Initial Disco support.

Clients get the nice Disco type to use, components will probably just
use the other types to build <iq/> responses.

src/xmpp/disco.go

@@ -0,0 +1,109 @@
+package xmpp
+
+import (
+	"encoding/xml"
+	"strings"
+)
+
+const (
+	nsDiscoInfo  = "http://jabber.org/protocol/disco#info"
+	nsDiscoItems = "http://jabber.org/protocol/disco#items"
+)
+
+// Service Discovery (XEP-0030) protocol. "Wraps" XMPP instance to provide a
+// more convenient API for Disco clients.
+type Disco struct {
+	XMPP *XMPP
+}
+
+// Iq get/result payload for "info" requests.
+type DiscoInfo struct {
+	XMLName  xml.Name        `xml:"http://jabber.org/protocol/disco#info query"`
+	Identity []DiscoIdentity `xml:"identity"`
+	Feature  []DiscoFeature  `xml:"feature"`
+}
+
+// Identity
+type DiscoIdentity struct {
+	Category string `xml:"category,attr"`
+	Type     string `xml:"type,attr"`
+	Name     string `xml:"name,attr"`
+}
+
+// Feature
+type DiscoFeature struct {
+	Var string `xml:"var,attr"`
+}
+
+// Iq get/result payload for "items" requests.
+type DiscoItems struct {
+	XMLName xml.Name    `xml:"http://jabber.org/protocol/disco#items query"`
+	Item    []DiscoItem `xml:"item"`
+}
+
+// Item.
+type DiscoItem struct {
+	JID  string `xml:"jid,attr"`
+	Node string `xml:"node,attr"`
+	Name string `xml:"name,attr"`
+}
+
+// Request information about the service identified by 'to'.
+func (disco *Disco) Info(to string, from string) (*DiscoInfo, error) {
+
+	if from == "" {
+		from = disco.XMPP.JID.Full()
+	}
+
+	req := &Iq{Id: UUID4(), Type: "get", To: to, From: from}
+	req.PayloadEncode(&DiscoInfo{})
+
+	resp, err := disco.XMPP.SendRecv(req)
+	if err != nil {
+		return nil, err
+	} else if resp.Error != nil {
+		return nil, resp.Error
+	}
+
+	info := &DiscoInfo{}
+	resp.PayloadDecode(info)
+
+	return info, err
+}
+
+// Request items in the service identified by 'to'.
+func (disco *Disco) Items(to string, from string) (*DiscoItems, error) {
+
+	if from == "" {
+		from = disco.XMPP.JID.Full()
+	}
+
+	req := &Iq{Id: UUID4(), Type: "get", To: to, From: from}
+	req.PayloadEncode(&DiscoItems{})
+
+	resp, err := disco.XMPP.SendRecv(req)
+	if err != nil {
+		return nil, err
+	} else if resp.Error != nil {
+		return nil, resp.Error
+	}
+
+	items := &DiscoItems{}
+	resp.PayloadDecode(items)
+
+	return items, err
+}
+
+var discoNamespacePrefix = strings.Split(nsDiscoInfo, "#")[0]
+
+// Matcher instance to match <iq/> stanzas with a disco payload.
+var DiscoPayloadMatcher = MatcherFunc(
+	func(v interface{}) bool {
+		iq, ok := v.(*Iq)
+		if !ok {
+			return false
+		}
+		ns := strings.Split(iq.PayloadName().Space, "#")[0]
+		return ns == discoNamespacePrefix
+	},
+)