//! # Networking library
//!
//! The `lb:net` library provides an asynchronous network API for creating TCP or UDP servers and
//! clients.
//!
//! ## Exports
//!
//! See [`lb_netlib`] for items exported by this library.
use derive_more::{From, FromStr};
use luaffi::{
    cdef,
    marker::{OneOf, fun},
    metatype,
};
use luajit::LUA_NOREF;
use std::{
    cell::{BorrowError, BorrowMutError, Ref, RefCell, RefMut},
    ffi::c_int,
    net::{AddrParseError, IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr},
    time::Duration,
};
use thiserror::Error;
use tokio::{
    io::{AsyncReadExt, AsyncWriteExt, Interest},
    net::{TcpListener, TcpSocket, TcpStream},
};

/// Errors that can be thrown by this library.
///
/// Functions which return this error will **throw** in Lua. The error message can be caught by
/// using [`pcall(f, ...)`](https://www.lua.org/manual/5.1/manual.html#pdf-pcall).
#[derive(Debug, Error)]
pub enum Error {
    /// Attempt to access an object while it is being modified.
    #[error("cannot access object while it is being modified")]
    Borrow(#[from] BorrowError),
    /// Attempt to modify an object while it is in use
    #[error("cannot modify object while it is in use")]
    BorrowMut(#[from] BorrowMutError),
    /// I/O error.
    #[error("{0}")]
    Io(#[from] std::io::Error),
    /// IP or socket address syntax error.
    #[error("{0}")]
    InvalidAddr(#[from] AddrParseError),
    /// Socket was already converted and can no longer be used.
    #[error("socket was already converted")]
    SocketConsumed,
}

type Result<T> = std::result::Result<T, Error>;

/// Items exported by the `lb:net` library.
///
/// This library can be acquired by calling
/// [`require("lb:net")`](https://www.lua.org/manual/5.1/manual.html#pdf-require) in Lua.
///
/// ```lua
/// local net = require("lb:net");
/// ```
#[cdef(module = "lb:net")]
pub struct lb_netlib;

#[metatype]
impl lb_netlib {
    #[new]
    extern "Lua-C" fn new() -> Self {
        Self
    }

    /// An IPv4 address representing localhost: `127.0.0.1`
    pub extern "Lua-C" fn localhost() -> lb_ipaddr {
        lb_ipaddr(Ipv4Addr::LOCALHOST.into())
    }

    /// An IPv6 address representing localhost: `::1`
    pub extern "Lua-C" fn localhost_v6() -> lb_ipaddr {
        lb_ipaddr(Ipv6Addr::LOCALHOST.into())
    }

    /// An IPv4 address representing an unspecified address: `0.0.0.0`
    pub extern "Lua-C" fn unspecified() -> lb_ipaddr {
        lb_ipaddr(Ipv4Addr::UNSPECIFIED.into())
    }

    /// An IPv6 address representing an unspecified address: `::`
    pub extern "Lua-C" fn unspecified_v6() -> lb_ipaddr {
        lb_ipaddr(Ipv6Addr::UNSPECIFIED.into())
    }

    /// An IPv4 address representing the broadcast address: `255.255.255.255`
    pub extern "Lua-C" fn broadcast() -> lb_ipaddr {
        lb_ipaddr(Ipv4Addr::BROADCAST.into())
    }

    /// Creates an IP address from the given input.
    ///
    /// If `addr` is an [`lb_ipaddr`], a copy of that value is returned. If `addr` is an
    /// [`lb_socketaddr`], the IP part of the socket address is returned. Otherwise, parses `addr`
    /// as an IP address string. Both IPv4 and IPv6 addresses are accepted.
    ///
    /// An address string may be something like `127.0.0.1`.
    ///
    /// The type of the parsed address can be checked using [`is_v4`](lb_ipaddr::is_v4) or
    /// [`is_v6`](lb_ipaddr::is_v6) functions on the returned [`lb_ipaddr`](lb_ipaddr) value.
    ///
    /// # Errors
    ///
    /// This function will throw an error if the input syntax is invalid.
    ///
    /// # Example
    ///
    /// ```lua
    /// local net = require("lb:net")
    /// local addr = net.ipaddr("192.168.1.1")
    ///
    /// assert(addr:is_v4())
    /// ```
    pub extern "Lua" fn ipaddr(
        addr: OneOf<(&str, &lb_ipaddr, &lb_socketaddr)>,
    ) -> Result<lb_ipaddr> {
        if __istype(__ct.lb_ipaddr, addr) {
            __new(__ct.lb_ipaddr, addr) // copy constructor
        } else if __istype(__ct.lb_socketaddr, addr) {
            s.ip()
        } else {
            Self::__parse_ipaddr(addr)
        }
    }

    extern "Lua-C" fn __parse_ipaddr(addr: &str) -> Result<lb_ipaddr> {
        Ok(addr.parse()?)
    }

