using System;
using System.IO;
using System.Security.Cryptography;
using ICSharpCode.SharpZipLib.Encryption;

namespace ICSharpCode.SharpZipLib.Zip.Compression.Streams
{
	/// <summary>
	/// A special stream deflating or compressing the bytes that are
	/// written to it.  It uses a Deflater to perform actual deflating.<br/>
	/// Authors of the original java version : Tom Tromey, Jochen Hoenicke
	/// </summary>
	public class DeflaterOutputStream : Stream
	{
		#region Constructors
		/// <summary>
		/// Creates a new DeflaterOutputStream with a default Deflater and default buffer size.
		/// </summary>
		/// <param name="baseOutputStream">
		/// the output stream where deflated output should be written.
		/// </param>
		public DeflaterOutputStream(Stream baseOutputStream)
			: this(baseOutputStream, new Deflater(), 512)
		{
		}

		/// <summary>
		/// Creates a new DeflaterOutputStream with the given Deflater and
		/// default buffer size.
		/// </summary>
		/// <param name="baseOutputStream">
		/// the output stream where deflated output should be written.
		/// </param>
		/// <param name="deflater">
		/// the underlying deflater.
		/// </param>
		public DeflaterOutputStream(Stream baseOutputStream, Deflater deflater)
			: this(baseOutputStream, deflater, 512)
		{
		}

		/// <summary>
		/// Creates a new DeflaterOutputStream with the given Deflater and
		/// buffer size.
		/// </summary>
		/// <param name="baseOutputStream">
		/// The output stream where deflated output is written.
		/// </param>
		/// <param name="deflater">
		/// The underlying deflater to use
		/// </param>
		/// <param name="bufferSize">
		/// The buffer size in bytes to use when deflating (minimum value 512)
		/// </param>
		/// <exception cref="ArgumentOutOfRangeException">
		/// bufsize is less than or equal to zero.
		/// </exception>
		/// <exception cref="ArgumentException">
		/// baseOutputStream does not support writing
		/// </exception>
		/// <exception cref="ArgumentNullException">
		/// deflater instance is null
		/// </exception>
		public DeflaterOutputStream(Stream baseOutputStream, Deflater deflater, int bufferSize)
		{
			if (baseOutputStream == null) {
				throw new ArgumentNullException("nameof(baseOutputStream)");
			}

			if (baseOutputStream.CanWrite == false) {
				throw new ArgumentException("Must support writing", "nameof(baseOutputStream)");
			}

			if (deflater == null) {
				throw new ArgumentNullException("nameof(deflater)");
			}

			if (bufferSize < 512) {
				throw new ArgumentOutOfRangeException("nameof(bufferSize)");
			}

			baseOutputStream_ = baseOutputStream;
			buffer_ = new byte[bufferSize];
			deflater_ = deflater;
		}
		#endregion

		#region Public API
		/// <summary>
		/// Finishes the stream by calling finish() on the deflater.
		/// </summary>
		/// <exception cref="SharpZipBaseException">
		/// Not all input is deflated
		/// </exception>
		public virtual void Finish()
		{
			deflater_.Finish();
			while (!deflater_.IsFinished) {
				int len = deflater_.Deflate(buffer_, 0, buffer_.Length);
				if (len <= 0) {
					break;
				}

				if (cryptoTransform_ != null) {
					EncryptBlock(buffer_, 0, len);
				}

				baseOutputStream_.Write(buffer_, 0, len);
			}

			if (!deflater_.IsFinished) {
				throw new SharpZipBaseException("Can't deflate all input?");
			}

			baseOutputStream_.Flush();

			if (cryptoTransform_ != null) {
				if (cryptoTransform_ is ZipAESTransform) {
					AESAuthCode = ((ZipAESTransform)cryptoTransform_).GetAuthCode();
				}
				cryptoTransform_.Dispose();
				cryptoTransform_ = null;
			}
		}

		/// <summary>
		/// Gets or sets a flag indicating ownership of underlying stream.
		/// When the flag is true <see cref="Stream.Dispose()" /> will close the underlying stream also.
		/// </summary>
		/// <remarks>The default value is true.</remarks>
		private bool isStreamOwner = true;
		public bool IsStreamOwner
		{
			get { return isStreamOwner;}
			set { isStreamOwner = value; }
		}

