/* ------------------------------------------------------------------------------------

  webauthn - MIT License - Hexagon <github.com/Hexagon>

  ------------------------------------------------------------------------------------

  License:

	Copyright (c) 2021 Hexagon <github.com/Hexagon>

	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:
	The above copyright notice and this permission notice shall be included in
	all copies or substantial portions of the Software.
	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	THE SOFTWARE.

  ------------------------------------------------------------------------------------  */

const 
	// Regular webauthn characters
	chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",

	// webauthnurl characters
	charsUrl = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",

	genLookup = (target) => {
		let lookupTemp = typeof Uint8Array === "undefined" ? [] : new Uint8Array(256);
		for (let i = 0; i < chars.length; i++) {
			lookupTemp[target.charCodeAt(i)] = i;
		}
		return lookupTemp;
	},
  
	// Use a lookup table to find the index.
	lookup = genLookup(chars),
	lookupUrl = genLookup(charsUrl); 

let webauthn = {};

/**
 * Convenience function for converting a webauthn encoded string to an ArrayBuffer instance
 * @public
 * 
 * @param {string} data - webauthn representation of data
 * @param {boolean} [urlMode] - If set to true, URL mode string will be expected
 * @returns {ArrayBuffer} - Decoded data
 */
webauthn.toArrayBuffer = (data, urlMode) => {
	let bufferLength = data.length * 0.75,
		len = data.length,
		i,
		p = 0,
		encoded1,
		encoded2,
		encoded3,
		encoded4;

	if (data[data.length - 1] === "=") {
		bufferLength--;
		if (data[data.length - 2] === "=") {
			bufferLength--;
		}
	}

	const 
		arraybuffer = new ArrayBuffer(bufferLength),
		bytes = new Uint8Array(arraybuffer),
		target = urlMode ? lookupUrl : lookup;

	for (i = 0; i < len; i += 4) {
		encoded1 = target[data.charCodeAt(i)];
		encoded2 = target[data.charCodeAt(i + 1)];
		encoded3 = target[data.charCodeAt(i + 2)];
		encoded4 = target[data.charCodeAt(i + 3)];

		bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
		bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
		bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
	}

	return arraybuffer;

};

/**
 * Convenience function for converting webauthn encoded string to an ArrayBuffer instance
 * @public
 * 
 * @param {ArrayBuffer} arrBuf - ArrayBuffer to be encoded
 * @param {boolean} [urlMode] - If set to true, URL mode string will be returned
 * @returns {string} - webauthn representation of data
 */
webauthn.fromArrayBuffer = (arrBuf, urlMode) => {
	let bytes = new Uint8Array(arrBuf),
		i,
		len = bytes.length,
		result = "",
		target = urlMode ? charsUrl : chars;

	for (i = 0; i < len; i += 3) {
		result += target[bytes[i] >> 2];
		result += target[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
		result += target[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
		result += target[bytes[i + 2] & 63];
	}

	if (len % 3 === 2) {
		result = result.substring(0, result.length - 1) + (urlMode ? "" : "=");
	} else if (len % 3 === 1) {
		result = result.substring(0, result.length - 2) + (urlMode ? "" : "==");
	}

	return result;
};

/**
 * Convenience function for converting webauthn to string
 * @public
 * 
 * @param {string} str - webauthn encoded string to be decoded
 * @returns {string} - Decoded string
 */
webauthn.toString = (str, urlMode) => {
	return Buffer.from(webauthn.toArrayBuffer(str, urlMode)).toString();
};

/**
 * Convenience function for converting a javascript string to webauthn
 * @public
 * 
 * @param {string} str - String to be converted to webauthn
 * @returns {string} - webauthn encoded string
 */
webauthn.fromString = (str, urlMode) => {
	return webauthn.fromArrayBuffer(Buffer.from(str), urlMode);
};

export default webauthn;
export { webauthn };