/*
 * UTF32Encoding.cs - Implementation of the
 *		"System.Text.UTF32Encoding" class.
 *
 * Author: Atsushi Enomoto <atsushi@ximian.com>
 *
 * Copyright (C) 2005 Novell, Inc.  http://www.novell.com
 *
 * The basic part (now almost nothing) is copied from UnicodeEncoding.cs.
 * Original copyrights goes here:
 *
 * Copyright (c) 2001, 2002  Southern Storm Software, Pty Ltd
 * Copyright (C) 2003, 2004 Novell, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

namespace System.Text
{

using System;

[Serializable]
public sealed class UTF32Encoding : Encoding
{
	// Magic numbers used by Windows for UTF32.
	internal const int UTF32_CODE_PAGE     = 12000;
	internal const int BIG_UTF32_CODE_PAGE = 12001;

	// Internal state.
	private bool bigEndian;
	private bool byteOrderMark;

	// Constructors.
	public UTF32Encoding () : this (false, true, false)
	{
	}

	public UTF32Encoding (bool bigEndian, bool byteOrderMark)
		: this (bigEndian, byteOrderMark, false)
	{
	}

	public UTF32Encoding (bool bigEndian, bool byteOrderMark, bool throwOnInvalidCharacters)
		: base ((bigEndian ? BIG_UTF32_CODE_PAGE : UTF32_CODE_PAGE))
	{
		this.bigEndian = bigEndian;
		this.byteOrderMark = byteOrderMark;

		if (throwOnInvalidCharacters)
			SetFallbackInternal (EncoderFallback.ExceptionFallback,
				DecoderFallback.ExceptionFallback);
		else
			SetFallbackInternal (new EncoderReplacementFallback ("\uFFFD"),
				new DecoderReplacementFallback ("\uFFFD"));

		if (bigEndian){
			body_name = "utf-32BE";
			encoding_name = "UTF-32 (Big-Endian)";
			header_name = "utf-32BE";
			web_name = "utf-32BE";
		} else {
			body_name = "utf-32";
			encoding_name = "UTF-32";
			header_name = "utf-32";
			web_name = "utf-32";
		}
		
		// Windows reports the same code page number for
		// both the little-endian and big-endian forms.
		windows_code_page = UTF32_CODE_PAGE;
	}

	// Get the number of bytes needed to encode a character buffer.
	[MonoTODO ("handle fallback")]
	public override int GetByteCount (char[] chars, int index, int count)
	{
		if (chars == null) {
			throw new ArgumentNullException ("chars");
		}
		if (index < 0 || index > chars.Length) {
			throw new ArgumentOutOfRangeException ("index", _("ArgRange_Array"));
		}
		if (count < 0 || count > (chars.Length - index)) {
			throw new ArgumentOutOfRangeException ("count", _("ArgRange_Array"));
		}
		int ret = 0;
		for (int i = index; i < index + count; i++) {
			if (Char.IsSurrogate (chars [i])) {
				if (i + 1 < chars.Length && Char.IsSurrogate (chars [i + 1]))
					ret += 4;
				else
					// FIXME: handle fallback
//					ret += DecoderFallback.MaxCharCount;
					ret += 4;
			}
			else
				ret += 4;
		}
		return ret;
	}

	// Get the bytes that result from encoding a character buffer.
	[MonoTODO ("handle fallback")]
	public override int GetBytes (char[] chars, int charIndex, int charCount,
								 byte[] bytes, int byteIndex)
	{
		if (chars == null) {
			throw new ArgumentNullException ("chars");
		}
		if (bytes == null) {
			throw new ArgumentNullException ("bytes");
		}
		if (charIndex < 0 || charIndex > chars.Length) {
			throw new ArgumentOutOfRangeException ("charIndex", _("ArgRange_Array"));
		}
		if (charCount < 0 || charCount > (chars.Length - charIndex)) {
			throw new ArgumentOutOfRangeException ("charCount", _("ArgRange_Array"));
		}
		if (byteIndex < 0 || byteIndex > bytes.Length) {
			throw new ArgumentOutOfRangeException ("byteIndex", _("ArgRange_Array"));
		}
		if ((bytes.Length - byteIndex) < (charCount * 4)) {
			throw new ArgumentException (_("Arg_InsufficientSpace"));
		}
		int posn = byteIndex;
		char ch;