		///	<summary>
		/// Allows client to determine if an entry can be patched after its added
		/// </summary>
		public bool CanPatchEntries {
			get {
				return baseOutputStream_.CanSeek;
			}
		}

		#endregion

		#region Encryption

		string password;

		ICryptoTransform cryptoTransform_;

		/// <summary>
		/// Returns the 10 byte AUTH CODE to be appended immediately following the AES data stream.
		/// </summary>
		protected byte[] AESAuthCode;

		/// <summary>
		/// Get/set the password used for encryption.
		/// </summary>
		/// <remarks>When set to null or if the password is empty no encryption is performed</remarks>
		public string Password {
			get {
				return password;
			}
			set {
				if ((value != null) && (value.Length == 0)) {
					password = null;
				} else {
					password = value;
				}
			}
		}

		/// <summary>
		/// Encrypt a block of data
		/// </summary>
		/// <param name="buffer">
		/// Data to encrypt.  NOTE the original contents of the buffer are lost
		/// </param>
		/// <param name="offset">
		/// Offset of first byte in buffer to encrypt
		/// </param>
		/// <param name="length">
		/// Number of bytes in buffer to encrypt
		/// </param>
		protected void EncryptBlock(byte[] buffer, int offset, int length)
		{
			cryptoTransform_.TransformBlock(buffer, 0, length, buffer, 0);
		}

		/// <summary>
		/// Initializes encryption keys based on given <paramref name="password"/>.
		/// </summary>
		/// <param name="password">The password.</param>
		protected void InitializePassword(string password)
		{
			var pkManaged = new PkzipClassicManaged();
			byte[] key = PkzipClassic.GenerateKeys(ZipConstants.ConvertToArray(password));
			cryptoTransform_ = pkManaged.CreateEncryptor(key, null);
		}

		/// <summary>
		/// Initializes encryption keys based on given password.
		/// </summary>
		protected void InitializeAESPassword(ZipEntry entry, string rawPassword,
											out byte[] salt, out byte[] pwdVerifier)
		{
			salt = new byte[entry.AESSaltLen];
			// Salt needs to be cryptographically random, and unique per file
			if (_aesRnd == null)
				_aesRnd = RandomNumberGenerator.Create();
			_aesRnd.GetBytes(salt);
			int blockSize = entry.AESKeySize / 8;   // bits to bytes

			cryptoTransform_ = new ZipAESTransform(rawPassword, salt, blockSize, true);
			pwdVerifier = ((ZipAESTransform)cryptoTransform_).PwdVerifier;
		}

		#endregion

		#region Deflation Support
		/// <summary>
		/// Deflates everything in the input buffers.  This will call
		/// <code>def.deflate()</code> until all bytes from the input buffers
		/// are processed.
		/// </summary>
		protected void Deflate()
		{
			while (!deflater_.IsNeedingInput) {
				int deflateCount = deflater_.Deflate(buffer_, 0, buffer_.Length);

				if (deflateCount <= 0) {
					break;
				}
				if (cryptoTransform_ != null) {
					EncryptBlock(buffer_, 0, deflateCount);
				}

				baseOutputStream_.Write(buffer_, 0, deflateCount);
			}

			if (!deflater_.IsNeedingInput) {
				throw new SharpZipBaseException("DeflaterOutputStream can't deflate all input?");
			}
		}
		#endregion

		#region Stream Overrides
		/// <summary>
		/// Gets value indicating stream can be read from
		/// </summary>
		public override bool CanRead {
			get {
				return false;
			}
		}

		/// <summary>
		/// Gets a value indicating if seeking is supported for this stream
		/// This property always returns false
		/// </summary>
		public override bool CanSeek {
			get {
				return false;
			}
		}

		/// <summary>
		/// Get value indicating if this stream supports writing
		/// </summary>
		public override bool CanWrite {
			get {
				return baseOutputStream_.CanWrite;
			}
		}

		/// <summary>
		/// Get current length of stream
		/// </summary>
		public override long Length {
			get {
				return baseOutputStream_.Length;
			}
		}

		/// <summary>
		/// Gets the current position within the stream.
		/// </summary>
		/// <exception cref="NotSupportedException">Any attempt to set position</exception>
		public override long Position {
			get {
				return baseOutputStream_.Position;
			}
			set {
				throw new NotSupportedException("Position property not supported");
			}
		}

