namespace Neo.Cryptography
{
    export class Base58
    {
        public static Alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";

        public static decode(input: string): Uint8Array
        {
            let bi = BigInteger.Zero;
            for (let i = input.length - 1; i >= 0; i--)
            {
                let index = Base58.Alphabet.indexOf(input[i]);
                if (index == -1)
                    throw new RangeError();
                bi = BigInteger.add(bi, BigInteger.multiply(BigInteger.pow(Base58.Alphabet.length, input.length - 1 - i), index));
            }
            let bytes: Uint8Array = bi.toUint8Array();
            let leadingZeros = 0;
            for (let i = 0; i < input.length && input[i] == Base58.Alphabet[0]; i++)
            {
                leadingZeros++;
            }
            let tmp = new Uint8Array(bytes.length + leadingZeros);
            for (let i = 0; i < bytes.length; i++)
                tmp[i + leadingZeros] = bytes[bytes.length - 1 - i];
            return tmp;
        }

        public static encode(input: Uint8Array): string
        {
            let value = BigInteger.fromUint8Array(input, 1, false);
            let s = "";
            while (!value.isZero())
            {
                let r = BigInteger.divRem(value, Base58.Alphabet.length);
                s = Base58.Alphabet[r.remainder.toInt32()] + s;
                value = r.result;
            }
            for (let i = 0; i < input.length; i++)
            {
                if (input[i] == 0)
                    s = Base58.Alphabet[0] + s;
                else
                    break;
            }
            return s;
        }
    }
}