cache.js

var cache = {};

/*
 * Returns whether or not the object is in our cache, and saved
 * within the last 12 hours.
 *
 * @param {Object} options 
 * @returns {int}
 *  - returns > 0 when (now - time saved) < 12 hours
 *  - returns 0 when (now - time saved) > 12 hours 
 *  - returns < 0 when not cached
 *
 */
module.exports.isCached = function(options) {
    options.host = options.host || 'api-gw.it.umich.edu';
    var searchQuery = options.host + options.path;

    if(searchQuery in cache) {
        var timeDiff = Date.now() - cache[searchQuery].timestamp;

        // (now - time saved) < 12 hours
        if(timeDiff < 43200000) {
            return 1;
        } else {
            return 0;
        }
    } else {
        return -1;
    }
};

/*
 * Get the object from our cache if it exists, else do not
 * call the callback
 *
 * @param {Object} options 
 * @callback callback
 *
 */
module.exports.getCachedResponse = function(options, callback) {
    options.host = options.host || 'api-gw.it.umich.edu';
    var searchQuery = options.host + options.path;
    
    if(searchQuery in cache) {
        callback({ result: cache[searchQuery].data });
    }
};

/*
 * Store a new object to our cache
 *
 * @param {Object} options 
 * @callback callback
 *
 */
module.exports.storeCachedResponse = function(options, responseObj) {
    options.host = options.host || 'api-gw.it.umich.edu';
    var searchQuery = options.host + options.path;
    
    cache[searchQuery] = { 
        timestamp: Date.now(),
        data: responseObj
    };
};

/*
 * Empty the cache
 *
 */
module.exports.emptyCache = function() {
    cache = {};
};