//	Spludlow Software
//	Copyright © Samuel P. Ludlow 2020 All Rights Reserved
//	Distributed under the terms of the GNU General Public License version 3
//	Distributed WITHOUT ANY WARRANTY; without implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE
//	https://www.spludlow.co.uk/LICENCE.TXT
//	The Spludlow logo is a registered trademark of Samuel P. Ludlow and may not be used without permission
//	v1.14

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.IO;

namespace Spludlow.Email
{
	/// <summary>
	///	Create 'MacBinary' files that can be extracted on a Macintosh to restore the data fork, File Type, and Creator Code
	/// Used with the 'AppleDouble' class, from files normally emailed from a Macintosh
	/// </summary>
	public class MacBinary
	{
		public MacBinary()
		{
		}

		public void Save(string filename, AppleDouble appleDouble)
		{
			using (BinaryWriter writer = new BinaryWriter(new FileStream(filename, FileMode.Create)))
			{
				byte tempByte;
				byte[] tempByteArray;
				short tempWord;
				int tempLong;

				//000 Byte old version number, must be kept at zero for compatibility
				tempByte = 0;
				writer.Write(tempByte);

				//001 Byte Length of filename (must be in the range 1-31)
				tempByte = (byte)appleDouble.FileName.Length;
				writer.Write(tempByte);

				//002 1 to 63 Bytes filename (only "length" bytes are significant).
				tempByteArray = new byte[63];
				for (int index = 0; index < tempByteArray.Length && index < appleDouble.FileNameData.Length; ++index)
					tempByteArray[index] = appleDouble.FileNameData[index];
				writer.Write(tempByteArray);

				//065 Long Word file type (normally expressed as four characters)
				writer.Write(appleDouble.FileType, 0, 4);

				//069 Long Word file creator (normally expressed as four characters)
				writer.Write(appleDouble.CreatorCode, 0, 4);

				//073 Byte original Finder flags
				//Bit 7 - isAlias.
				//Bit 6 - isInvisible.
				//Bit 5 - hasBundle.
				//Bit 4 - nameLocked.
				//Bit 3 - isStationery.
				//Bit 2 - hasCustomIcon.
				//Bit 1 - reserved.
				//Bit 0 - hasBeenInited.
				tempByte = 0;
				writer.Write(tempByte);

				//074 Byte zero fill, must be zero for compatibility
				tempByte = 0;
				writer.Write(tempByte);

				//075 Word file's vertical position within its window.
				tempWord = 0;
				writer.Write(tempWord);

				//077 Word file's horizontal position within its window.
				tempWord = 0;
				writer.Write(tempWord);

				//079 Word file's window or folder ID.
				tempWord = 0;
				writer.Write(tempWord);

				//081 Byte "Protected" flag (in low order bit).
				tempByte = 0;
				writer.Write(tempByte);

				//082 Byte zero fill, must be zero for compatibility
				tempByte = 0;
				writer.Write(tempByte);

				//083 Long Word Data Fork length (bytes, zero if no Data Fork).
				writer.Write(ReverseInt32(appleDouble.DataFork.Length));

				//087 Long Word Resource Fork length (bytes, zero if no R.F.).
				writer.Write(ReverseInt32(appleDouble.ResourceFork.Length));

				//091 Long Word File's creation date
				tempLong = 0;
				writer.Write(tempLong);

				//095 Long Word File's "last modified" date.
				tempLong = 0;
				writer.Write(tempLong);

				//099 Word length of Get Info comment to be sent after the resource fork (if implemented, see below).
				tempWord = 0;
				writer.Write(tempWord);

				//101 Byte Finder Flags, bits 0-7. (Bits 8-15 are already in byte 73)
				//Bit 7 - hasNoInits
				//Bit 6 - isShared
				//Bit 5 - requiresSwitchLaunch
				//Bit 4 - ColorReserved
				//Bits 1-3 - color
				//Bit 0 - isOnDesk
				tempByte = 0;
				writer.Write(tempByte);

				//*102 Long Word signature for indentification purposes (‘mBIN’)
				tempByteArray = new byte[4];
				tempByteArray[0] = (byte)'m';
				tempByteArray[1] = (byte)'B';
				tempByteArray[2] = (byte)'I';
				tempByteArray[3] = (byte)'N';
				writer.Write(tempByteArray, 0, 4);

				//*106 Byte script of file name (from the fdScript field of an fxInfo record)
				tempByte = 0;
				writer.Write(tempByte);

				//*107 Byte extended Finder flags (from the fdXFlags field of an fxInfo record)
				tempByte = 0;
				writer.Write(tempByte);

				//108-115 Unused (must be zeroed by creators, must be ignored by readers)
				tempByteArray = new byte[8];
				writer.Write(tempByteArray, 0, 8);

				//116 Long Word Length of total files when packed files are unpacked. As of the
				//writing of this document, this field has never been used.
				tempLong = 0;
				writer.Write(tempLong);

				//120 Word Length of a secondary header. If this is non-zero, skip this many bytes (rounded up to the next multiple of 128). This is for future expansion only, when sending files with MacBinary, this word should be zero.
				tempWord = 0;
				writer.Write(tempWord);

				//*122 Byte Version number of MacBinary III that the uploading program is written for (the version is 130 for MacBinary III)
				tempByte = 130;
				writer.Write(tempByte);

				//123 Byte Minimum MacBinary version needed to read this file (set this value at 129 for backwards compatibility with MacBinary II)
				tempByte = 129;
				writer.Write(tempByte);

				//124 Word CRC of previous 124 bytes
				tempWord = 0;
				writer.Write(tempWord);

				// Round it to 128
				tempWord = 0;
				writer.Write(tempWord);

				// Data Fork
				if (appleDouble.DataFork.Length != 0)
				{
					writer.Write(appleDouble.DataFork);

					int pad = PadBytesNeeded(appleDouble.DataFork.Length);
					if (pad > 0)
					{
						tempByteArray = new byte[pad];
						writer.Write(tempByteArray, 0, pad);
					}
				}

				// Resource fork
				if (appleDouble.ResourceFork.Length != 0)
				{
					writer.Write(appleDouble.ResourceFork);

					int pad = PadBytesNeeded(appleDouble.ResourceFork.Length);
					if (pad > 0)
					{
						tempByteArray = new byte[pad];
						writer.Write(tempByteArray, 0, pad);
					}
				}

			}
		}

		private int PadBytesNeeded(int size)
		{
			int pad = 128 - (size % 128);

			if (pad == 128)
				pad = 0;

			return pad;
		}

		private static int ReverseInt32(int input)
		{
			byte[] temp = BitConverter.GetBytes(input);
			Array.Reverse(temp);
			return BitConverter.ToInt32(temp, 0);
		}
	}
}