// 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 file contains the three layers of processing for the

// communication with the server: transport (where TLS happens), XML

// (where strings are converted to go structures), and Stream (where

// we respond to XMPP events on behalf of the library client), or send

// those events to the client.

package xmpp

import (

	"crypto/md5"

	"crypto/rand"

	"crypto/tls"

	"encoding/base64"

	"encoding/xml"

	"fmt"

	"io"

	"math/big"

	"net"

	"reflect"

	"regexp"

	"strings"

	"time"

)

// Callback to handle a stanza with a particular id.

type stanzaHandler struct {

	id string

	// Return true means pass this to the application

	f func(Stanza) bool

}

func (cl *Client) readTransport(w io.WriteCloser) {

	defer w.Close()

	p := make([]byte, 1024)

	for {

		if cl.socket == nil {

			cl.waitForSocket()

		}

		cl.socket.SetReadDeadline(time.Now().Add(time.Second))

		nr, err := cl.socket.Read(p)

		if nr == 0 {

			if errno, ok := err.(*net.OpError); ok {

				if errno.Timeout() {

					continue

				}

			}

			Warn.Logf("read: %s", err)

			break

		}

		nw, err := w.Write(p[:nr])

		if nw < nr {

			Warn.Logf("read: %s", err)

			break

		}

	}

}

func (cl *Client) writeTransport(r io.Reader) {

	defer cl.socket.Close()

	p := make([]byte, 1024)

	for {

		nr, err := r.Read(p)

		if nr == 0 {

			Warn.Logf("write: %s", err)

			break

		}

		nw, err := cl.socket.Write(p[:nr])

		if nw < nr {

			Warn.Logf("write: %s", err)

			break

		}

	}

}

func readXml(r io.Reader, ch chan<- interface{},

	extStanza map[xml.Name]reflect.Type) {

	if _, ok := Debug.(*noLog); !ok {

		pr, pw := io.Pipe()

		go tee(r, pw, "S: ")

		r = pr

	}

	defer close(ch)

	// This trick loads our namespaces into the parser.

	nsstr := fmt.Sprintf(`<a xmlns="%s" xmlns:stream="%s">`,

		NsClient, NsStream)

	nsrdr := strings.NewReader(nsstr)

	p := xml.NewDecoder(io.MultiReader(nsrdr, r))

	p.Token()

Loop:

	for {

		// Sniff the next token on the stream.

		t, err := p.Token()

		if t == nil {

			if err != io.EOF {

				Warn.Logf("read: %s", err)

			}

			break

		}

		var se xml.StartElement

		var ok bool

		if se, ok = t.(xml.StartElement); !ok {

			continue

		}

		// Allocate the appropriate structure for this token.

		var obj interface{}

		switch se.Name.Space + " " + se.Name.Local {

		case NsStream + " stream":

			st, err := parseStream(se)

			if err != nil {

				Warn.Logf("unmarshal stream: %s", err)

				break Loop

			}

			ch <- st

			continue

		case "stream error", NsStream + " error":

			obj = &streamError{}

		case NsStream + " features":

			obj = &Features{}

		case NsTLS + " proceed", NsTLS + " failure":

			obj = &starttls{}

		case NsSASL + " challenge", NsSASL + " failure",

			NsSASL + " success":

			obj = &auth{}

		case NsClient + " iq":

			obj = &Iq{}

		case NsClient + " message":

			obj = &Message{}

		case NsClient + " presence":

			obj = &Presence{}

		default:

			obj = &Generic{}

			Info.Logf("Ignoring unrecognized: %s %s", se.Name.Space,

				se.Name.Local)

		}

		// Read the complete XML stanza.

		err = p.DecodeElement(obj, &se)

		if err != nil {

			Warn.Logf("unmarshal: %s", err)

			break Loop

		}

		// If it's a Stanza, we try to unmarshal its innerxml

		// into objects of the appropriate respective

		// types. This is specified by our extensions.

		if st, ok := obj.(Stanza); ok {

			err = parseExtended(st.GetHeader(), extStanza)

			if err != nil {

				Warn.Logf("ext unmarshal: %s", err)

				break Loop

			}

		}

		// Put it on the channel.

		ch <- obj

	}

}

func parseExtended(st *Header, extStanza map[xml.Name]reflect.Type) error {

	// Now parse the stanza's innerxml to find the string that we

	// can unmarshal this nested element from.

