pub mod discovery;
pub mod error;
pub mod http_server;
pub mod models;
pub mod transfer;

use std::{
    collections::HashMap,
    net::{Ipv4Addr, SocketAddr, SocketAddrV4},
    sync::{Arc, OnceLock},
    time::Duration,
};

use models::Device;
use serde::{Deserialize, Serialize};
use tokio::{
    net::UdpSocket,
    sync::{Mutex, mpsc},
    task::JoinHandle,
};
use transfer::Session;

pub const DEFAULT_PORT: u16 = 53317;
pub const MULTICAST_IP: Ipv4Addr = Ipv4Addr::new(224, 0, 0, 167);
pub const LISTENING_SOCKET_ADDR: SocketAddrV4 =
    SocketAddrV4::new(Ipv4Addr::from_bits(0), DEFAULT_PORT);

type ShutdownSender = mpsc::Sender<()>;

/// Contains the main network and backend state for an application session.
#[derive(Clone)]
pub struct JoecalState {
    pub device: Device,
    pub peers: Arc<Mutex<HashMap<String, (SocketAddr, Device)>>>,
    pub sessions: Arc<Mutex<HashMap<String, Session>>>, // Session ID to Session
    pub running_state: Arc<Mutex<RunningState>>,
    pub socket: Arc<UdpSocket>,
    pub client: reqwest::Client,
    stop_tx: OnceLock<ShutdownSender>,
}

impl JoecalState {
    pub async fn new(device: Device) -> crate::error::Result<Self> {
        let socket = UdpSocket::bind(LISTENING_SOCKET_ADDR).await?;
        socket.set_multicast_loop_v4(true)?;
        socket.set_multicast_ttl_v4(2)?; // one hop out from localnet
        socket.join_multicast_v4(MULTICAST_IP, Ipv4Addr::from_bits(0))?;

        Ok(Self {
            device,
            client: reqwest::Client::new(),
            socket: socket.into(),
            peers: Default::default(),
            sessions: Default::default(),
            running_state: Default::default(),
            stop_tx: Default::default(),
        })
    }

    pub async fn start(
        &self,
        config: &Config,
    ) -> crate::error::Result<(JoinHandle<()>, JoinHandle<()>, JoinHandle<()>)> {
        let state = self.clone();
        let konfig = config.clone();
        let server_handle = {
            let (tx, shutdown_rx) = mpsc::channel(1);
            self.stop_tx.get_or_init(|| tx);
            tokio::spawn(async move {
                if let Err(e) = state.start_http_server(shutdown_rx, &konfig).await {
                    eprintln!("HTTP server error: {e}");
                }
            })
        };
        let state = self.clone();
        let konfig = config.clone();
        let udp_handle = {
            tokio::spawn(async move {
                if let Err(e) = state.listen_multicast(&konfig).await {
                    eprintln!("UDP listener error: {e}");
                }
            })
        };

        let state = self.clone();
        let config = config.clone();
        let announcement_handle = {
            tokio::spawn(async move {
                loop {
                    let rstate = state.running_state.lock().await;
                    if *rstate == RunningState::Stopping {
                        break;
                    }
                    if let Err(e) = state.announce(None, &config).await {
                        eprintln!("Announcement error: {e}");
                    }
                    tokio::time::sleep(std::time::Duration::from_secs(5)).await;
                }
            })
        };

        Ok((server_handle, udp_handle, announcement_handle))
    }

    pub async fn stop(&self) {
        loop {
            let mut rstate = self.running_state.lock().await;
            *rstate = RunningState::Stopping;
            if self
                .stop_tx
                .get()
                .expect("Could not get stop signal transmitter")
                .send(())
                .await
                .is_ok()
            {
                break;
            } else {
                tokio::time::sleep(Duration::from_millis(777)).await;
            }
        }
    }

    pub async fn refresh_peers(&self) {
        let mut peers = self.peers.lock().await;
        peers.clear();
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum RunningState {
    Running,
    Stopping,
}

impl Default for RunningState {
    fn default() -> Self {
        Self::Running
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Config {
    pub multicast_addr: SocketAddrV4,
    pub port: u16,
    pub download_dir: String,
}

impl Default for Config {
    fn default() -> Self {
        let home = std::env::home_dir().unwrap_or("/tmp".into());
        let dd = home.join("joecalsend-downloads");
        Self {
            multicast_addr: SocketAddrV4::new(MULTICAST_IP, DEFAULT_PORT),
            port: DEFAULT_PORT,
            download_dir: dd.to_string_lossy().into(),
        }
    }
}