Host Switcher

/*
 * Application: HostSwitcher.exe
 * 
 * Authors:  Daniel Liedke
 * 
 * Purpose: Quickly and easy change hosts file
 *  
 * ------------------------------------------------------------------------------------------
 * CHANGE LOG
 * ------------------------------------------------------------------------------------------
 * Date		    Author				Change Details 
 * ------------------------------------------------------------------------------------------
 * 06-15-2010   Daniel Liedke          Initial version created.
 * 
 */

using System;
using System.IO;
using System.Text;
using System.Diagnostics;
using System.Windows.Forms;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace HostSwitcher
{
    public partial class MainScreen : Form
    {
        #region Class Variables/Structs

        private FileSystemWatcher fileWatcher;

        public struct stHost
        {
            public string HostDescription;
            public string HostComment;
            public string IP;
            public bool Selected;
        }

        #endregion

        #region Initialization

        public MainScreen()
        {
            InitializeComponent();
        }

        private void MainScreen_Load(object sender, EventArgs e)
        {
            CreateHostsFileWatcher();
            BuildHostsTray();
        }

        private void tmrUI_Tick(object sender, EventArgs e)
        {
            // Hides the main screen after load
            tmrUI.Enabled = false;
            this.Visible = false;
        }

        #endregion

        #region Parse Hosts and Create Host Tray

        private IList<stHost> ParseHostsFile(ref bool noHosts)
        {
            noHosts = true;
            IList<string> lineList = new List<string>();
            IList<stHost> hostList = new List<stHost>();

            try
            {
                // Reads all lines from hosts file
                FileInfo fileInfo = new FileInfo(GetHostsFilename());
                StreamReader sr = fileInfo.OpenText();
                while (sr.EndOfStream == false)
                {
                    string line = sr.ReadLine();
                    line = line.Trim();

                    //if (string.IsNullOrEmpty(line) == false)
                    {
                        lineList.Add(line.Replace("\t", " ").Replace("\r", " ").Replace("\n", " "));
                    }
                }
                sr.Close();

                // Creates a host list
                for (int f = 0; f < lineList.Count; f++)
                {
                    // If we found an host entry with a comment in the line before, ex:
                    //
                    // # DIT - x.acme.com       [host comment]
                    // #38.25.63.10				acme          [host ip]   [host address]
                    //
                    if (lineList[f].StartsWith("# ") &&
                        (f + 1) < lineList.Count &&
                        (StartWithNumberCommented(lineList[f + 1]) || StartWithNumber(lineList[f + 1])))
                    {
                        // Get host comment
                        string hostComment = lineList[f].Replace("# ", "");
                        
                        // Retrieve host details line
                        string hostDetailsLine = lineList[f + 1];
                        
                        // Get host IP
                        string hostIp = hostDetailsLine.Replace("#", "");
                        if (hostIp.IndexOf(" ") > -1)
                        {
                            hostIp = hostIp.Substring(0, hostIp.IndexOf(" "));
                        }
                                               
                        // Get host address
                        string hostAddress = string.Empty;
                        if ((hostDetailsLine.IndexOf(" ") > -1) && hostDetailsLine.IndexOf(" ") < hostDetailsLine.Length)
                        {
                            hostAddress = hostDetailsLine.Substring(hostDetailsLine.IndexOf(" ")).Trim();
                        }

                        // Creates the host description with comment, addresss and IP
                        string hostDescription = hostComment + " [" + hostAddress + " at " + hostIp + "]";
                        
                        // Check if host is not commented out
                        bool selected = StartWithNumber(hostDetailsLine);


                        // Search for repeated IP entries
                        bool hostAlreadyExists = false;
                        foreach (stHost hostItemSearch in hostList)
                        {
                            if (hostItemSearch.IP == hostIp)
                            {
                                hostAlreadyExists = true;
                            }
                        }