    /// Creates a socket address from the given input.
    ///
    /// A socket address is an IP address with a prescribed port number.
    ///
    /// If `addr` is an [`lb_socketaddr`], a copy of that value is returned. If `addr` is an
    /// [`lb_ipaddr`], a socket address with that IP part is returned. Otherwise, parses `addr` as a
    /// socket address string. Both IPv4 and IPv6 addresses are accepted.
    ///
    /// If `port` is specified, it is always used as the port part of the returned socket address.
    /// Otherwise, `0` is used as the default.
    ///
    /// An address string may be something like `127.0.0.1:3000`.
    ///
    /// # Errors
    ///
    /// This function will throw an error if the input syntax is invalid.
    ///
    /// # Example
    ///
    /// ```lua
    /// local net = require("lb:net")
    /// local addr = net.socketaddr("::1", 8080)
    ///
    /// assert(addr:ip():is_v6())
    /// assert(addr:port() == 8080)
    /// assert(addr:is_loopback())
    /// ```
    pub extern "Lua" fn socketaddr(
        addr: OneOf<(&str, &lb_ipaddr, &lb_socketaddr)>,
        port: Option<u16>,
    ) -> Result<lb_socketaddr> {
        if port != () {
            Self::__new_skaddr(Self::ipaddr(addr), port)
        } else {
            if __istype(__ct.lb_socketaddr, addr) {
                __new(__ct.lb_socketaddr, addr) // copy constructor
            } else if __istype(__ct.lb_ipaddr, addr) {
                Self::__new_skaddr(addr, 0) // default port 0
            } else {
                Self::__parse_skaddr(addr)
            }
        }
    }

    extern "Lua-C" fn __new_skaddr(ip: &lb_ipaddr, port: u16) -> lb_socketaddr {
        SocketAddr::new(ip.0, port).into()
    }

    extern "Lua-C" fn __parse_skaddr(addr: &str) -> Result<lb_socketaddr> {
        Ok(if let Ok(addr) = addr.parse() {
            SocketAddr::new(addr, 0).into() // default port 0
        } else {
            addr.parse::<SocketAddr>()?.into()
        })
    }

    /// Creates a new TCP socket configured for IPv4.
    ///
    /// This calls `socket(2)` with `AF_INET` and `SOCK_STREAM`.
    ///
    /// # Errors
    ///
    /// This function may throw an error if the socket could not be created.
    pub extern "Lua-C" fn tcp() -> Result<lb_tcpsocket> {
        Ok(lb_tcpsocket::new(TcpSocket::new_v4()?))
    }

    /// Creates a new TCP socket configured for IPv6.
    ///
    /// This calls `socket(2)` with `AF_INET6` and `SOCK_STREAM`.
    ///
    /// # Errors
    ///
    /// This function may throw an error if the socket could not be created.
    pub extern "Lua-C" fn tcp_v6() -> Result<lb_tcpsocket> {
        Ok(lb_tcpsocket::new(TcpSocket::new_v6()?))
    }

    /// Creates a new TCP socket bound to the given address and port.
    ///
    /// This function accepts the same arguments as [`socketaddr`](Self::socketaddr). It creates a
    /// new TCP socket configured to use either IPv4 or IPv6 depending on the type of the given
    /// address, and binds it to that address.
    ///
    /// # Errors
    ///
    /// This function may throw an error if the socket could not be created or bound to the
    /// specified address.
    ///
    /// # Example
    ///
    /// ```lua
    /// local net = require("lb:net")
    /// local socket = net.bind_tcp("127.0.0.1", 8080)
    ///
    /// assert(socket:local_addr():ip():is_loopback())
    /// assert(socket:local_addr():port() == 8080)
    /// ```
    pub async extern "Lua" fn bind_tcp(
        addr: OneOf<(&str, &lb_ipaddr, &lb_socketaddr)>,
        port: Option<u16>,
    ) -> Result<lb_tcpsocket> {
        let addr = Self::socketaddr(addr, port);
        let socket;
        if addr.ip().is_v6() {
            socket = Self::tcp_v6();
        } else {
            socket = Self::tcp();
        }
        socket.bind(addr);
        socket
    }

    /// Creates a new TCP socket listening on the given address and port.
    ///
    /// This is a convenience function that combines [`bind_tcp`](Self::bind_tcp) and
    /// [`listen`](lb_tcpsocket::listen). It accepts the same arguments as
    /// [`socketaddr`](Self::socketaddr).
    ///
    /// # Errors
    ///
    /// This function may throw an error if the socket could not be created, bound to the specified
    /// address, or could not transition to the listening state.
    pub async extern "Lua" fn listen_tcp(
        addr: OneOf<(&str, &lb_ipaddr, &lb_socketaddr)>,
        port: Option<u16>,
    ) -> Result<lb_tcplistener> {
        Self::bind_tcp(addr, port).listen(1024)
    }

