mini-dbx/index.js

A JSON based super lightweight database!!

var fs = require('fs'),
mu = require('mini-util');

var _lockSave = false
var _needSave = {}

var PATTERN_SHARP = /##?/g,

/**
 * Compile filter string to function.
 * @param filter {string}
 */
compile = (function () {
	var cache = {
		'': function () { return true; }
	};

	return function (filter) {
		filter = filter || '';
		if (!cache[filter]) {
			filter = 'return ('
				+ filter.replace(PATTERN_SHARP, function (sharp) {
						return sharp === '#' ? '__index' : '#';
					})
				+ ');'
			cache[filter] = new Function('$', '__index', filter);
		}
		return cache[filter];
	};
}()),

/**
 * Create a Storage instance.
 * @param filename {string}
 */
factory = (function () {
	var cache = {};

	return function (filename) {
		var instance = cache[filename];

		if (!instance) {
			instance = cache[filename] = new Storage({
				filename: filename
			});
		}

		return instance;
	};
}()),

/**
 * Test whether an array value matches a filter.
 * @param filter {string}
 * @param value {*}
 * @param index {number}
 * @return {boolean}
 */
match = function (filter, value, index) {
	return !!compile(filter)(value, index);
},

/**
 * deep clone object
 */
clone = function (source){
	if(!mu.isObject(source)){
		throw new Error('invalid object , only object can be cloned !');
	}
	var copy;
	try{
		copy = JSON.parse(JSON.stringify(source));
	}catch(e){
		copy = {};
	}
	return copy;
},

// Storage constructor.
Storage = mu.inherit(Object, {
	/**
	 * Initializer.
	 * @param config {Object}
	 */
	constructor: function (config) {
		var filename = this._filename = config.filename;

		if (!fs.existsSync(filename)) {
			fs.writeFileSync(filename, '{}');
		}

		this._data = JSON.parse(
			fs.readFileSync(filename, 'utf-8'));
	},
	/**
	 * Save change to disk.
	 * @param cb {function}
	 */
	_save: function (cb) {
		//here lock save
		if(!_lockSave){
			_lockSave = true
			var filename = this._filename,
			data = this._data;
			setTimeout(() => {
				//console.log(filename)
				fs.writeFile(filename, JSON.stringify(data,null,2), function(){
					_lockSave = false
					if(_needSave.filename){
						_needSave.filename =false
						__save(cb)
					}
					else
						cb()
				} );
			}, 50);
			
		}
		else{
			_needSave[this._filename] = true
		}
	},

	/**
	 * Insert a new record.
	 * @param key {string}
	 * @param value {*}
	 * @param [cb] {function}
	 * @return {Object}
	 */
	insert: function (key, value, cb) {
		var data = this._data;

		if (!data[key]) {
			data[key] = [ value ];
		} else {
			data[key].push(value);
		}

		this._save(function (err){
			if(mu.isFunction(cb)){
				cb(err,value);
			}
		});

		return this;
	},

	/**
	 * Remove records.
	 * @param key {string}
	 * @param [filter] {string}
	 * @param [cb] {function}
	 * @return {Object}
	 */
	remove: function (key, filter, cb) {
		var data = this._data,
			arr = data[key],
			removed = [],
			i;
		if(mu.isFunction(filter)){
			cb = filter;
			filter = null;
		}
		if (arr) {
			for (i = 0; i < arr.length; ++i) {
				if (match(filter, arr[i], i)) {
					removed.push(arr[i]);
					// Set to undefined first to keep indexes of other value unchanged.
					arr[i] = undefined;
				}
			}

			arr = arr.filter(function (value) { // Compact array.
				return value !== undefined;
			});
			if (arr.length === 0) {
				// Delete empty property.
				delete data[key];
			} else {
				data[key] = arr;
			}
		}

		this._save(function (err){
			if(mu.isFunction(cb)){
				cb(err,removed);
			}
		});

		return this;
	},

	/**
	 * Select records.
	 * @param key {string}
	 * @param [filter] {string}
	 * @param [cb] {function}
	 * @return {Array}
	 */
	select: function (key, filter, cb) {
		var data = this._data,
			arr = data[key],
			result = [],
			i, len;
		if(mu.isFunction(filter)){
			cb = filter;
			filter = null;
		}
		if (arr) {
			for (i = 0, len = arr.length; i < len; ++i) {
				if (match(filter, arr[i], i)) {
					result.push(clone(arr[i]));//  deep clone
				}
			}
		}
		if(mu.isFunction(cb)){
			setImmediate(function(){
				cb(null,result);
			});
		}
		return result;
	},

	/**
	 * Update records.
	 * @param key {string}
	 * @param value {*}
	 * @param [filter] {string}
	 * @param [cb] {function}
	 * @return {Object}
	 */
	update: function (key, value, filter, cb) {
		var data = this._data,
			arr = data[key],
			updated = [],
			i, len;
		if(mu.isFunction(filter)){
			cb = filter;
			filter = null;
		}
		if (arr) {
			for (i = 0, len = arr.length; i < len; ++i) {
				if (match(filter, arr[i], i)) {
					// arr[i] = value;
					arr[i] = mu.mix(arr[i],value);
					updated.push(arr[i]);
				}
			}
		}

		this._save(function (err){
			if(mu.isFunction(cb)){
				cb(err,updated);
			}
		});

		return this;
	}
});

module.exports = factory;