		while (charCount-- > 0) {
			ch = chars[charIndex++];
			if (Char.IsSurrogate (ch)) {
				if (charCount-- > 0) {
					int value = 0x400 * (ch - 0xD800) + 0x10000 + chars [charIndex++] - 0xDC00;
					if (bigEndian) {
						for (int i = 0; i < 4; i++) {
							bytes [posn + 3 - i] = (byte) (value % 0x100);
							value >>= 8;
						}
						posn += 4;
					} else {
						for (int i = 0; i < 4; i++) {
							bytes [posn++] = (byte) (value % 0x100);
							value >>= 8;
						}
					}
				} else {
					// Illegal surrogate
					// FIXME: use fallback
					if (bigEndian) {
						bytes[posn++] = 0;
						bytes[posn++] = 0;
						bytes[posn++] = 0;
						bytes[posn++] = (byte) '?';
					} else {
						bytes[posn++] = (byte) '?';
						bytes[posn++] = 0;
						bytes[posn++] = 0;
						bytes[posn++] = 0;
					}
				}
			} else {
				if (bigEndian) {
					bytes[posn++] = 0;
					bytes[posn++] = 0;
					bytes[posn++] = (byte)(ch >> 8);
					bytes[posn++] = (byte)ch;
				} else {
					bytes[posn++] = (byte)ch;
					bytes[posn++] = (byte)(ch >> 8);
					bytes[posn++] = 0;
					bytes[posn++] = 0;
				}
			}
		}

		return posn - byteIndex;
	}

	// Get the number of characters needed to decode a byte buffer.
	public override int GetCharCount (byte[] bytes, int index, int count)
	{
		if (bytes == null) {
			throw new ArgumentNullException ("bytes");
		}
		if (index < 0 || index > bytes.Length) {
			throw new ArgumentOutOfRangeException ("index", _("ArgRange_Array"));
		}
		if (count < 0 || count > (bytes.Length - index)) {
			throw new ArgumentOutOfRangeException ("count", _("ArgRange_Array"));
		}
		return count / 4;
	}

	// Get the characters that result from decoding a byte buffer.
	public override int GetChars (byte[] bytes, int byteIndex, int byteCount,
								 char[] chars, int charIndex)
	{
		if (bytes == null) {
			throw new ArgumentNullException ("bytes");
		}
		if (chars == null) {
			throw new ArgumentNullException ("chars");
		}
		if (byteIndex < 0 || byteIndex > bytes.Length) {
			throw new ArgumentOutOfRangeException ("byteIndex", _("ArgRange_Array"));
		}
		if (byteCount < 0 || byteCount > (bytes.Length - byteIndex)) {
			throw new ArgumentOutOfRangeException ("byteCount", _("ArgRange_Array"));
		}
		if (charIndex < 0 || charIndex > chars.Length) {
			throw new ArgumentOutOfRangeException ("charIndex", _("ArgRange_Array"));
		}

/*
		// Determine the byte order in the incoming buffer.
		bool isBigEndian;
		if (byteCount >= 2) {
			if (bytes[byteIndex] == (byte)0xFE && bytes[byteIndex + 1] == (byte)0xFF) {
				isBigEndian = true;
			} else if (bytes[byteIndex] == (byte)0xFF && bytes[byteIndex + 1] == (byte)0xFE) {
				isBigEndian = false;
			} else {
				isBigEndian = bigEndian;
			}
		} else {
			isBigEndian = bigEndian;
		}
*/

		// Validate that we have sufficient space in "chars".
		if ((chars.Length - charIndex) < (byteCount / 4)) {
			throw new ArgumentException (_("Arg_InsufficientSpace"));
		}

