Implemented ICal update

src/calanonsync/caldav.go

@@ -10,6 +10,7 @@ import (
 	"log"
 	"net/http"
 	"net/url"
+	"regexp"
 	"strings"
 	"text/template"
 	"time"
@@ -73,6 +74,31 @@ func (i ICal) getTimeField(f string) time.Time {
 	return time.Time{}
 }
 
+var fieldMatch = regexp.MustCompile(`^(\w+)[;:]`)
+
+// Update the ical structure with a new start/end time (and the
+// timestamp of the last modification).
+func (ical *ICal) Update(newStart, newEnd time.Time) {
+	for i, line := range ical.eventData {
+		match := fieldMatch.FindStringSubmatch(line)
+		if match == nil {
+			continue
+		}
+
+		// For last modification
+		now := time.Now().UTC()
+
+		switch match[1] {
+		case "DTSTART":
+			ical.eventData[i] = "DTSTART:" + newStart.UTC().Format(ICAL_TIME) + "Z"
+		case "DTEND":
+			ical.eventData[i] = "DTEND:" + newEnd.UTC().Format(ICAL_TIME) + "Z"
+		case "DTSTAMP", "LAST-MODIFIED":
+			ical.eventData[i] = match[1] + ":" + now.Format(ICAL_TIME) + "Z"
+		}
+	}
+}
+
 // Retrieve the start time of the event.
 func (i ICal) Start() time.Time {
 	return i.getTimeField("DTSTART")

src/calanonsync/caldav_test.go

@@ -73,6 +73,68 @@ func TestParseICal(t *testing.T) {
 	})
 }
 
+func TestICal_Update(t *testing.T) {
+	newStart := time.Date(2019, 10, 05, 10, 25, 0, 0, time.UTC)
+	newEnd := time.Date(2019, 10, 05, 10, 55, 30, 0, time.UTC)
+
+	t.Run("Values updated", func(t *testing.T) {
+		ical, _ := ParseICal(strings.NewReader(icsSimple))
+		ical.Update(newStart, newEnd)
+
+		if ical.Start() != newStart {
+			t.Error("Start not updated correctly")
+		}
+		if ical.End() != newEnd {
+			t.Error("End not updated correctly")
+		}
+
+		if ical.getTimeField("DTSTAMP").Sub(time.Now()) > 5*time.Second {
+			t.Error("Timestamp doesn't seem to be updated")
+		}
+	})
+	t.Run("Other values untouched", func(t *testing.T) {
+		// Use a ICal structure with dummy/unknown fields but also without
+		// DTSTAMP or LAST-MODIFIED, so we can do a string comparison against
+		// known values.
+		ical, _ := ParseICal(strings.NewReader(`BEGIN:VCALENDAR
+PRODID:-//some//thing//EN
+VERSION:2.0
+UNKNOWN:FIELD
+SOME;MORE:STUFF
+BEGIN:VEVENT
+UID:WHATEVERID
+SUMMARY:Summary
+CLASS:PUBLIC
+DTSTART:20180308T113000Z
+DTEND:20180308T130000Z
+CREATED:20180401T182238Z
+END:VEVENT
+EVEN;MORE:STUFF
+END:VCALENDAR`))
+
+		ical.Update(newStart, newEnd)
+
+		if ical.String() != `BEGIN:VCALENDAR
+PRODID:-//some//thing//EN
+VERSION:2.0
+UNKNOWN:FIELD
+SOME;MORE:STUFF
+BEGIN:VEVENT
+UID:WHATEVERID
+SUMMARY:Summary
+CLASS:PUBLIC
+DTSTART:20191005T102500Z
+DTEND:20191005T105530Z
+CREATED:20180401T182238Z
+END:VEVENT
+EVEN;MORE:STUFF
+END:VCALENDAR` {
+
+			t.Error("The resulting ICS seems wrong.")
+		}
+	})
+}
+
 const icsWithTZ = `BEGIN:VCALENDAR
 PRODID:-//Ximian//NONSGML Evolution Calendar//EN
 VERSION:2.0