biot-core/lib/fs.js

```sh $ npm install $ cd examples $ node balance.js ```

let root = {},
	bFsInitialized = false,
	isCordova = global.window && window.cordova,
	desktopApp;

let fs;
if (!isCordova) {
	fs = require('fs' + '');
	desktopApp = require('ocore/desktop_app.js' + '');
}

root.init = function (cb) {
	if (!isCordova) return cb(null);
	if (bFsInitialized) return cb(null);

	function onFileSystemSuccess(fileSystem) {
		console.log('File system started: ', fileSystem.name, fileSystem.root.name);
		bFsInitialized = true;
		return cb(fileSystem);
	}

	function fail(evt) {
		const msg = 'Could not init file system: ' + evt.target.error.code;
		console.log(msg);
		return cb(null);
	}

	window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, onFileSystemSuccess, fail);
};

root.readFileFromForm = function (file, cb) {
	if (isCordova) {
		const reader = new FileReader();
		reader.onloadend = function () {
			const fileBuffer = Buffer.from(new Uint8Array(this.result));
			cb(null, fileBuffer);
		};
		reader.readAsArrayBuffer(file);
	}
	else {
		return cb(null, fs.createReadStream(file.path));
	}
};

root.readFile = function (path, cb) {
	if (isCordova) {
		root.init(function () {
			window.resolveLocalFileSystemURL(path, function (fileEntry) {
				fileEntry.file(function (file) {
					root.readFileFromForm(file, cb);
				});
			}, function (e) {
				if(e.code === 1) return cb(true);
				throw new Error('error: ' + JSON.stringify(e));
			});
		});
	}
	else {
		fs.readFile(path, function (err, data) {
			return err ? cb(err) : cb(null, data);
		});
	}
};

root.getPath = function (path, cb) {
	return cb(null, path.replace(/\\/g, '/'));
};

root.nwWriteFile = function (path, data, cb) {
	if (!isCordova) {
		fs.writeFile(path, data, function (err) {
			return err ? cb(err) : cb(null);
		});
	}
	else {
		cb('use cordovaWriteFile')
	}
};

// example: fileSystemService.cordovaWriteFile(cordova.file.externalRootDirectory, 'testFolder', 'testFile.txt', 'testText :)', function(err) {
root.cordovaWriteFile = function (cordovaFile, path, fileName, data, cb) {
	if (isCordova) {
		root.init(function () {
			window.resolveLocalFileSystemURL(cordovaFile, function (dirEntry) {
				if (!path || path == '.' || path == '/') {
					_cordovaWriteFile(dirEntry, fileName, data, cb);
				}
				else {
					dirEntry.getDirectory(path, {create: true, exclusive: false}, function (dirEntry1) {
						_cordovaWriteFile(dirEntry1, fileName, data, cb);
					}, cb);
				}
			}, cb);
		});
	}
	else {
		cb('use nwWriteFile');
	}
};

function _cordovaWriteFile(dirEntry, name, data, cb) {
	if (typeof data != 'string') data = data.buffer;
	dirEntry.getFile(name, {create: true, exclusive: false}, function (file) {
		file.createWriter(function (writer) {
			writer.onwriteend = function () {
				cb(null);
			};
			writer.write(data);
		}, cb);
	}, cb);
}

root.readdir = function (path, cb) {
	if (isCordova) {
		root.init(function () {
			window.resolveLocalFileSystemURL(path,
				function (fileSystem) {
					const reader = fileSystem.createReader();
					reader.readEntries(
						function (entries) {
							cb(null, entries.map(function (entry) {
								return entry.name
							}));
						},
						function (err) {
							cb(err);
						}
					);
				}, function (err) {
					cb(err);
				}
			);
		});
	}
	else {
		fs.readdir(path, function (err, entries) {
			return err ? cb(err) : cb(null, entries);
		});
	}
};

root.nwMoveFile = function (oldPath, newPath, cb) {
	const read = fs.createReadStream(oldPath);
	const write = fs.createWriteStream(newPath);

	read.pipe(write);
	read.on('end', function () {
		fs.unlink(oldPath, cb);
	});
};

root.nwUnlink = function (path, cb) {
	fs.unlink(path, cb);
};

root.nwRmDir = function (path, cb) {
	fs.rmdir(path, cb);
};

root.nwExistsSync = function (path) {
	return fs.existsSync(path);
};


root.getParentDirPath = function () {
	if (!isCordova) return false;
	switch (window.cordova.platformId) {
		case 'ios':
			return window.cordova.file.applicationStorageDirectory + '/Library';
		case 'android':
		default:
			return window.cordova.file.applicationStorageDirectory;
	}
};

root.getDatabaseDirName = function () {
	if (!isCordova) return false;
	switch (window.cordova.platformId) {
		case 'ios':
			return 'LocalDatabase';
		case 'android':
		default:
			return 'databases';
	}
};

root.getDatabaseDirPath = function () {
	if (isCordova) {
		return root.getParentDirPath() + '/' + root.getDatabaseDirName();
	}
	else {
		return desktopApp.getAppDataDir();
	}
};

root.recursiveMkdir = function (path, mode, callback) {
	var parentDir = require('path' + '').dirname(path);

	fs.stat(parentDir, function (err, stats) {
		if (err && err.code !== 'ENOENT')
			throw Error("failed to stat dir: " + err);

		if (err && err.code === 'ENOENT') {
			root.recursiveMkdir(parentDir, mode, function (err) {
				if (err)
					callback(err);
				else
					fs.mkdir(path, mode, callback);
			});
		} else {
			fs.mkdir(path, mode, callback);
		}
	});
};

root.cordovaExists = function (path, cb) {
	root.readFile(path, (err, data) => {
		if (err || !data){
			return cb(false);
		}else{
			return cb(true);
		}
	});
};

module.exports = root;