                        // Make sure we don´t add repeated IP entries
                        // And also only entries with host IP and host address
                        if (hostAlreadyExists == false &&
                            string.IsNullOrEmpty(hostIp) == false &&
                            string.IsNullOrEmpty(hostAddress) == false)
                        {
                            // Create and add new host object to the list
                            stHost hostItem = new stHost();
                            hostItem.HostDescription = hostDescription;
                            hostItem.HostComment = hostComment;
                            hostItem.IP = hostIp;
                            hostItem.Selected = selected;
                            hostList.Add(hostItem);

                            // If we found a single selected host, no hosts menu option can´t be enabled
                            if (selected)
                            {
                                noHosts = false;
                            }
                        }
                    }
                    else if ((StartWithNumberCommented(lineList[f]) || StartWithNumber(lineList[f])) &&
                        (f - 1) >= 0 &&
                        lineList[f-1].StartsWith("# ")==false)
                    {
                        // Parse strings in both formats:
                        //
                        // #102.54.94.97 rhino.acme.com # Rhino server     [host ip]  [host address] [host comment]
                        //
                        // #10.4.2.4 www.test1234567.com        [host ip]  [host address]
                        //

                        // Retrieve host ip
                        string hostIp = lineList[f].Replace("#", "");
                        if (hostIp.IndexOf(" ") > -1)
                        {
                            hostIp = hostIp.Substring(0, hostIp.IndexOf(" "));
                        }

                        // Gets host address and comment
                        string hostFullText = string.Empty;
                        if (lineList[f].IndexOf(" ") > -1)
                        {
                            hostFullText = lineList[f].Substring(lineList[f].IndexOf(" ") + 1).TrimStart();
                        }

                        // Gets only host address
                        string hostAddress = hostFullText;
                        if (hostFullText.IndexOf(" ") > -1)
                        {
                            hostAddress = hostFullText.Substring(0, hostFullText.IndexOf(" ")).Trim();
                        }

                        // Gets only host comment
                        string hostComment = string.Empty;
                        if (hostFullText.IndexOf("#") > -1 && ((hostFullText.IndexOf("#") + 1) < hostFullText.Length))
                        {
                            hostComment = hostFullText.Substring(hostFullText.IndexOf("#") + 1).Trim();
                        }

                        // Creates the host description with comment, addresss and IP
                        string hostDescription = hostComment + " [" + hostAddress + " at " + hostIp + "]";
                             
                        // Check if host is not commented out
                        bool selected = StartWithNumber(lineList[f]);


                        // Search for repeated IP entries
                        bool hostAlreadyExists = false;
                        foreach (stHost hostItemSearch in hostList)
                        {
                            if (hostItemSearch.IP == hostIp)
                            {
                                hostAlreadyExists = true;
                            }
                        }

                        // Make sure we don´t add repeated IP entries
                        // And also only entries with host IP and host address
                        if (hostAlreadyExists == false &&
                            string.IsNullOrEmpty(hostIp)==false &&
                            string.IsNullOrEmpty(hostAddress)==false)
                        {
                            // Create and add new host object to the list
                            stHost hostItem = new stHost();
                            hostItem.HostDescription = hostDescription;
                            hostItem.HostComment = hostComment;
                            hostItem.IP = hostIp;
                            hostItem.Selected = selected;
                            hostList.Add(hostItem);

                            // If we found a single selected host, no hosts menu option can´t be enabled
                            if (selected)
                            {
                                noHosts = false;
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error parsing hosts file: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

            return hostList;
        }

        private void BuildHostsTray()
        {
            try
            {
                // Parse current hosts file
                bool noHosts = false;
                IList<stHost> hostList = ParseHostsFile(ref noHosts);

                // Clear tray menu
                cmsHosts.Items.Clear();

                // Add default "No hosts" option
                System.Windows.Forms.ToolStripMenuItem menuItemNone = new System.Windows.Forms.ToolStripMenuItem();
                menuItemNone.Name = "";
                menuItemNone.Text = "[No hosts]";
                menuItemNone.Checked = noHosts;
                menuItemNone.MouseUp += new MouseEventHandler(menuItem_MouseUp);
                cmsHosts.Items.Add(menuItemNone);