		// Convert the characters.
		int posn = charIndex;
		if (bigEndian) {
			while (byteCount >= 4) {
				chars[posn++] = (char) (
						bytes[byteIndex] << 24 |
						bytes[byteIndex + 1] << 16 |
						bytes[byteIndex + 2] << 8 |
						bytes[byteIndex + 3]);
				byteIndex += 4;
				byteCount -= 4;
			}
		} else {
			while (byteCount >= 4) {
				chars[posn++] = (char) (
						bytes[byteIndex] |
						bytes[byteIndex + 1] << 8 |
						bytes[byteIndex + 2] << 16 |
						bytes[byteIndex + 3] << 24);
				byteIndex += 4;
				byteCount -= 4;
			}
		}
		return posn - charIndex;
	}

	// Get the maximum number of bytes needed to encode a
	// specified number of characters.
	public override int GetMaxByteCount (int charCount)
	{
		if (charCount < 0) {
			throw new ArgumentOutOfRangeException ("charCount", _("ArgRange_NonNegative"));
		}
		return charCount * 4;
	}

	// Get the maximum number of characters needed to decode a
	// specified number of bytes.
	public override int GetMaxCharCount (int byteCount)
	{
		if (byteCount < 0) {
			throw new ArgumentOutOfRangeException
				("byteCount", _("ArgRange_NonNegative"));
		}
		return byteCount / 4;
	}

	// Get a UTF32-specific decoder that is attached to this instance.
	public override Decoder GetDecoder ()
	{
		return new UTF32Decoder (bigEndian);
	}

	// Get the UTF32 preamble.
	public override byte[] GetPreamble ()
	{
		if (byteOrderMark) {
			byte[] preamble = new byte[4];
			if (bigEndian) {
				preamble[2] = (byte)0xFE;
				preamble[3] = (byte)0xFF;
			} else {
				preamble[0] = (byte)0xFF;
				preamble[1] = (byte)0xFE;
			}
			return preamble;
		}
		
		return EmptyArray<byte>.Value;
	}

	// Determine if this object is equal to another.
	public override bool Equals (Object value)
	{
		UTF32Encoding enc = (value as UTF32Encoding);
		if (enc != null) {
			return (codePage == enc.codePage &&
					bigEndian == enc.bigEndian &&
					byteOrderMark == enc.byteOrderMark &&
					base.Equals (value));
		} else {
			return false;
		}
	}

	// Get the hash code for this object.
	public override int GetHashCode ()
	{
		int basis = base.GetHashCode ();
		if (bigEndian)
			basis ^= 0x1F;
		if (byteOrderMark)
			basis ^= 0x3F;
		return basis;
	}

	// UTF32 decoder implementation.
	private sealed class UTF32Decoder : Decoder
	{
		private bool bigEndian;
		private int leftOverByte;
		private int leftOverLength;

		// Constructor.
		public UTF32Decoder (bool bigEndian)
		{
			this.bigEndian = bigEndian;
			leftOverByte = -1;
		}

		// Override inherited methods.
		public override int GetCharCount (byte[] bytes, int index, int count)
		{
			if (bytes == null) {
				throw new ArgumentNullException ("bytes");
			}
			if (index < 0 || index > bytes.Length) {
				throw new ArgumentOutOfRangeException ("index", _("ArgRange_Array"));
			}
			if (count < 0 || count > (bytes.Length - index)) {
				throw new ArgumentOutOfRangeException ("count", _("ArgRange_Array"));
			}
			if (leftOverByte != -1) {
				return (count + 1) / 4;
			} else {
				return count / 4;
			}
		}
		
		public override int GetChars (byte[] bytes, int byteIndex,
									 int byteCount, char[] chars,
									 int charIndex)
		{
			if (bytes == null) {
				throw new ArgumentNullException ("bytes");
			}
			if (chars == null) {
				throw new ArgumentNullException ("chars");
			}
			if (byteIndex < 0 || byteIndex > bytes.Length) {
				throw new ArgumentOutOfRangeException ("byteIndex", _("ArgRange_Array"));
			}
			if (byteCount < 0 || byteCount > (bytes.Length - byteIndex)) {
				throw new ArgumentOutOfRangeException ("byteCount", _("ArgRange_Array"));
			}
			if (charIndex < 0 || charIndex > chars.Length) {
				throw new ArgumentOutOfRangeException ("charIndex", _("ArgRange_Array"));
			}

