//------------------------------------------------------------
// Copyright (c) Microsoft Corporation.  All rights reserved.
//------------------------------------------------------------

namespace System.IdentityModel
{
    using System.IO;
    using System.Security.Cryptography;
    using System.IdentityModel.Tokens;
    using System.Xml;
    using System.Text;

    // for sequential use by one thread
    sealed class SignatureResourcePool
    {
        const int BufferSize = 64;
        CanonicalizationDriver canonicalizationDriver;
        HashStream hashStream;
        HashAlgorithm hashAlgorithm;
#if NO
        XmlC14NWriter integratedWriter;
#endif
        XmlDictionaryWriter utf8Writer;
        byte[] encodingBuffer;
        char[] base64Buffer;

        public char[] TakeBase64Buffer()
        {
            if (this.base64Buffer == null)
            {
                this.base64Buffer = new char[BufferSize];
            }
            return this.base64Buffer;
        }

        public CanonicalizationDriver TakeCanonicalizationDriver()
        {
            if (this.canonicalizationDriver == null)
            {
                this.canonicalizationDriver = new CanonicalizationDriver();
            }
            else
            {
                this.canonicalizationDriver.Reset();
            }
            return this.canonicalizationDriver;
        }

        public byte[] TakeEncodingBuffer()
        {
            if (this.encodingBuffer == null)
            {
                this.encodingBuffer = new byte[BufferSize];
            }
            return this.encodingBuffer;
        }

        public HashAlgorithm TakeHashAlgorithm(string algorithm)
        {
            if ( this.hashAlgorithm == null )
            {
                if ( string.IsNullOrEmpty( algorithm ) )
                {
                    throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgument( algorithm, SR.GetString( SR.EmptyOrNullArgumentString, "algorithm" ) );
                }

                this.hashAlgorithm = CryptoHelper.CreateHashAlgorithm( algorithm );
            }
            else
            {
                this.hashAlgorithm.Initialize();
            }
           
            return this.hashAlgorithm;
        }

        public HashStream TakeHashStream(HashAlgorithm hash)
        {
            if (this.hashStream == null)
            {
                this.hashStream = new HashStream(hash);
            }
            else
            {
                this.hashStream.Reset(hash);
            }
            return this.hashStream;
        }

        public HashStream TakeHashStream(string algorithm)
        {
            return TakeHashStream(TakeHashAlgorithm(algorithm));
        }
#if NO
        public XmlC14NWriter TakeIntegratedWriter(Stream stream)
        {
            return TakeIntegratedWriter(stream, false, null);
        }

        public XmlC14NWriter TakeIntegratedWriter(Stream stream, bool includeComments, string[] inclusivePrefixes)
        {
            if (this.integratedWriter == null)
            {
                this.integratedWriter = new XmlC14NWriter(stream, includeComments, inclusivePrefixes);
            }
            else
            {
                this.integratedWriter.SetOutput(stream, includeComments, inclusivePrefixes);
            }
            return this.integratedWriter;
        }
#endif

        public XmlDictionaryWriter TakeUtf8Writer()
        {
            if (this.utf8Writer == null)
            {
                this.utf8Writer = XmlDictionaryWriter.CreateTextWriter(Stream.Null, Encoding.UTF8, false);
            }
            else
            {
                ((IXmlTextWriterInitializer) this.utf8Writer).SetOutput(Stream.Null, Encoding.UTF8, false);
            }
            return this.utf8Writer;
        }
    }
}