module net

import time

const udp_default_read_timeout = time.second / 10
const udp_default_write_timeout = time.second / 10

struct UdpSocket {
    Socket
    l Addr
    // TODO(emily): replace with option again
    // when i figure out how to coerce it properly
mut:
    has_r bool
    r     Addr
}

pub struct UdpConn {
pub mut:
    sock UdpSocket
mut:
    write_deadline time.Time
    read_deadline  time.Time
    read_timeout   time.Duration
    write_timeout  time.Duration
    is_blocking    bool = true
}

@[_pack: '1']
struct Ipv4MulticastRequest {
    multiaddr    [4]u8
    interface_ip [4]u8
}

@[_pack: '1']
struct Ipv6MulticastRequest {
    multiaddr       [16]u8
    interface_index u32
}

pub fn dial_udp(raddr string) !&UdpConn {
    addrs := resolve_addrs_fuzzy(raddr, .udp)!

    for addr in addrs {
        // create a local socket for this
        // bind to any port (or file) (we dont care in this
        // case because we only care about the remote)
        if sock := new_udp_socket_for_remote(addr) {
            mut conn := &UdpConn{
                sock:          sock
                read_timeout:  udp_default_read_timeout
                write_timeout: udp_default_write_timeout
            }
            $if net_nonblocking_sockets ? {
                conn.is_blocking = false
            }
            return conn
        }
    }

    return error('none')
}

// pub fn dial_udp(laddr string, raddr string) ?&UdpConn {
//     local := resolve_addr(laddr, .inet, .udp)?

//     sbase := new_udp_socket()?

//     sock := UdpSocket{
//         handle: sbase.handle
//         l: local
//         r: resolve_wrapper(raddr)
//     }
// }

pub fn (mut c UdpConn) write_ptr(b &u8, len int) !int {
    remote := c.sock.remote() or { return err_no_udp_remote }
    return c.write_to_ptr(remote, b, len)
}

pub fn (mut c UdpConn) write(buf []u8) !int {
    return c.write_ptr(buf.data, buf.len)
}

pub fn (mut c UdpConn) write_string(s string) !int {
    return c.write_ptr(s.str, s.len)
}

pub fn (mut c UdpConn) write_to_ptr(addr Addr, b &u8, len int) !int {
    res := C.sendto(c.sock.handle, b, len, 0, voidptr(&addr), addr.len())
    if res >= 0 {
        return res
    }
    code := error_code()
    if code == int(error_ewouldblock) {
        c.wait_for_write()!
        socket_error(C.sendto(c.sock.handle, b, len, 0, voidptr(&addr), addr.len()))!
    } else {
        wrap_error(code)!
    }
    return error('none')
}

// write_to blocks and writes the buf to the remote addr specified
pub fn (mut c UdpConn) write_to(addr Addr, buf []u8) !int {
    return c.write_to_ptr(addr, buf.data, buf.len)
}

// write_to_string blocks and writes the buf to the remote addr specified
pub fn (mut c UdpConn) write_to_string(addr Addr, s string) !int {
    return c.write_to_ptr(addr, s.str, s.len)
}

// read_ptr reads from the socket into `buf_ptr` up to `len` bytes, returning the number of bytes read and the `Addr` read from.
pub fn (c &UdpConn) read_ptr(buf_ptr &u8, len int) !(int, Addr) {
    mut addr := Addr{
        addr: AddrData{
            Ip6: Ip6{}
        }
    }
    addr_len := sizeof(Addr)
    mut res := 0
    if c.is_blocking {
        // Honor read deadlines/timeouts before entering a blocking recvfrom call.
        c.wait_for_read()!
        res = wrap_read_result(C.recvfrom(c.sock.handle, voidptr(buf_ptr), len, 0, voidptr(&addr),
            &addr_len))!
    } else {
        res = wrap_read_result(C.recvfrom(c.sock.handle, voidptr(buf_ptr), len, 0, voidptr(&addr),
            &addr_len))!
    }
    if res > 0 {
        return res, addr
    }
    code := error_code()
    if code in [int(error_ewouldblock), int(error_eagain), C.EINTR] {
        c.wait_for_read()!
        // same setup as in tcp
        res = wrap_read_result(C.recvfrom(c.sock.handle, voidptr(buf_ptr), len, 0, voidptr(&addr),
            &addr_len))!
        res2 := socket_error(res)!
        return res2, addr
    } else {
        wrap_error(code)!
    }
    return error('none')
}

