// SignaturePolicyIdentifier.cs
//
// XAdES Starter Kit for Microsoft .NET 3.5 (and above)
// 2010 Microsoft France
// Published under the CECILL-B Free Software license agreement.
// (http://www.cecill.info/licences/Licence_CeCILL-B_V1-en.txt)
// 
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, 
// WHETHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED 
// WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE. 
// THE ENTIRE RISK OF USE OR RESULTS IN CONNECTION WITH THE USE OF THIS CODE 
// AND INFORMATION REMAINS WITH THE USER.

using System;
using System.Security.Cryptography;
using System.Xml;

namespace Microsoft.Xades
{
    /// <summary>
    /// This class contains an identifier of a signature policy
    /// </summary>
    public class SignaturePolicyIdentifier
    {
        #region Private variables
        private SignaturePolicyId signaturePolicyId;
        private bool signaturePolicyImplied;
        #endregion

        #region Public properties
        /// <summary>
        /// The SignaturePolicyId element is an explicit and unambiguous identifier
        /// of a Signature Policy together with a hash value of the signature
        /// policy, so it can be verified that the policy selected by the signer is
        /// the one being used by the verifier. An explicit signature policy has a
        /// globally unique reference, which, in this way, is bound to an
        /// electronic signature by the signer as part of the signature
        /// calculation.
        /// </summary>
        public SignaturePolicyId SignaturePolicyId
        {
            get
            {
                return this.signaturePolicyId;
            }
            set
            {
                this.signaturePolicyId = value;
                this.signaturePolicyImplied = false;
            }
        }

        /// <summary>
        /// The empty SignaturePolicyImplied element will appear when the
        /// data object(s) being signed and other external data imply the
        /// signature policy
        /// </summary>
        public bool SignaturePolicyImplied
        {
            get
            {
                return this.signaturePolicyImplied;
            }
            set
            {
                this.signaturePolicyImplied = value;
                if (this.signaturePolicyImplied == true)
                {
                    this.signaturePolicyId = null;
                }
            }
        }
        #endregion

        #region Constructors
        /// <summary>
        /// Default constructor
        /// </summary>
        public SignaturePolicyIdentifier()
        {
            this.signaturePolicyId = new SignaturePolicyId();
            this.signaturePolicyImplied = false;
        }
        #endregion

        #region Public methods
        /// <summary>
        /// Check to see if something has changed in this instance and needs to be serialized
        /// </summary>
        /// <returns>Flag indicating if a member needs serialization</returns>
        public bool HasChanged()
        {
            bool retVal = false;

            if (this.signaturePolicyId != null && this.signaturePolicyId.HasChanged())
            {
                retVal = true;
            }

            if (this.signaturePolicyImplied)
            {
                retVal = true;
            }

            return retVal;
        }

        /// <summary>
        /// Load state from an XML element
        /// </summary>
        /// <param name="xmlElement">XML element containing new state</param>
        public void LoadXml(System.Xml.XmlElement xmlElement)
        {
            XmlNamespaceManager xmlNamespaceManager;
            XmlNodeList xmlNodeList;

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

            xmlNamespaceManager = new XmlNamespaceManager(xmlElement.OwnerDocument.NameTable);
            xmlNamespaceManager.AddNamespace("xsd", XadesSignedXml.XadesNamespaceUri);

            xmlNodeList = xmlElement.SelectNodes("xsd:SignaturePolicyId", xmlNamespaceManager);
            if (xmlNodeList.Count != 0)
            {
                this.signaturePolicyId = new SignaturePolicyId();
                this.signaturePolicyId.LoadXml((XmlElement)xmlNodeList.Item(0));
                this.signaturePolicyImplied = false;
            }
            else
            {
                xmlNodeList = xmlElement.SelectNodes("xsd:SignaturePolicyImplied", xmlNamespaceManager);
                if (xmlNodeList.Count != 0)
                {
                    this.signaturePolicyImplied = true;
                    this.signaturePolicyId = null;
                }
                else
                {
                    throw new CryptographicException("SignaturePolicyId or SignaturePolicyImplied missing");
                }
            }
        }

        /// <summary>
        /// Returns the XML representation of the this object
        /// </summary>
        /// <returns>XML element containing the state of this object</returns>
        public XmlElement GetXml()
        {
            XmlDocument creationXmlDocument;
            XmlElement retVal;
            XmlElement bufferXmlElement;

            creationXmlDocument = new XmlDocument();
            retVal = creationXmlDocument.CreateElement("xades", "SignaturePolicyIdentifier", XadesSignedXml.XadesNamespaceUri);

            if (this.signaturePolicyImplied)
            { //Append empty element as required
                bufferXmlElement = creationXmlDocument.CreateElement("xades", "SignaturePolicyImplied", XadesSignedXml.XadesNamespaceUri);
                retVal.AppendChild(bufferXmlElement);
            }
            else
            {
                if (this.signaturePolicyId != null && this.signaturePolicyId.HasChanged())
                {
                    retVal.AppendChild(creationXmlDocument.ImportNode(this.signaturePolicyId.GetXml(), true));
                }
                else
                {
                    throw new CryptographicException("SignaturePolicyId or SignaturePolicyImplied missing in SignaturePolicyIdentifier");
                }
            }

            return retVal;
        }
        #endregion
    }
}