		/// <summary>
		/// Sets the current position of this stream to the given value. Not supported by this class!
		/// </summary>
		/// <param name="offset">The offset relative to the <paramref name="origin"/> to seek.</param>
		/// <param name="origin">The <see cref="SeekOrigin"/> to seek from.</param>
		/// <returns>The new position in the stream.</returns>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override long Seek(long offset, SeekOrigin origin)
		{
			throw new NotSupportedException("DeflaterOutputStream Seek not supported");
		}

		/// <summary>
		/// Sets the length of this stream to the given value. Not supported by this class!
		/// </summary>
		/// <param name="value">The new stream length.</param>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override void SetLength(long value)
		{
			throw new NotSupportedException("DeflaterOutputStream SetLength not supported");
		}

		/// <summary>
		/// Read a byte from stream advancing position by one
		/// </summary>
		/// <returns>The byte read cast to an int.  THe value is -1 if at the end of the stream.</returns>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override int ReadByte()
		{
			throw new NotSupportedException("DeflaterOutputStream ReadByte not supported");
		}

		/// <summary>
		/// Read a block of bytes from stream
		/// </summary>
		/// <param name="buffer">The buffer to store read data in.</param>
		/// <param name="offset">The offset to start storing at.</param>
		/// <param name="count">The maximum number of bytes to read.</param>
		/// <returns>The actual number of bytes read.  Zero if end of stream is detected.</returns>
		/// <exception cref="NotSupportedException">Any access</exception>
		public override int Read(byte[] buffer, int offset, int count)
		{
			throw new NotSupportedException("DeflaterOutputStream Read not supported");
		}

		/// <summary>
		/// Flushes the stream by calling <see cref="DeflaterOutputStream.Flush">Flush</see> on the deflater and then
		/// on the underlying stream.  This ensures that all bytes are flushed.
		/// </summary>
		public override void Flush()
		{
			deflater_.Flush();
			Deflate();
			baseOutputStream_.Flush();
		}

		/// <summary>
		/// Calls <see cref="Finish"/> and closes the underlying
		/// stream when <see cref="IsStreamOwner"></see> is true.
		/// </summary>
		protected override void Dispose(bool disposing)
		{
			if (!isClosed_) {
				isClosed_ = true;

				try {
					Finish();
					if (cryptoTransform_ != null) {
						GetAuthCodeIfAES();
						cryptoTransform_.Dispose();
						cryptoTransform_ = null;
					}
				} finally {
					if (IsStreamOwner) {
						baseOutputStream_.Dispose();
					}
				}
			}
		}

		private void GetAuthCodeIfAES()
		{
			if (cryptoTransform_ is ZipAESTransform) {
				AESAuthCode = ((ZipAESTransform)cryptoTransform_).GetAuthCode();
			}
		}

		/// <summary>
		/// Writes a single byte to the compressed output stream.
		/// </summary>
		/// <param name="value">
		/// The byte value.
		/// </param>
		public override void WriteByte(byte value)
		{
			byte[] b = new byte[1];
			b[0] = value;
			Write(b, 0, 1);
		}

		/// <summary>
		/// Writes bytes from an array to the compressed stream.
		/// </summary>
		/// <param name="buffer">
		/// The byte array
		/// </param>
		/// <param name="offset">
		/// The offset into the byte array where to start.
		/// </param>
		/// <param name="count">
		/// The number of bytes to write.
		/// </param>
		public override void Write(byte[] buffer, int offset, int count)
		{
			deflater_.SetInput(buffer, offset, count);
			Deflate();
		}
		#endregion

		#region Instance Fields
		/// <summary>
		/// This buffer is used temporarily to retrieve the bytes from the
		/// deflater and write them to the underlying output stream.
		/// </summary>
		byte[] buffer_;

		/// <summary>
		/// The deflater which is used to deflate the stream.
		/// </summary>
		protected Deflater deflater_;

		/// <summary>
		/// Base stream the deflater depends on.
		/// </summary>
		protected Stream baseOutputStream_;

		bool isClosed_;
		#endregion

		#region Static Fields

		// Static to help ensure that multiple files within a zip will get different random salt
		private static RandomNumberGenerator _aesRnd = RandomNumberGenerator.Create();
		#endregion
	}
}