using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;
using CryptoPro.Sharpei.Xml;
using OpenEhr.V1.Its.Xml.RM;
using OpenHealth.Common.Extensions;
using OpenHealth.Common.OpenEHR.Extensions;
using OpenHealth.KnowledgeManager.Definition;

namespace OpenHealth.Storage.Ehr
{
	public class VersionSigner : IVersionSigner
	{
		readonly ICertificateContainer _certificateContainer;
	    readonly IKnowledgeManager _knowledgeManager;

		public VersionSigner(ICertificateContainer certificateContainer, IKnowledgeManager knowledgeManager)
		{
			Contract.Requires(certificateContainer != null);
            Contract.Requires(knowledgeManager != null);

			_certificateContainer = certificateContainer;
		    _knowledgeManager = knowledgeManager;
		}

		public string GetSignatureForVersion(VERSION version)
		{
            var composition = version.Cast<ORIGINAL_VERSION>().data as COMPOSITION;

            // При создании Ehr в data приходит EHR_STATUS, а не COMPOSITION
            if (composition == null)
                return string.Empty;

		    X509Certificate2 certificate = GetCertificate(composition.archetype_details.template_id.value);

			if (certificate == null)
				return string.Empty;

			var doc = new XmlDocument
			          	{
			          		PreserveWhitespace = false
			          	};
			doc.LoadXml(version.Serialize<VERSION>());

			var reference = new Reference { DigestMethod = CPSignedXml.XmlDsigGost3411Url, Uri = string.Empty };
			// Добавляем transform на подписываемые данные для удаления вложенной подписи.
			reference.AddTransform(new XmlDsigEnvelopedSignatureTransform());
			// Добавляем transform для канонизации.
			reference.AddTransform(new XmlDsigC14NTransform());

			var keyInfo = new KeyInfo();
			keyInfo.AddClause(new KeyInfoX509Data(certificate));

			var signedXml = new SignedXml(doc)
			                	{
			                		SigningKey = certificate.PrivateKey
			                	};
			signedXml.AddReference(reference);
			signedXml.KeyInfo = keyInfo;

			signedXml.ComputeSignature();

			XmlElement xmlElement = signedXml.GetXml();

			return Convert.ToBase64String(Encoding.UTF8.GetBytes(xmlElement.InnerXml));
		}

		X509Certificate2 GetCertificate(string templateId)
		{
			if (_certificateContainer == null)
				return null;

            if (templateId.IsNullOrWhiteSpace())
                return _certificateContainer.DefaultCertificate;

            var path = _knowledgeManager.GetFullPathById(templateId);

            return _certificateContainer.Certificates
                .Where(c => path.Contains(c.Key) && c.Key.IsNullOrWhiteSpace().Not())
                .DefaultIfEmpty(new KeyValuePair<string, X509Certificate2>("", _certificateContainer.DefaultCertificate))
                .FirstOrDefault().Value;
		}
	}
}