function safe(read, fallback) {
    try {
        const value = read();
        return value === null || value === undefined ? fallback : value;
    } catch (_) {
        return fallback;
    }
}

function participantText(participant) {
    const name = String(safe(() => participant.displayName(), "")).trim();
    const email = String(safe(() => participant.email(), "")).trim();
    if (!name) {
        return email;
    }
    if (!email || name.toLowerCase() === email.toLowerCase()) {
        return name;
    }
    return `${name} <${email}>`;
}

function run(argv) {
    if (argv.length !== 2) {
        throw new Error("Usage: calendar-events.js <from-iso8601> <to-iso8601>");
    }

    const from = new Date(argv[0]);
    const to = new Date(argv[1]);
    const calendar = Application("Calendar");
    const result = [];

    for (const sourceCalendar of calendar.calendars()) {
        const events = sourceCalendar.events.whose({
            _and: [
                { startDate: { _lessThan: to } },
                { endDate: { _greaterThan: from } }
            ]
        })();
        for (const event of events) {
            const start = event.startDate();
            const end = event.endDate();
            const attendees = safe(() => event.attendees(), [])
                .map(participantText)
                .filter(value => value.length > 0);
            const organizer = String(safe(() => event.organizer(), "")).trim();
            if (organizer && !attendees.includes(organizer)) {
                attendees.unshift(organizer);
            }

            result.push({
                id: String(safe(() => event.uid(), `${start.toISOString()}|${event.summary()}`)),
                subject: String(safe(() => event.summary(), "")),
                start: start.toISOString(),
                end: end.toISOString(),
                location: String(safe(() => event.location(), "")),
                notes: String(safe(() => event.description(), "")),
                url: String(safe(() => event.url(), "")),
                attendees: attendees,
                isCanceled: String(safe(() => event.status(), ""))
                    .toLowerCase()
                    .includes("cancel")
            });
        }
    }

    result.sort((left, right) => left.start.localeCompare(right.start));
    return JSON.stringify(result);
}