    /// Establishes a new TCP connection to the server at the given address and port.
    ///
    /// This function accepts the same arguments as [`socketaddr`](Self::socketaddr). It creates a
    /// new TCP socket and connects it to the specified address.
    ///
    /// # Errors
    ///
    /// This function may throw an error if the socket could not be created or connected to the
    /// specified address.
    pub async extern "Lua" fn connect_tcp(
        addr: OneOf<(&str, &lb_ipaddr, &lb_socketaddr)>,
        port: Option<u16>,
    ) -> Result<lb_tcpstream> {
        let addr = Self::socketaddr(addr, port);
        let socket;
        if addr.ip().is_v6() {
            socket = Self::tcp_v6();
        } else {
            socket = Self::tcp();
        }
        socket.connect(addr)
    }
}

/// IP address, either IPv4 or IPv6.
///
/// # Example
///
/// This example creates an [`lb_ipaddr`] by parsing an IP address string.
///
/// ```lua
/// local net = require("lb:net");
/// local addr = net.ipaddr("127.0.0.1"); -- ipv4 loopback address
///
/// assert(addr:is_v4());
/// assert(addr:is_loopback());
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq, From, FromStr)]
#[cdef]
pub struct lb_ipaddr(#[opaque] IpAddr);

#[metatype]
impl lb_ipaddr {
    /// Returns `true` if this is an IPv4 address.
    pub extern "Lua-C" fn is_v4(&self) -> bool {
        self.0.is_ipv4()
    }

    /// Returns `true` if this is an IPv6 address.
    pub extern "Lua-C" fn is_v6(&self) -> bool {
        self.0.is_ipv6()
    }

    /// Returns the string `"v4"` if this is an IPv4 address, or `"v6"` if this is an IPv6 address.
    pub extern "Lua" fn family(&self) -> String {
        if self.is_v6() { "v6" } else { "v4" }
    }

    /// Returns `true` if this is a loopback address.
    ///
    /// For IPv4, this is any address in the `127.0.0.0/8` range.
    ///
    /// For IPv6, this is the address `::1`.
    pub extern "Lua-C" fn is_loopback(&self) -> bool {
        self.0.is_loopback()
    }

    /// Returns `true` if this address is unspecified.
    ///
    /// For IPv4, this is the address `0.0.0.0`.
    ///
    /// For IPv6, this is the address `::`.
    pub extern "Lua-C" fn is_unspecified(&self) -> bool {
        self.0.is_unspecified()
    }

    /// Returns `true` if this address is a multicast address.
    ///
    /// For IPv4, this is any address in the `224.0.0.0/4` range.
    ///
    /// For IPv6, this is any address in the `ff00::/8` range.
    pub extern "Lua-C" fn is_multicast(&self) -> bool {
        self.0.is_multicast()
    }

    /// Returns `true` if this is an IPv4 private address.
    ///
    /// For IPv4, this is any address in one of these ranges:
    ///
    /// - `10.0.0.0/8`
    /// - `172.16.0.0/12`
    /// - `192.168.0.0/16`
    ///
    /// For IPv6, this always returns `false`.
    pub extern "Lua-C" fn is_v4_private(&self) -> bool {
        match self.0 {
            IpAddr::V4(v4) => v4.is_private(),
            IpAddr::V6(_) => false,
        }
    }

    /// Returns `true` if this is an IPv4 link-local address.
    ///
    /// For IPv4, this is any address in the `169.254.0.0/16` range.
    ///
    /// For IPv6, this always returns `false`.
    pub extern "Lua-C" fn is_v4_link_local(&self) -> bool {
        match self.0 {
            IpAddr::V4(v4) => v4.is_link_local(),
            IpAddr::V6(_) => false,
        }
    }

    /// Returns `true` if this is an IPv4 broadcast address.
    ///
    /// For IPv4, this is the address `255.255.255.255`.
    ///
    /// For IPv6, this always returns `false`.
    pub extern "Lua-C" fn is_v4_broadcast(&self) -> bool {
        match self.0 {
            IpAddr::V4(v4) => v4.is_broadcast(),
            IpAddr::V6(_) => false,
        }
    }

    /// Returns `true` if this is an IPv4 documentation address.
    ///
    /// For IPv4, this is any address in one of these ranges:
    ///
    /// - `192.0.2.0/24` (TEST-NET-1)
    /// - `198.51.100.0/24` (TEST-NET-2)
    /// - `203.0.113.0/24` (TEST-NET-3)
    ///
    /// For IPv6, this always returns `false`.
    pub extern "Lua-C" fn is_v4_documentation(&self) -> bool {
        match self.0 {
            IpAddr::V4(v4) => v4.is_documentation(),
            IpAddr::V6(_) => false,
        }
    }

    /// Returns `true` if this is an IPv6 unique local address.
    ///
    /// For IPv4, this always returns `false`.
    ///
    /// For IPv6, this is any address in the `fc00::/7` range.
    pub extern "Lua-C" fn is_v6_unique_local(&self) -> bool {
        match self.0 {
            IpAddr::V4(_) => false,
            IpAddr::V6(v6) => v6.is_unique_local(),
        }
    }

