use std::{
    error::Error, io::{BufRead, BufReader, Read, Write}, 
    net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6, TcpListener, TcpStream}, 
    str::FromStr, sync::Arc
};

use ignore_result::Ignore;
use log::{debug, info};
use rustls::{ServerConnection, StreamOwned};
use threadpool::ThreadPool;

use super::{
    tls::create_server_config,
    config::{
        Config,
        SiteConfig,
        IpForwarding
    }
};

pub struct FlowgateServer {
    config: Arc<Config>,
}

struct Connection {
    stream: BufReader<TcpStream>, 
    config: SiteConfig,
    keep_alive: bool, 
    host: String,
}

impl FlowgateServer {
    pub fn new(config: Arc<Config>) -> Self {
        FlowgateServer { config }
    }

    pub fn run(self) {
        self.start().join();
    }

    pub fn start(self) -> ThreadPool {
        let local_self = Arc::new(self);

        let threadpool = ThreadPool::new(local_self.config.threadpool_size);

        let mut handles = Vec::new();

        handles.push(local_self.clone().start_http(&threadpool));
        handles.push(local_self.clone().start_https(&threadpool));

        threadpool
    }

    pub fn start_http(self: Arc<Self>, threadpool: &ThreadPool) {
        threadpool.execute({ 
            let local_self = self.clone();
            let threadpool = threadpool.clone();
            move || { local_self.run_http(&threadpool).ignore(); } 
        })
    }

    pub fn start_https(self: Arc<Self>, threadpool: &ThreadPool) {
        threadpool.execute({ 
            let local_self = self.clone();
            let threadpool = threadpool.clone();
            move || { local_self.run_https(&threadpool).ignore(); } 
        })
    }

    pub fn run_http(self: Arc<Self>, threadpool: &ThreadPool) -> Result<(), Box<dyn Error>> {
        if let Some(host) = self.config.http_host.clone() {
            let listener = TcpListener::bind(&host)?;

            info!("HTTP server runned on {}", &host);

            for stream in listener.incoming() {
                if let Ok(mut stream) = stream {
                    let local_self = self.clone();

                    let Ok(addr) = stream.peer_addr() else { continue };
                    let Ok(_) = stream.set_write_timeout(Some(local_self.config.connection_timeout)) else { continue };
                    let Ok(_) = stream.set_read_timeout(Some(local_self.config.connection_timeout)) else { continue };

                    threadpool.execute(move || {
                        debug!("{} open connection", addr);

                        local_self.accept_stream(
                            &mut stream,
                            addr,
                            false
                        );
                        
                        debug!("{} close connection", addr);
                    });
                }
            }
        }

        Ok(())
    }

    pub fn run_https(self: Arc<Self>, threadpool: &ThreadPool) -> Result<(), Box<dyn Error>> {
        if let Some(host) = self.config.https_host.clone() {
            let listener = TcpListener::bind(&host)?;

            info!("HTTPS server runned on {}", &host);

            let config = Arc::new(create_server_config(self.config.clone()));

            for stream in listener.incoming() {
                if let Ok(stream) = stream {
                    let local_self = self.clone();
                    let config = config.clone();

                    let Ok(addr) = stream.peer_addr() else { continue };
                    let Ok(_) = stream.set_write_timeout(Some(local_self.config.connection_timeout)) else { continue };
                    let Ok(_) = stream.set_read_timeout(Some(local_self.config.connection_timeout)) else { continue };

                    threadpool.execute(move || {
                        let Ok(connection) = ServerConnection::new(config) else { return };
                        debug!("{} open connection", addr);
                        let mut stream = StreamOwned::new(connection, stream);

                        while stream.conn.is_handshaking() {
                            let Ok(_) = stream.conn.complete_io(&mut stream.sock) else { debug!("{} close connection", addr);return };
                        }
                        local_self.accept_stream(
                            &mut stream,
                            addr,
                            true
                        );

                        debug!("{} close connection", addr);
                    });
                }
            }
        }

        Ok(())
    }

    fn accept_stream(
        self: Arc<Self>, 
        stream: &mut (impl Read + Write + Shutdown), 
        addr: SocketAddr,
        https: bool
    ) -> Option<()> {
        let mut conn = self.clone().read_request(stream, addr, https, None)?;

        if conn.keep_alive && conn.config.enable_keep_alive {
            loop {
                if !conn.config.support_keep_alive {
                    conn.stream.shutdown();
                    conn.stream = BufReader::new(conn.config.connect()?);
                }
                conn = self.clone().read_request(stream, addr, https, Some(conn))?;
            }
        }

        conn.stream.shutdown();
        stream.shutdown();

