using System;
using System.Collections.Generic;
using System.Drawing;
using System.Text;
using System.IO;
using System.Windows.Forms;
using System.Security.Cryptography.X509Certificates;
using Opc.Ua.Gds;
using System.Threading.Tasks;

namespace Opc.Ua.GdsClient
{
    public partial class ApplicationCertificateControl : UserControl
    {
        public ApplicationCertificateControl()
        {
            InitializeComponent();
        }

        private GlobalDiscoveryClientConfiguration m_configuration;
        private GlobalDiscoveryServer m_gds;
        private RegisteredApplication m_application;
        private X509Certificate2 m_certificate;

        public async void Initialize(
            GlobalDiscoveryClientConfiguration configuration,
            GlobalDiscoveryServer gds,
            RegisteredApplication application,
            bool isHttps)
        {
            m_configuration = configuration;
            m_gds = gds;
            m_application = application;
            m_certificate = null;

            CertificateRequestTimer.Enabled = false;
            RequestProgressLabel.Visible = false;
            ApplyChangesButton.Enabled = false;

            CertificateControl.ShowNothing();

            X509Certificate2 certificate = null;

            if (!isHttps)
            {
                if (application != null)
                {
                    if (!String.IsNullOrEmpty(application.CertificatePublicKeyPath))
                    {
                        string file = Utils.GetAbsoluteFilePath(application.CertificatePublicKeyPath, true, false, false);

                        if (file != null)
                        {
                            certificate = new X509Certificate2(file);
                        }
                    }
                    else if (!String.IsNullOrEmpty(application.CertificateStorePath))
                    {
                        CertificateIdentifier id = new CertificateIdentifier();

                        id.StorePath = application.CertificateStorePath;
                        id.StoreType = CertificateStoreIdentifier.DetermineStoreType(id.StoreType);
                        id.SubjectName = application.CertificateSubjectName.Replace("localhost", System.Net.Dns.GetHostName());

                        certificate = await id.Find(true);
                    }
                }
            }
            else
            {
                if (application != null)
                {
                    if (!String.IsNullOrEmpty(application.HttpsCertificatePublicKeyPath))
                    {
                        string file = Utils.GetAbsoluteFilePath(application.HttpsCertificatePublicKeyPath, true, false, false);

                        if (file != null)
                        {
                            certificate = new X509Certificate2(file);
                        }
                    }
                    else
                    {
                        foreach (string disoveryUrl in application.DiscoveryUrl)
                        {
                            if (Uri.IsWellFormedUriString(disoveryUrl, UriKind.Absolute))
                            {
                                Uri url = new Uri(disoveryUrl);

                                CertificateIdentifier id = new CertificateIdentifier()
                                {
                                    StoreType = CertificateStoreType.X509Store,
                                    StorePath = "CurrentUser\\UA_MachineDefault",
                                    SubjectName = "CN=" + url.DnsSafeHost
                                };

                                certificate = await id.Find();
                            }
                        }
                    }
                }
            }

            if (certificate != null)
            {
                try
                {
                    CertificateControl.Tag = certificate.Thumbprint;
                }
                catch (Exception)
                {
                    MessageBox.Show(
                        Parent,
                        "The certificate does not appear to be valid. Please check configuration settings.",
                        Parent.Text,
                        MessageBoxButtons.OK,
                        MessageBoxIcon.Error);

                    certificate = null;
                }
            }

            WarningLabel.Visible = certificate == null;

            if (certificate != null)
            {
                m_certificate = certificate;
                CertificateControl.ShowValue(null, "Application Certificate", new CertificateWrapper() { Certificate = certificate }, true);
            }
        }

        private string[] GetDomainNames()
        {
            List<string> domainNames = new List<string>();

            if (m_application.DiscoveryUrl != null)
            {
                foreach (var discoveryUrl in m_application.DiscoveryUrl)
                {
                    if (Uri.IsWellFormedUriString(discoveryUrl, UriKind.Absolute))
                    {
                        string name = new Uri(discoveryUrl).DnsSafeHost;

                        if (name == "localhost")
                        {
                            name = System.Net.Dns.GetHostName();
                        }

                        bool found = false;

                        foreach (var domainName in domainNames)
                        {
                            if (String.Compare(domainName, name, StringComparison.OrdinalIgnoreCase) == 0)
                            {
                                found = true;
                                break;
                            }
                        }

                        if (!found)
                        {
                            domainNames.Add(name);
                        }
                    }
                }
            }

            if (domainNames != null && domainNames.Count > 0)
            {
                return domainNames.ToArray();
            }

            if (m_certificate != null)
            {
                var names = Utils.GetDomainsFromCertficate(m_certificate);

                if (names != null && names.Count > 0)
                {
                    domainNames.AddRange(names);
                    return domainNames.ToArray();
                }

                var fields = Utils.ParseDistinguishedName(m_certificate.Subject);

                string name = null;

                foreach (var field in fields)
                {
                    if (field.StartsWith("DC="))
                    {
                        if (name != null)
                        {
                            name += ".";
                        }

