/* ========================================================================
 * Copyright (c) 2005-2020 The OPC Foundation, Inc. All rights reserved.
 *
 * OPC Foundation MIT License 1.00
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 * 
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * The complete license agreement can be found here:
 * http://opcfoundation.org/License/MIT/1.00/
 * ======================================================================*/

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Threading.Tasks;
using System.Windows.Forms;
using Opc.Ua.Client.ComplexTypes;

namespace Opc.Ua.Client.Controls
{
    /// <summary>
    /// A tool bar used to connect to a server.
    /// </summary>
    public partial class ConnectServerCtrl : UserControl
    {
        #region Constructors
        /// <summary>
        /// Initializes the object.
        /// </summary>
        public ConnectServerCtrl()
        {
            InitializeComponent();
            m_CertificateValidation = new CertificateValidationEventHandler(CertificateValidator_CertificateValidation);
            m_endpoints = new Dictionary<Uri, EndpointDescription>();
        }
        #endregion

        #region Private Fields
        private ApplicationConfiguration m_configuration;
        private Session m_session;
        private SessionReconnectHandler m_reconnectHandler;
        private CertificateValidationEventHandler m_CertificateValidation;
        private EventHandler m_ReconnectComplete;
        private EventHandler m_ReconnectStarting;
        private EventHandler m_KeepAliveComplete;
        private EventHandler m_ConnectComplete;
        private StatusStrip m_StatusStrip;
        private ToolStripItem m_ServerStatusLB;
        private ToolStripItem m_StatusUpateTimeLB;
        private Dictionary<Uri, EndpointDescription> m_endpoints;
        #endregion

        #region Public Members
        /// <summary>
        /// Default session values.
        /// </summary>
        public static readonly uint DefaultSessionTimeout = 60000;
        public static readonly int DefaultDiscoverTimeout = 15000;
        public static readonly int DefaultReconnectPeriod = 10;

        /// <summary>
        /// A strip used to display session status information.
        /// </summary>
        public StatusStrip StatusStrip
        {
            get => m_StatusStrip;

            set
            {
                if (!Object.ReferenceEquals(m_StatusStrip, value))
                {
                    m_StatusStrip = value;

                    if (value != null)
                    {
                        m_ServerStatusLB = new ToolStripStatusLabel();
                        m_StatusUpateTimeLB = new ToolStripStatusLabel();
                        m_StatusStrip.Items.Add(m_ServerStatusLB);
                        m_StatusStrip.Items.Add(m_StatusUpateTimeLB);
                    }
                }
            }
        }

        /// <summary>
        /// A control that contains the last time a keep alive was returned from the server.
        /// </summary>
        public ToolStripItem ServerStatusControl { get => m_ServerStatusLB; set => m_ServerStatusLB = value; }

        /// <summary>
        /// A control that contains the last time a keep alive was returned from the server.
        /// </summary>
        public ToolStripItem StatusUpateTimeControl { get => m_StatusUpateTimeLB; set => m_StatusUpateTimeLB = value; }

        /// <summary>
        /// The name of the session to create.
        /// </summary>
        public string SessionName { get; set; }

        /// <summary>
        /// Gets or sets a flag indicating that the domain checks should be ignored when connecting.
        /// </summary>
        public bool DisableDomainCheck { get; set; }

        /// <summary>
        /// Gets the cached EndpointDescription for a Url.
        /// </summary>
        public EndpointDescription GetEndpointDescription(Uri url)
        {
            EndpointDescription endpointDescription;
            if (m_endpoints.TryGetValue(url, out endpointDescription))
            {
                return endpointDescription;
            }
            return null;
        }

        /// <summary>
        /// The URL displayed in the control.
        /// </summary>
        public string ServerUrl
        {
            get
            {
                if (UrlCB.SelectedIndex >= 0)
                {
                    return (string)UrlCB.SelectedItem;
                }

                return UrlCB.Text;
            }

            set
            {
                UrlCB.SelectedIndex = -1;
                UrlCB.Text = value;
            }
        }

        /// <summary>
        /// Whether to use security when connecting.
        /// </summary>
        public bool UseSecurity
        {
            get => UseSecurityCK.Checked;
            set => UseSecurityCK.Checked = value;
        }