    /// Returns `true` if this is an IPv6 unicast address with link-local scope.
    ///
    /// For IPv4, this always returns `false`.
    ///
    /// For IPv6, this is any address in the `fe80::/10` range.
    pub extern "Lua-C" fn is_v6_unicast_link_local(&self) -> bool {
        match self.0 {
            IpAddr::V4(_) => false,
            IpAddr::V6(v6) => v6.is_unicast_link_local(),
        }
    }

    /// Converts this address to IPv4.
    ///
    /// For IPv4, this returns the address unchanged.
    ///
    /// For IPv6, this returns the original IPv4 address if it is an IPv4-mapped or IPv4-compatible
    /// IPv6 address. Otherwise, this returns `nil`.
    pub extern "Lua-C" fn to_v4(&self) -> Option<Self> {
        match self.0 {
            IpAddr::V4(_) => Some(*self),
            IpAddr::V6(v6) => v6.to_ipv4().map(|v| Self(v.into())),
        }
    }

    /// Converts this address to IPv6.
    ///
    /// For IPv4, this returns the IPv4-mapped IPv6 address as defined by
    /// [`Ipv4Addr::to_ipv6_mapped`].
    ///
    /// For IPv6, this returns the address unchanged.
    pub extern "Lua-C" fn to_v6(&self) -> Self {
        match self.0 {
            IpAddr::V4(v4) => Self(v4.to_ipv6_mapped().into()),
            IpAddr::V6(_) => *self,
        }
    }

    /// Returns the canonical form of this address.
    ///
    /// For IPv4, this returns the address unchanged.
    ///
    /// For IPv6, this returns the original IPv4 address if it is an IPv4-mapped or IPv4-compatible
    /// IPv6 address. Otherwise, this returns the address unchanged.
    pub extern "Lua-C" fn to_canonical(&self) -> Self {
        match self.0 {
            IpAddr::V4(_) => *self,
            IpAddr::V6(v6) => v6.to_ipv4().map_or(*self, |v| Self(v.into())),
        }
    }

    /// Returns `true` if the given addresses are equal.
    ///
    /// Two addresses are considered equal if they are of the same family (IPv4 or IPv6) and
    /// represent the same address in octets.
    #[eq]
    pub extern "Lua-C" fn equals(left: &Self, right: &Self) -> bool {
        left.0 == right.0
    }

    /// Returns `true` if the left address is less than the right address.
    ///
    /// IPv4 addresses are always less than IPv6 addresses.
    #[lt]
    pub extern "Lua-C" fn less_than(left: &Self, right: &Self) -> bool {
        left.0 < right.0
    }

    /// Returns `true` if the left address is less than or equal to the right address.
    ///
    /// IPv4 addresses are always less than IPv6 addresses.
    #[le]
    pub extern "Lua-C" fn less_than_or_equals(left: &Self, right: &Self) -> bool {
        left.0 <= right.0
    }

    /// Returns the string representation of this address.
    #[tostring]
    pub extern "Lua-C" fn tostring(&self) -> String {
        self.0.to_string()
    }
}

/// Socket address, which is an IP address with a port number.
///
/// This represents a combination of an IP address and a port, such as `127.0.0.1:8080` or
/// `[::1]:443`. It is used to specify endpoints for network connections and listeners, and can be
/// constructed by [`socketaddr`](lb_libnet::socketaddr).
#[derive(Debug, Clone, Copy, PartialEq, Eq, From, FromStr)]
#[cdef]
pub struct lb_socketaddr(#[opaque] SocketAddr);

#[metatype]
impl lb_socketaddr {
    /// Returns the IP part of this address.
    pub extern "Lua-C" fn ip(&self) -> lb_ipaddr {
        self.0.ip().into()
    }

    /// Returns the port part of this address.
    pub extern "Lua-C" fn port(&self) -> u16 {
        self.0.port()
    }

    /// Returns a new socket address with the given IP address and the same port.
    pub extern "Lua-C" fn with_ip(&self, ip: &lb_ipaddr) -> Self {
        SocketAddr::new(ip.0, self.port()).into()
    }

    /// Returns a new socket address with the given port and the same IP address.
    pub extern "Lua-C" fn with_port(&self, port: u16) -> Self {
        SocketAddr::new(self.ip().0, port).into()
    }

    /// Returns `true` if the given addresses are equal.
    #[eq]
    pub extern "Lua-C" fn equals(left: &Self, right: &Self) -> bool {
        left.0 == right.0
    }

    /// Returns `true` if the left address is less than the right address.
    #[lt]
    pub extern "Lua-C" fn less_than(left: &Self, right: &Self) -> bool {
        left.0 < right.0
    }

    /// Returns `true` if the left address is less than or equal to the right address.
    #[le]
    pub extern "Lua-C" fn less_than_or_equals(left: &Self, right: &Self) -> bool {
        left.0 <= right.0
    }