        Some(())
    }

    fn read_request(
        self: Arc<Self>, 
        stream: &mut (impl Read + Write + Shutdown), 
        addr: SocketAddr,
        https: bool,
        conn: Option<Connection>
    ) -> Option<Connection> {
        let mut addr = addr;

        let mut stream = BufReader::new(stream);

        match &self.config.incoming_ip_forwarding {
            IpForwarding::Simple => {
                let mut header = Vec::new();
                stream.read_until(b'\n', &mut header).ok()?;
                header.truncate(header.len()-1);

                addr = SocketAddr::from_str(&String::from_utf8(header).ok()?).ok()?;
            },
            IpForwarding::Modern => {
                let mut header = [0];
                stream.read(&mut header).ok()?;

                addr = match header[0] {
                    0x01 => {
                        let mut octets = [0; 4];
                        stream.read(&mut octets).ok()?;

                        let mut port = [0; 2];
                        stream.read(&mut port).ok()?;
                        let port = u16::from_be_bytes(port);

                        SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::from(octets), port))
                    }, 0x02 => {
                        let mut octets = [0; 16];
                        stream.read(&mut octets).ok()?;

                        let mut port = [0; 2];
                        stream.read(&mut port).ok()?;
                        let port = u16::from_be_bytes(port);

                        SocketAddr::V6(SocketAddrV6::new(Ipv6Addr::from(octets), port, 0, 0))
                    }, _ => { return None },
                };
            },
            _ => {}
        }

        let mut raw_status = read_until(&mut stream, b"\r\n")?;

        let mut request = Vec::new();
        request.append(&mut raw_status.clone());

        raw_status.truncate(raw_status.len() - 2);
        
        let status =  String::from_utf8(raw_status.clone()).ok()?;
        let status = status.split(" ").collect::<Vec<&str>>();

        debug!("{} {} read status", addr, status[1]);

        let mut content_length = 0;
        let mut host = None;
        let mut is_chunked = false;
        let mut keep_alive = false;

        let mut headers = Vec::new();

        loop {
            let mut header = read_until(&mut stream, b"\r\n")?;
            header.truncate(header.len() - 2);

            if header.is_empty() {
                break;
            }

            let header = String::from_utf8(header).ok()?;
            let (key, value) = header.split_once(": ")?;

            headers.push((key.to_string(), value.to_string()));
            
            match key.to_lowercase().as_str() {
                "transfer-encoding" => {
                    if value.contains("chunked") {
                        is_chunked = true;
                    }
                },
                "host" => {
                    host = Some(value.to_string());
                },
                "connection" => {
                    keep_alive = value.to_lowercase().contains("keep-alive");
                },
                "content-length" => {
                    content_length = value.parse::<usize>().ok()?;
                },
                _ => {
                    if let IpForwarding::Header(header) = &self.config.incoming_ip_forwarding {
                        if key.to_lowercase() == header.to_lowercase() {
                            addr = SocketAddr::from_str(value).ok()?;
                        }
                    }
                },
            }
        }

        debug!("{} {} read headers", addr, status[1]);

        let mut conn: Connection = if conn.is_none() {
            let host = host?;
            let site = self.config.get_site(&host)?.clone();

            Connection {
                stream: BufReader::new(site.connect()?),
                config: site,
                keep_alive,
                host
            }
        } else {
            conn?
        };

        debug!("{} {} got connection", addr, status[1]);


        match &conn.config.ip_forwarding {
            IpForwarding::Simple => {
                request.append(&mut addr.to_string().as_bytes().to_vec());
                request.push(b'\n');
            },
            IpForwarding::Modern => {
                match addr.ip() {
                    IpAddr::V4(ip) => {
                        request.push(0x01);
                        request.append(&mut ip.octets().to_vec());
                    }, IpAddr::V6(ip) => {
                        request.push(0x02);
                        request.append(&mut ip.octets().to_vec());
                    }
                }
                request.append(&mut addr.port().to_be_bytes().to_vec());
            },
            _ => {}
        }

        for (key, value) in headers {
            let mut value = value.to_string();

            match key.to_lowercase().as_str() {
                "host" => {
                    if let Some(replace_host) = conn.config.replace_host.clone() {
                        value = replace_host;
                    }
                },
                _ => {}
            }

            if let IpForwarding::Header(header) = &conn.config.ip_forwarding {
                if key.to_lowercase() == header.to_lowercase() {
                    continue;
                }
            }

            request.append(&mut key.as_bytes().to_vec());
            request.append(&mut b": ".to_vec());
            request.append(&mut value.as_bytes().to_vec());
            request.append(&mut b"\r\n".to_vec());
        }
        
        if let IpForwarding::Header(header) = &conn.config.ip_forwarding {
            request.append(&mut header.as_bytes().to_vec());
            request.append(&mut b": ".to_vec());
            request.append(&mut addr.to_string().as_bytes().to_vec());
            request.append(&mut b"\r\n".to_vec());
        }

        request.append(&mut b"\r\n".to_vec());

        debug!("{:?}", String::from_utf8_lossy(&request));

        conn.stream.get_mut().write_all(&request).ok()?;

        debug!("{} {} sent request to server", addr, status[1]);

        if content_length > 0 {
            let buffer = stream.buffer().to_vec();
    
            conn.stream.get_mut().write_all(&buffer).ok()?;
            stream.consume(buffer.len());

            let mut read = buffer.len();