        /// <summary>
        /// The locales to use when creating the session.
        /// </summary>
        public string[] PreferredLocales { get; set; }

        /// <summary>
        /// The user identity to use when creating the session.
        /// </summary>
        public IUserIdentity UserIdentity { get; set; }

        /// <summary>
        /// The client application configuration.
        /// </summary>
        public ApplicationConfiguration Configuration
        {
            get => m_configuration;

            set
            {
                if (!Object.ReferenceEquals(m_configuration, value))
                {
                    if (m_configuration != null)
                    {
                        m_configuration.CertificateValidator.CertificateValidation -= m_CertificateValidation;
                    }

                    m_configuration = value;

                    if (m_configuration != null)
                    {
                        m_configuration.CertificateValidator.CertificateValidation += m_CertificateValidation;
                    }
                }
            }
        }

        /// <summary>
        /// The currently active session. 
        /// </summary>
        public Session Session => m_session;

        /// <summary>
        /// The number of seconds between reconnect attempts (0 means reconnect is disabled).
        /// </summary>
        public int ReconnectPeriod { get; set; } = DefaultReconnectPeriod;

        /// <summary>
        /// The discover timeout.
        /// </summary>
        public int DiscoverTimeout { get; set; } = DefaultDiscoverTimeout;

        /// <summary>
        /// The session timeout.
        /// </summary>
        public uint SessionTimeout { get; set; } = DefaultSessionTimeout;

        /// <summary>
        /// Raised when a good keep alive from the server arrives.
        /// </summary>
        public event EventHandler KeepAliveComplete
        {
            add { m_KeepAliveComplete += value; }
            remove { m_KeepAliveComplete -= value; }
        }

        /// <summary>
        /// Raised when a reconnect operation starts.
        /// </summary>
        public event EventHandler ReconnectStarting
        {
            add { m_ReconnectStarting += value; }
            remove { m_ReconnectStarting -= value; }
        }

        /// <summary>
        /// Raised when a reconnect operation completes.
        /// </summary>
        public event EventHandler ReconnectComplete
        {
            add { m_ReconnectComplete += value; }
            remove { m_ReconnectComplete -= value; }
        }

        /// <summary>
        /// Raised after successfully connecting to or disconnecing from a server.
        /// </summary>
        public event EventHandler ConnectComplete
        {
            add { m_ConnectComplete += value; }
            remove { m_ConnectComplete -= value; }
        }

        /// <summary>
        /// Sets the URLs shown in the control.
        /// </summary>
        public void SetAvailableUrls(IList<string> urls)
        {
            UrlCB.Items.Clear();

            if (urls != null)
            {
                foreach (string url in urls)
                {
                    int index = url.LastIndexOf("/discovery", StringComparison.InvariantCultureIgnoreCase);

                    if (index != -1)
                    {
                        UrlCB.Items.Add(url.Substring(0, index));
                        continue;
                    }

                    UrlCB.Items.Add(url);
                }

                if (UrlCB.Items.Count > 0)
                {
                    UrlCB.SelectedIndex = 0;
                }
            }
        }

        /// <summary>
        /// Creates a new session.
        /// </summary>
        /// <returns>The new session object.</returns>
        private async Task<Session> Connect(
            ITransportWaitingConnection connection,
            EndpointDescription endpointDescription,
            bool useSecurity,
            uint sessionTimeout = 0)
        {
            // disconnect from existing session.
            InternalDisconnect();

            // select the best endpoint.
            if (endpointDescription == null)
            {
                endpointDescription = CoreClientUtils.SelectEndpoint(m_configuration, connection, useSecurity, DiscoverTimeout);
            }

            EndpointConfiguration endpointConfiguration = EndpointConfiguration.Create(m_configuration);
            ConfiguredEndpoint endpoint = new ConfiguredEndpoint(null, endpointDescription, endpointConfiguration);

            m_session = await Session.Create(
                m_configuration,
                connection,
                endpoint,
                false,
                !DisableDomainCheck,
                (String.IsNullOrEmpty(SessionName)) ? m_configuration.ApplicationName : SessionName,
                sessionTimeout,
                UserIdentity,
                PreferredLocales);

