libzotero/lib/Cache.js

javascript libZotero

'use strict';

var log = require('./Log.js').Logger('libZotero:Cache');

//build a consistent string from an object to use as a cache key
//put object key/value pairs into array, sort array, and concatenate
//array with '/'
module.exports = function (store) {
	this.store = store;
	var registry = this.store._registry;
	if (registry === null || typeof registry == 'undefined') {
		registry = {};
		this.store._registry = JSON.stringify(registry);
	}
};

module.exports.prototype.objectCacheString = function (params) {
	var paramVarsArray = [];
	Object.keys(params).forEach(function (index) {
		var value = params[index];
		if (!value) {
			return;
		} else if (Array.isArray(value)) {
			value.forEach(function (v) {
				paramVarsArray.push(index + '/' + encodeURIComponent(v));
			});
		} else {
			paramVarsArray.push(index + '/' + encodeURIComponent(value));
		}
	});
	paramVarsArray.sort();
	log.debug(paramVarsArray, 4);
	var objectCacheString = paramVarsArray.join('/');
	return objectCacheString;
};

//should use setItem and getItem if I extend that to the case where no Storage object is available in the browser
module.exports.prototype.save = function (params, object, cachetags) {
	//cachetags for expiring entries
	if (!Array.isArray(cachetags)) {
		cachetags = [];
	}
	//get registry object from storage
	var registry = JSON.parse(this.store._registry);
	if (!registry) {
		registry = {};
	}
	var objectCacheString = this.objectCacheString(params);
	//save object in storage
	this.store[objectCacheString] = JSON.stringify(object);
	//make registry entry for object
	var registryEntry = { 'id': objectCacheString, saved: Date.now(), cachetags: cachetags };
	registry[objectCacheString] = registryEntry;
	//save registry back to storage
	this.store._registry = JSON.stringify(registry);
};

module.exports.prototype.load = function (params) {
	log.debug('Zotero.Cache.load', 3);
	var objectCacheString = this.objectCacheString(params);
	log.debug(objectCacheString, 4);
	try {
		var s = this.store[objectCacheString];
		if (!s) {
			log.warn('No value found in cache store - ' + objectCacheString, 3);
			return null;
		} else {
			return JSON.parse(s);
		}
	} catch (e) {
		log.error('Error parsing retrieved cache data: ' + objectCacheString + ' : ' + s);
		return null;
	}
};

module.exports.prototype.expireCacheTag = function (tag) {
	log.debug('Zotero.Cache.expireCacheTag', 3);
	var registry = JSON.parse(this.store._registry);
	var store = this.store;
	Object.keys(registry).forEach(function (index) {
		var value = registry[index];
		if (value.cachetags.indexOf(tag) != -1) {
			log.debug('tag ' + tag + ' found for item ' + value['id'] + ' : expiring', 4);
			delete store[value['id']];
			delete registry[value['id']];
		}
	});
};

module.exports.prototype.clear = function () {
	if (typeof this.store.clear == 'function') {
		this.store.clear();
	} else {
		this.store = {};
	}
};