PaywallAccess

/** @license
 * Copyright 2015 - present The AMP HTML Authors. All Rights Reserved.
 *
 * 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.
 */

"use strict";

var url = require('url');
var MAX_FIRST_CLICK_FREE_VIEWS = 3;
var MAX_VIEWS = 3;

var READER_ID_TO_MAPPING = {};
var FIRST_CLICK_FREE_DOMAINS = ['google.com'];
var FIRST_CLICK_FREE_TEST_PATH = 'fcf';

/**
 * A simple paywall implementation. It understands AMP Reader Ids
 * and users. Supported features are:
 *
 * - Metered paywall
 * - First-click-free
 * - Subscriptions
 * - Users can view articles repeatedly
 */
class PaywallAccess {

	constructor() {
		this.numViews = 0;
		this.viewedUrls = {};
		this.viewedUrlsByReferrer = {};
		this.user = null;
	}

	/**
	* Returns true if the user is a subscriber.
	*/
	
	isSubscriber() {
		if (!this.user) {
			return false;
		}

		return this.user.subscriber;
	}

	/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
	/**
	* Determines based on the request referrer whether
	* First-Click-Free is supported.
	*/
	isFirstClickFree(referrer) {
		
		var host = url.parse(referrer);
		
		if(FIRST_CLICK_FREE_DOMAINS.indexOf(host) == -1 &&
			// for testing
		referrer.indexOf(FIRST_CLICK_FREE_TEST_PATH) == -1) {
			return false;
		}

		return !this.viewedUrlsByReferrer[host] ||
		this.viewedUrlsByReferrer[host] < MAX_FIRST_CLICK_FREE_VIEWS;
	}

	///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
	/**
	* Registers a viewed article. Counts views per referrer.
	*/
	registerView(referrer, viewedUrl) {

		if (!this.hasAccess(referrer, viewedUrl)) {
			return;
		}

		if (this.isFirstClickFree(referrer)) {
		
			var host = url.parse(referrer);

			if (this.viewedUrlsByReferrer[host]) {
			
				this.viewedUrlsByReferrer[host]++;

			} else {

				this.viewedUrlsByReferrer[host] = 1;
			}

		} else if (!this.user && !this.viewedUrls[viewedUrl]) {
		
			this.numViews++;
	
		}
	
		this.viewedUrls[viewedUrl] = true;
	}

	///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
	/**
	* Returns true if the user has access to the given URL.
	*/
	hasAccess(referrer, url) {
		return this.isSubscriber() ||
		this.hasAlreadyVisisted(url) ||
		this.isFirstClickFree(referrer) ||
		this.numViews < MAX_VIEWS;
	}

	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
	/**
	* Returns true if the user has already viewed this article.
	*/
	hasAlreadyVisisted(url) {
		return this.viewedUrls[url];
	}
}

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * The maximum number of views per non-subscriber.
 */
exports.MAX_VIEWS = MAX_VIEWS;

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/**
 * Returns an existing paywall access for known
 * Reader IDs or creates a new one otherwise.
 */
exports.getOrCreate = function(readerId) {

	var clientAuth = READER_ID_TO_MAPPING[readerId];
	if (!clientAuth) {
	
		clientAuth = new PaywallAccess();
		READER_ID_TO_MAPPING[readerId] = clientAuth;
	}
	return clientAuth;
};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/**
 * Returns paywall access for the given Reader ID.
 */
exports.findByReaderId = function(readerId) {
	return READER_ID_TO_MAPPING[readerId];
 };

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/**
* Deletes paywall access for the given Reader ID.
*/
exports.deleteByReaderId = function(readerId) {
	delete READER_ID_TO_MAPPING[readerId];
};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/**
* Deletes paywall access for the given email address.
*/
exports.deleteByEmail = function(email) {
	// very inefficient - don't try this at home
	for (var readerId in READER_ID_TO_MAPPING) {
		var user = READER_ID_TO_MAPPING[readerId].user;
		if (user && user.email == email) {
			this.deleteByReaderId(readerId);
		}
	}
};