            // set up keep alive callback.
            m_session.KeepAlive += new KeepAliveEventHandler(Session_KeepAlive);

            // raise an event.
            DoConnectComplete(null);

            try
            {
                UpdateStatus(false, DateTime.Now, "Connected, loading complex type system.");
                var typeSystemLoader = new ComplexTypeSystem(m_session);
                await typeSystemLoader.Load();
            }
            catch (Exception e)
            {
                UpdateStatus(true, DateTime.Now, "Connected, failed to load complex type system.");
                Utils.Trace(e, "Failed to load complex type system.");
            }

            // return the new session.
            return m_session;
        }

        /// <summary>
        /// Creates a new session.
        /// </summary>
        /// <returns>The new session object.</returns>
        public Task<Session> Connect()
        {
            // determine the URL that was selected.
            string serverUrl = UrlCB.Text;
            if (UrlCB.SelectedIndex >= 0)
            {
                serverUrl = (string)UrlCB.SelectedItem;
            }
            bool useSecurity = UseSecurityCK.Checked;
            return Connect(serverUrl, useSecurity);
        }

        /// <summary>
        /// Creates a new session.
        /// </summary>
        /// <returns>The new session object.</returns>
        private async Task<Session> Connect(
            string serverUrl,
            bool useSecurity,
            uint sessionTimeout = 0)
        {
            // disconnect from existing session.
            InternalDisconnect();

            // select the best endpoint.
            var endpointDescription = CoreClientUtils.SelectEndpoint(serverUrl, useSecurity, DiscoverTimeout);
            var endpointConfiguration = EndpointConfiguration.Create(m_configuration);
            var endpoint = new ConfiguredEndpoint(null, endpointDescription, endpointConfiguration);

            m_session = await Session.Create(
                m_configuration,
                endpoint,
                false,
                !DisableDomainCheck,
                (String.IsNullOrEmpty(SessionName)) ? m_configuration.ApplicationName : SessionName,
                sessionTimeout == 0 ? DefaultSessionTimeout : sessionTimeout,
                UserIdentity,
                PreferredLocales);

            // set up keep alive callback.
            m_session.KeepAlive += new KeepAliveEventHandler(Session_KeepAlive);

            // raise an event.
            DoConnectComplete(null);

            try
            {
                UpdateStatus(false, DateTime.Now, "Connected, loading complex type system.");
                var typeSystemLoader = new ComplexTypeSystem(m_session);
                await typeSystemLoader.Load();
            }
            catch (Exception e)
            {
                UpdateStatus(true, DateTime.Now, "Connected, failed to load complex type system.");
                Utils.Trace(e, "Failed to load complex type system.");
            }

            // return the new session.
            return m_session;
        }

        /// <summary>
        /// Creates a new session.
        /// </summary>
        /// <param name="serverUrl">The URL of a server endpoint.</param>
        /// <param name="useSecurity">Whether to use security.</param>
        /// <returns>The new session object.</returns>
        public async Task<Session> ConnectAsync(
            string serverUrl = null,
            bool useSecurity = false,
            uint sessionTimeout = 0
            )
        {
            if (serverUrl == null)
            {
                serverUrl = UrlCB.Text;

                if (UrlCB.SelectedIndex >= 0)
                {
                    serverUrl = (string)UrlCB.SelectedItem;
                }

                useSecurity = UseSecurityCK.Checked;
            }
            else
            {
                UrlCB.Text = serverUrl;
                UseSecurityCK.Checked = useSecurity;
            }

            return await Task.Run(() => Connect(serverUrl, useSecurity, sessionTimeout));
        }

        /// <summary>
        /// Create a new reverse connection.
        /// </summary>
        /// <param name="connection"></param>
        /// <param name="useSecurity"></param>
        public async Task<Session> ConnectAsync(
            ITransportWaitingConnection connection,
            bool useSecurity,
            int discoverTimeout = -1,
            uint sessionTimeout = 0
            )
        {
            if (connection.EndpointUrl == null)
            {
                throw new ArgumentException("Endpoint URL is not valid.");
            }