    /// Returns the string representation of this address.
    #[tostring]
    pub extern "Lua-C" fn tostring(&self) -> String {
        self.0.to_string()
    }
}

/// TCP socket which has not yet been converted to an [`lb_tcpstream`] or [`lb_tcplistener`].
///
/// This type represents a TCP socket in its initial state, before it is connected or set to listen.
/// It can be configured (e.g., socket options, bind address) before being converted to an
/// [`lb_tcpstream`] (via [`connect`](lb_tcpsocket::connect)) or [`lb_tcplistener`] (via
/// [`listen`](lb_tcpsocket::listen)), after which it can no longer be used.
#[derive(Debug)]
#[cdef]
pub struct lb_tcpsocket(#[opaque] RefCell<Option<TcpSocket>>);

#[metatype]
impl lb_tcpsocket {
    fn new(socket: TcpSocket) -> Self {
        Self(RefCell::new(Some(socket)))
    }

    fn socket<'s>(&'s self) -> Result<Ref<'s, TcpSocket>> {
        let socket = self.0.borrow();
        match *socket {
            Some(_) => Ok(Ref::map(socket, |s| s.as_ref().unwrap())),
            None => Err(Error::SocketConsumed),
        }
    }

    /// Gets the value of the `SO_KEEPALIVE` option on this socket.
    pub extern "Lua-C" fn keepalive(&self) -> Result<bool> {
        Ok(self.socket()?.keepalive()?)
    }

    /// Sets value for the `SO_KEEPALIVE` option on this socket.
    ///
    /// This enables or disables periodic keepalive messages on the connection.
    pub extern "Lua-C" fn set_keepalive(&self, enabled: bool) -> Result<()> {
        Ok(self.socket()?.set_keepalive(enabled)?)
    }

    /// Gets the value of the `SO_REUSEADDR` option on this socket.
    pub extern "Lua-C" fn reuseaddr(&self) -> Result<bool> {
        Ok(self.socket()?.reuseaddr()?)
    }

    /// Sets value for the `SO_REUSEADDR` option on this socket.
    ///
    /// This allows the socket to bind to an address that is already in use.
    pub extern "Lua-C" fn set_reuseaddr(&self, enabled: bool) -> Result<()> {
        Ok(self.socket()?.set_reuseaddr(enabled)?)
    }

    /// Gets the value of the `SO_REUSEPORT` option on this socket.
    pub extern "Lua-C" fn reuseport(&self) -> Result<bool> {
        Ok(self.socket()?.reuseport()?)
    }

    /// Sets value for the `SO_REUSEPORT` option on this socket.
    ///
    /// This allows multiple sockets to bind to the same port.
    pub extern "Lua-C" fn set_reuseport(&self, enabled: bool) -> Result<()> {
        Ok(self.socket()?.set_reuseport(enabled)?)
    }

    /// Gets the value of the `SO_SNDBUF` option on this socket.
    pub extern "Lua-C" fn sendbuf(&self) -> Result<u32> {
        Ok(self.socket()?.send_buffer_size()?)
    }

    /// Sets value for the `SO_SNDBUF` option on this socket.
    ///
    /// This sets the size of the send buffer in bytes.
    pub extern "Lua-C" fn set_sendbuf(&self, size: u32) -> Result<()> {
        Ok(self.socket()?.set_send_buffer_size(size)?)
    }

    /// Gets the value of the `SO_RCVBUF` option on this socket.
    pub extern "Lua-C" fn recvbuf(&self) -> Result<u32> {
        Ok(self.socket()?.recv_buffer_size()?)
    }

    /// Sets value for the `SO_RCVBUF` option on this socket.
    ///
    /// This sets the size of the receive buffer in bytes.
    pub extern "Lua-C" fn set_recvbuf(&self, size: u32) -> Result<()> {
        Ok(self.socket()?.set_recv_buffer_size(size)?)
    }

    /// Gets the value of the `SO_LINGER` option on this socket, in seconds.
    pub extern "Lua-C" fn linger(&self) -> Result<f64> {
        Ok(self
            .socket()?
            .linger()?
            .map(|n| n.as_secs_f64())
            .unwrap_or(0.))
    }

    /// Sets the value of the `SO_LINGER` option on this socket.
    ///
    /// This controls how long the socket will remain open after close if unsent data is present.
    pub extern "Lua-C" fn set_linger(&self, secs: f64) -> Result<()> {
        let secs = secs.max(0.);
        Ok(self
            .socket()?
            .set_linger((secs != 0.).then_some(Duration::from_secs_f64(secs)))?)
    }

    /// Gets the value of the `TCP_NODELAY` option on this socket.
    pub extern "Lua-C" fn nodelay(&self) -> Result<bool> {
        Ok(self.socket()?.nodelay()?)
    }

