// Copyright (c) Jan-Niklas Schäfer. All rights reserved.

// Licensed under the MIT License. See LICENSE file in the project root for full license information.

using System;

using System.Text;

namespace ThinkSharp.Licensing

{

public class Encoder

{

private readonly string myValidCharacters;

private readonly int myEncodingLength;

public Encoder() : this(Constants.ValidCharacters, -1)

{

}

public Encoder(int encodingLength) : this(Constants.ValidCharacters, encodingLength)

{

}

public Encoder(string validCharacters) : this(validCharacters, -1)

{

}

public Encoder(string validCharacters, int encodingLength)

{

myValidCharacters = validCharacters;

myEncodingLength = encodingLength;

}

public string Encode(string input)

{

return Encode(Encoding.UTF8.GetBytes(input), myEncodingLength < 0 ? input.Length : myEncodingLength);

}

public string Encode(byte[] bytes)

{

if (bytes == null)

throw new ArgumentNullException(nameof(bytes));

return Encode(bytes, myEncodingLength < 0 ? bytes.Length : myEncodingLength);

}

private string Encode(byte[] bytes, int length)

{

var random = new Random(99);

if (length < 0)

throw new ArgumentException("length must be a positive number");

var buffer = new byte[length];

random.NextBytes(buffer);

for (int i = 0; i < buffer.Length; i++)

buffer[i] ^= bytes[i%bytes.Length];

var builder = new StringBuilder();

foreach (var b in buffer)

builder.Append(myValidCharacters[b % myValidCharacters.Length]);

return builder.ToString();

}

}

}