/* Copyright (c) 1996-2016, OPC Foundation. All rights reserved.
   The source code in this file is covered under a dual-license scenario:
     - RCL: for OPC Foundation members in good-standing
     - GPL V2: everybody else
   RCL license terms accompanied with this source code. See http://opcfoundation.org/License/RCL/1.00/
   GNU General Public License as published by the Free Software Foundation;
   version 2 of the License are accompanied with this source code. See http://opcfoundation.org/License/GPLv2
   This source code is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*/

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

namespace NetCoreConsoleClient
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Console.WriteLine(".Net Core OPC UA Console Client sample");
            string endpointURL;
            if (args.Length == 0)
            {
                // use OPC UA .Net Sample server 
                endpointURL = "opc.tcp://" + Utils.GetHostName() + ":51210/UA/SampleServer";
            }
            else
            {
                endpointURL = args[0];
            }
            try
            {
                Task t = ConsoleSampleClient(endpointURL);
                t.Wait();
            }
            catch (Exception e)
            {
                Console.WriteLine("Exit due to Exception: {0}", e.Message);
            }
        }

        public static async Task ConsoleSampleClient(string endpointURL)
        {
            Console.WriteLine("1 - Create an Application Configuration.");
            var config = new ApplicationConfiguration()
            {
                ApplicationName = "UA Sample Client",
                ApplicationType = ApplicationType.Client,
                ApplicationUri = "urn:localhost:OPCFoundation:SampleClient",
                SecurityConfiguration = new SecurityConfiguration
                {
                    ApplicationCertificate = new CertificateIdentifier
                    {
                        StoreType = "Directory",
                        StorePath = "./OPC Foundation/CertificateStores/MachineDefault",
                        SubjectName = Utils.Format("CN={0}, DC={1}", "UA Sample Client", Utils.GetHostName())
                    },
                    TrustedPeerCertificates = new CertificateTrustList
                    {
                        StoreType = "Directory",
                        StorePath = "./OPC Foundation/CertificateStores/UA Applications",
                    },
                    TrustedIssuerCertificates = new CertificateTrustList
                    {
                        StoreType = "Directory",
                        StorePath = "./OPC Foundation/CertificateStores/UA Certificate Authorities",
                    },
                    RejectedCertificateStore = new CertificateTrustList
                    {
                        StoreType = "Directory",
                        StorePath = "./OPC Foundation/CertificateStores/RejectedCertificates",
                    },
                    NonceLength = 32,
                    AutoAcceptUntrustedCertificates = true
                },
                TransportConfigurations = new TransportConfigurationCollection(),
                TransportQuotas = new TransportQuotas { OperationTimeout = 15000 },
                ClientConfiguration = new ClientConfiguration { DefaultSessionTimeout = 60000 }
            };
            await config.Validate(ApplicationType.Client);

            bool haveAppCertificate = config.SecurityConfiguration.ApplicationCertificate.Certificate != null;

            if (haveAppCertificate && config.SecurityConfiguration.AutoAcceptUntrustedCertificates)
            {
                config.CertificateValidator.CertificateValidation += new CertificateValidationEventHandler(CertificateValidator_CertificateValidation);
            }

            if (!haveAppCertificate)
            {
                Console.WriteLine("    WARN: missing application certificate, using unsecure connection.");
            }

            Console.WriteLine("2 - Discover endpoints of {0}.", endpointURL);
            Uri endpointURI = new Uri(endpointURL);
            var endpointCollection = DiscoverEndpoints(config, endpointURI, 10);
            var selectedEndpoint = SelectUaTcpEndpoint(endpointCollection, haveAppCertificate);

            Console.WriteLine("3 - Create a session with OPC UA server.");
            var endpointConfiguration = EndpointConfiguration.Create(config);
            var endpoint = new ConfiguredEndpoint(selectedEndpoint.Server, endpointConfiguration);
            endpoint.Update(selectedEndpoint);
            var session = await Session.Create(config, endpoint, true, ".Net Core OPC UA Console Client", 60000, null, null);

            Console.WriteLine("4 - Browse the OPC UA server namespace.");
            ReferenceDescriptionCollection references;
            Byte[] continuationPoint;

            references = session.FetchReferences(ObjectIds.ObjectsFolder);

            session.Browse(
                null,
                null,
                ObjectIds.ObjectsFolder,
                0u,
                BrowseDirection.Forward,
                ReferenceTypeIds.HierarchicalReferences,
                true,
                (uint)NodeClass.Variable | (uint)NodeClass.Object | (uint)NodeClass.Method,
                out continuationPoint,
                out references);

