// Code to handle the nebula worker

use std::error::Error;
use std::{io, thread};
use std::io::{BufRead, BufReader, BufWriter, Read, Write};
use std::net::{IpAddr, Shutdown, SocketAddr, TcpListener, TcpStream};
use std::sync::mpsc::{Receiver, TryRecvError};
use log::{debug, error, info, trace, warn};
use serde::{Deserialize, Serialize};
use crate::apiworker::APIWorkerMessage;
use crate::config::TFClientConfig;
use crate::daemon::ThreadMessageSender;
use crate::nebulaworker::NebulaWorkerMessage;

pub enum SocketWorkerMessage {
    Shutdown
}

pub fn socketworker_main(config: TFClientConfig, transmitter: ThreadMessageSender, rx: Receiver<SocketWorkerMessage>) {
    info!("socketworker_main called, entering realmain");
    match _main(config, transmitter, rx) {
        Ok(_) => (),
        Err(e) => {
            error!("Error in socket thread: {}", e);
        }
    };
}

fn _main(config: TFClientConfig, transmitter: ThreadMessageSender, rx: Receiver<SocketWorkerMessage>) -> Result<(), Box<dyn Error>> {
    let listener = TcpListener::bind(SocketAddr::new(IpAddr::from([127, 0, 0, 1]), config.listen_port))?;
    listener.set_nonblocking(true)?;

    loop {
        match listener.accept() {
            Ok(stream) => {
                let transmitter_clone = transmitter.clone();
                thread::spawn(|| {
                    match handle_stream(stream, transmitter_clone) {
                        Ok(_) => (),
                        Err(e) => {
                            error!("Error in client thread: {}", e);
                        }
                    }
                });
            },
            Err(e) if e.kind() == io::ErrorKind::WouldBlock => (),
            Err(e) => { Err(e)?; }
        }

        match rx.try_recv() {
            Ok(msg) => {
                match msg {
                    SocketWorkerMessage::Shutdown => {
                        info!("recv on command socket: shutdown, stopping");
                        break;
                    }
                }
            },
            Err(e) => {
                match e {
                    TryRecvError::Empty => {}
                    TryRecvError::Disconnected => {
                        error!("socketworker command socket disconnected, shutting down to prevent orphaning");
                        break;
                    }
                }
            }
        }
    }

    Ok(())
}

fn handle_stream(stream: (TcpStream, SocketAddr), transmitter: ThreadMessageSender) -> Result<(), io::Error> {
    info!("Incoming client");
    match handle_client(stream.0, transmitter) {
        Ok(()) => (),
        Err(e) if e.kind() == io::ErrorKind::TimedOut => {
            warn!("Client timed out, connection aborted");
        },
        Err(e) if e.kind() == io::ErrorKind::NotConnected => {
            warn!("Client connection severed");
        },
        Err(e) if e.kind() == io::ErrorKind::BrokenPipe => {
            warn!("Client connection returned error: broken pipe");
        },
        Err(e) if e.kind() == io::ErrorKind::ConnectionAborted => {
            warn!("Client aborted connection");
        },
        Err(e) => {
            error!("Error in client handler: {}", e);
            return Err(e);
        }
    };
    Ok(())
}

fn handle_client(stream: TcpStream, transmitter: ThreadMessageSender) -> Result<(), io::Error> {
    info!("Handling connection from {}", stream.peer_addr()?);

    let mut client = Client {
        state: ClientState::WaitHello,
        reader: BufReader::new(&stream),
        writer: BufWriter::new(&stream),
        stream: &stream
    };

    loop {
        let mut command = String::new();
        client.reader.read_line(&mut command)?;

        let command: JsonMessage = serde_json::from_str(&command)?;

        trace!("recv {:?} from {}", command, client.stream.peer_addr()?);

        let should_disconnect;

        match client.state {
            ClientState::WaitHello => {
                should_disconnect = waithello_handle(&mut client, &transmitter, command)?;
            }
            ClientState::SentHello => {
                should_disconnect = senthello_handle(&mut client, &transmitter, command)?;
            }
        }

        if should_disconnect { break; }
    }

    // Gracefully close the connection
    stream.shutdown(Shutdown::Both)?;

