domotz-remote-pawn/src/persistence/cache.js

Domotz Agent

/** This file is part of Domotz Agent.
  * Copyright (C) 2016  Domotz Ltd
  *
  * Domotz Agent is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
  *
  * Domotz Agent is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Domotz Agent.  If not, see <http://www.gnu.org/licenses/>.
  **/
/**
 *
 * Created by Iacopo Papalini <ipapalini@domotz.com> on 17/09/15.
 */


module.exports.factory = function(procUtils, fs) {

    function getBaseDir(scope) {
        return process.env.DOMOTZ_ROOT_DIR + '/var/cache/' + scope + '/';
    }

    function fileName(basePath, key) {
        return basePath + key + '.cache';
    }

    function testCache(cache) {
        try {
            var stats = fs.lstatSync(cache);
            return stats.isFile();
        }
        catch (error) {
            console.error("CACHE - error performing fs stat on " + cache);
            return false;
        }
    }

    function createCache(scope) {

        var basePath = getBaseDir(scope);

        procUtils.exec('mkdir -p ' + basePath);

        return {
            test: function (key) {
                var cache = fileName(basePath, key);
                return testCache(cache);
            },
            get: function (key, missCallback, hitCallback) {
                var cache = fileName(basePath, key);
                if (!testCache(cache)) {
                    return missCallback();
                }
                fs.readFile(cache, function (err, data) {
                    if (err) {
                        const fileName = cache;
                        console.error("CACHE - Error reading file %s, cache miss", fileName);
                        missCallback();
                    }
                    try {
                        return hitCallback(JSON.parse(data)['cached-value']);
                    }
                    catch (error) {
                        console.error("CACHE - Error parsing file %s contents, cache miss", fileName);
                        missCallback();
                    }
                });

            },
            set: function (key, value) {
                var cache = fileName(basePath, key);
                var data = {'cached-value': value};
                var tempFile = cache + Math.random();
                fs.writeFile(tempFile, JSON.stringify(data), function (err) {
                    if (err) {
                        console.error("CACHE - Cannot set cache value");
                        return console.error(err.stack);
                    }

                    procUtils.exec('mv ' + tempFile + ' ' + cache);
                    console.info("CACHE - (%s): Key stored in cache in scope %s", key, scope);
                });
            },
            reset: function () {
                procUtils.exec('rm -fr ' + basePath);
            }
        };
    }


    return {
        createCache: createCache
    };

};