using System;
using System.Collections;

using Org.BouncyCastle.Asn1;

namespace Org.BouncyCastle.Asn1.Cms
{
	public class ContentInfo
		: Asn1Encodable
	{
		private readonly DerObjectIdentifier	contentType;
		private readonly Asn1Encodable			content;

		public static ContentInfo GetInstance(
			object obj)
		{
			if (obj == null || obj is ContentInfo)
			{
				return (ContentInfo) obj;
			}

			if (obj is Asn1Sequence)
			{
				return new ContentInfo((Asn1Sequence) obj);
			}

			throw new ArgumentException("unknown object in factory: " + obj.GetType().Name);
		}

		private ContentInfo(
			Asn1Sequence seq)
		{
			if (seq.Count < 1 || seq.Count > 2)
				throw new ArgumentException("Bad sequence size: " + seq.Count, "seq");

			contentType = (DerObjectIdentifier) seq[0];

			if (seq.Count > 1)
			{
				Asn1TaggedObject optOcts = (Asn1TaggedObject) seq[1];
				if (optOcts.TagNo != 0)
					throw new ArgumentException("Tag number for 'content' must be 0");

				content = optOcts.GetObject();
			}
		}

		public ContentInfo(
			DerObjectIdentifier	contentType,
			Asn1Encodable		content)
		{
			this.contentType = contentType;
			this.content = content;
		}

		public DerObjectIdentifier ContentType
		{
			get { return contentType; }
		}

		public Asn1Encodable Content
		{
			get { return content; }
		}

		/**
		 * Produce an object suitable for an Asn1OutputStream.
		 * <pre>
		 * ContentInfo ::= Sequence {
		 *          contentType ContentType,
		 *          content
		 *          [0] EXPLICIT ANY DEFINED BY contentType OPTIONAL }
		 * </pre>
		 */
		public override Asn1Object ToAsn1Object()
		{
			Asn1EncodableVector v = new Asn1EncodableVector(contentType);

			if (content != null)
			{
				v.Add(new BerTaggedObject(0, content));
			}

			return new BerSequence(v);
		}
	}
}