using System;
using System.IO;
using System.Net;
using System.Diagnostics;
using System.Net.Security;
using System.Windows.Forms;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;

namespace MeshCentralRouter
{
    public partial class UpdateForm : Form
    {
        private string url = null;
        private string hash = null;
        private int size = 0;
        private string[] args = null;
        private string serverTlsCertHash = null;

        public UpdateForm(string url, string hash, int size, string[] args, string serverhash)
        {
            InitializeComponent();
            this.url = url;
            this.hash = hash;
            this.size = size;
            this.args = args;
            this.serverTlsCertHash = serverhash;
        }

        private void okButton_Click(object sender, EventArgs e)
        {
            DownloadUpdate();
        }

        private void Client_DownloadProgressChanged(object sender, System.Net.DownloadProgressChangedEventArgs e)
        {
            updateProgressBar.Value = e.ProgressPercentage;
        }

        private void DownloadUpdate()
        {
            HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
            Uri x = webRequest.RequestUri;
            webRequest.Method = "GET";
            webRequest.Timeout = 10000;
            webRequest.BeginGetResponse(new AsyncCallback(DownloadUpdateRespone), webRequest);
            webRequest.ServerCertificateValidationCallback += RemoteCertificateValidationCallback;
            updateProgressBar.Visible = true;
        }

        public bool RemoteCertificateValidationCallback(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
        {
            // Check MeshCentral server's TLS certificate. This is our first security layer.
            if ((serverTlsCertHash != null) && (serverTlsCertHash != certificate.GetCertHashString().ToLower()) && (serverTlsCertHash != GetMeshKeyHash(certificate).ToLower()) && (serverTlsCertHash != GetMeshCertHash(certificate).ToLower())) return false;
            return true;
        }

        public delegate void updateProgressHandler(int ptr, int total);
        public void updateProgress(int ptr, int total)
        {
            if (this.InvokeRequired) { this.Invoke(new updateProgressHandler(updateProgress), ptr, total); return; }
            updateProgressBar.Visible = true;
            updateProgressBar.Maximum = total;
            if (ptr <= total) { updateProgressBar.Value = ptr; } else { updateProgressBar.Value = total; }
        }

        public delegate void updateMessageHandler(string msg, int buttons);
        public void updateMessage(string msg, int buttons)
        {
            if (this.InvokeRequired) { this.Invoke(new updateMessageHandler(updateMessage), msg, buttons); return; }
            mainLabel.Text = msg;
            okButton.Enabled = ((buttons & 1) != 0);
            cancelButton.Enabled = ((buttons & 2) != 0);
            updateProgressBar.Visible = ((buttons & 4) != 0);
        }

        private void DownloadUpdateRespone(IAsyncResult asyncResult)
        {
            long received = 0;
            HttpWebRequest webRequest = (HttpWebRequest)asyncResult.AsyncState;
            try
            {
                // Hash our own executable
                using (HttpWebResponse webResponse = (HttpWebResponse)webRequest.EndGetResponse(asyncResult))
                {
                    byte[] buffer = new byte[4096];
                    FileStream fileStream = File.OpenWrite(System.Reflection.Assembly.GetEntryAssembly().Location + ".update.exe");
                    using (Stream input = webResponse.GetResponseStream())
                    {
                        int size = input.Read(buffer, 0, buffer.Length);
                        while (size > 0)
                        {
                            fileStream.Write(buffer, 0, size);
                            received += size;
                            updateProgress((int)received, (int)size);
                            size = input.Read(buffer, 0, buffer.Length);
                        }
                    }
                    fileStream.Flush();
                    fileStream.Close();

                    // Hash the resulting file
                    byte[] downloadHash;
                    using (var sha384 = SHA384Managed.Create()) { using (var stream = File.OpenRead(System.Reflection.Assembly.GetEntryAssembly().Location + ".update.exe")) { downloadHash = sha384.ComputeHash(stream); } }
                    string downloadHashHex = BitConverter.ToString(downloadHash).Replace("-", string.Empty).ToLower();
                    if (downloadHashHex != hash) {
                        updateMessage("Invalid download.", 2);
                        File.Delete(System.Reflection.Assembly.GetEntryAssembly().Location + ".update.exe");
                    } else {
                        updateMessage("Updating...", 0);
                        Process.Start(System.Reflection.Assembly.GetEntryAssembly().Location + ".update.exe", "-update:" + System.Reflection.Assembly.GetEntryAssembly().Location + " " + string.Join(" ", args));
                        Application.Exit();
                    }
                }
            }
            catch (Exception ex) { updateMessage("Error: " + ex.ToString(), 2); }
        }


        // Return a modified base64 SHA384 hash string of the certificate public key
        public static string GetMeshKeyHash(X509Certificate cert)
        {
            return ByteArrayToHexString(new SHA384Managed().ComputeHash(cert.GetPublicKey()));
        }

        // Return a modified base64 SHA384 hash string of the certificate
        public static string GetMeshCertHash(X509Certificate cert)
        {
            return ByteArrayToHexString(new SHA384Managed().ComputeHash(cert.GetRawCertData()));
        }

        public static string ByteArrayToHexString(byte[] Bytes)
        {
            StringBuilder Result = new StringBuilder(Bytes.Length * 2);
            string HexAlphabet = "0123456789ABCDEF";
            foreach (byte B in Bytes) { Result.Append(HexAlphabet[(int)(B >> 4)]); Result.Append(HexAlphabet[(int)(B & 0xF)]); }
            return Result.ToString();
        }

    }
}