			// Convert the characters.
			int posn = charIndex;
			int leftOver = leftOverByte;
			int length = chars.Length;
			char ch;

			int remain = 4 - leftOverLength;
			if (leftOverLength > 0 && byteCount > remain) {
				if (bigEndian) {
					for (int i = 0; i < remain; i++)
						leftOver += bytes [byteIndex++] << (4 - byteCount--);
				} else {
					for (int i = 0; i < remain; i++)
						leftOver += bytes [byteIndex++] << byteCount--;
				}
				if (leftOver > char.MaxValue && posn + 1 < length
					|| posn < length)
					throw new ArgumentException (_("Arg_InsufficientSpace"));
				if (leftOver > char.MaxValue) {
					chars [posn++] = (char) ((leftOver - 10000) / 0x400 + 0xD800);
					chars [posn++] = (char) ((leftOver - 10000) % 0x400 + 0xDC00);
				}
				else
					chars [posn++] = (char) leftOver;

				leftOver = -1;
				leftOverLength = 0;
			}

			while (byteCount > 3) {
				if (bigEndian) {
					ch = (char) (
					     bytes[byteIndex++] << 24 |
					     bytes[byteIndex++] << 16 |
					     bytes[byteIndex++] << 8 |
					     bytes[byteIndex++]);
				} else {
					ch = (char) (
					     bytes[byteIndex++] |
					     bytes[byteIndex++] << 8 |
					     bytes[byteIndex++] << 16 |
					     bytes[byteIndex++] << 24);
				}
				byteCount -= 4;

				if (posn < length) {
					chars[posn++] = ch;
				} else {
					throw new ArgumentException (_("Arg_InsufficientSpace"));
				}
			}
			if (byteCount > 0) {
				leftOverLength = byteCount;
				leftOver = 0;
				if (bigEndian) {
					for (int i = 0; i < byteCount; i++)
						leftOver += bytes [byteIndex++] << (4 - byteCount--);
				} else {
					for (int i = 0; i < byteCount; i++)
						leftOver += bytes [byteIndex++] << byteCount--;
				}
				leftOverByte = leftOver;
			}

			// Finished - return the converted length.
			return posn - charIndex;
		}

	} // class UTF32Decoder
	
	[CLSCompliantAttribute(false)]
	public unsafe override int GetByteCount (char *chars, int count)
	{
		if (chars == null)
			throw new ArgumentNullException ("chars");
		return count * 4;
	}

	// a bunch of practically missing implementations (but should just work)

	public override int GetByteCount (string s)
	{
		return base.GetByteCount (s);
	}

	[CLSCompliantAttribute (false)]
	public override unsafe int GetBytes (char *chars, int charCount, byte *bytes, int byteCount)
	{
		return base.GetBytes (chars, charCount, bytes, byteCount);
	}

	public override int GetBytes (string s, int charIndex, int charCount, byte [] bytes, int byteIndex)
	{
		return base.GetBytes (s, charIndex, charCount, bytes, byteIndex);
	}

	[CLSCompliantAttribute (false)]
	public override unsafe int GetCharCount (byte *bytes, int count)
	{
		return base.GetCharCount (bytes, count);
	}

	[CLSCompliantAttribute (false)]
	public override unsafe int GetChars (byte *bytes, int byteCount, char* chars, int charCount)
	{
		return base.GetChars (bytes, byteCount, chars, charCount);
	}

	public override string GetString (byte [] bytes, int index, int count)
	{
		return base.GetString (bytes, index, count);
	}

	public override Encoder GetEncoder ()
	{
		return base.GetEncoder ();
	}
}; // class UTF32Encoding

}; // namespace System.Text