use std::io;
use std::net::SocketAddrV4;
use tokio::net::{TcpListener, TcpStream};
use tokio::io::{AsyncReadExt, AsyncWriteExt};

use tauri::{AppHandle, Manager};

mod errors;
use errors::RequestError;


pub async fn serve(addr: SocketAddrV4, app_handle: AppHandle) -> io::Result<()> {
    let listener = TcpListener::bind(&addr).await?;
    println!("Listening on {addr}");
    loop {
        let new_handle = app_handle.app_handle();
        match listener.accept().await {
            Ok((stream, _)) => {
                tokio::spawn(async {
                    if let Err(e) = handle(stream, new_handle).await {
                        eprintln!("{e}");
                    }
                });
            },
            Err(e) => {
                eprintln!("Error accepting connection: {e}");
            }
        }
    }
}


// it doesn't really return a String, we just need to placate the compiler
async fn stall(stream: &mut TcpStream) -> Result<String, tokio::io::Error> {
    let delay = std::time::Duration::from_secs(1);
    loop {
        tokio::time::sleep(delay).await;
        stream.write(b"x").await?;
    }
}


async fn handle(mut stream: TcpStream, app_handle: AppHandle) -> Result<(), RequestError> {
    let mut buf = [0; 8192]; // it's what tokio's BufReader uses
    let mut n = 0;
    loop {
        n += stream.read(&mut buf[n..]).await?;
        if &buf[(n - 4)..n] == b"\r\n\r\n" {break;}
        if n == buf.len() {return Err(RequestError::RequestTooLarge);}
    }

    println!("{}", std::str::from_utf8(&buf).unwrap());

    stream.write(b"HTTP/1.0 200 OK\r\n").await?;
    stream.write(b"Content-Type: application/json\r\n").await?;
    stream.write(b"X-Creddy-delaying-tactic: ").await?;

    let creds = tokio::select!{
        r = stall(&mut stream) => r?, // this will never return Ok, just Err if it can't write to the stream
        c = get_creds(&app_handle) => c?,
    };

    stream.write(b"\r\nContent-Length: ").await?;
    stream.write(creds.as_bytes().len().to_string().as_bytes()).await?;
    stream.write(b"\r\n\r\n").await?;
    stream.write(creds.as_bytes()).await?;
    stream.write(b"\r\n\r\n").await?;
    Ok(())
}


use tokio::io::{stdin, stdout, BufReader, AsyncBufReadExt};
use crate::storage;

use tokio::sync::oneshot;
use std::sync::Mutex;

async fn get_creds(app_handle: &AppHandle) -> io::Result<String> {
    {     
        let state_guard = app_handle.state::<Mutex<crate::AppState>>();
        let mut state = state_guard.lock().unwrap();
        state.num_requests += 1;
        let req = crate::CredentialsRequest {
            request_id: state.num_requests
        };
        app_handle.emit_all("credentials-request", req).unwrap();
        // lock gets released here in case somebody else needs app state while we're waiting
    }

    let (tx, rx) = oneshot::channel();
    app_handle.once_global("request-response", |event| {
        let response = event.payload().unwrap_or("").to_string();
        tx.send(response).unwrap();
    });
    // Error is only returned if the rx is closed/dropped before receiving, which should never happen
    // LOL who am I kidding this happens all the time
    // fix it later
    
    // todo: handle "denied" response
    let _response = rx.await.unwrap();
    let state_guard = app_handle.state::<Mutex<crate::AppState>>();
    let state = state_guard.lock().unwrap();

    Ok(state.current_session.clone().unwrap())
}