    /// Sets the value of the `TCP_NODELAY` option on this socket.
    ///
    /// This enables or disables Nagle's algorithm, which delays sending small packets.
    pub extern "Lua-C" fn set_nodelay(&self, enabled: bool) -> Result<()> {
        Ok(self.socket()?.set_nodelay(enabled)?)
    }

    /// Gets the local address that this socket is bound to.
    pub extern "Lua-C" fn local_addr(&self) -> Result<lb_socketaddr> {
        Ok(self.socket()?.local_addr()?.into())
    }

    /// Binds this socket to the given local address.
    pub extern "Lua-C" fn bind(&self, addr: &lb_socketaddr) -> Result<()> {
        Ok(self.socket()?.bind(addr.0)?)
    }

    /// Transitions this socket to the listening state.
    ///
    /// This consumes the socket and returns a new [`lb_tcplistener`] that can accept incoming
    /// connections. This socket object can no longer be used after this call.
    pub extern "Lua-C" fn listen(&self, backlog: u32) -> Result<lb_tcplistener> {
        let socket = self.0.borrow_mut().take().ok_or(Error::SocketConsumed)?;
        Ok(lb_tcplistener::new(socket.listen(backlog)?))
    }

    /// Connects this socket to the given remote socket address, transitioning it to an established
    /// state.
    ///
    /// This consumes the socket and returns a new [`lb_tcpstream`] that can be used to send and
    /// receive data. This socket object can no longer be used after this call.
    ///
    /// # Errors
    ///
    /// This function may throw an error if connection could not be established to the given remote
    /// address.
    pub async extern "Lua-C" fn connect(&self, addr: &lb_socketaddr) -> Result<lb_tcpstream> {
        let socket = self.0.borrow_mut().take().ok_or(Error::SocketConsumed)?;
        Ok(lb_tcpstream::new(socket.connect(addr.0).await?))
    }
}

/// TCP connection between a local and a remote socket.
///
/// This represents an established TCP connection. It is created by connecting an [`lb_tcpsocket`]
/// to a remote socket address (via [`connect`](lb_tcpsocket::connect)) or accepting a connection
/// from an [`lb_tcplistener`] (via [`accept`](lb_tcplistener::accept)). It provides methods for
/// reading from and writing to the stream asynchronously.
///
/// This type supports reading and writing data in both directions concurrently. Typically you would
/// spawn one reader and one writer task to handle incoming and outgoing data respectively.
/// Connection is closed when this object goes out of scope and gets garbage collected, or when
/// [`shutdown`](Self::shutdown) is explicitly called.
///
/// # Example
///
/// This examples spawns a reader task and a writer task to operate on the stream concurrently.
///
/// ```lua
/// local task = require("lb:task")
/// local net = require("lb:net")
/// local socket = net.connect_tcp("127.0.0.1:1234")
///
/// print("local address:", socket:local_addr())
/// print("remote address:", socket:peer_addr())
///
/// local reader = spawn(function()
///     for chunk in socket, 1024 do
///         if chunk ~= nil then
///             print("received:", chunk)
///         else
///             print("read half closed")
///         end
///     done
/// end)
///
/// local writer = spawn(function()
///     for i = 1, 10 do
///         socket:write(("message %d\n"):format(i))
///         print("sent message", i)
///     done
/// end)
///
/// task.join(reader, writer)
/// ```
#[derive(Debug)]
#[cdef]
pub struct lb_tcpstream {
    #[opaque]
    read: RefCell<tokio::net::tcp::OwnedReadHalf>,
    #[opaque]
    write: RefCell<tokio::net::tcp::OwnedWriteHalf>,
}

#[metatype]
impl lb_tcpstream {
    fn new(stream: TcpStream) -> Self {
        let (read, write) = stream.into_split();
        Self {
            read: RefCell::new(read),
            write: RefCell::new(write),
        }
    }

    fn read_half<'s>(&'s self) -> Result<RefMut<'s, tokio::net::tcp::OwnedReadHalf>> {
        Ok(self.read.try_borrow_mut()?)
    }

    fn write_half<'s>(&'s self) -> Result<RefMut<'s, tokio::net::tcp::OwnedWriteHalf>> {
        Ok(self.write.try_borrow_mut()?)
    }

    /// Gets the remote socket address of this stream.
    pub extern "Lua-C" fn peer_addr(&self) -> Result<lb_socketaddr> {
        Ok(self.read_half()?.peer_addr()?.into())
    }

    /// Gets the local socket address of this stream.
    pub extern "Lua-C" fn local_addr(&self) -> Result<lb_socketaddr> {
        Ok(self.read_half()?.local_addr()?.into())
    }

