mut self, stage: T) -> &mut Self {
        let system_dispatcher = self.system_exec.as_mut().unwrap();
        system_dispatcher.add_stage(stage);

        self
    }

    /// Add a stage that executes after another one.
    /// 
    /// Parameters:
    /// * `before` - The stage that will run before `after`.
    /// * `after` - The stage that will run after `before`.
    pub fn add_stage_after<T: Stage, U: Stage>(&mut self, before: T, after: U) -> &mut Self {
        let system_dispatcher = self.system_exec.as_mut().unwrap();
        system_dispatcher.add_stage_after(before, after);

        self
    }

    /// Add a system to an already existing stage.
    /// 
    /// # Panics
    /// Panics if the stage was not already added to the executor
    pub fn add_system_to_stage<T, S, A>(&mut self, stage: T,
            name: &str, system: S, depends: &[&str]) -> &mut Self
    where
        T: Stage,
        S: IntoSystem<A>,
        <S as IntoSystem<A>>::System: 'static
    {
        let system_dispatcher = self.system_exec.as_mut().unwrap();
        system_dispatcher.add_system_to_stage(stage, name, system.into_system(), depends);

        self
    }
        
    /// Add a startup system that will be ran right after plugins are setup.
    /// They will only be ran once
    pub fn with_startup_system<S>(&mut self, system: S) -> &mut Self
    where
        S: System + 'static
    {
        self.startup_systems.push_back(Box::new(system));

        self
    }

    /// Add a plugin to the game. These will be executed before the window is initiated and opened
    pub fn with_plugin<P>(&mut self, plugin: P) -> &mut Self
    where
        P: Plugin + 'static
    {
        self.plugins.push_back(Box::new(plugin));

        self
    }

    /// Override the default (empty) world
    /// 
    /// This isn't recommended, you should create a startup system and add it to `with_startup_system`
    pub fn with_world(&mut self, world: World) -> &mut Self {
        self.world = Some(world);

        self
    }

    /// Start the game
    pub async fn run(&mut self) {
        // init logging
        let (stdout_layer, _stdout_nb) = non_blocking(std::io::stdout());
        tracing_subscriber::registry()
            .with(fmt::layer().with_writer(stdout_layer))
            .with(filter::Targets::new()
                .with_target("lyra_engine", Level::TRACE)
                .with_target("wgpu_core", Level::WARN)
                .with_default(Level::DEBUG))
            .init();

        // setup all the plugins
        while let Some(plugin) = self.plugins.pop_front() {
            plugin.as_ref().setup(self);
        }

        let world = self.world.take().unwrap_or_default();

        // run startup systems
        while let Some(mut startup) = self.startup_systems.pop_front() {
            let startup = startup.as_mut();
            let world_ptr = NonNull::from(&world);
            startup.setup(world_ptr).expect("World returned an error!");
            startup.execute(world_ptr).expect("World returned an error!");
        }

        // start winit event loops
        let event_loop = EventLoop::new();
        let window = Arc::new(WindowBuilder::new().build(&event_loop).unwrap());
        
        let system_dispatcher = self.system_exec.take().unwrap();
        let mut g_loop = GameLoop::new(Arc::clone(&window), world, system_dispatcher).await;
        g_loop.on_init().await;

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