using System;
using System.Collections;
using System.Collections.Specialized;
using System.Diagnostics;
using System.Text;
using System.IO;

namespace NntpLib
{
	public abstract class ArticleDecoder
	{
		protected Stream outStream  = null;

		public ArticleDecoder(Stream OutputStream)
		{
			outStream = OutputStream;
		}

		public abstract bool DecodeLine(string line);
	}

	public class YencDecoder : ArticleDecoder
	{
		bool inBody = false;
		bool inCode = false;
		string beginLine;

		public YencDecoder(Stream OutputStream, string BeginLine) : base(OutputStream)
		{
			this.beginLine = BeginLine;
		}

		/// <summary>
		/// Returns true when we're done (we've found the
		/// encoded block, and completed decoding it)
		/// </summary>
		public override bool DecodeLine(string line)
		{
			if (!inBody)
			{
				if (line.StartsWith("=ybegin "))
				{
					inBody = true;
					return false;
				};
			}

			if (line.StartsWith("=yend "))
			{
				// Done
				return true;
			}

			if (!inCode)
			{
				if (line.StartsWith("=ypart "))
					inCode = true;

				return false;
			};

			if (line.EndsWith("="))
			{
				Debugger.Break();
			};

			byte[] lineBytes = Encoding.UTF8.GetBytes(line);
			byte[] outBytes = new byte[lineBytes.Length];
			int outByte = 0;
			for (int i=0; i<lineBytes.Length; i++)
			{
				lineBytes[i] = (byte)((lineBytes[i] + 42) & 0xff);
				char ch = (char)lineBytes[i];
				if (ch == '=')
				{
					i++;
					outBytes[outByte++] = (byte)((lineBytes[i]+64)&0xff);
				} else
				{
					outBytes[outByte++] = lineBytes[i];
				};
			};

			outStream.Write(outBytes, 0, outByte);
			return false;
		}
	}

	/// <summary>
	/// Summary description for Article.
	/// </summary>
	public class UuDecoder : ArticleDecoder
	{
		bool inBody = false;
		bool inCode = false;
		string beginLine;

		public UuDecoder(Stream OutputStream, string BeginLine) : base(OutputStream)
		{
			beginLine = BeginLine;
		}

		public static byte[] uuDecode(string sBuffer) 
		{ 
			// Create an output array
			byte[] outBuffer = new byte[(sBuffer.Length-1)/4*3];
			int outIdx = 0;

			// Get the string as an array of ASCII bytes
			byte[] asciiBytes = Encoding.ASCII.GetBytes(sBuffer);
			for (int i=0; i<asciiBytes.Length; i++)
				asciiBytes[i] = (byte)((asciiBytes[i]-0x20) & 0x3f);
			
			// Convert each block fo 4 input bytes into 3 
			// output bytes
			for (int i = 1; i <= (asciiBytes.Length-1); i += 4) 
			{ 
				outBuffer[outIdx++] = (byte)(asciiBytes[i] << 2 | asciiBytes[i+1] >> 4);
				outBuffer[outIdx++] = (byte)(asciiBytes[i+1] << 4 | asciiBytes[i+2] >> 2);
				outBuffer[outIdx++] = (byte)(asciiBytes[i+2] << 6 | asciiBytes[i+3]);
			} 

			return outBuffer;
		} 

		/// <summary>
		/// Returns true when we're done (we've found the
		/// encoded block, and completed decoding it)
		/// </summary>
		public override bool DecodeLine(string line)
		{
			if (line.Length == 0 && !inBody)
			{
				inBody = true;
				return false;
			};

			if (inBody && line.StartsWith("begin"))
			{
				inCode = true;
				return false;
			};

			if (inCode)
			{
				if (line.Length < 5)
					return true;

				byte[] data = uuDecode(line);
				outStream.Write(data, 0, data.Length);
			};

			return false;
		}	
	}
}