	reader := strings.NewReader(st.Innerxml)

	p := xml.NewDecoder(reader)

	for {

		t, err := p.Token()

		if err == io.EOF {

			break

		}

		if err != nil {

			return err

		}

		if se, ok := t.(xml.StartElement); ok {

			if typ, ok := extStanza[se.Name]; ok {

				nested := reflect.New(typ).Interface()

				// Unmarshal the nested element and

				// stuff it back into the stanza.

				err := p.DecodeElement(nested, &se)

				if err != nil {

					return err

				}

				st.Nested = append(st.Nested, nested)

			}

		}

	}

	return nil

}

func writeXml(w io.Writer, ch <-chan interface{}) {

	if _, ok := Debug.(*noLog); !ok {

		pr, pw := io.Pipe()

		go tee(pr, w, "C: ")

		w = pw

	}

	defer func(w io.Writer) {

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

			c.Close()

		}

	}(w)

	enc := xml.NewEncoder(w)

	for obj := range ch {

		if st, ok := obj.(*stream); ok {

			_, err := w.Write([]byte(st.String()))

			if err != nil {

				Warn.Logf("write: %s", err)

			}

		} else {

			err := enc.Encode(obj)

			if err != nil {

				Warn.Logf("marshal: %s", err)

				break

			}

		}

	}

}

func (cl *Client) readStream(srvIn <-chan interface{}, cliOut chan<- Stanza) {

	defer close(cliOut)

	handlers := make(map[string]func(Stanza) bool)

Loop:

	for {

		select {

		case h := <-cl.handlers:

			handlers[h.id] = h.f

		case x, ok := <-srvIn:

			if !ok {

				break Loop

			}

			switch obj := x.(type) {

			case *stream:

				handleStream(obj)

			case *streamError:

				cl.handleStreamError(obj)

			case *Features:

				cl.handleFeatures(obj)

			case *starttls:

				cl.handleTls(obj)

			case *auth:

				cl.handleSasl(obj)

			case Stanza:

				send := true

				id := obj.GetHeader().Id

				if handlers[id] != nil {

					f := handlers[id]

					delete(handlers, id)

					send = f(obj)

				}

				if send {

					cliOut <- obj

				}

			default:

				Warn.Logf("Unhandled non-stanza: %T %#v", x, x)

			}

		}

	}

}

// This loop is paused until resource binding is complete. Otherwise

// the app might inject something inappropriate into our negotiations

// with the server. The control channel controls this loop's

// activity.

func writeStream(srvOut chan<- interface{}, cliIn <-chan Stanza,

	control <-chan int) {

	defer close(srvOut)

	var input <-chan Stanza

Loop:

	for {

		select {

		case status := <-control:

			switch status {

			case 0:

				input = nil

			case 1:

				input = cliIn

			case -1:

				break Loop

			}

		case x, ok := <-input:

			if !ok {

				break Loop

			}

			if x == nil {

				Info.Log("Refusing to send nil stanza")

				continue

			}

			srvOut <- x

		}

	}

}

func handleStream(ss *stream) {

}

func (cl *Client) handleStreamError(se *streamError) {

	Info.Logf("Received stream error: %v", se)

}

func (cl *Client) handleFeatures(fe *Features) {

	cl.Features = fe

	if fe.Starttls != nil {

		start := &starttls{XMLName: xml.Name{Space: NsTLS,

			Local: "starttls"}}

		cl.sendXml <- start

		return

	}

	if len(fe.Mechanisms.Mechanism) > 0 {

		cl.chooseSasl(fe)

		return

	}

	if fe.Bind != nil {

		cl.bind(fe.Bind)

		return

	}

}

// readTransport() is running concurrently. We need to stop it,

// negotiate TLS, then start it again. It calls waitForSocket() in

// its inner loop; see below.

func (cl *Client) handleTls(t *starttls) {

	tcp := cl.socket

	// Set the socket to nil, and wait for the reader routine to

	// signal that it's paused.

	cl.socket = nil

	cl.socketSync.Add(1)

	cl.socketSync.Wait()

	// Negotiate TLS with the server.

	tls := tls.Client(tcp, &cl.tlsConfig)

	// Make the TLS connection available to the reader, and wait

	// for it to signal that it's working again.

	cl.socketSync.Add(1)

	cl.socket = tls

	cl.socketSync.Wait()

	Info.Log("TLS negotiation succeeded.")

	cl.Features = nil