1 files changed, 112 insertions, 0 deletions
diff --git a/pim/lib/cal/compose.go b/pim/lib/cal/compose.go
new file mode 100644
index 0000000..1960696
--- /dev/null
+++ b/pim/lib/cal/compose.go
@@ -0,0 +1,112 @@
+package cal
+
+import (
+	"bufio"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/emersion/go-ical"
+)
+
+// Compose builds an event from the same key: value form the tree emits.
+//
+//	summary: lunch, then a walk; maybe
+//	start: 1787500800
+//	end: 1787504400
+//	location: the wire
+//	attendee: bob@example.com
+//	attendee: carol@example.com
+//	organizer: you@example.com
+//	description: anything
+//
+// Accepting this rather than raw icalendar keeps the escaping where the
+// parser already lives. A shell script writing SUMMARY: by hand has to
+// know that a comma means something, and will eventually forget; here
+// it writes what it means and go-ical spells it.
+//
+// Times are epoch seconds, because that is what date(1) hands a script.
+func Compose(r *bufio.Reader, uid string) (*ical.Calendar, error) {
+	f := map[string][]string{}
+	for {
+		line, err := r.ReadString('\n')
+		if line = strings.TrimRight(line, "\r\n"); line != "" {
+			k, v, ok := strings.Cut(line, ":")
+			if !ok {
+				return nil, fmt.Errorf("compose: %q is not key: value", line)
+			}
+			k = strings.ToLower(strings.TrimSpace(k))
+			f[k] = append(f[k], strings.TrimSpace(v))
+		}
+		if err != nil {
+			break
+		}
+	}
+
+	one := func(k string) string {
+		if v := f[k]; len(v) > 0 {
+			return v[0]
+		}
+		return ""
+	}
+	at := func(k string) (time.Time, error) {
+		v := one(k)
+		if v == "" {
+			return time.Time{}, fmt.Errorf("compose: no %s", k)
+		}
+		n, err := strconv.ParseInt(v, 10, 64)
+		if err != nil {
+			return time.Time{}, fmt.Errorf("compose: %s: want epoch seconds, got %q", k, v)
+		}
+		return time.Unix(n, 0).UTC(), nil
+	}
+
+	if one("summary") == "" {
+		return nil, fmt.Errorf("compose: no summary")
+	}
+	start, err := at("start")
+	if err != nil {
+		return nil, err
+	}
+	end, err := at("end")
+	if err != nil {
+		return nil, err
+	}
+
+	ev := ical.NewEvent()
+	ev.Props.SetText(ical.PropUID, uid)
+	ev.Props.SetDateTime(ical.PropDateTimeStamp, time.Now().UTC())
+	ev.Props.SetDateTime(ical.PropDateTimeStart, start)
+	ev.Props.SetDateTime(ical.PropDateTimeEnd, end)
+	ev.Props.SetText(ical.PropSummary, one("summary"))
+	if v := one("location"); v != "" {
+		ev.Props.SetText(ical.PropLocation, v)
+	}
+	if v := one("description"); v != "" {
+		ev.Props.SetText(ical.PropDescription, v)
+	}
+	if v := one("organizer"); v != "" {
+		p := ical.NewProp(ical.PropOrganizer)
+		p.Value = "mailto:" + v
+		ev.Props.Set(p)
+		// the organiser is attending their own meeting
+		a := ical.NewProp(ical.PropAttendee)
+		a.Value = "mailto:" + v
+		a.Params.Set(ical.ParamParticipationStatus, "ACCEPTED")
+		ev.Props.Add(a)
+	}
+	for _, who := range f["attendee"] {
+		a := ical.NewProp(ical.PropAttendee)
+		a.Value = "mailto:" + who
+		a.Params.Set(ical.ParamParticipationStatus, "NEEDS-ACTION")
+		a.Params.Set("RSVP", "TRUE")
+		ev.Props.Add(a)
+	}
+
+	c := ical.NewCalendar()
+	c.Props.SetText(ical.PropProductID, "-//9front//pim//EN")
+	c.Props.SetText(ical.PropVersion, "2.0")
+	c.Children = append(c.Children, ev.Component)
+	return c, nil
+}