feat: usos sign-in, private calendar feed and timetable archive

internal/ical/ical.go

@@ -0,0 +1,114 @@
+package ical
+
+import (
+	"io"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"usoscal/internal/store"
+)
+
+const (
+	stamp     = "20060102T150405Z"
+	lineLimit = 75
+)
+
+func Summary(event store.Event) string {
+	if event.Kind == "" || event.Kind == event.Title {
+		return event.Title
+	}
+	return event.Title + " (" + event.Kind + ")"
+}
+
+func Location(event store.Event) string {
+	place := event.Room
+	switch {
+	case place != "" && event.Building != "":
+		place += " (" + event.Building + ")"
+	case place == "":
+		place = event.Building
+	}
+	return joinNonEmpty(", ", place, event.Address)
+}
+
+func Description(event store.Event) string {
+	about := event.Kind
+	if event.Group != "" {
+		about = joinNonEmpty(", ", about, "group "+event.Group)
+	}
+	lecturers := ""
+	if event.Lecturers != "" {
+		lecturers = "Lecturer: " + event.Lecturers
+	}
+	return joinNonEmpty("\n", about, lecturers, event.URL)
+}
+
+func Write(w io.Writer, name, host string, events []store.Event) error {
+	var b strings.Builder
+	line(&b, "BEGIN:VCALENDAR")
+	line(&b, "VERSION:2.0")
+	line(&b, "PRODID:-//usoscal//EN")
+	line(&b, "CALSCALE:GREGORIAN")
+	line(&b, "METHOD:PUBLISH")
+	line(&b, "X-WR-CALNAME:"+escape(name))
+	line(&b, "X-WR-TIMEZONE:Europe/Warsaw")
+	line(&b, "REFRESH-INTERVAL;VALUE=DURATION:PT6H")
+	line(&b, "X-PUBLISHED-TTL:PT6H")
+	for _, event := range events {
+		line(&b, "BEGIN:VEVENT")
+		line(&b, "UID:"+event.UID+"@"+host)
+		line(&b, "DTSTAMP:"+utc(event.UpdatedAt))
+		line(&b, "LAST-MODIFIED:"+utc(event.UpdatedAt))
+		line(&b, "DTSTART:"+utc(event.Start))
+		line(&b, "DTEND:"+utc(event.End))
+		line(&b, "SUMMARY:"+escape(Summary(event)))
+		if location := Location(event); location != "" {
+			line(&b, "LOCATION:"+escape(location))
+		}
+		if description := Description(event); description != "" {
+			line(&b, "DESCRIPTION:"+escape(description))
+		}
+		if event.URL != "" {
+			line(&b, "URL:"+event.URL)
+		}
+		line(&b, "END:VEVENT")
+	}
+	line(&b, "END:VCALENDAR")
+	_, err := io.WriteString(w, b.String())
+	return err
+}
+
+func utc(t time.Time) string {
+	return t.UTC().Format(stamp)
+}
+
+func joinNonEmpty(separator string, parts ...string) string {
+	kept := parts[:0:0]
+	for _, part := range parts {
+		if part != "" {
+			kept = append(kept, part)
+		}
+	}
+	return strings.Join(kept, separator)
+}
+
+var escaper = strings.NewReplacer(`\`, `\\`, ";", `\;`, ",", `\,`, "\r\n", `\n`, "\n", `\n`, "\r", "")
+
+func escape(text string) string {
+	return escaper.Replace(text)
+}
+
+func line(b *strings.Builder, content string) {
+	for len(content) > lineLimit {
+		cut := lineLimit
+		for cut > 0 && !utf8.RuneStart(content[cut]) {
+			cut--
+		}
+		b.WriteString(content[:cut])
+		b.WriteString("\r\n ")
+		content = content[cut:]
+	}
+	b.WriteString(content)
+	b.WriteString("\r\n")
+}