using System;
using System.Collections;
using System.IO;

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.Cms;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Crypto;

namespace Org.BouncyCastle.Cms
{
    /**
    * Parsing class for an CMS Enveloped Data object from an input stream.
    * <p>
    * Note: that because we are in a streaming mode only one recipient can be tried and it is important
    * that the methods on the parser are called in the appropriate order.
    * </p>
    * <p>
    * Example of use - assuming the first recipient matches the private key we have.
    * <pre>
    *      CmsEnvelopedDataParser     ep = new CmsEnvelopedDataParser(inputStream);
    *
    *      RecipientInformationStore  recipients = ep.GetRecipientInfos();
    *
    *      Collection  c = recipients.getRecipients();
    *      Iterator    it = c.iterator();
    *
    *      if (it.hasNext())
    *      {
    *          RecipientInformation   recipient = (RecipientInformation)it.next();
    *
    *          CMSTypedStream recData = recipient.getContentStream(privateKey);
    *
    *          processDataStream(recData.getContentStream());
    *      }
    *  </pre>
    *  Note: this class does not introduce buffering - if you are processing large files you should create
    *  the parser with:
    *  <pre>
    *          CmsEnvelopedDataParser     ep = new CmsEnvelopedDataParser(new BufferedInputStream(inputStream, bufSize));
    *  </pre>
    *  where bufSize is a suitably large buffer size.
	* </p>
    */
    public class CmsEnvelopedDataParser
        : CmsContentInfoParser
    {
        internal RecipientInformationStore	recipientInfoStore;
        internal EnvelopedDataParser		envelopedData;

		private AlgorithmIdentifier			_encAlg;
        private Asn1.Cms.AttributeTable		_unprotectedAttributes;
        private bool						_attrNotRead;

        public CmsEnvelopedDataParser(
            byte[] envelopedData)
            : this(new MemoryStream(envelopedData, false))
        {
        }

        public CmsEnvelopedDataParser(
            Stream envelopedData)
            : base(envelopedData)
        {
            this._attrNotRead = true;
            this.envelopedData = new EnvelopedDataParser(
				(Asn1SequenceParser)this.contentInfo.GetContent(Asn1Tags.Sequence));

            //
            // load the RecipientInfoStore
            //
            Asn1SetParser s = this.envelopedData.GetRecipientInfos();
            IList baseInfos = new ArrayList();

			IAsn1Convertible entry;
			while ((entry = s.ReadObject()) != null)
			{
				baseInfos.Add(RecipientInfo.GetInstance(entry.ToAsn1Object()));
			}

			//
            // read the encrypted content info
            //
            EncryptedContentInfoParser encInfo = this.envelopedData.GetEncryptedContentInfo();

            this._encAlg = encInfo.ContentEncryptionAlgorithm;

            //
            // prime the recipients
            //
            IList infos = new ArrayList();
			Stream dataStream = ((Asn1OctetStringParser)encInfo.GetEncryptedContent(Asn1Tags.OctetString)).GetOctetStream();

			foreach (Asn1.Cms.RecipientInfo info in baseInfos)
            {
				Asn1Encodable recipInfo = info.Info;
                if (recipInfo is Asn1.Cms.KeyTransRecipientInfo)
                {
                    infos.Add(new KeyTransRecipientInformation(
                        (KeyTransRecipientInfo) recipInfo, _encAlg, dataStream));
                }
                else if (recipInfo is Asn1.Cms.KekRecipientInfo)
                {
                    infos.Add(new KekRecipientInformation(
                        (KekRecipientInfo) recipInfo, _encAlg, dataStream));
                }
				else if (recipInfo is KeyAgreeRecipientInfo)
				{
					infos.Add(new KeyAgreeRecipientInformation(
						(KeyAgreeRecipientInfo) recipInfo, _encAlg, dataStream));
				}
				else if (recipInfo is PasswordRecipientInfo)
				{
					infos.Add(new PasswordRecipientInformation(
						(PasswordRecipientInfo) recipInfo, _encAlg, dataStream));
				}
            }

			this.recipientInfoStore = new RecipientInformationStore(infos);
        }

		public AlgorithmIdentifier EncryptionAlgorithmID
		{
			get { return _encAlg; }
		}

		/**
         * return the object identifier for the content encryption algorithm.
         */
        public string EncryptionAlgOid
        {
			get { return _encAlg.ObjectID.Id; }
        }

		/**
         * return the ASN.1 encoded encryption algorithm parameters, or null if
         * there aren't any.
         */
		public Asn1Object EncryptionAlgParams
		{
			get
			{
				Asn1Encodable ae = _encAlg.Parameters;

				return ae == null ? null : ae.ToAsn1Object();
			}
		}

		/**
         * return a store of the intended recipients for this message
         */
        public RecipientInformationStore GetRecipientInfos()
        {
            return this.recipientInfoStore;
        }

        /**
         * return a table of the unprotected attributes indexed by
         * the OID of the attribute.
         * @throws IOException
         */
        public Asn1.Cms.AttributeTable GetUnprotectedAttributes()
        {
            if (_unprotectedAttributes == null && _attrNotRead)
            {
                Asn1SetParser asn1Set = this.envelopedData.GetUnprotectedAttrs();

                _attrNotRead = false;

                if (asn1Set != null)
                {
                    Asn1EncodableVector v = new Asn1EncodableVector();
                    IAsn1Convertible o;

                    while ((o = asn1Set.ReadObject()) != null)
                    {
                        Asn1SequenceParser seq = (Asn1SequenceParser)o;

						v.Add(seq.ToAsn1Object());
                    }

					_unprotectedAttributes = new Asn1.Cms.AttributeTable(new DerSet(v));
                }
            }

			return _unprotectedAttributes;
        }
    }
}