                        name += field.Substring(3);
                    }
                }

                if (names != null)
                {
                    domainNames.AddRange(names);
                    return domainNames.ToArray();
                }
            }

            return new string[] { System.Net.Dns.GetHostName() };
        }

        private void RequestNewButton_Click(object sender, EventArgs e)
        {
            try
            {
                // check if we already have a private key
                NodeId requestId = null;
                if (!string.IsNullOrEmpty(m_application.CertificateStorePath))
                {
                    CertificateIdentifier id = new CertificateIdentifier();
                    id.StoreType = CertificateStoreIdentifier.DetermineStoreType(m_application.CertificateStorePath);
                    id.StorePath = m_application.CertificateStorePath;
                    id.SubjectName = m_application.CertificateSubjectName.Replace("localhost", System.Net.Dns.GetHostName());

                    Task<X509Certificate2> t = id.Find(true);
                    t.Wait();
                    m_certificate = t.Result;
                }

                if (m_certificate == null)
                {
                    // no private key
                    requestId = m_gds.StartNewKeyPairRequest(
                        m_application.ApplicationId,
                        null,
                        null,
                        m_application.CertificateSubjectName.Replace("localhost", System.Net.Dns.GetHostName()),
                        GetDomainNames(),
                        "PFX",
                        null);
                }
                else
                {
                    byte[] certificateRequest = CertificateAuthority.CreateRequest(m_certificate, 256);
                    requestId = m_gds.StartSigningRequest(m_application.ApplicationId, null, null, certificateRequest);
                }

                m_application.CertificateRequestId = requestId.ToString();
                CertificateRequestTimer.Enabled = true;
                RequestProgressLabel.Visible = true;
                WarningLabel.Visible = false;
            }
            catch (Exception exception)
            {
                MessageBox.Show(Parent.Text + ": " + exception.Message);
            }
        }

        private async void CertificateRequestTimer_Tick(object sender, EventArgs e)
        {
            try
            {
                NodeId requestId = NodeId.Parse(m_application.CertificateRequestId);

                byte[] privateKeyPFX = null;
                byte[][] issuerCertificates = null;

                byte[] certificate = m_gds.FinishRequest(
                    m_application.ApplicationId,
                    requestId,
                    out privateKeyPFX,
                    out issuerCertificates);

                if (certificate == null)
                {
                    // request not done yet, try again in a few seconds
                    return;
                }
                
                CertificateRequestTimer.Enabled = false;
                RequestProgressLabel.Visible = false;

                X509Certificate2 newCert = new X509Certificate2(certificate);

                if (!String.IsNullOrEmpty(m_application.CertificateStorePath) && !String.IsNullOrEmpty(m_application.CertificateSubjectName))
                {
                    CertificateIdentifier cid = new CertificateIdentifier()
                    {
                        StorePath = m_application.CertificateStorePath,
                        StoreType = CertificateStoreIdentifier.DetermineStoreType(m_application.CertificateStorePath),
                        SubjectName = m_application.CertificateSubjectName.Replace("localhost", System.Net.Dns.GetHostName())
                    };
                    
                    // update store
                    using (var store = CertificateStoreIdentifier.OpenStore(m_application.CertificateStorePath))
                    {
                        // if we used a CSR, we already have a private key and therefore didn't request one from the GDS
                        // in this case, privateKey is null
                        if (privateKeyPFX == null)
                        {
                            X509Certificate2 oldCertificate = await cid.Find(true);
                            newCert = CertificateAuthority.Combine(newCert, oldCertificate);
                            await store.Delete(oldCertificate.Thumbprint);
                        }
                        else
                        {
                            newCert = new X509Certificate2(privateKeyPFX, string.Empty, X509KeyStorageFlags.Exportable);
                            newCert = CertificateFactory.Load(newCert, true);
                        }
                            
                        await store.Add(newCert);
                    }
                }
                
                // update trust list.
                if (!String.IsNullOrEmpty(m_application.TrustListStorePath))
                {
                    using (ICertificateStore store = CertificateStoreIdentifier.OpenStore(m_application.TrustListStorePath))
                    {
                        foreach (byte[] issuerCertificate in issuerCertificates)
                        {
                            X509Certificate2 x509 = new X509Certificate2(issuerCertificate);
                            X509Certificate2Collection certs = await store.FindByThumbprint(x509.Thumbprint);
                            if (certs.Count == 0)
                            {
                                await store.Add(new X509Certificate2(issuerCertificate));
                            }
                        }
                    }
                }
                        
                m_certificate = newCert;
                CertificateControl.ShowValue(null, "Application Certificate", new CertificateWrapper() { Certificate = m_certificate }, true);
            }
            catch (Exception exception)
            {
                var sre = exception as ServiceResultException;

                if (sre != null && sre.StatusCode == StatusCodes.BadNothingToDo)
                {
                    return;
                }

                MessageBox.Show(Parent.Text + ": " + exception.Message);
                CertificateRequestTimer.Enabled = false;
            }
        }
               
        private void Button_MouseEnter(object sender, EventArgs e)
        {
            ((Control)sender).BackColor = Color.CornflowerBlue;
        }

        private void Button_MouseLeave(object sender, EventArgs e)
        {
            ((Control)sender).BackColor = Color.MidnightBlue;
        }

    }
}