// read reads from the socket into buf up to buf.len returning the number of bytes read
pub fn (mut c UdpConn) read(mut buf []u8) !(int, Addr) {
    return c.read_ptr(buf.data, buf.len)!
}

pub fn (c &UdpConn) read_deadline() !time.Time {
    if c.read_deadline.unix() == 0 {
        return c.read_deadline
    }
    return error('none')
}

pub fn (mut c UdpConn) set_read_deadline(deadline time.Time) {
    c.read_deadline = deadline
}

pub fn (c &UdpConn) write_deadline() !time.Time {
    if c.write_deadline.unix() == 0 {
        return c.write_deadline
    }
    return error('none')
}

pub fn (mut c UdpConn) set_write_deadline(deadline time.Time) {
    c.write_deadline = deadline
}

pub fn (c &UdpConn) read_timeout() time.Duration {
    return c.read_timeout
}

pub fn (mut c UdpConn) set_read_timeout(t time.Duration) {
    c.read_timeout = t
}

pub fn (c &UdpConn) write_timeout() time.Duration {
    return c.write_timeout
}

pub fn (mut c UdpConn) set_write_timeout(t time.Duration) {
    c.write_timeout = t
}

@[inline]
pub fn (c &UdpConn) wait_for_read() ! {
    return wait_for_read(c.sock.handle, c.read_deadline, c.read_timeout)
}

@[inline]
pub fn (mut c UdpConn) wait_for_write() ! {
    return wait_for_write(c.sock.handle, c.write_deadline, c.write_timeout)
}

pub fn (c &UdpConn) str() string {
    // TODO
    return 'UdpConn'
}

pub fn (mut c UdpConn) close() ! {
    return c.sock.close()
}

// join_multicast_group joins the UDP socket to an IPv4 or IPv6 multicast group.
// For IPv4 sockets, `iface_addr` must be an IPv4 address or `''` to use the default interface.
// For IPv6 sockets, `iface_addr` must be a numeric interface index or `''` to use the default interface.
pub fn (mut c UdpConn) join_multicast_group(multicast_addr string, iface_addr string) ! {
    family := c.multicast_family()!
    match family {
        .ip {
            mreq := Ipv4MulticastRequest{
                multiaddr:    parse_ipv4_multicast_addr(multicast_addr)!
                interface_ip: parse_ipv4_interface_addr(iface_addr)!
            }
            c.sock.set_option_raw(C.IPPROTO_IP, C.IP_ADD_MEMBERSHIP, &mreq,
                sizeof(Ipv4MulticastRequest))!
        }
        .ip6 {
            mreq := Ipv6MulticastRequest{
                multiaddr:       parse_ipv6_multicast_addr(multicast_addr)!
                interface_index: parse_ipv6_interface_index(iface_addr)!
            }
            c.sock.set_option_raw(C.IPPROTO_IPV6, ipv6_membership_socket_option(true), &mreq,
                sizeof(Ipv6MulticastRequest))!
        }
        else {
            return error('net: udp multicast is only supported on ip and ip6 sockets')
        }
    }
}

// leave_multicast_group leaves an IPv4 or IPv6 multicast group previously joined by the socket.
// `iface_addr` follows the same rules as `join_multicast_group`.
pub fn (mut c UdpConn) leave_multicast_group(multicast_addr string, iface_addr string) ! {
    family := c.multicast_family()!
    match family {
        .ip {
            mreq := Ipv4MulticastRequest{
                multiaddr:    parse_ipv4_multicast_addr(multicast_addr)!
                interface_ip: parse_ipv4_interface_addr(iface_addr)!
            }
            c.sock.set_option_raw(C.IPPROTO_IP, C.IP_DROP_MEMBERSHIP, &mreq,
                sizeof(Ipv4MulticastRequest))!
        }
        .ip6 {
            mreq := Ipv6MulticastRequest{
                multiaddr:       parse_ipv6_multicast_addr(multicast_addr)!
                interface_index: parse_ipv6_interface_index(iface_addr)!
            }
            c.sock.set_option_raw(C.IPPROTO_IPV6, ipv6_membership_socket_option(false), &mreq,
                sizeof(Ipv6MulticastRequest))!
        }
        else {
            return error('net: udp multicast is only supported on ip and ip6 sockets')
        }
    }
}

