// Copyright 2011 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.

// This package implements a simple XMPP client according to RFCs 3920

// and 3921, plus the various XEPs at http://xmpp.org/protocols/.

package xmpp

// BUG(cjyar) Figure out why the library doesn't exit when the server

// closes its stream to us.

import (

	"bytes"

	"fmt"

	"io"

	"log"

	"net"

	"os"

	"sync"

	"xml"

)

const (

	// Version of RFC 3920 that we implement.

	Version = "1.0"

	// Various XML namespaces.

	nsStreams = "urn:ietf:params:xml:ns:xmpp-streams"

	nsStream = "http://etherx.jabber.org/streams"

	nsTLS = "urn:ietf:params:xml:ns:xmpp-tls"

	nsSASL = "urn:ietf:params:xml:ns:xmpp-sasl"

	nsBind = "urn:ietf:params:xml:ns:xmpp-bind"

	nsSession = "urn:ietf:params:xml:ns:xmpp-session"

	// DNS SRV names

	serverSrv = "xmpp-server"

	clientSrv = "xmpp-client"

	// BUG(cjyar) Make this a parameter to NewClient, not a

	// constant. We should have both a log level and a

	// syslog.Writer, so the app can control how much time we

	// spend generating log messages, as well as where they go.

	debug = true

)

// The client in a client-server XMPP connection.

type Client struct {

	// This client's JID. This will be updated asynchronously by

	// the time StartSession() returns.

	Jid JID

	password string

	socket net.Conn

	socketSync sync.WaitGroup

	saslExpected string

	authDone bool

	idMutex sync.Mutex

	nextId int64

	handlers chan *stanzaHandler

	inputControl chan int

	// This channel may be used as a convenient way to generate a

	// unique id for an iq, message, or presence stanza.

	Id <-chan string

	// Incoming XMPP stanzas from the server will be published on

	// this channel. Information which is only used by this

	// library to set up the XMPP stream will not appear here.

	In <-chan Stanza

	// Outgoing XMPP stanzas to the server should be sent to this

	// channel.

	Out chan<- Stanza

	xmlOut chan<- interface{}

}

var _ io.Closer = &Client{}

// Connect to the appropriate server and authenticate as the given JID

// with the given password. This function will return as soon as a TCP

// connection has been established, but before XMPP stream negotiation

// has completed. The negotiation will occur asynchronously, and any

// send operation to Client.Out will block until negotiation (resource

// binding) is complete.

func NewClient(jid *JID, password string) (*Client, os.Error) {

	// Resolve the domain in the JID.

	_, srvs, err := net.LookupSRV(clientSrv, "tcp", jid.Domain)

	if err != nil {

		return nil, os.NewError("LookupSrv " + jid.Domain +

			": " + err.String())

	}

	var tcp *net.TCPConn

	for _, srv := range srvs {

		addrStr := fmt.Sprintf("%s:%d", srv.Target, srv.Port)

		addr, err := net.ResolveTCPAddr("tcp", addrStr)

		if err != nil {

			err = os.NewError(fmt.Sprintf("ResolveTCPAddr(%s): %s",

				addrStr, err.String()))

			continue

		}

		tcp, err = net.DialTCP("tcp", nil, addr)

		if err != nil {

			err = os.NewError(fmt.Sprintf("DialTCP(%s): %s",

				addr, err.String()))

			continue

		}

	}

	if tcp == nil {

		return nil, err

	}

	cl := new(Client)

	cl.password = password

	cl.Jid = *jid

	cl.socket = tcp

	cl.handlers = make(chan *stanzaHandler, 1)

	cl.inputControl = make(chan int)

	idCh := make(chan string)

	cl.Id = idCh

	// Start the unique id generator.

	go makeIds(idCh)

	// Start the transport handler, initially unencrypted.

	tlsr, tlsw := cl.startTransport()

	// Start the reader and writers that convert to and from XML.

	xmlIn := startXmlReader(tlsr)

	cl.xmlOut = startXmlWriter(tlsw)