    /// Waits for this stream to be ready in the given half.
    ///
    /// The argument `half` can be `"read"` for the readable half, `"write"` for the writable half,
    /// or `nil` for both.
    pub async extern "Lua-C" fn ready(&self, half: Option<&str>) -> Result<()> {
        let ty = match half {
            None => Interest::READABLE | Interest::WRITABLE,
            Some("read") => Interest::READABLE,
            Some("write") => Interest::WRITABLE,
            _ => Err(std::io::Error::new(
                std::io::ErrorKind::InvalidInput,
                "invalid ready interest",
            ))?,
        };

        self.read_half()?.ready(ty).await?;
        Ok(())
    }

    /// Reads exactly `len` bytes from this stream.
    ///
    /// If the connection was closed, this returns `nil`.
    pub async extern "Lua-C" fn read(&self, len: u32) -> Result<Option<Vec<u8>>> {
        let mut buf = vec![0; len as usize];
        Ok(match self.read_half()?.read_exact(&mut buf).await {
            Ok(_) => Some(buf),
            Err(err) if err.kind() == std::io::ErrorKind::UnexpectedEof => None,
            Err(err) => return Err(err.into()),
        })
    }

    /// Reads up to `len` bytes from this stream.
    ///
    /// The returned bytes may be less than `len` in length if the stream had less data available in
    /// queue. If the connection was closed, this returns `nil`.
    pub async extern "Lua-C" fn read_partial(&self, len: u32) -> Result<Option<Vec<u8>>> {
        let mut buf = vec![0; len as usize];
        let n = self.read_half()?.read(&mut buf).await?;
        Ok(if n == 0 {
            None
        } else {
            buf.truncate(n);
            Some(buf)
        })
    }

    /// Attempts to read up to `len` bytes from this stream without waiting.
    ///
    /// The returned bytes may be less than `len` in length if the stream had less data available in
    /// queue. If there was no data available or the connection was closed, this returns `nil`.
    pub extern "Lua-C" fn try_read(&self, len: u32) -> Result<Option<Vec<u8>>> {
        let mut buf = vec![0; len as usize];
        Ok(match self.read_half()?.try_read(&mut buf) {
            Ok(0) => None,
            Ok(n) => {
                buf.truncate(n);
                Some(buf)
            }
            Err(err) if err.kind() == std::io::ErrorKind::WouldBlock => None,
            Err(err) => return Err(err.into()),
        })
    }

    /// Writes the given bytes to this stream.
    pub async extern "Lua-C" fn write(&self, buf: &[u8]) -> Result<()> {
        Ok(self.write_half()?.write_all(buf).await?)
    }

    /// Writes the given bytes to this stream and returns the number of bytes successfully written.
    pub async extern "Lua-C" fn write_partial(&self, buf: &[u8]) -> Result<u32> {
        Ok(self.write_half()?.write(buf).await? as u32)
    }

    /// Peeks up to `len` bytes at incoming data without consuming it.
    ///
    /// Successive calls will return the same data until it is consumed by the [`read`](Self::read)
    /// family of functions.
    pub async extern "Lua-C" fn peek(&self, len: u32) -> Result<Option<Vec<u8>>> {
        let mut buf = vec![0; len as usize];
        let n = self.read_half()?.peek(&mut buf).await?;
        Ok(if n == 0 {
            None
        } else {
            buf.truncate(n);
            Some(buf)
        })
    }

    /// Shuts down this connection.
    pub async extern "Lua-C" fn shutdown(&self) -> Result<()> {
        Ok(self.write_half()?.shutdown().await?)
    }

    #[call]
    pub async extern "Lua" fn call(&self, len: u32) -> Result<Option<Vec<u8>>> {
        self.read_partial(len)
    }
}

/// TCP socket server, listening for connections.
///
/// This type represents a TCP server socket that can accept incoming connections. It is created by
/// transitioning an [`lb_tcpsocket`] to the listening state via [`listen`](lb_tcpsocket::listen).
#[derive(Debug)]
#[cdef]
pub struct lb_tcplistener {
    #[opaque]
    listener: TcpListener,
    __on_accept_ref: c_int,
}

#[metatype]
impl lb_tcplistener {
    fn new(listener: TcpListener) -> Self {
        Self {
            listener,
            __on_accept_ref: LUA_NOREF,
        }
    }

    /// Returns the local socket address that this listener is bound to.
    pub extern "Lua-C" fn local_addr(&self) -> Result<lb_socketaddr> {
        Ok(self.listener.local_addr()?.into())
    }

    /// Gets the value of the `IP_TTL` option for this socket.
    pub extern "Lua-C" fn ttl(&self) -> Result<u32> {
        Ok(self.listener.ttl()?)
    }

    /// Sets the value for the `IP_TTL` option on this socket.
    pub extern "Lua-C" fn set_ttl(&self, ttl: u32) -> Result<()> {
        Ok(self.listener.set_ttl(ttl)?)
    }