// set_multicast_ttl sets the IPv4 TTL or IPv6 hop limit used for outgoing multicast traffic.
// Valid values are between 0 and 255 inclusive.
pub fn (mut c UdpConn) set_multicast_ttl(ttl int) ! {
    if ttl < 0 || ttl > 255 {
        return error('net: multicast ttl must be between 0 and 255')
    }
    match c.multicast_family()! {
        .ip {
            c.sock.set_option_int(C.IPPROTO_IP, C.IP_MULTICAST_TTL, ttl)!
        }
        .ip6 {
            c.sock.set_option_int(C.IPPROTO_IPV6, C.IPV6_MULTICAST_HOPS, ttl)!
        }
        else {
            return error('net: udp multicast is only supported on ip and ip6 sockets')
        }
    }
}

// set_multicast_loop enables or disables local loopback for outgoing multicast packets.
pub fn (mut c UdpConn) set_multicast_loop(enable bool) ! {
    value := int(enable)
    match c.multicast_family()! {
        .ip {
            c.sock.set_option_int(C.IPPROTO_IP, C.IP_MULTICAST_LOOP, value)!
        }
        .ip6 {
            c.sock.set_option_int(C.IPPROTO_IPV6, C.IPV6_MULTICAST_LOOP, value)!
        }
        else {
            return error('net: udp multicast is only supported on ip and ip6 sockets')
        }
    }
}

// set_multicast_interface sets the outgoing multicast interface for the UDP socket.
// For IPv4 sockets, `iface_addr` must be an IPv4 address or `''` to clear it to the default interface.
// For IPv6 sockets, `iface_addr` must be a numeric interface index or `''` to use the default interface.
pub fn (mut c UdpConn) set_multicast_interface(iface_addr string) ! {
    match c.multicast_family()! {
        .ip {
            addr := parse_ipv4_interface_addr(iface_addr)!
            c.sock.set_option_raw(C.IPPROTO_IP, C.IP_MULTICAST_IF, &addr[0], sizeof([4]u8))!
        }
        .ip6 {
            index := parse_ipv6_interface_index(iface_addr)!
            c.sock.set_option_int(C.IPPROTO_IPV6, C.IPV6_MULTICAST_IF, int(index))!
        }
        else {
            return error('net: udp multicast is only supported on ip and ip6 sockets')
        }
    }
}

pub fn listen_udp(laddr string) !&UdpConn {
    addrs := resolve_addrs_fuzzy(laddr, .udp)!
    // TODO(emily):
    // here we are binding to the first address
    // and that is probably not ideal
    addr := addrs[0]
    mut conn := &UdpConn{
        sock:          new_udp_socket(addr)!
        read_timeout:  udp_default_read_timeout
        write_timeout: udp_default_write_timeout
    }
    $if net_nonblocking_sockets ? {
        conn.is_blocking = false
    }
    return conn
}

fn new_udp_socket(local_addr Addr) !&UdpSocket {
    family := local_addr.family()

    sockfd := socket_error(C.socket(i32(family), i32(SocketType.udp), 0))!
    mut s := &UdpSocket{
        handle: sockfd
        l:      local_addr
        r:      Addr{
            addr: AddrData{
                Ip6: Ip6{}
            }
        }
    }

    s.set_option_bool(.reuse_addr, true)!

    if family == .ip6 {
        s.set_dualstack(true)!
    }

    $if net_nonblocking_sockets ? {
        set_blocking(sockfd, false)!
    }

    // cast to the correct type
    socket_error(C.bind(s.handle, voidptr(&local_addr), local_addr.len()))!
    return s
}

fn new_udp_socket_for_remote(raddr Addr) !&UdpSocket {
    // Invent a sutible local address for this remote addr
    // Appease compiler
    mut addr := Addr{
        addr: AddrData{
            Ip6: Ip6{}
        }
    }
    match raddr.family() {
        .ip {
            // Use ip dualstack
            addr = new_ip(0, addr_ip_any)
        }
        .ip6 {
            // Use ip6 dualstack
            addr = new_ip6(0, addr_ip6_any)
        }
        .unix {
            addr = temp_unix()!
        }
        else {
            panic('Invalid family')
        }
    }