	// Start the XMPP stream handler which filters stream-level

	// events and responds to them.

	clIn := cl.startStreamReader(xmlIn, cl.xmlOut)

	clOut := cl.startStreamWriter(cl.xmlOut)

	// Initial handshake.

	hsOut := &stream{To: jid.Domain, Version: Version}

	cl.xmlOut <- hsOut

	cl.In = clIn

	cl.Out = clOut

	return cl, nil

}

func (c *Client) Close() os.Error {

	tryClose(c.In, c.Out)

	return nil

}

func (cl *Client) startTransport() (io.Reader, io.Writer) {

	inr, inw := io.Pipe()

	outr, outw := io.Pipe()

	go cl.readTransport(inw)

	go cl.writeTransport(outr)

	return inr, outw

}

func startXmlReader(r io.Reader) <-chan interface{} {

	ch := make(chan interface{})

	go readXml(r, ch)

	return ch

}

func startXmlWriter(w io.Writer) chan<- interface{} {

	ch := make(chan interface{})

	go writeXml(w, ch)

	return ch

}

func (cl *Client) startStreamReader(xmlIn <-chan interface{}, srvOut chan<- interface{}) <-chan Stanza {

	ch := make(chan Stanza)

	go cl.readStream(xmlIn, ch)

	return ch

}

func (cl *Client) startStreamWriter(xmlOut chan<- interface{}) chan<- Stanza {

	ch := make(chan Stanza)

	go writeStream(xmlOut, ch, cl.inputControl)

	return ch

}

func tee(r io.Reader, w io.Writer, prefix string) {

	defer tryClose(r, w)

	buf := bytes.NewBuffer(nil)

	for {

		var c [1]byte

		n, _ := r.Read(c[:])

		if n == 0 {

			break

		}

		n, _ = w.Write(c[:n])

		if n == 0 {

			break

		}

		buf.Write(c[:n])

		if c[0] == '\n' || c[0] == '>' {

			fmt.Printf("%s%s\n", prefix, buf.String())

			buf.Reset()

		}

	}

	leftover := buf.String()

	if leftover != "" {

		fmt.Printf("%s%s\n", prefix, leftover)

	}

}

func tryClose(xs ...interface{}) {

	f1 := func(ch chan<- interface{}) {

		defer func() {

			recover()

		}()

		close(ch)

	}

	f2 := func(ch <-chan interface{}) {

		defer func() {

			recover()

		}()

		close(ch)

	}

	for _, x := range xs {

		if c, ok := x.(io.Closer) ; ok {

			c.Close()

		} else if ch, ok := x.(chan<- interface{}) ; ok {

			f1(ch)

		} else if ch, ok := x.(<-chan interface{}) ; ok {

			f2(ch)

		}

	}

}

func makeIds(ch chan<- string) {

	id := int64(1)

	for {

		str := fmt.Sprintf("id_%d", id)

		ch <- str

		id++

	}

}

// bindDone is called when we've finished resource binding (and all

// the negotiations that precede it). Now we can start accepting

// traffic from the app.

func (cl *Client) bindDone() {

	cl.inputControl <- 1

}

// Start an XMPP session. This should typically be done immediately

// after creating the new Client. Once the session has been

// established, pr will be sent as an initial presence; nil means

// don't send initial presence. The initial presence can be a

// newly-initialized Presence struct. See RFC 3921, Section 3.

func (cl *Client) StartSession(pr *Presence) os.Error {

	id := <- cl.Id

	iq := &Iq{To: cl.Jid.Domain, Id: id, Type: "set", Any:

		&Generic{XMLName: xml.Name{Space: nsSession, Local:

				"session"}}}

	ch := make(chan os.Error)

	f := func(st Stanza) bool {

		if st.XType() == "error" {

			log.Printf("Can't start session: %v", st)

			ch <- st.XError()

			return false

		}

		if pr != nil {

			cl.Out <- pr

		}

		ch <- nil

		return false

	}

	cl.HandleStanza(id, f)

	cl.Out <- iq

	// Now wait until the callback is called.

	return <-ch

}