            UrlCB.Text = connection.EndpointUrl.ToString();
            UseSecurityCK.Checked = useSecurity;

            EndpointDescription endpointDescription = null;

            if (!m_endpoints.TryGetValue(connection.EndpointUrl, out endpointDescription))
            {
                // Discovery uses the reverse connection and closes it
                // return and wait for next reverse hello
                endpointDescription = CoreClientUtils.SelectEndpoint(m_configuration, connection, useSecurity, discoverTimeout);
                m_endpoints[connection.EndpointUrl] = endpointDescription;
                return null;
            }

            return await Connect(connection, endpointDescription, UseSecurityCK.Checked, sessionTimeout);
        }

        /// <summary>
        /// Disconnects from the server.
        /// </summary>
        public Task DisconnectAsync()
        {
            UpdateStatus(false, DateTime.UtcNow, "Disconnected");
            return Task.Run(() => InternalDisconnect());
        }

        /// <summary>
        /// Disconnects from the server.
        /// </summary>
        private void InternalDisconnect()
        {
            // stop any reconnect operation.
            if (m_reconnectHandler != null)
            {
                m_reconnectHandler.Dispose();
                m_reconnectHandler = null;
            }

            // disconnect any existing session.
            if (m_session != null)
            {
                m_session.KeepAlive -= Session_KeepAlive;
                m_session.Close(10000);
                m_session = null;
            }

            // raise an event.
            DoConnectComplete(null);
        }

        /// <summary>
        /// Disconnects from the server.
        /// </summary>
        public void Disconnect()
        {
            UpdateStatus(false, DateTime.UtcNow, "Disconnected");

            // stop any reconnect operation.
            InternalDisconnect();
        }

        /// <summary>
        /// Prompts the user to choose a server on another host.
        /// </summary>
        public void Discover(string hostName)
        {
            string endpointUrl = new DiscoverServerDlg().ShowDialog(m_configuration, hostName);

            if (endpointUrl != null)
            {
                ServerUrl = endpointUrl;
            }
        }
        #endregion

        #region Private Methods
        /// <summary>
        /// Raises the connect complete event on the main GUI thread.
        /// </summary>
        private void DoConnectComplete(object state)
        {
            if (m_ConnectComplete != null)
            {
                if (this.InvokeRequired)
                {
                    this.BeginInvoke(new System.Threading.WaitCallback(DoConnectComplete), state);
                    return;
                }

                m_ConnectComplete(this, null);
            }
        }

        /// <summary>
        /// Finds the endpoint that best matches the current settings.
        /// </summary>
        private EndpointDescription SelectEndpoint()
        {
            try
            {
                Cursor = Cursors.WaitCursor;

                // determine the URL that was selected.
                string discoveryUrl = UrlCB.Text;

                if (UrlCB.SelectedIndex >= 0)
                {
                    discoveryUrl = (string)UrlCB.SelectedItem;
                }

                // return the selected endpoint.
                return CoreClientUtils.SelectEndpoint(discoveryUrl, UseSecurityCK.Checked, DiscoverTimeout);
            }
            finally
            {
                Cursor = Cursors.Default;
            }
        }
        #endregion

        #region Event Handlers
        private delegate void UpdateStatusCallback(bool error, DateTime time, string status, params object[] arg);
        /// <summary>
        /// Updates the status control.
        /// </summary>
        /// <param name="error">Whether the status represents an error.</param>
        /// <param name="time">The time associated with the status.</param>
        /// <param name="status">The status message.</param>
        /// <param name="args">Arguments used to format the status message.</param>
        private void UpdateStatus(bool error, DateTime time, string status, params object[] args)
        {
            if (this.InvokeRequired)
            {
                this.BeginInvoke(new UpdateStatusCallback(UpdateStatus), error, time, status, args);
                return;
            }

            if (m_ServerStatusLB != null)
            {
                m_ServerStatusLB.Text = String.Format(status, args);
                m_ServerStatusLB.ForeColor = (error) ? Color.Red : Color.Empty;
            }

            if (m_StatusUpateTimeLB != null)
            {
                m_StatusUpateTimeLB.Text = time.ToLocalTime().ToString("hh:mm:ss");
                m_StatusUpateTimeLB.ForeColor = (error) ? Color.Red : Color.Empty;
            }
        }

