"use strict";
// private property
const _keyStr =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

// public method for encoding
exports.encode = function (input) {
	let output = "";
	let chr1, chr2, chr3, enc1, enc2, enc3, enc4;
	let i = 0;

	while (i < input.length) {
		chr1 = input.charCodeAt(i++);
		chr2 = input.charCodeAt(i++);
		chr3 = input.charCodeAt(i++);

		enc1 = chr1 >> 2;
		enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
		enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
		enc4 = chr3 & 63;

		if (isNaN(chr2)) {
			enc3 = enc4 = 64;
		} else if (isNaN(chr3)) {
			enc4 = 64;
		}

		output =
			output +
			_keyStr.charAt(enc1) +
			_keyStr.charAt(enc2) +
			_keyStr.charAt(enc3) +
			_keyStr.charAt(enc4);
	}

	return output;
};

// public method for decoding
exports.decode = function (input) {
	let output = "";
	let chr1, chr2, chr3;
	let enc1, enc2, enc3, enc4;
	let i = 0;

	input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

	while (i < input.length) {
		enc1 = _keyStr.indexOf(input.charAt(i++));
		enc2 = _keyStr.indexOf(input.charAt(i++));
		enc3 = _keyStr.indexOf(input.charAt(i++));
		enc4 = _keyStr.indexOf(input.charAt(i++));

		chr1 = (enc1 << 2) | (enc2 >> 4);
		chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
		chr3 = ((enc3 & 3) << 6) | enc4;

		output += String.fromCharCode(chr1);

		if (enc3 !== 64) {
			output += String.fromCharCode(chr2);
		}
		if (enc4 !== 64) {
			output += String.fromCharCode(chr3);
		}
	}

	return output;
};