Refactor and move parsing and stanza to a separate package

stanza/presence.go

@@ -0,0 +1,139 @@
+package stanza
+
+import (
+	"encoding/xml"
+	"reflect"
+)
+
+// ============================================================================
+// Presence Packet
+
+// Presence implements RFC 6120 - A.5 Client Namespace (a part)
+type Presence struct {
+	XMLName xml.Name `xml:"presence"`
+	Attrs
+	Show       PresenceShow    `xml:"show,omitempty"`
+	Status     string          `xml:"status,omitempty"`
+	Priority   int8            `xml:"priority,omitempty"` // default: 0
+	Error      Err             `xml:"error,omitempty"`
+	Extensions []PresExtension `xml:",omitempty"`
+}
+
+func (Presence) Name() string {
+	return "presence"
+}
+
+func NewPresence(a Attrs) Presence {
+	return Presence{
+		XMLName: xml.Name{Local: "presence"},
+		Attrs:   a,
+	}
+}
+
+// Get search and extracts a specific extension on a presence stanza.
+// It receives a pointer to an PresExtension. It will panic if the caller
+// does not pass a pointer.
+// It will return true if the passed extension is found and set the pointer
+// to the extension passed as parameter to the found extension.
+// It will return false if the extension is not found on the presence.
+//
+// Example usage:
+//   var muc xmpp.MucPresence
+//   if ok := msg.Get(&muc); ok {
+//     // muc presence extension has been found
+//	 }
+func (pres *Presence) Get(ext PresExtension) bool {
+	target := reflect.ValueOf(ext)
+	if target.Kind() != reflect.Ptr {
+		panic("you must pass a pointer to the message Get method")
+	}
+
+	for _, e := range pres.Extensions {
+		if reflect.TypeOf(e) == target.Type() {
+			source := reflect.ValueOf(e)
+			if source.Kind() != reflect.Ptr {
+				source = source.Elem()
+			}
+			target.Elem().Set(source.Elem())
+			return true
+		}
+	}
+	return false
+}
+
+type presenceDecoder struct{}
+
+var presence presenceDecoder
+
+func (presenceDecoder) decode(p *xml.Decoder, se xml.StartElement) (Presence, error) {
+	var packet Presence
+	err := p.DecodeElement(&packet, &se)
+	// TODO Add default presence type (when omitted)
+	return packet, err
+}
+
+// UnmarshalXML implements custom parsing for presence stanza
+func (pres *Presence) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	pres.XMLName = start.Name
+
+	// Extract packet attributes
+	for _, attr := range start.Attr {
+		if attr.Name.Local == "id" {
+			pres.Id = attr.Value
+		}
+		if attr.Name.Local == "type" {
+			pres.Type = StanzaType(attr.Value)
+		}
+		if attr.Name.Local == "to" {
+			pres.To = attr.Value
+		}
+		if attr.Name.Local == "from" {
+			pres.From = attr.Value
+		}
+		if attr.Name.Local == "lang" {
+			pres.Lang = attr.Value
+		}
+	}
+
+	// decode inner elements
+	for {
+		t, err := d.Token()
+		if err != nil {
+			return err
+		}
+
+		switch tt := t.(type) {
+
+		case xml.StartElement:
+			if presExt := TypeRegistry.GetPresExtension(tt.Name); presExt != nil {
+				// Decode message extension
+				err = d.DecodeElement(presExt, &tt)
+				if err != nil {
+					return err
+				}
+				pres.Extensions = append(pres.Extensions, presExt)
+			} else {
+				// Decode standard message sub-elements
+				var err error
+				switch tt.Name.Local {
+				case "show":
+					err = d.DecodeElement(&pres.Show, &tt)
+				case "status":
+					err = d.DecodeElement(&pres.Status, &tt)
+				case "priority":
+					err = d.DecodeElement(&pres.Priority, &tt)
+				case "error":
+					err = d.DecodeElement(&pres.Error, &tt)
+				}
+				if err != nil {
+					return err
+				}
+			}
+
+		case xml.EndElement:
+			if tt == start.End() {
+				return nil
+			}
+		}
+	}
+}