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// Copyright 2010 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package net

import (
        "time"
)

func parseDialNetwork(net string) (afnet string, proto int, err error) {
        i := last(net, ':')
        if i < 0 { // no colon
                switch net {
                case "tcp", "tcp4", "tcp6":
                case "udp", "udp4", "udp6":
                case "unix", "unixgram", "unixpacket":
                default:
                        return "", 0, UnknownNetworkError(net)
                }
                return net, 0, nil
        }
        afnet = net[:i]
        switch afnet {
        case "ip", "ip4", "ip6":
                protostr := net[i+1:]
                proto, i, ok := dtoi(protostr, 0)
                if !ok || i != len(protostr) {
                        proto, err = lookupProtocol(protostr)
                        if err != nil {
                                return "", 0, err
                        }
                }
                return afnet, proto, nil
        }
        return "", 0, UnknownNetworkError(net)
}

func resolveNetAddr(op, net, addr string) (afnet string, a Addr, err error) {
        afnet, _, err = parseDialNetwork(net)
        if err != nil {
                return "", nil, &OpError{op, net, nil, err}
        }
        if op == "dial" && addr == "" {
                return "", nil, &OpError{op, net, nil, errMissingAddress}
        }
        switch afnet {
        case "tcp", "tcp4", "tcp6":
                if addr != "" {
                        a, err = ResolveTCPAddr(afnet, addr)
                }
        case "udp", "udp4", "udp6":
                if addr != "" {
                        a, err = ResolveUDPAddr(afnet, addr)
                }
        case "ip", "ip4", "ip6":
                if addr != "" {
                        a, err = ResolveIPAddr(afnet, addr)
                }
        case "unix", "unixgram", "unixpacket":
                if addr != "" {
                        a, err = ResolveUnixAddr(afnet, addr)
                }
        }
        return
}

// Dial connects to the address addr on the network net.
//
// Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only),
// "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4"
// (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and "unixpacket".
//
// For TCP and UDP networks, addresses have the form host:port.
// If host is a literal IPv6 address, it must be enclosed
// in square brackets.  The functions JoinHostPort and SplitHostPort
// manipulate addresses in this form.
//
// Examples:
//      Dial("tcp", "12.34.56.78:80")
//      Dial("tcp", "google.com:80")
//      Dial("tcp", "[de:ad:be:ef::ca:fe]:80")
//
// For IP networks, addr must be "ip", "ip4" or "ip6" followed
// by a colon and a protocol number or name.
//
// Examples:
//      Dial("ip4:1", "127.0.0.1")
//      Dial("ip6:ospf", "::1")
//
func Dial(net, addr string) (Conn, error) {
        _, addri, err := resolveNetAddr("dial", net, addr)
        if err != nil {
                return nil, err
        }
        return dialAddr(net, addr, addri)
}

func dialAddr(net, addr string, addri Addr) (c Conn, err error) {
        switch ra := addri.(type) {
        case *TCPAddr:
                c, err = DialTCP(net, nil, ra)
        case *UDPAddr:
                c, err = DialUDP(net, nil, ra)
        case *IPAddr:
                c, err = DialIP(net, nil, ra)
        case *UnixAddr:
                c, err = DialUnix(net, nil, ra)
        default:
                err = &OpError{"dial", net + " " + addr, nil, UnknownNetworkError(net)}
        }
        if err != nil {
                return nil, err
        }
        return
}

// DialTimeout acts like Dial but takes a timeout.
// The timeout includes name resolution, if required.
func DialTimeout(net, addr string, timeout time.Duration) (Conn, error) {
        // TODO(bradfitz): the timeout should be pushed down into the
        // net package's event loop, so on timeout to dead hosts we
        // don't have a goroutine sticking around for the default of
        // ~3 minutes.
        t := time.NewTimer(timeout)
        defer t.Stop()
        type pair struct {
                Conn
                error
        }
        ch := make(chan pair, 1)
        resolvedAddr := make(chan Addr, 1)
        go func() {
                _, addri, err := resolveNetAddr("dial", net, addr)
                if err != nil {
                        ch <- pair{nil, err}
                        return
                }
                resolvedAddr <- addri // in case we need it for OpError
                c, err := dialAddr(net, addr, addri)
                ch <- pair{c, err}
        }()
        select {
        case <-t.C:
                // Try to use the real Addr in our OpError, if we resolved it
                // before the timeout. Otherwise we just use stringAddr.
                var addri Addr
                select {
                case a := <-resolvedAddr:
                        addri = a
                default:
                        addri = &stringAddr{net, addr}
                }
                err := &OpError{
                        Op:   "dial",
                        Net:  net,
                        Addr: addri,
                        Err:  &timeoutError{},
                }
                return nil, err
        case p := <-ch:
                return p.Conn, p.error
        }
        panic("unreachable")
}

type stringAddr struct {
        net, addr string
}

func (a stringAddr) Network() string { return a.net }
func (a stringAddr) String() string  { return a.addr }

// Listen announces on the local network address laddr.
// The network string net must be a stream-oriented network:
// "tcp", "tcp4", "tcp6", or "unix", or "unixpacket".
func Listen(net, laddr string) (Listener, error) {
        afnet, a, err := resolveNetAddr("listen", net, laddr)
        if err != nil {
                return nil, err
        }
        switch afnet {
        case "tcp", "tcp4", "tcp6":
                var la *TCPAddr
                if a != nil {
                        la = a.(*TCPAddr)
                }
                return ListenTCP(afnet, la)
        case "unix", "unixpacket":
                var la *UnixAddr
                if a != nil {
                        la = a.(*UnixAddr)
                }
                return ListenUnix(net, la)
        }
        return nil, UnknownNetworkError(net)
}

// ListenPacket announces on the local network address laddr.
// The network string net must be a packet-oriented network:
// "udp", "udp4", "udp6", "ip", "ip4", "ip6" or "unixgram".
func ListenPacket(net, addr string) (PacketConn, error) {
        afnet, a, err := resolveNetAddr("listen", net, addr)
        if err != nil {
                return nil, err
        }
        switch afnet {
        case "udp", "udp4", "udp6":
                var la *UDPAddr
                if a != nil {
                        la = a.(*UDPAddr)
                }
                return ListenUDP(net, la)
        case "ip", "ip4", "ip6":
                var la *IPAddr
                if a != nil {
                        la = a.(*IPAddr)
                }
                return ListenIP(net, la)
        case "unixgram":
                var la *UnixAddr
                if a != nil {
                        la = a.(*UnixAddr)
                }
                return DialUnix(net, la, nil)
        }
        return nil, UnknownNetworkError(net)
}