mcmartins/jsondbfs

/**
 * (C) Copyright 2016 Manuel Martins.
 *
 * This module is inspired by json_file_system.
 * (json_file_system is Copyright (c) 2014 Jalal Hejazi,
 *  Licensed under the MIT license.)
 *
 * 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.
 *
 * Created by: ManuelMartins
 * Created on: 26-01-2016
 *
 */

'use strict';

var ENCODING = 'utf-8';
var fs = require('fs');
var _ = require('underscore');
var uuid = require('uuid');
var lockFile = require('lockfile');

/**
 * Generates an UUID string without '-'
 */
module.exports.generateUUID = function generateUUID() {
  return uuid.v4().replace('/-/g', '');
};

/**
 * Flattens an Array
 */
module.exports.flatten = _.flatten;

/**
 * Clones an Array
 */
module.exports.clone = _.clone;

/**
 * File system methods to handlefile IO
 */
module.exports.fileSystem = {

  write: function write(file, content, callback) {
    process.nextTick(function(){
      if (typeof content === 'function') {
        callback = content;
        content = [];
      }
      content = JSON.stringify(_.flatten(content), null, 0);
      fs.writeFile(file, content, function afterWriteFile(err) {
        return callback(err);
      });
    });
  },

  read: function read(file, callback) {
    return fs.readFile(file, ENCODING, function afterReadFile(err, content) {
      if (err) {
        return callback(err);
      } else {
        return callback(undefined, JSON.parse(content));
      }
    });
  },

  readSync: function readSync(file) {
    return JSON.parse(fs.readFileSync(file, ENCODING));
  },

  exists: function exists(file, callback) {
    return fs.exists(file, callback);
  },

  lock: function lock(file, callback) {
    var fileLock = generateLockFileName(file);
    lockFile.lock(fileLock, _lockOptions, callback);
  },

  unlock: function unlock(file, callback) {
    callback = callback || function afterUnlockFile(err) {
      if (err) {
        console.log('Oopss we couldn\'t release the lock!');
        throw err;
      }
    };
    var fileLock = generateLockFileName(file);
    lockFile.unlock(fileLock, callback);
  }
};

var _lockOptions = {
  wait: 15000,
  pollPeriod: 100,
  stale: 15000,
  retries: 1000,
  retryWait: 100
};

function generateLockFileName(file) {
  return file + '.lock';
}