pim: invite, and a way to say what you mean

pim/invite makes an event and, when it names attendees, sends the
invitation -- which on a caldav server with auto-schedule is the same
act. -p writes the object to standard output instead, so it can go to
upas/marshal as iMIP, into a directory an ical/fs is serving, or
nowhere in particular. There is no separate verb for inviting because
to a calendar there is no separate thing.

It writes the tree's own key: value form rather than icalendar. The
first version spelled SUMMARY: by hand and got "lunch, then a walk"
wrong: a comma is a separator there and wants escaping. Parsing with
go-ical and generating by hand is the wrong asymmetry, so calfs grew
Compose, and now the same shape the tree emits is the shape it accepts.
The one UID we ever mint -- as organiser we own the event -- is minted
there too.

pim/invites lists what is waiting for an answer, which is what makes
pim/rsvp usable: it walks the date tree rather than every event, since
an invitation you never answered last March is not news.

agenda and show take -d date now, via seconds(1), which parses a human
date where date(1) only formats one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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
+}