        /// <summary>
        /// Handles a keep alive event from a session.
        /// </summary>
        private void Session_KeepAlive(Session session, KeepAliveEventArgs e)
        {
            if (this.InvokeRequired)
            {
                this.BeginInvoke(new KeepAliveEventHandler(Session_KeepAlive), session, e);
                return;
            }

            try
            {
                // check for events from discarded sessions.
                if (!Object.ReferenceEquals(session, m_session))
                {
                    return;
                }

                // start reconnect sequence on communication error.
                if (ServiceResult.IsBad(e.Status))
                {
                    if (ReconnectPeriod <= 0)
                    {
                        UpdateStatus(true, e.CurrentTime, "Communication Error ({0})", e.Status);
                        return;
                    }

                    UpdateStatus(true, e.CurrentTime, "Reconnecting in {0}s", ReconnectPeriod);

                    if (m_reconnectHandler == null)
                    {
                        if (m_ReconnectStarting != null)
                        {
                            m_ReconnectStarting(this, e);
                        }

                        m_reconnectHandler = new SessionReconnectHandler();
                        m_reconnectHandler.BeginReconnect(m_session, ReconnectPeriod * 1000, Server_ReconnectComplete);
                    }

                    return;
                }

                // update status.
                UpdateStatus(false, e.CurrentTime, "Connected [{0}]", session.Endpoint.EndpointUrl);

                // raise any additional notifications.
                if (m_KeepAliveComplete != null)
                {
                    m_KeepAliveComplete(this, e);
                }
            }
            catch (Exception exception)
            {
                ClientUtils.HandleException(this.Text, exception);
            }
        }

        /// <summary>
        /// Handles a click on the connect button.
        /// </summary>
        private async void Server_ConnectMI_Click(object sender, EventArgs e)
        {
            try
            {
                await ConnectAsync();
            }
            catch (ServiceResultException sre)
            {
                if (sre.StatusCode == StatusCodes.BadCertificateHostNameInvalid)
                {
                    if (GuiUtils.HandleDomainCheckError(this.FindForm().Text, sre.Result))
                    {
                        DisableDomainCheck = true;
                    };
                }
            }
            catch (Exception exception)
            {
                ClientUtils.HandleException(this.Text, exception);
            }
        }

        /// <summary>
        /// Handles a reconnect event complete from the reconnect handler.
        /// </summary>
        private void Server_ReconnectComplete(object sender, EventArgs e)
        {
            if (this.InvokeRequired)
            {
                this.BeginInvoke(new EventHandler(Server_ReconnectComplete), sender, e);
                return;
            }

            try
            {
                // ignore callbacks from discarded objects.
                if (!Object.ReferenceEquals(sender, m_reconnectHandler))
                {
                    return;
                }

                m_session = m_reconnectHandler.Session;
                m_reconnectHandler.Dispose();
                m_reconnectHandler = null;

                // raise any additional notifications.
                if (m_ReconnectComplete != null)
                {
                    m_ReconnectComplete(this, e);
                }
            }
            catch (Exception exception)
            {
                ClientUtils.HandleException(this.Text, exception);
            }
        }

        /// <summary>
        /// Handles a certificate validation error.
        /// </summary>
        private void CertificateValidator_CertificateValidation(CertificateValidator sender, CertificateValidationEventArgs e)
        {
            if (this.InvokeRequired)
            {
                this.Invoke(new CertificateValidationEventHandler(CertificateValidator_CertificateValidation), sender, e);
                return;
            }

            try
            {
                if (!m_configuration.SecurityConfiguration.AutoAcceptUntrustedCertificates)
                {
                    GuiUtils.HandleCertificateValidationError(this.FindForm(), sender, e);
                }
                else
                {
                    e.Accept = true;
                }
            }
            catch (Exception exception)
            {
                ClientUtils.HandleException(this.Text, exception);
            }
        }
        #endregion
    }
}