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// Copyright (C) 2017 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
(function(window) {
'use strict';
// Prevent redefinition.
if (window.GrEtagDecorator) { return; }
// Limit cache size because /change/detail responses may be large.
const MAX_CACHE_SIZE = 30;
function GrEtagDecorator() {
this._etags = new Map();
this._payloadCache = new Map();
}
/**
* Get or upgrade fetch options to include an ETag in a request.
* @param {string} url The URL being fetched.
* @param {!Object=} opt_options Optional options object in which to include
* the ETag request header. If omitted, the result will be a fresh option
* set.
* @return {!Object}
*/
GrEtagDecorator.prototype.getOptions = function(url, opt_options) {
const etag = this._etags.get(url);
if (!etag) {
return opt_options;
}
const options = Object.assign({}, opt_options);
options.headers = options.headers || new Headers();
options.headers.set('If-None-Match', this._etags.get(url));
return options;
};
/**
* Handle a response to a request with ETag headers, potentially incorporating
* its result in the payload cache.
*
* @param {string} url The URL of the request.
* @param {!Response} response The response object.
* @param {string} payload The raw, unparsed JSON contained in the response
* body. Note: because response.text() cannot be read twice, this must be
* provided separately.
*/
GrEtagDecorator.prototype.collect = function(url, response, payload) {
if (!response ||
!response.ok ||
response.status !== 200 ||
response.status === 304) {
// 304 Not Modified means etag is still valid.
return;
}
this._payloadCache.set(url, payload);
const etag = response.headers && response.headers.get('etag');
if (!etag) {
this._etags.delete(url);
} else {
this._etags.set(url, etag);
this._truncateCache();
}
};
/**
* Get the cached payload for a given URL.
* @param {string} url
* @return {string|undefined} Returns the unparsed JSON payload from the
* cache.
*/
GrEtagDecorator.prototype.getCachedPayload = function(url) {
return this._payloadCache.get(url);
};
/**
* Limit the cache size to MAX_CACHE_SIZE.
*/
GrEtagDecorator.prototype._truncateCache = function() {
for (const url of this._etags.keys()) {
if (this._etags.size <= MAX_CACHE_SIZE) {
break;
}
this._etags.delete(url);
this._payloadCache.delete(url);
}
};
window.GrEtagDecorator = GrEtagDecorator;
})(window);
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