            debug!("{} {} send part of body to server", addr, status[1]);

            while read < content_length {
                let mut buf = vec![0; 4096];
                let size = conn.stream.get_mut().read(&mut buf).ok()?;

                if size == 0 { break }

                buf.truncate(size);
                read += size;

                debug!("{} {} send response body part {} to clientr", addr, status[1], size);

                stream.get_mut().write_all(&buf).ok()?;
            }
        } else if is_chunked {
            transfer_chunked(&mut stream, conn.stream.get_mut())?;
        } else {
            let buffer = stream.buffer().to_vec();
    
            conn.stream.get_mut().write_all(&buffer).ok()?;
            stream.consume(buffer.len());
        }

        debug!("{} {} send body to server", addr, status[1]);

        if conn.config.support_keep_alive {
            let mut response = Vec::new();

            let raw_status = read_until(&mut conn.stream, b"\r\n")?;

            response.append(&mut raw_status.clone());

            let mut content_length = 0;
            let mut is_chunked = false;

            loop {
                let mut header = read_until(&mut conn.stream, b"\r\n")?;

                response.append(&mut header.clone());

                if header.len() == 2 {
                    break;
                }

                header.truncate(header.len() - 2);

                let header = String::from_utf8(header).ok()?;
                let (key, value) = header.split_once(": ")?;
                
                match key.to_lowercase().as_str() {
                    "transfer-encoding" => {
                        if value.contains("chunked") {
                            is_chunked = true;
                        }
                    },
                    "content-length" => {
                        content_length = value.parse::<usize>().ok()?;
                    },
                    _ => {}
                }
            }
            
            stream.get_mut().write_all(&response).ok()?;

            debug!("{} {} send response header to clientr", addr, status[1]);

            if content_length > 0 {
                let buffer = conn.stream.buffer().to_vec();
    
                stream.get_mut().write_all(&buffer).ok()?;
                conn.stream.consume(buffer.len());

                debug!("{} {} send response body part {} to clientr", addr, status[1], buffer.len());

                let mut read = buffer.len();

                while read < content_length {
                    let mut buf = vec![0; 4096];
                    let size = conn.stream.get_mut().read(&mut buf).ok()?;

                    if size == 0 { break }

                    buf.truncate(size);
                    read += size;

                    debug!("{} {} send response body part {} to clientr", addr, status[1], size);

                    stream.get_mut().write_all(&buf).ok()?;
                }
            } else if is_chunked {
                transfer_chunked(&mut conn.stream, stream.get_mut())?;
            } else {
                let buffer = conn.stream.buffer().to_vec();
    
                stream.get_mut().write_all(&buffer).ok()?;
                conn.stream.consume(buffer.len());
            }

            debug!("{} {} send response body to clientr", addr, status[1]);
        } else {
            let buffer = conn.stream.buffer();

            stream.get_mut().write_all(buffer).ok()?;
            conn.stream.consume(buffer.len());

            let mut buf = vec![0;4096];
            while let Ok(n) = conn.stream.get_mut().read(&mut buf) {
                if n == 0 { break }
                buf.truncate(n);
                stream.get_mut().write_all(&buf).ok()?;
                buf = vec![0;4096];
            }
        }

        info!("{addr} > {} {}://{}{}", status[0], if https { "https" } else { "http" }, conn.host, status[1]);

        Some(conn)
    }
}

fn read_until(stream: &mut impl BufRead, delimiter: &[u8]) -> Option<Vec<u8>> {
    let mut data = Vec::new();

    let last_byte = *delimiter.last()?;

    loop {
        let mut buf = Vec::new();
        let buf_len = stream.read_until(last_byte, &mut buf).ok()?;
        debug!("read buf len until {} {:?}", buf_len, String::from_utf8_lossy(&buf));
        if buf_len == 0 {
            return None
        }
        data.append(&mut buf);
        if data.ends_with(delimiter) {
            break;
        }
    }

    Some(data)
}

fn transfer_chunked(src: &mut impl BufRead, dest: &mut impl Write) -> Option<()> {
    loop {
        let mut length = read_until(src, b"\r\n")?;
        dest.write_all(&length).ok()?;
        length.truncate(length.len()-2);
        let length = String::from_utf8(length).ok()?;
        let length = usize::from_str_radix(length.as_str(), 16).ok()?;

        let mut data = vec![0u8; length+2];
        src.read_exact(&mut data).ok()?;
        dest.write_all(&data).ok()?;

        if length == 0 {
            break;
        }
    }

    Some(())
}

pub trait Shutdown {
    fn shutdown(&self);
}

impl Shutdown for TcpStream {
    fn shutdown(&self) {
        TcpStream::shutdown(self, std::net::Shutdown::Both).ignore();  
    }
}

impl <T: Shutdown> Shutdown for BufReader<T> {
    fn shutdown(&self) {
        self.get_ref().shutdown();
    }
}

impl <C, T: Read + Write + Shutdown> Shutdown for StreamOwned<C, T> {
    fn shutdown(&self) {
        self.sock.shutdown();
    }
}