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

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

// implementation is structured as a stack of layers, with TCP at the

// bottom and the application at the top. The application receives and

// sends structures representing XMPP stanzas. Additional stanza

// parsers can be inserted into the stack of layers as extensions.

package xmpp

import (

	"bytes"

	"crypto/tls"

	"encoding/xml"

	"errors"

	"fmt"

	"io"

	"net"

	"reflect"

	"sync"

)

const (

	// Version of RFC 3920 that we implement.

	XMPPVersion = "1.0"

	// Various XML namespaces.

	NsClient  = "jabber:client"

	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"

)

// Flow control for preventing sending stanzas until negotiation has

// completed.

type sendCmd bool

var (

	sendAllow sendCmd = true

	sendDeny  sendCmd = false

)

// A filter can modify the XMPP traffic to or from the remote

// server. It's part of an Extension. The filter function will be

// called in a new goroutine, so it doesn't need to return. The filter

// should close its output when its input is closed.

type Filter func(in <-chan Stanza, out chan<- Stanza)

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

type Extension struct {

	// Maps from an XML namespace to a function which constructs a

	// structure to hold the contents of stanzas in that

	// namespace.

	StanzaHandlers map[xml.Name]reflect.Type

	// If non-nil, will be called once to start the filter

	// running. RecvFilter intercepts incoming messages on their

	// way from the remote server to the application; SendFilter

	// intercepts messages going the other direction.

	RecvFilter Filter

	SendFilter Filter

}

// 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

	handlers     chan *callback

	inputControl chan sendCmd

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

	// this channel. Information which is used by this library to

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

	Recv <-chan Stanza

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

	// channel.

	Send    chan<- Stanza

	sendXml chan<- interface{}

	// The client's roster is also known as the buddy list. It's

	// the set of contacts which are known to this JID, or which

	// this JID is known to.

	Roster Roster

	// 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

	sendFilterAdd, recvFilterAdd chan Filter

	// Allows the user to override the TLS configuration.

	tlsConfig tls.Config

}

// 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.Send will block until negotiation

// (resource binding) is complete. The caller must immediately start

// reading from Client.Recv.

func NewClient(jid *JID, password string, tlsconf tls.Config, exts []Extension) (*Client, error) {

	// Include the mandatory extensions.

	roster := newRosterExt()

	exts = append(exts, roster.Extension)

	exts = append(exts, bindExt)

	// Resolve the domain in the JID.

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

	if err != nil {

		return nil, fmt.Errorf("LookupSrv %s: %v", jid.Domain, err)

	}

	if len(srvs) == 0 {

		return nil, fmt.Errorf("LookupSrv %s: no results", jid.Domain)

	}

	var tcp *net.TCPConn

	for _, srv := range srvs {

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

		var addr *net.TCPAddr

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

		if err != nil {

			err = fmt.Errorf("ResolveTCPAddr(%s): %s",

				addrStr, err.Error())

			continue

		}

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

		if tcp != nil {

			break

		}

	}

	if tcp == nil {

		return nil, err

	}

	cl := new(Client)

	cl.Roster = *roster

	cl.password = password

	cl.Jid = *jid

	cl.socket = tcp

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

	cl.inputControl = make(chan sendCmd)

	cl.tlsConfig = tlsconf

	cl.sendFilterAdd = make(chan Filter)

	cl.recvFilterAdd = make(chan Filter)

	extStanza := make(map[xml.Name]reflect.Type)

	for _, ext := range exts {

		for k, v := range ext.StanzaHandlers {

			if _, ok := extStanza[k]; ok {

				return nil, fmt.Errorf("duplicate handler %s",

					k)

			}

			extStanza[k] = v

		}

	}

	// Start the transport handler, initially unencrypted.

	recvReader, recvWriter := io.Pipe()

	sendReader, sendWriter := io.Pipe()

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

	// Start the reader and writer that convert between XML and

	// XMPP stanzas.

	recvRawXmpp := make(chan Stanza)

	sendRawXmpp := make(chan Stanza)

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

	// app sees.

	recvFiltXmpp := make(chan Stanza)

	cl.Recv = recvFiltXmpp

	go filterMgr(cl.recvFilterAdd, recvRawXmpp, recvFiltXmpp)

	sendFiltXmpp := make(chan Stanza)

	cl.Send = sendFiltXmpp

	go filterMgr(cl.sendFilterAdd, sendFiltXmpp, sendRawXmpp)

	// Set up the initial filters.

	for _, ext := range exts {

		cl.AddRecvFilter(ext.RecvFilter)

		cl.AddSendFilter(ext.SendFilter)

	}

	// Initial handshake.

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

	cl.sendXml <- hsOut

	return cl, nil

}

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] == '>' {

			Debug.Log(buf)

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

		}

	}

	leftover := buf.String()

	if leftover != "" {

		Debug.Log(buf)

	}

}

// 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 <- sendAllow

}

// Start an XMPP session. A typical XMPP client should call this

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

// and broadcast an initial presence. The presence can be as simple as

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

// 3. After calling this, a normal client should call Roster.Update().

func (cl *Client) StartSession(pr *Presence) error {

	id := NextId()

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

		Nested: []interface{}{Generic{XMLName: xml.Name{Space: NsSession, Local: "session"}}}}}

	ch := make(chan error)

	f := func(st Stanza) bool {

		iq, ok := st.(*Iq)

		if !ok {

			Warn.Log("iq reply not iq; can't start session")

			ch <- errors.New("bad session start reply")

			return false

		}

		if iq.Type == "error" {

			Warn.Logf("Can't start session: %v", iq)

			ch <- iq.Error

			return false

		}

		ch <- nil

		return false

	}

	cl.SetCallback(id, f)

	cl.Send <- iq

	// Now wait until the callback is called.

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

		return err

	}

	if pr != nil {

		cl.Send <- pr

	}

	return nil

}