    Ok(())
}

struct Client<'a> {
    state: ClientState,
    reader: BufReader<&'a TcpStream>,
    writer: BufWriter<&'a TcpStream>,
    stream: &'a TcpStream
}

fn waithello_handle(client: &mut Client, _transmitter: &ThreadMessageSender, command: JsonMessage) -> Result<bool, io::Error> {
    trace!("state: WaitHello, handing with waithello_handle");
    let mut should_disconnect = false;

    match command {
        JsonMessage::Hello { version } => {
            if version != JSON_API_VERSION {
                should_disconnect = true;
                client.stream.write_all(&ctob(JsonMessage::Goodbye {
                    reason: DisconnectReason::UnsupportedVersion {
                        expected: JSON_API_VERSION,
                        got: version
                    }
                }))?;
            }
            client.stream.write_all(&ctob(JsonMessage::Hello {
                version: JSON_API_VERSION
            }))?;
            client.state = ClientState::SentHello;
            trace!("setting state to SentHello");
        },
        JsonMessage::Goodbye { reason } => {
            info!("Client sent disconnect: {:?}", reason);
            should_disconnect = true;
        },
        _ => {
            debug!("message type unexpected in WaitHello state");
            should_disconnect = true;
            client.stream.write_all(&ctob(JsonMessage::Goodbye {
                reason: DisconnectReason::UnexpectedMessageType,
            }))?;
        }
    }

    Ok(should_disconnect)
}

fn senthello_handle(client: &mut Client, transmitter: &ThreadMessageSender, command: JsonMessage) -> Result<bool, io::Error> {
    trace!("state: SentHello, handing with senthello_handle");
    let mut should_disconnect = false;

    match command {
        JsonMessage::Goodbye { reason } => {
            info!("Client sent disconnect: {:?}", reason);
            should_disconnect = true;
        },

        JsonMessage::Shutdown {} => {
            info!("Requested to shutdown by local control socket. Sending shutdown message to threads");
            match transmitter.nebula_thread.send(NebulaWorkerMessage::Shutdown) {
                Ok(_) => (),
                Err(e) => {
                    error!("Error sending shutdown message to nebula worker thread: {}", e);
                }
            }
            match transmitter.api_thread.send(APIWorkerMessage::Shutdown) {
                Ok(_) => (),
                Err(e) => {
                    error!("Error sending shutdown message to api worker thread: {}", e);
                }
            }
            match transmitter.socket_thread.send(SocketWorkerMessage::Shutdown) {
                Ok(_) => (),
                Err(e) => {
                    error!("Error sending shutdown message to socket worker thread: {}", e);
                }
            }
        }

        _ => {
            debug!("message type unexpected in SentHello state");
            should_disconnect = true;
            client.stream.write_all(&ctob(JsonMessage::Goodbye {
                reason: DisconnectReason::UnexpectedMessageType,
            }))?;
        }
    }

    Ok(should_disconnect)
}

fn ctob(command: JsonMessage) -> Vec<u8> {
    let command_str = serde_json::to_string(&command).unwrap() + "\n";
    command_str.into_bytes()
}

enum ClientState {
    WaitHello,
    SentHello
}

pub const JSON_API_VERSION: i32 = 1;

#[derive(Serialize, Deserialize, Debug)]
#[serde(tag = "method")]
enum JsonMessage {
    #[serde(rename = "hello")]
    Hello {
        version: i32
    },
    #[serde(rename = "goodbye")]
    Goodbye {
        reason: DisconnectReason
    },
    #[serde(rename = "shutdown")]
    Shutdown {}
}

#[derive(Serialize, Deserialize, Debug)]
enum DisconnectReason {
    #[serde(rename = "unsupported_version")]
    UnsupportedVersion { expected: i32, got: i32 },
    #[serde(rename = "unexpected_message_type")]
    UnexpectedMessageType,
    #[serde(rename = "done")]
    Done
}