var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
var b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/;
export const btoa = function(string) {
	string = String(string);
	var bitmap, a, b, c, result = "",
		i = 0,
		rest = string.length % 3;
	for (; i < string.length;) {
		if ((a = string.charCodeAt(i++)) > 255 ||
			(b = string.charCodeAt(i++)) > 255 ||
			(c = string.charCodeAt(i++)) > 255)
			throw new TypeError(
				"Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range."
			);
		bitmap = (a << 16) | (b << 8) | c;
		result += b64.charAt(bitmap >> 18 & 63) + b64.charAt(bitmap >> 12 & 63) +
			b64.charAt(bitmap >> 6 & 63) + b64.charAt(bitmap & 63);
	}
	return rest ? result.slice(0, rest - 3) + "===".substring(rest) : result;
};

export const atob = function(string) {
	string = String(string).replace(/[\t\n\f\r ]+/g, "");
	if (!b64re.test(string))
		throw new TypeError(
			"Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.");
	string += "==".slice(2 - (string.length & 3));
	var bitmap, result = "",
		r1, r2, i = 0;
	for (; i < string.length;) {
		bitmap = b64.indexOf(string.charAt(i++)) << 18 | b64.indexOf(string.charAt(i++)) << 12 |
			(r1 = b64.indexOf(string.charAt(i++))) << 6 | (r2 = b64.indexOf(string.charAt(i++)));
		result += r1 === 64 ? String.fromCharCode(bitmap >> 16 & 255) :
			r2 === 64 ? String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255) :
			String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255, bitmap & 255);
	}
	return result;
};

function b64DecodeUnicode(str) {
	return decodeURIComponent(exports.weAtob(str).replace(/(.)/g, function(p) {
		var code = p.charCodeAt(0).toString(16).toUpperCase();
		if (code.length < 2) {
			code = "0" + code;
		}
		return "%" + code;
	}));
}

function base64_url_decode(str) {
	var output = str.replace(/-/g, "+").replace(/_/g, "/");
	switch (output.length % 4) {
		case 0:
			break;
		case 2:
			output += "==";
			break;
		case 3:
			output += "=";
			break;
		default:
			throw "Illegal base64url string!";
	}
	try {
		return b64DecodeUnicode(output);
	} catch (err) {
		return exports.weAtob(output);
	}
}

function weappJwtDecode(token, options) {
	if (typeof token !== "string") {
		throw ("Invalid token specified");
	}
	options = options || {};
	var pos = options.header === true ? 0 : 1;
	try {
		return JSON.parse(base64_url_decode(token.split(".")[pos]));
	} catch (e) {
		throw ("Invalid token specified: " + e.message);
	}
}