use notify::{RecommendedWatcher, RecursiveMode, Watcher};
use oden_js::{
    module::loader::{ModuleLoader, ModuleSource},
    Context, ContextRef, Result, Runtime, Value,
};
use std::ffi::OsStr;
use std::sync::mpsc::{channel, Receiver, Sender};
use std::sync::{Arc, Mutex};
use std::time::Instant;
use tracy_client::span;
use winit::event::*;

pub mod graphics;
mod input;
mod io;
mod time;

use graphics::GraphicsCommand;

mod typescript;
use typescript::transpile_to_javascript;

struct Loader {
    watcher: Arc<Mutex<RecommendedWatcher>>,
}

impl Loader {
    pub fn new(reload_trigger: Sender<()>) -> Loader {
        let watcher = Arc::new(Mutex::new(
            notify::recommended_watcher(move |_| {
                let _ = reload_trigger.send(());
            })
            .expect("Unable to create watcher"),
        ));
        Loader { watcher }
    }
}

impl ModuleLoader for Loader {
    fn load(&self, _context: &ContextRef, name: &str) -> Result<ModuleSource> {
        eprintln!("Loading {name}...");
        let path = io::resolve_path(name, &["ts"])?;
        let contents = std::fs::read_to_string(&path)?;
        let contents = if path.extension().and_then(OsStr::to_str) == Some("ts") {
            transpile_to_javascript(name, contents)?
        } else {
            contents
        };

        let mut watcher = self.watcher.lock().unwrap();
        let _ = watcher.watch(&path, RecursiveMode::NonRecursive);
        Ok(ModuleSource::JavaScript(contents))
    }
}

pub struct ScriptContext {
    context: Context,
    update: Value,
    draw: Value,
    suspend: Value,

    state: Value,

    gfx: graphics::GraphicsAPI,
    gfx_receive: Receiver<graphics::GraphicsCommand>,

    time: time::TimeAPI,
    input: input::InputAPI,
}

impl ScriptContext {
    pub fn new(suspend_state: Option<Vec<u8>>, reload_trigger: Sender<()>) -> Result<Self> {
        let mut runtime = Runtime::new();
        runtime.set_module_loader(Loader::new(reload_trigger));

        let mut context = Context::new(runtime);
        context.add_intrinsic_bigfloat();
        context.add_intrinsic_bigdecimal();
        context.add_intrinsic_operators();

        let (gfx_send, gfx_receive) = channel();

        let gfx = graphics::GraphicsAPI::define(&context, gfx_send.clone())?;
        let _io = io::IoAPI::define(&context)?;
        let time = time::TimeAPI::define(&context)?;
        let input = input::InputAPI::define(&context)?;

        let module = context.import_module("./main.ts", "")?;

        let init = module.get_export(&context, "init")?;
        let suspend = module.get_export(&context, "suspend")?;
        let resume = module.get_export(&context, "resume")?;
        let update = module.get_export(&context, "update")?;
        let draw = module.get_export(&context, "draw")?;

        let mut state = init.call(&context, &[])?;
        if let Some(buffer) = suspend_state {
            if !resume.is_undefined() {
                let serialized_state = context.deserialize(&buffer)?;
                state = resume.call(&context, &[&serialized_state, &state])?;
            }
        }

        Ok(ScriptContext {
            context,

            suspend,
            update,
            draw,

            state,

            gfx,
            gfx_receive,

            time,
            input,
        })
    }

    /// Allow the script to save its state before we destroy it and re-create
    /// it.
    pub fn suspend(&self) -> Option<Vec<u8>> {
        let _span = span!("script suspend");
        if !self.suspend.is_undefined() {
            let suspend_state = self
                .suspend
                .call(&self.context, &[&self.state])
                .expect("Exception in suspend");
            Some(
                suspend_state
                    .serialize(&self.context)
                    .expect("Unable to serialize state"),
            )
        } else {
            None
        }
    }

    // TODO: The script could really be on a background thread you know.
    //       We would want a bi-directional gate for frames to not let the
    //       game thread go to fast probably? And to discard whole frames &c.

    pub fn input(&mut self, event: &WindowEvent) -> bool {
        match event {
            WindowEvent::KeyboardInput { input, .. } => self.input.handle_keyboard_input(input),
            _ => false,
        }
    }

    pub fn update(&mut self) {
        let _span = span!("script update");

        // Do we update the frame time before of after async completion?
        // Hmmmmm.
        self.time.set_frame_time(Instant::now());

        // Tell the runtime to process all pending "jobs". This includes
        // promise completions.
        {
            let _span = span!("process jobs");
            self.context
                .process_all_jobs()
                .expect("Error processing async jobs");
        }

        // Now run the update function.
        {
            let _span = span!("javascript update");
            let old_state = &self.state;
            self.state = self
                .update
                .call(&self.context, &[old_state])
                .expect("Exception in update");
        }
    }

    pub fn render(&mut self) -> Vec<graphics::GraphicsCommand> {
        let _span = span!("script render");

        self.draw
            .call(&self.context, &[&self.state])
            .expect("Exception in draw");
        self.gfx.end_frame();

        let mut commands = Vec::new();
        loop {
            match self.gfx_receive.recv().unwrap() {
                GraphicsCommand::EndFrame => break,
                other => commands.push(other),
            }
        }
        commands
    }
}