from __pyjamas__ import JS


class Notification(object):
    """
    If the browser supports it, the user allowed it to and the tab is in the
    background, send desktop notifications on messages.

    Requires both Web Notifications and Page Visibility API.
    """

    def __init__(self):
        JS("""
        this.enabled = false;

        if (!('hidden' in document))
            document.hidden = false;

        if (!('Notification' in window))
            return;

        if (Notification.permission === 'granted')
            this.enabled = true;

        else if (Notification.permission === 'default') {
            Notification.requestPermission(function(permission){
                if (permission !== 'granted')
                    return;

                this.enabled = true;
            });
        }
        """)

    def notify(self, title, body, icon='/media/icons/apps/48/sat.png'):
        JS("""
        if (this.enabled && document.hidden) {
            notification = Notification(title, {body: body, icon: icon});

            // Probably won’t work, but it doesn’t hurt to try.
            notification.addEventListener('click', function() {
                window.focus();
            });
        }
        """)