// 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/. 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"

	"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"

)

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

}

// Allows the user to override the TLS configuration.

var TlsConfig tls.Config

// 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 remote will be published on

	// this channel. Information which is 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

}

// 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, error) {

	// Include the mandatory extensions.

	exts = append(exts, bindExt)

	// Resolve the domain in the JID.

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

	if err != nil {

		return nil, errors.New("LookupSrv " + jid.Domain +

			": " + err.Error())

	}

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

				addrStr, err.Error())

			continue

		}

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

		if err == nil {

			break

		}

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

	}

	if tcp == nil {

		return nil, err

	}

	cl := new(Client)

	cl.Uid = NextId()

	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.

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

	// app sees.

	// Initial handshake.

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

	cl.xmlOut <- 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 <- 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

	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.HandleStanza(id, f)

	cl.Out <- iq

	// Now wait until the callback is called.

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

		return err

	}

	if pr != nil {

		cl.Out <- pr

	}

	return nil

}