DataCache.js

/**
 * Constructor for DataCache.
 * More info on caching: https://developers.google.com/apps-script/reference/cache/cache
 *
 * @param {object} cacheService - GDS caching service
 * @param {Date} startDate - beggining of GDS request interval
 * @param {Date} endDate - end of GDS request interval
 *
 * @return {object} DataCache.
 */
function DataCache(cacheService, cacheKey) {
    this.service = cacheService;
    this.cacheKey = cacheKey;

    return this;
}

/** @const - 6 hours, Google's max */
DataCache.REQUEST_CACHING_TIME = 21600;

/** @const - 100 KB */
DataCache.MAX_CACHE_SIZE = 100 * 1024;

/**
 * Gets stored value
 *
 * @return {String} Response string
 */
DataCache.prototype.get = function() {
    var value = '';
    var chunk = '';
    var chunkIndex = 0;

    do {
        var chunkKey = this.getChunkKey(chunkIndex);
        chunk = this.service.get(chunkKey);
        value += (chunk || '');
        chunkIndex++;
    } while (chunk && chunk.length == DataCache.MAX_CACHE_SIZE);

    return value;
};

/**
 * Stores value in cache.
 *
 * @param {String} key - cache key
 * @param {String} value
 */
DataCache.prototype.set = function(value) {
    this.storeChunks(value);
};

DataCache.prototype.storeChunks = function(value) {
    var chunks = this.splitInChunks(value);

    for (var i = 0; i < chunks.length; i++) {
        var chunkKey = this.getChunkKey(i);
        this.service.put(chunkKey, chunks[i], DataCache.REQUEST_CACHING_TIME);
    }
};

DataCache.prototype.getChunkKey = function(chunkIndex) {
    return this.cacheKey + '_' + chunkIndex;
};

DataCache.prototype.splitInChunks = function(str) {
    var size = DataCache.MAX_CACHE_SIZE;
    var numChunks = Math.ceil(str.length / size);
    var chunks = new Array(numChunks);

    for (var i = 0, o = 0; i < numChunks; ++i, o += size) {
        chunks[i] = str.substr(o, size);
    }

    return chunks;
};