/**
* @workInProgress
* @ngdoc service
* @name angular.service.$xhr.cache
* @function
* @requires $xhr
*
* @description
* Acts just like the {@link angular.service.$xhr $xhr} service but caches responses for `GET`
* requests. All cache misses are delegated to the $xhr service.
*
* @property {function()} delegate Function to delegate all the cache misses to. Defaults to
* the {@link angular.service.$xhr $xhr} service.
* @property {object} data The hashmap where all cached entries are stored.
*
* @param {string} method HTTP method.
* @param {string} url Destination URL.
* @param {(string|Object)=} post Request body.
* @param {function(number, (string|Object))} callback Response callback.
* @param {boolean=} [verifyCache=false] If `true` then a result is immediately returned from cache
* (if present) while a request is sent to the server for a fresh response that will update the
* cached entry. The `callback` function will be called when the response is received.
* @param {boolean=} [sync=false] in case of cache hit execute `callback` synchronously.
*/
angularServiceInject('$xhr.cache', function($xhr, $defer, $log){
var inflight = {}, self = this;
function cache(method, url, post, callback, verifyCache, sync){
if (isFunction(post)) {
callback = post;
post = null;
}
if (method == 'GET') {
var data, dataCached;
if (dataCached = cache.data[url]) {
if (sync) {
callback(200, copy(dataCached.value));
} else {
$defer(function() { callback(200, copy(dataCached.value)); });
}
if (!verifyCache)
return;
}
if (data = inflight[url]) {
data.callbacks.push(callback);
} else {
inflight[url] = {callbacks: [callback]};
cache.delegate(method, url, post, function(status, response){
if (status == 200)
cache.data[url] = { value: response };
var callbacks = inflight[url].callbacks;
delete inflight[url];
forEach(callbacks, function(callback){
try {
(callback||noop)(status, copy(response));
} catch(e) {
$log.error(e);
}
});
});
}
} else {
cache.data = {};
cache.delegate(method, url, post, callback);
}
}
cache.data = {};
cache.delegate = $xhr;
return cache;
}, ['$xhr.bulk', '$defer', '$log']);
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