    /// Registers a callback to be invoked with each new incoming connection before it is converted
    /// to an [`lb_tcpstream`].
    ///
    /// The callback receives a temporary [`lb_tcplistener_stream`] object, which can be used to
    /// configure socket options (such as [`set_nodelay`](lb_tcplistener_stream),
    /// [`set_linger`](lb_tcplistener_stream), etc.) before the stream is converted to an
    /// [`lb_tcpstream`]. The callback is called synchronously during [`accept`](Self::accept) and
    /// should complete as quickly as possible. The provided configurable object is only valid
    /// within the callback and is converted to an [`lb_tcpstream`] as soon as it returns.
    pub extern "Lua" fn on_accept(&self, cb: fun<(&lb_tcplistener_stream,), ()>) {
        assert(
            rawequal(cb, ()) || r#type(cb) == "function",
            concat!("function expected in argument 'cb', got ", r#type(cb)),
        );
        __unref(self.__on_accept_ref);
        self.__on_accept_ref = __ref(cb);
    }

    /// Accepts a new incoming TCP connection.
    ///
    /// If an [`on_accept`](Self::on_accept) callback is registered, it is invoked with a temporary
    /// [`lb_tcplistener_stream`] object representing the new connection. This allows configuration
    /// of socket options for this specific connection, before the stream is converted to an
    /// [`lb_tcpstream`] and returned for the connection to be read from or written to.
    #[call]
    pub async extern "Lua" fn accept(&self) -> Result<lb_tcpstream> {
        let stream = self.__accept();
        let on_accept = __registry[self.__on_accept_ref];
        if on_accept != () {
            on_accept(stream);
        }
        stream.__convert()
    }

    async extern "Lua-C" fn __accept(&self) -> Result<lb_tcplistener_stream> {
        let (stream, _) = self.listener.accept().await?;
        Ok(lb_tcplistener_stream::new(stream))
    }

    #[gc]
    extern "Lua" fn gc(&self) {
        __unref(self.__on_accept_ref);
    }
}

/// TCP connection that has just been accepted by [`lb_tcplistener`].
///
/// This type is passed to the [`on_accept`](lb_tcplistener::on_accept) callback on
/// [`lb_tcplistener`], allowing socket options to be set before the stream is converted to an
/// [`lb_tcpstream`]. After conversion, this object can no longer be used.
#[derive(Debug)]
#[cdef]
pub struct lb_tcplistener_stream(#[opaque] RefCell<Option<TcpStream>>);

#[metatype]
impl lb_tcplistener_stream {
    fn new(stream: TcpStream) -> Self {
        Self(RefCell::new(Some(stream)))
    }

    fn stream<'s>(&'s self) -> Result<Ref<'s, TcpStream>> {
        let socket = self.0.borrow();
        match *socket {
            Some(_) => Ok(Ref::map(socket, |s| s.as_ref().unwrap())),
            None => Err(Error::SocketConsumed),
        }
    }

    /// Returns the local socket address that the listener is bound to.
    pub extern "Lua-C" fn local_addr(&self) -> Result<lb_socketaddr> {
        Ok(self.stream()?.local_addr()?.into())
    }

    /// Returns the remote socket address of this stream.
    pub extern "Lua-C" fn peer_addr(&self) -> Result<lb_socketaddr> {
        Ok(self.stream()?.peer_addr()?.into())
    }

    /// Gets the value of the `TCP_NODELAY` option on this stream.
    pub extern "Lua-C" fn nodelay(&self) -> Result<bool> {
        Ok(self.stream()?.nodelay()?)
    }

    /// Sets the value of the `TCP_NODELAY` option on this stream.
    ///
    /// This enables or disables Nagle's algorithm, which delays sending small packets.
    pub extern "Lua-C" fn set_nodelay(&self, enabled: bool) -> Result<()> {
        Ok(self.stream()?.set_nodelay(enabled)?)
    }

    /// Gets the value of the `SO_LINGER` option on this stream, in seconds.
    pub extern "Lua-C" fn linger(&self) -> Result<f64> {
        Ok(self
            .stream()?
            .linger()?
            .map(|n| n.as_secs_f64())
            .unwrap_or(0.))
    }

    /// Sets the value of the `SO_LINGER` option on this stream.
    ///
    /// This controls how long the stream will remain open after close if unsent data is present.
    pub extern "Lua-C" fn set_linger(&self, secs: f64) -> Result<()> {
        let secs = secs.max(0.);
        Ok(self
            .stream()?
            .set_linger((secs != 0.).then_some(std::time::Duration::from_secs_f64(secs)))?)
    }

    /// Gets the value of the `IP_TTL` option for this stream.
    pub extern "Lua-C" fn ttl(&self) -> Result<u32> {
        Ok(self.stream()?.ttl()?)
    }

    /// Sets the value for the `IP_TTL` option on this stream.
    pub extern "Lua-C" fn set_ttl(&self, ttl: u32) -> Result<()> {
        Ok(self.stream()?.set_ttl(ttl)?)
    }

    extern "Lua-C" fn __convert(&self) -> Result<lb_tcpstream> {
        Ok(lb_tcpstream::new(
            self.0.borrow_mut().take().ok_or(Error::SocketConsumed)?,
        ))
    }
}