using System.IO;

namespace Org.BouncyCastle.Utilities.Encoders;

public class Base64Encoder : IEncoder
{
	protected readonly byte[] encodingTable = new byte[64]
	{
		65, 66, 67, 68, 69, 70, 71, 72, 73, 74,
		75, 76, 77, 78, 79, 80, 81, 82, 83, 84,
		85, 86, 87, 88, 89, 90, 97, 98, 99, 100,
		101, 102, 103, 104, 105, 106, 107, 108, 109, 110,
		111, 112, 113, 114, 115, 116, 117, 118, 119, 120,
		121, 122, 48, 49, 50, 51, 52, 53, 54, 55,
		56, 57, 43, 47
	};

	protected byte padding = 61;

	protected readonly byte[] decodingTable = new byte[128];

	protected void InitialiseDecodingTable()
	{
		Arrays.Fill(decodingTable, byte.MaxValue);
		for (int i = 0; i < encodingTable.Length; i++)
		{
			decodingTable[encodingTable[i]] = (byte)i;
		}
	}

	public Base64Encoder()
	{
		InitialiseDecodingTable();
	}

	public int Encode(byte[] data, int off, int length, Stream outStream)
	{
		int num = length % 3;
		int num2 = length - num;
		for (int i = off; i < off + num2; i += 3)
		{
			int num3 = data[i] & 0xFF;
			int num4 = data[i + 1] & 0xFF;
			int num5 = data[i + 2] & 0xFF;
			outStream.WriteByte(encodingTable[(num3 >>> 2) & 0x3F]);
			outStream.WriteByte(encodingTable[((num3 << 4) | (num4 >>> 4)) & 0x3F]);
			outStream.WriteByte(encodingTable[((num4 << 2) | (num5 >>> 6)) & 0x3F]);
			outStream.WriteByte(encodingTable[num5 & 0x3F]);
		}
		switch (num)
		{
		case 1:
		{
			int num6 = data[off + num2] & 0xFF;
			int num8 = (num6 >> 2) & 0x3F;
			int num9 = (num6 << 4) & 0x3F;
			outStream.WriteByte(encodingTable[num8]);
			outStream.WriteByte(encodingTable[num9]);
			outStream.WriteByte(padding);
			outStream.WriteByte(padding);
			break;
		}
		case 2:
		{
			int num6 = data[off + num2] & 0xFF;
			int num7 = data[off + num2 + 1] & 0xFF;
			int num8 = (num6 >> 2) & 0x3F;
			int num9 = ((num6 << 4) | (num7 >> 4)) & 0x3F;
			int num10 = (num7 << 2) & 0x3F;
			outStream.WriteByte(encodingTable[num8]);
			outStream.WriteByte(encodingTable[num9]);
			outStream.WriteByte(encodingTable[num10]);
			outStream.WriteByte(padding);
			break;
		}
		}
		return num2 / 3 * 4 + ((num != 0) ? 4 : 0);
	}

	private bool ignore(char c)
	{
		if (c != '\n' && c != '\r' && c != '\t')
		{
			return c == ' ';
		}
		return true;
	}

	public int Decode(byte[] data, int off, int length, Stream outStream)
	{
		int num = 0;
		int num2 = off + length;
		while (num2 > off && ignore((char)data[num2 - 1]))
		{
			num2--;
		}
		int i = off;
		int num3 = num2 - 4;
		for (i = nextI(data, i, num3); i < num3; i = nextI(data, i, num3))
		{
			byte b = decodingTable[data[i++]];
			i = nextI(data, i, num3);
			byte b2 = decodingTable[data[i++]];
			i = nextI(data, i, num3);
			byte b3 = decodingTable[data[i++]];
			i = nextI(data, i, num3);
			byte b4 = decodingTable[data[i++]];
			if ((b | b2 | b3 | b4) >= 128)
			{
				throw new IOException("invalid characters encountered in base64 data");
			}
			outStream.WriteByte((byte)((b << 2) | (b2 >> 4)));
			outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
			outStream.WriteByte((byte)((b3 << 6) | b4));
			num += 3;
		}
		return num + decodeLastBlock(outStream, (char)data[num2 - 4], (char)data[num2 - 3], (char)data[num2 - 2], (char)data[num2 - 1]);
	}

	private int nextI(byte[] data, int i, int finish)
	{
		while (i < finish && ignore((char)data[i]))
		{
			i++;
		}
		return i;
	}

	public int DecodeString(string data, Stream outStream)
	{
		int num = 0;
		int num2 = data.Length;
		while (num2 > 0 && ignore(data[num2 - 1]))
		{
			num2--;
		}
		int i = 0;
		int num3 = num2 - 4;
		for (i = nextI(data, i, num3); i < num3; i = nextI(data, i, num3))
		{
			byte b = decodingTable[(uint)data[i++]];
			i = nextI(data, i, num3);
			byte b2 = decodingTable[(uint)data[i++]];
			i = nextI(data, i, num3);
			byte b3 = decodingTable[(uint)data[i++]];
			i = nextI(data, i, num3);
			byte b4 = decodingTable[(uint)data[i++]];
			if ((b | b2 | b3 | b4) >= 128)
			{
				throw new IOException("invalid characters encountered in base64 data");
			}
			outStream.WriteByte((byte)((b << 2) | (b2 >> 4)));
			outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
			outStream.WriteByte((byte)((b3 << 6) | b4));
			num += 3;
		}
		return num + decodeLastBlock(outStream, data[num2 - 4], data[num2 - 3], data[num2 - 2], data[num2 - 1]);
	}

	private int decodeLastBlock(Stream outStream, char c1, char c2, char c3, char c4)
	{
		if (c3 == padding)
		{
			if (c4 != padding)
			{
				throw new IOException("invalid characters encountered at end of base64 data");
			}
			byte b = decodingTable[(uint)c1];
			byte b2 = decodingTable[(uint)c2];
			if ((b | b2) >= 128)
			{
				throw new IOException("invalid characters encountered at end of base64 data");
			}
			outStream.WriteByte((byte)((b << 2) | (b2 >> 4)));
			return 1;
		}
		if (c4 == padding)
		{
			byte b3 = decodingTable[(uint)c1];
			byte b4 = decodingTable[(uint)c2];
			byte b5 = decodingTable[(uint)c3];
			if ((b3 | b4 | b5) >= 128)
			{
				throw new IOException("invalid characters encountered at end of base64 data");
			}
			outStream.WriteByte((byte)((b3 << 2) | (b4 >> 4)));
			outStream.WriteByte((byte)((b4 << 4) | (b5 >> 2)));
			return 2;
		}
		byte b6 = decodingTable[(uint)c1];
		byte b7 = decodingTable[(uint)c2];
		byte b8 = decodingTable[(uint)c3];
		byte b9 = decodingTable[(uint)c4];
		if ((b6 | b7 | b8 | b9) >= 128)
		{
			throw new IOException("invalid characters encountered at end of base64 data");
		}
		outStream.WriteByte((byte)((b6 << 2) | (b7 >> 4)));
		outStream.WriteByte((byte)((b7 << 4) | (b8 >> 2)));
		outStream.WriteByte((byte)((b8 << 6) | b9));
		return 3;
	}

	private int nextI(string data, int i, int finish)
	{
		while (i < finish && ignore(data[i]))
		{
			i++;
		}
		return i;
	}
}