            Console.WriteLine(" DisplayName, BrowseName, NodeClass");
            foreach (var rd in references)
            {
                Console.WriteLine(" {0}, {1}, {2}", rd.DisplayName, rd.BrowseName, rd.NodeClass);
                ReferenceDescriptionCollection nextRefs;
                byte[] nextCp;
                session.Browse(
                    null,
                    null,
                    ExpandedNodeId.ToNodeId(rd.NodeId, session.NamespaceUris),
                    0u,
                    BrowseDirection.Forward,
                    ReferenceTypeIds.HierarchicalReferences,
                    true,
                    (uint)NodeClass.Variable | (uint)NodeClass.Object | (uint)NodeClass.Method,
                    out nextCp,
                    out nextRefs);

                foreach (var nextRd in nextRefs)
                {
                    Console.WriteLine("   + {0}, {1}, {2}", nextRd.DisplayName, nextRd.BrowseName, nextRd.NodeClass);
                }
            }

            Console.WriteLine("5 - Create a subscription with publishing interval of 1 second.");
            var subscription = new Subscription(session.DefaultSubscription) { PublishingInterval = 1000 };

            Console.WriteLine("6 - Add a list of items (server current time and status) to the subscription.");
            var list = new List<MonitoredItem> {
                new MonitoredItem(subscription.DefaultItem)
                {
                    DisplayName = "ServerStatusCurrentTime", StartNodeId = "i=2258"
                }
            };
            list.ForEach(i => i.Notification += OnNotification);
            subscription.AddItems(list);

            Console.WriteLine("7 - Add the subscription to the session.");
            session.AddSubscription(subscription);
            subscription.Create();

            Console.WriteLine("8 - Running...Press any key to exit...");
            Console.ReadKey(true);
        }

        private static void OnNotification(MonitoredItem item, MonitoredItemNotificationEventArgs e)
        {
            foreach (var value in item.DequeueValues())
            {
                Console.WriteLine("{0}: {1}, {2}, {3}", item.DisplayName, value.Value, value.SourceTimestamp, value.StatusCode);
            }
        }

        private static void CertificateValidator_CertificateValidation(CertificateValidator validator, CertificateValidationEventArgs e)
        {
            Console.WriteLine("Accepted Certificate: {0}", e.Certificate.Subject);
            e.Accept = (e.Error.StatusCode == StatusCodes.BadCertificateUntrusted);
        }

        private static EndpointDescriptionCollection DiscoverEndpoints(ApplicationConfiguration config, Uri discoveryUrl, int timeout)
        {
            // use a short timeout.
            EndpointConfiguration configuration = EndpointConfiguration.Create(config);
            configuration.OperationTimeout = timeout;

            using (DiscoveryClient client = DiscoveryClient.Create(
                discoveryUrl,
                EndpointConfiguration.Create(config)))
            {
                try
                {
                    EndpointDescriptionCollection endpoints = client.GetEndpoints(null);
                    ReplaceLocalHostWithRemoteHost(endpoints, discoveryUrl);
                    return endpoints;
                }
                catch (Exception e)
                {
                    Console.WriteLine("Could not fetch endpoints from url: {0}", discoveryUrl);
                    Console.WriteLine("Reason = {0}", e.Message);
                    throw e;
                }
            }
        }

        private static EndpointDescription SelectUaTcpEndpoint(EndpointDescriptionCollection endpointCollection, bool haveCert)
        {
            EndpointDescription bestEndpoint = null;
            foreach (EndpointDescription endpoint in endpointCollection)
            {
                if (endpoint.TransportProfileUri == Profiles.UaTcpTransport)
                {
                    if (bestEndpoint == null || 
                        haveCert && (endpoint.SecurityLevel > bestEndpoint.SecurityLevel) ||
                        !haveCert && (endpoint.SecurityLevel < bestEndpoint.SecurityLevel))
                    {
                        bestEndpoint = endpoint;
                    }
                }
            }
            return bestEndpoint;
        }

        private static void ReplaceLocalHostWithRemoteHost(EndpointDescriptionCollection endpoints, Uri discoveryUrl)
        {
            foreach (EndpointDescription endpoint in endpoints)
            {
                endpoint.EndpointUrl = Utils.ReplaceLocalhost(endpoint.EndpointUrl, discoveryUrl.DnsSafeHost);
                StringCollection updatedDiscoveryUrls = new StringCollection();
                foreach (string url in endpoint.Server.DiscoveryUrls)
                {
                    updatedDiscoveryUrls.Add(Utils.ReplaceLocalhost(url, discoveryUrl.DnsSafeHost));
                }
                endpoint.Server.DiscoveryUrls = updatedDiscoveryUrls;
            }
        }
    }
}