using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Opc.Ua;
using Opc.Ua.Client;

namespace MasterClient.Client
{
	class OpcUaMaster : ICommClient
	{
		private readonly string ENDPOINT_TMPL = "opc.tcp://{0}:{1}";
		private Session session;

		private string ip;
		private int port;

		public void Connect()
		{
			try
			{
				if (GetStatus())
					Disconnect();

				ConfiguredEndpoint endPoint = new ConfiguredEndpoint(null, new EndpointDescription(CreateEndpointURL()));

				ApplicationConfiguration config = CreateOpcUaConfig();

				session = Session.Create(config, endPoint, true, "MySession", 1000, null, null).Result;
			}
			catch (Exception ex)
			{
				throw ex;
			}
		}

		public void Disconnect()
		{
			if (!GetStatus())
				throw new Exception("Not connected");

			try
			{
				session.Close();
			}
			catch (Exception ex)
			{
				throw ex;
			}
		}

		public bool GetStatus()
		{
			return session != null && session.Connected;
		}

		public string ReadValue(string name)
		{
			if (!GetStatus())
				throw new Exception("Not connected");

			try
			{
				return session.ReadValue(name).Value.ToString();
			}
			catch (Exception ex)
			{
				throw ex;
			}
		}

		public void SetServer(string ip, int port)
		{
			this.ip = ip;
			this.port = port;
		}

		public void WriteValue(string name, string value)
		{
			if (!GetStatus())
				throw new Exception("Not connected");

			try
			{
				WriteValue nodeToWrite = new WriteValue()
				{
					NodeId = new NodeId(name),
					AttributeId = Attributes.Value,
					Value = new DataValue()
				};

				Variant writeValue = new Variant(value);
				nodeToWrite.Value.WrappedValue = writeValue;

				WriteValueCollection nodesToWrite = new WriteValueCollection();
				nodesToWrite.Add(nodeToWrite);

				StatusCodeCollection results = null;
				DiagnosticInfoCollection diagnosticInfos = null;

				ResponseHeader responseHeader = session.Write(
					null,
					nodesToWrite,
					out results,
					out diagnosticInfos);

				ClientBase.ValidateResponse(results, nodesToWrite);
				ClientBase.ValidateDiagnosticInfos(diagnosticInfos, nodesToWrite);

				if (StatusCode.IsBad(results[0]))
					throw ServiceResultException.Create(results[0], 0, diagnosticInfos, responseHeader.StringTable);
			}
			catch (Exception ex)
			{
				throw ex;
			}
		}

		private ApplicationConfiguration CreateOpcUaConfig()
		{
			ApplicationConfiguration config = new ApplicationConfiguration()
			{
				ApplicationName = "OPC-UA-Client",
				ApplicationType = ApplicationType.Client,

				SecurityConfiguration = new SecurityConfiguration()
				{
					ApplicationCertificate = new CertificateIdentifier()
				},

				ClientConfiguration = new ClientConfiguration()
				{
					DefaultSessionTimeout = 30 * 1000
				}
			};

			config.Validate(ApplicationType.Client);

			return config;
		}

		private string CreateEndpointURL()
		{
			return string.Format(ENDPOINT_TMPL, ip, port);
		}
	}
}