// 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

import (

	"bytes"

	"fmt"

	"io"

	"net"

	"os"

	"sync"

	"syslog"

	"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"

	NsRoster  = "jabber:iq:roster"

	// DNS SRV names

	serverSrv = "xmpp-server"

	clientSrv = "xmpp-client"

)

var (

	// If non-nil when NewClient() is called, log messages will be

	// sent to this writer.

	Log *syslog.Writer

	// Threshold for which messages are logged.

	Loglevel syslog.Priority = syslog.LOG_NOTICE

)

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

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

var Id <-chan string

func init() {

	// Start the unique id generator.

	idCh := make(chan string)

	Id = idCh

	go func(ch chan<- string) {

		id := int64(1)

		for {

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

			ch <- str

			id++

		}

	}(idCh)

}

// Extensions can add stanza filters and/or new XML element types.

type Extension struct {

	StanzaHandlers map[string]func(*xml.Name) interface{}

	Start          func(*Client)

}

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

type Client struct {

	// This client's unique ID. It's unique within the context of

	// this process, so if multiple Client objects exist, each

	// will be distinguishable by its Uid.

	Uid string

	// 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

	handlers     chan *stanzaHandler

	inputControl chan int

	// 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{}

	// Features advertised by the remote. This will be updated

	// asynchronously as new features are received throughout the

	// connection process. It should not be updated once

	// StartSession() returns.

	Features  *Features

	filterOut chan<- <-chan Stanza

	filterIn  <-chan <-chan Stanza

}

// 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, exts []Extension) (*Client,

os.Error) {

	// Include the mandatory extensions.

	exts = append(exts, rosterExt)

	exts = append(exts, bindExt)

	// 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.Uid = <-Id

	cl.password = password

	cl.Jid = *jid

	cl.socket = tcp

	cl.handlers = make(chan *stanzaHandler, 100)

	cl.inputControl = make(chan int)

	extStanza := make(map[string]func(*xml.Name) interface{})

	for _, ext := range exts {

		for k, v := range ext.StanzaHandlers {

			extStanza[k] = v

		}

	}

	// Start the transport handler, initially unencrypted.

	tlsr, tlsw := cl.startTransport()

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

	xmlIn := startXmlReader(tlsr, extStanza)

	cl.xmlOut = startXmlWriter(tlsw)

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

	// events and responds to them.

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

	clOut := cl.startStreamWriter(cl.xmlOut)

	cl.Out = clOut

	// Start the manager for the filters that can modify what the

	// app sees.

	clIn := cl.startFilter(stIn)

	cl.In = clIn

	// Add filters for our extensions.

	for _, ext := range exts {

		ext.Start(cl)

	}

	// Initial handshake.

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

	cl.xmlOut <- hsOut

	return cl, nil

}

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

	inr, inw := io.Pipe()

	outr, outw := io.Pipe()

	go cl.readTransport(inw)

	go cl.writeTransport(outr)

	return inr, outw

}

func startXmlReader(r io.Reader,

extStanza map[string]func(*xml.Name) interface{}) <-chan interface{} {

	ch := make(chan interface{})

	go readXml(r, ch, extStanza)

	return ch

}

func startXmlWriter(w io.WriteCloser) 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 (cl *Client) startFilter(srvIn <-chan Stanza) <-chan Stanza {

	cliIn := make(chan Stanza)

	filterOut := make(chan (<-chan Stanza))

	filterIn := make(chan (<-chan Stanza))

	nullFilter := make(chan Stanza)

	go filterBottom(srvIn, nullFilter)

	go filterTop(filterOut, filterIn, nullFilter, cliIn)

	cl.filterOut = filterOut

	cl.filterIn = filterIn

	return cliIn

}

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

	defer func(w io.Writer) {

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

			c.Close()

		}

	}(w)

	buf := bytes.NewBuffer([]uint8(prefix))

	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] == '>' {

			Log.Debug(buf.String())

			buf.Reset()

		}

	}

	leftover := buf.String()

	if leftover != "" {

		Log.Debug(buf.String())

	}

}

// 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. A typical XMPP client should call this

// immediately after creating the Client in order to start the

// session, retrieve the roster, and broadcast an initial

// presence. The presence can be as simple as a newly-initialized

// Presence struct.  See RFC 3921, Section 3.

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

	id := <-Id

	iq := &Iq{To: cl.Jid.Domain, Id: id, Type: "set", Nested: []interface{}{Generic{XMLName: xml.Name{Space: NsSession, Local: "session"}}}}

	ch := make(chan os.Error)

	f := func(st Stanza) bool {

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

			if Log != nil {

				Log.Err(fmt.Sprintf("Can't start session: %v",

					st))

			}

			ch <- st.GetError()

			return false

		}

		ch <- nil

		return false

	}

	cl.HandleStanza(id, f)

	cl.Out <- iq

	// Now wait until the callback is called.

	if err := <-ch; err != nil {

		return err

	}

	if getRoster {

		err := fetchRoster(cl)

		if err != nil {

			return err

		}

	}

	if pr != nil {

		cl.Out <- pr

	}

	return nil

}

// AddFilter adds a new filter to the top of the stack through which

// incoming stanzas travel on their way up to the client. The new

// filter's output channel is given to this function, and it returns a

// new input channel which the filter should read from. When its input

// channel closes, the filter should close its output channel.

func (cl *Client) AddFilter(out <-chan Stanza) <-chan Stanza {

	cl.filterOut <- out

	return <-cl.filterIn

}