filer/lib/intercom.js

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define(function(require) {
// Based on https://github.com/diy/intercom.js/blob/master/lib/intercom.js
// Copyright 2012 DIY Co Apache License, Version 2.0
// http://www.apache.org/licenses/LICENSE-2.0
var EventEmitter = require('eventemitter');
var guid = require('src/shared').guid;
function throttle(delay, fn) {
var last = 0;
return function() {
var now = Date.now();
if (now - last > delay) {
last = now;
fn.apply(this, arguments);
}
};
}
function extend(a, b) {
if (typeof a === 'undefined' || !a) { a = {}; }
if (typeof b === 'object') {
for (var key in b) {
if (b.hasOwnProperty(key)) {
a[key] = b[key];
}
}
}
return a;
}
var localStorage = (function(window) {
if (typeof window.localStorage === 'undefined') {
return {
getItem : function() {},
setItem : function() {},
removeItem : function() {}
};
}
return window.localStorage;
}(this));
function Intercom() {
var self = this;
var now = Date.now();
this.origin = guid();
this.lastMessage = now;
this.receivedIDs = {};
this.previousValues = {};
var storageHandler = function() {
self._onStorageEvent.apply(self, arguments);
};
if (document.attachEvent) {
document.attachEvent('onstorage', storageHandler);
} else {
window.addEventListener('storage', storageHandler, false);
}
}
Intercom.prototype._transaction = function(fn) {
var TIMEOUT = 1000;
var WAIT = 20;
var self = this;
var executed = false;
var listening = false;
var waitTimer = null;
function lock() {
if (executed) {
return;
}
var now = Date.now();
var activeLock = localStorage.getItem(INDEX_LOCK)|0;
if (activeLock && now - activeLock < TIMEOUT) {
if (!listening) {
self._on('storage', lock);
listening = true;
}
waitTimer = window.setTimeout(lock, WAIT);
return;
}
executed = true;
localStorage.setItem(INDEX_LOCK, now);
fn();
unlock();
}
function unlock() {
if (listening) {
self._off('storage', lock);
}
if (waitTimer) {
window.clearTimeout(waitTimer);
}
localStorage.removeItem(INDEX_LOCK);
}
lock();
};
Intercom.prototype._cleanup_emit = throttle(100, function() {
var self = this;
self._transaction(function() {
var now = Date.now();
var threshold = now - THRESHOLD_TTL_EMIT;
var changed = 0;
var messages;
try {
messages = JSON.parse(localStorage.getItem(INDEX_EMIT) || '[]');
} catch(e) {
messages = [];
}
for (var i = messages.length - 1; i >= 0; i--) {
if (messages[i].timestamp < threshold) {
messages.splice(i, 1);
changed++;
}
}
if (changed > 0) {
localStorage.setItem(INDEX_EMIT, JSON.stringify(messages));
}
});
});
Intercom.prototype._cleanup_once = throttle(100, function() {
var self = this;
self._transaction(function() {
var timestamp, ttl, key;
var table;
var now = Date.now();
var changed = 0;
try {
table = JSON.parse(localStorage.getItem(INDEX_ONCE) || '{}');
} catch(e) {
table = {};
}
for (key in table) {
if (self._once_expired(key, table)) {
delete table[key];
changed++;
}
}
if (changed > 0) {
localStorage.setItem(INDEX_ONCE, JSON.stringify(table));
}
});
});
Intercom.prototype._once_expired = function(key, table) {
if (!table) {
return true;
}
if (!table.hasOwnProperty(key)) {
return true;
}
if (typeof table[key] !== 'object') {
return true;
}
var ttl = table[key].ttl || THRESHOLD_TTL_ONCE;
var now = Date.now();
var timestamp = table[key].timestamp;
return timestamp < now - ttl;
};
Intercom.prototype._localStorageChanged = function(event, field) {
if (event && event.key) {
return event.key === field;
}
var currentValue = localStorage.getItem(field);
if (currentValue === this.previousValues[field]) {
return false;
}
this.previousValues[field] = currentValue;
return true;
};
Intercom.prototype._onStorageEvent = function(event) {
event = event || window.event;
var self = this;
if (this._localStorageChanged(event, INDEX_EMIT)) {
this._transaction(function() {
var now = Date.now();
var data = localStorage.getItem(INDEX_EMIT);
var messages;
try {
messages = JSON.parse(data || '[]');
} catch(e) {
messages = [];
}
for (var i = 0; i < messages.length; i++) {
if (messages[i].origin === self.origin) continue;
if (messages[i].timestamp < self.lastMessage) continue;
if (messages[i].id) {
if (self.receivedIDs.hasOwnProperty(messages[i].id)) continue;
self.receivedIDs[messages[i].id] = true;
}
self.trigger(messages[i].name, messages[i].payload);
}
self.lastMessage = now;
});
}
this._trigger('storage', event);
};
Intercom.prototype._emit = function(name, message, id) {
id = (typeof id === 'string' || typeof id === 'number') ? String(id) : null;
if (id && id.length) {
if (this.receivedIDs.hasOwnProperty(id)) return;
this.receivedIDs[id] = true;
}
var packet = {
id : id,
name : name,
origin : this.origin,
timestamp : Date.now(),
payload : message
};
var self = this;
this._transaction(function() {
var data = localStorage.getItem(INDEX_EMIT) || '[]';
var delimiter = (data === '[]') ? '' : ',';
data = [data.substring(0, data.length - 1), delimiter, JSON.stringify(packet), ']'].join('');
localStorage.setItem(INDEX_EMIT, data);
self.trigger(name, message);
window.setTimeout(function() {
self._cleanup_emit();
}, 50);
});
};
Intercom.prototype.emit = function(name, message) {
this._emit.apply(this, arguments);
this._trigger('emit', name, message);
};
Intercom.prototype.once = function(key, fn, ttl) {
if (!Intercom.supported) {
return;
}
var self = this;
this._transaction(function() {
var data;
try {
data = JSON.parse(localStorage.getItem(INDEX_ONCE) || '{}');
} catch(e) {
data = {};
}
if (!self._once_expired(key, data)) {
return;
}
data[key] = {};
data[key].timestamp = Date.now();
if (typeof ttl === 'number') {
data[key].ttl = ttl * 1000;
}
localStorage.setItem(INDEX_ONCE, JSON.stringify(data));
fn();
window.setTimeout(function() {
self._cleanup_once();
}, 50);
});
};
extend(Intercom.prototype, EventEmitter.prototype);
Intercom.supported = (typeof localStorage !== 'undefined');
var INDEX_EMIT = 'intercom';
var INDEX_ONCE = 'intercom_once';
var INDEX_LOCK = 'intercom_lock';
var THRESHOLD_TTL_EMIT = 50000;
var THRESHOLD_TTL_ONCE = 1000 * 3600;
Intercom.destroy = function() {
localStorage.removeItem(INDEX_LOCK);
localStorage.removeItem(INDEX_EMIT);
localStorage.removeItem(INDEX_ONCE);
};
Intercom.getInstance = (function() {
var intercom;
return function() {
if (!intercom) {
intercom = new Intercom();
}
return intercom;
};
})();
return Intercom;
});