Use NullableInt to encode presence history values

pres_muc.go

@@ -2,6 +2,7 @@ package xmpp
 
 import (
 	"encoding/xml"
+	"strconv"
 	"time"
 )
 
@@ -16,12 +17,130 @@ type MucPresence struct {
 	History  History  `xml:"history,omitempty"`
 }
 
+const timeLayout = "2006-01-02T15:04:05Z"
+
 // History implements XEP-0045: Multi-User Chat - 19.1
 type History struct {
-	MaxChars   *int       `xml:"maxchars,attr,omitempty"`
-	MaxStanzas *int       `xml:"maxstanzas,attr,omitempty"`
-	Seconds    *int       `xml:"seconds,attr,omitempty"`
-	Since      *time.Time `xml:"since,attr,omitempty"`
+	XMLName    xml.Name
+	MaxChars   NullableInt `xml:"maxchars,attr,omitempty"`
+	MaxStanzas NullableInt `xml:"maxstanzas,attr,omitempty"`
+	Seconds    NullableInt `xml:"seconds,attr,omitempty"`
+	Since      time.Time   `xml:"since,attr,omitempty"`
+}
+
+type NullableInt struct {
+	Value int
+	isSet bool
+}
+
+func NewNullableInt(val int) NullableInt {
+	return NullableInt{val, true}
+}
+
+func (n NullableInt) Get() (v int, ok bool) {
+	return n.Value, n.isSet
+}
+
+// UnmarshalXML implements custom parsing for history element
+func (h *History) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	h.XMLName = start.Name
+
+	// Extract attributes
+	for _, attr := range start.Attr {
+		switch attr.Name.Local {
+		case "maxchars":
+			v, err := strconv.Atoi(attr.Value)
+			if err != nil {
+				return err
+			}
+			h.MaxChars = NewNullableInt(v)
+		case "maxstanzas":
+			v, err := strconv.Atoi(attr.Value)
+			if err != nil {
+				return err
+			}
+			h.MaxStanzas = NewNullableInt(v)
+		case "seconds":
+			v, err := strconv.Atoi(attr.Value)
+			if err != nil {
+				return err
+			}
+			h.Seconds = NewNullableInt(v)
+		case "since":
+			t, err := time.Parse(timeLayout, attr.Value)
+			if err != nil {
+				return err
+			}
+			h.Since = t
+		}
+	}
+
+	// Consume remaining data until element end
+	for {
+		t, err := d.Token()
+		if err != nil {
+			return err
+		}
+
+		switch tt := t.(type) {
+		case xml.EndElement:
+			if tt == start.End() {
+				return nil
+			}
+		}
+	}
+}
+
+func (h History) MarshalXML(e *xml.Encoder, start xml.StartElement) (err error) {
+	mc, isMcSet := h.MaxChars.Get()
+	ms, isMsSet := h.MaxStanzas.Get()
+	s, isSSet := h.Seconds.Get()
+
+	// We do not have any value, ignore history element
+	if h.Since.IsZero() && !isMcSet && !isMsSet && !isSSet {
+		return nil
+	}
+
+	// Encode start element and attributes
+	start.Name = xml.Name{Local: "history"}
+
+	if isMcSet {
+		attr := xml.Attr{
+			Name:  xml.Name{Local: "maxchars"},
+			Value: strconv.Itoa(mc),
+		}
+		start.Attr = append(start.Attr, attr)
+	}
+
+	if isMsSet {
+		attr := xml.Attr{
+			Name:  xml.Name{Local: "maxstanzas"},
+			Value: strconv.Itoa(ms),
+		}
+		start.Attr = append(start.Attr, attr)
+	}
+
+	if isSSet {
+		attr := xml.Attr{
+			Name:  xml.Name{Local: "seconds"},
+			Value: strconv.Itoa(s),
+		}
+		start.Attr = append(start.Attr, attr)
+	}
+
+	if !h.Since.IsZero() {
+		attr := xml.Attr{
+			Name:  xml.Name{Local: "since"},
+			Value: h.Since.Format(timeLayout),
+		}
+		start.Attr = append(start.Attr, attr)
+	}
+	if err := e.EncodeToken(start); err != nil {
+		return err
+	}
+
+	return e.EncodeToken(xml.EndElement{Name: start.Name})
+
 }
 
 func init() {

pres_muc_test.go

@@ -46,16 +46,18 @@ func TestMucHistory(t *testing.T) {
 
 	var parsedPresence xmpp.Presence
 	if err := xml.Unmarshal([]byte(str), &parsedPresence); err != nil {
-		t.Errorf("Unmarshal(%s) returned error", str)
+		t.Errorf("Unmarshal(%s) returned error: %s", str, err)
+		return
 	}
 
 	var muc xmpp.MucPresence
 	if ok := parsedPresence.Get(&muc); !ok {
 		t.Error("muc presence extension was not found")
+		return
 	}
 
-	if *muc.History.MaxStanzas != 20 {
-		t.Errorf("incorrect max stanza: '%d'", muc.History.MaxStanzas)
+	if v, ok := muc.History.MaxStanzas.Get(); !ok || v != 20 {
+		t.Errorf("incorrect MaxStanzas: '%#v'", muc.History.MaxStanzas)
 	}
 }
 
@@ -79,13 +81,14 @@ func TestMucNoHistory(t *testing.T) {
 	},
 		Extensions: []xmpp.PresExtension{
 			xmpp.MucPresence{
-				History: xmpp.History{MaxStanzas: &maxstanzas},
+				History: xmpp.History{MaxStanzas: xmpp.NewNullableInt(maxstanzas)},
 			},
 		},
 	}
 	data, err := xml.Marshal(&pres)
 	if err != nil {
 		t.Error("error on encode:", err)
+		return
 	}
 
 	if string(data) != str {