/*
 * decaffeinate suggestions:
 * DS101: Remove unnecessary use of Array.from
 * DS102: Remove unnecessary code created because of implicit returns
 * DS207: Consider shorter variations of null checks
 * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
 */
let SafeReader;
const fs = require("fs");
const logger = require("logger-sharelatex");

module.exports = (SafeReader = {

	// safely read up to size bytes from a file and return result as a
	// string

	readFile(file, size, encoding, callback) {
		if (callback == null) { callback = function(error, result) {}; }
		return fs.open(file, 'r', function(err, fd) {
			if ((err != null) && (err.code === 'ENOENT')) { return callback(); }
			if (err != null) { return callback(err); }

			// safely return always closing the file
			const callbackWithClose = (err, ...result) =>
				fs.close(fd, function(err1) {
					if (err != null) { return callback(err); }
					if (err1 != null) { return callback(err1); }
					return callback(null, ...Array.from(result));
				})
			;

			const buff = new Buffer(size, 0); // fill with zeros
			return fs.read(fd, buff, 0, buff.length, 0, function(err, bytesRead, buffer) {
				if (err != null) { return callbackWithClose(err); }
				const result = buffer.toString(encoding, 0, bytesRead);
				return callbackWithClose(null, result, bytesRead);
			});
		});
	}
});