CalDAV support (#15)

pkg/caldav/caldav.go

@@ -0,0 +1,95 @@
+package caldav
+
+import (
+	"code.vikunja.io/api/pkg/utils"
+	"strconv"
+	"time"
+)
+
+// Event holds a single caldav event
+type Event struct {
+	Summary     string
+	Description string
+	UID         string
+	Alarms      []Alarm
+
+	TimestampUnix int64
+	StartUnix     int64
+	EndUnix       int64
+}
+
+// Alarm holds infos about an alarm from a caldav event
+type Alarm struct {
+	TimeUnix    int64
+	Description string
+}
+
+// Config is the caldav calendar config
+type Config struct {
+	Name   string
+	ProdID string
+}
+
+// ParseEvents parses an array of caldav events and gives them back as string
+func ParseEvents(config *Config, events []*Event) (caldavevents string) {
+	caldavevents += `BEGIN:VCALENDAR
+VERSION:2.0
+METHOD:PUBLISH
+X-PUBLISHED-TTL:PT4H
+X-WR-CALNAME:` + config.Name + `
+PRODID:-//` + config.ProdID + `//EN`
+
+	for _, e := range events {
+
+		if e.UID == "" {
+			e.UID = makeCalDavTimeFromUnixTime(e.TimestampUnix) + utils.Sha256(e.Summary)
+		}
+
+		caldavevents += `
+BEGIN:VEVENT
+UID:` + e.UID + `
+SUMMARY:` + e.Summary + `
+DESCRIPTION:` + e.Description + `
+DTSTAMP:` + makeCalDavTimeFromUnixTime(e.TimestampUnix) + `
+DTSTART:` + makeCalDavTimeFromUnixTime(e.StartUnix) + `
+DTEND:` + makeCalDavTimeFromUnixTime(e.EndUnix)
+
+		for _, a := range e.Alarms {
+			if a.Description == "" {
+				a.Description = e.Summary
+			}
+
+			caldavevents += `
+BEGIN:VALARM
+TRIGGER:` + calcAlarmDateFromReminder(e.StartUnix, a.TimeUnix) + `
+ACTION:DISPLAY
+DESCRIPTION:` + a.Description + `
+END:VALARM`
+		}
+		caldavevents += `
+END:VEVENT`
+	}
+
+	caldavevents += `
+END:VCALENDAR` // Need a line break
+
+	return
+}
+
+func makeCalDavTimeFromUnixTime(unixtime int64) (caldavtime string) {
+	tm := time.Unix(unixtime, 0)
+	return tm.Format("20060102T150405")
+}
+
+func calcAlarmDateFromReminder(eventStartUnix, reminderUnix int64) (alarmTime string) {
+	if eventStartUnix > reminderUnix {
+		alarmTime += `-`
+	}
+	alarmTime += `PT`
+	diff := eventStartUnix - reminderUnix
+	if diff < 0 { // Make it positive
+		diff = diff * -1
+	}
+	alarmTime += strconv.Itoa(int(diff/60)) + "M"
+	return
+}