    mut sock := new_udp_socket(addr)!
    sock.has_r = true
    sock.r = raddr

    return sock
}

fn (c &UdpConn) multicast_family() !AddrFamily {
    family := c.sock.l.family()
    if family !in [.ip, .ip6] {
        return error('net: udp multicast is only supported on ip and ip6 sockets')
    }
    return family
}

fn normalize_ip_literal(address string) string {
    if address.len >= 2 && address[0] == `[` && address[address.len - 1] == `]` {
        return address[1..address.len - 1]
    }
    return address
}

fn parse_ipv4_interface_addr(iface_addr string) ![4]u8 {
    if iface_addr.len == 0 {
        return [4]u8{}
    }
    address := normalize_ip_literal(iface_addr)
    mut parsed := [4]u8{}
    if C.inet_pton(i32(AddrFamily.ip), &char(address.str), &parsed[0]) != 1 {
        return error('net: ipv4 multicast interface must be an ipv4 address')
    }
    return parsed
}

fn parse_ipv4_multicast_addr(multicast_addr string) ![4]u8 {
    address := normalize_ip_literal(multicast_addr)
    mut parsed := [4]u8{}
    if C.inet_pton(i32(AddrFamily.ip), &char(address.str), &parsed[0]) != 1 {
        return error('net: invalid ipv4 multicast address `${multicast_addr}`')
    }
    if parsed[0] < 224 || parsed[0] > 239 {
        return error('net: `${multicast_addr}` is not an ipv4 multicast address')
    }
    return parsed
}

fn parse_ipv6_multicast_addr(multicast_addr string) ![16]u8 {
    address := normalize_ip_literal(multicast_addr)
    mut parsed := [16]u8{}
    if C.inet_pton(i32(AddrFamily.ip6), &char(address.str), &parsed[0]) != 1 {
        return error('net: invalid ipv6 multicast address `${multicast_addr}`')
    }
    if parsed[0] != 0xff {
        return error('net: `${multicast_addr}` is not an ipv6 multicast address')
    }
    return parsed
}

fn parse_ipv6_interface_index(iface_addr string) !u32 {
    if iface_addr.len == 0 {
        return 0
    }
    for ch in iface_addr {
        if ch < `0` || ch > `9` {
            return error('net: ipv6 multicast interface must be a numeric interface index')
        }
    }
    return iface_addr.u32()
}

fn ipv6_membership_socket_option(join bool) int {
    $if windows {
        return if join { C.IPV6_ADD_MEMBERSHIP } else { C.IPV6_DROP_MEMBERSHIP }
    } $else {
        return if join { C.IPV6_JOIN_GROUP } else { C.IPV6_LEAVE_GROUP }
    }
}

fn (mut s UdpSocket) set_option_raw(level int, opt int, value voidptr, value_len u32) ! {
    socket_error(C.setsockopt(s.handle, level, opt, value, value_len))!
}

fn (mut s UdpSocket) set_option_int(level int, opt int, value int) ! {
    s.set_option_raw(level, opt, &value, sizeof(int))!
}

// set_option_bool sets a boolean socket option on the UDP socket.
pub fn (mut s UdpSocket) set_option_bool(opt SocketOption, value bool) ! {
    // TODO: reenable when this `in` operation works again
    // if opt !in opts_can_set {
    //     return err_option_not_settable
    // }
    // if opt !in opts_bool {
    //     return err_option_wrong_type
    // }
    x := int(value)
    s.set_option_int(C.SOL_SOCKET, int(opt), x)!
}

// set_dualstack enables or disables dual-stack behavior for IPv6 UDP sockets.
pub fn (mut s UdpSocket) set_dualstack(on bool) ! {
    x := int(!on)
    s.set_option_int(C.IPPROTO_IPV6, int(SocketOption.ipv6_only), x)!
}

// close shuts down and closes the socket for communication.
pub fn (mut s UdpSocket) close() ! {
    shutdown(s.handle)
    return close(s.handle)
}

// select waits for no more than `timeout` for the IO operation, defined by `test`, to be available.
pub fn (mut s UdpSocket) select(test Select, timeout time.Duration) !bool {
    return select(s.handle, test, timeout)
}

// remote returns the remote `Addr` address of the socket or `none` if no remote is has been resolved.
pub fn (s &UdpSocket) remote() ?Addr {
    if s.has_r {
        return s.r
    }
    return none
}