async function check_or_enable_notification_permission() {
    if (!("Notification" in window)) {
        return false;
    }

    if (Notification.permission === "granted") {
        return true;
    }

    if (Notification.permission !== "denied") {
        // We need to ask the user for permission
        const permission = await Notification.requestPermission()
        if (permission === "granted") {
            return true;
        }
    }

    return false;
}

async function create(title, text) {
    const notifications_enabled = await check_or_enable_notification_permission();
    if (notifications_enabled) {
        return new Notification(title, {
            body: text,
            icon: 'favicon/android-chrome-192x192.png'
        });
    }
}

module.exports = {
    enabled: check_or_enable_notification_permission,
    create: create,
    queue: async function(title, text, dispatch_datetime, on_create) {
        const enabled = await check_or_enable_notification_permission();
        if (!enabled) {
            return;
        }

        const now = new Date();
        const next_notification_date = new Date(dispatch_datetime);
        const timeout_remaining = next_notification_date.getTime() - now.getTime();

        return setTimeout(function() {
            create(title, text);
            on_create();
        }, timeout_remaining);
    }
};