                // Add menu separator
                System.Windows.Forms.ToolStripSeparator toolStripMenuItem1 = new System.Windows.Forms.ToolStripSeparator(); ;
                toolStripMenuItem1.Size = new System.Drawing.Size(149, 6);
                cmsHosts.Items.Add(toolStripMenuItem1);

                // Add all commented host entries
                foreach (stHost host in hostList)
                {
                    System.Windows.Forms.ToolStripMenuItem menuItem = new System.Windows.Forms.ToolStripMenuItem();
                    menuItem.Name = host.IP;
                    menuItem.Text = host.HostDescription;
                    menuItem.Tag = host.HostComment;
                    menuItem.Checked = host.Selected;
                    menuItem.MouseUp += new MouseEventHandler(menuItem_MouseUp);
                    cmsHosts.Items.Add(menuItem);
                }

                // Add menu separator
                System.Windows.Forms.ToolStripSeparator toolStripMenuItem2 = new System.Windows.Forms.ToolStripSeparator();
                toolStripMenuItem2.Size = new System.Drawing.Size(149, 6);
                cmsHosts.Items.Insert(cmsHosts.Items.Count, toolStripMenuItem2);

                // Add "View Hosts File" option
                System.Windows.Forms.ToolStripMenuItem viewHostsToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
                viewHostsToolStripMenuItem.Name = "viewHostsToolStripMenuItem";
                viewHostsToolStripMenuItem.Size = new System.Drawing.Size(152, 22);
                viewHostsToolStripMenuItem.Text = "&View Hosts File";
                viewHostsToolStripMenuItem.Click += new EventHandler(viewHostsToolStripMenuItem_Click);
                cmsHosts.Items.Insert(cmsHosts.Items.Count, viewHostsToolStripMenuItem);

                // Add menu separator
                System.Windows.Forms.ToolStripSeparator toolStripMenuItem3 = new System.Windows.Forms.ToolStripSeparator();
                toolStripMenuItem3.Size = new System.Drawing.Size(149, 6);
                cmsHosts.Items.Insert(cmsHosts.Items.Count, toolStripMenuItem3);

                // Add "Exit" application option
                System.Windows.Forms.ToolStripMenuItem exitToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
                exitToolStripMenuItem.Name = "exitToolStripMenuItem";
                exitToolStripMenuItem.Size = new System.Drawing.Size(152, 22);
                exitToolStripMenuItem.Text = "&Exit";
                exitToolStripMenuItem.Click += new System.EventHandler(this.exitToolStripMenuItem_Click);
                cmsHosts.Items.Insert(cmsHosts.Items.Count, exitToolStripMenuItem);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error creating tray menu: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        #endregion

        #region Update Hosts

        private void menuItem_MouseUp(object sender, MouseEventArgs e)
        {
            try
            {
                if (e.Button == MouseButtons.Left)
                {
                    // When left clicking menu, update hosts
                    ToolStripMenuItem itemSelected = ((ToolStripMenuItem)(sender));
                    string ipHost = itemSelected.Name;
                    UpdateHosts(ipHost);

                    // Uncheck all host items
                    foreach (ToolStripItem item in cmsHosts.Items)
                    {
                        if (item.GetType() == typeof(ToolStripMenuItem))
                        {
                            ((ToolStripMenuItem)item).Checked = false;
                        }
                    }

                    // Check selected host item
                    itemSelected.Checked = true;
                }
                else if (e.Button == MouseButtons.Right)
                {
                    // When right clicking menu, copy host name
                    ToolStripMenuItem itemSelected = ((ToolStripMenuItem)(sender));
                    Clipboard.SetText(GetHostAddress(itemSelected));
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error in tray menu mouse up: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private string GetHostAddress(ToolStripMenuItem menuItem)
        {
            string hostAddress = menuItem.Text;

            try
            {
                string tag = menuItem.Tag as string;

                //
                // Attempts to get server name from a string like
                // DIT - dit.acme.com
                //
                if (string.IsNullOrEmpty(tag) == false && tag.IndexOf(".") > -1)
                {
                    int f = 0;
                    for (f = tag.IndexOf("."); f >= 0; f--)
                    {
                        if (tag[f] == ' ')
                        {
                            break;
                        }
                    }
                    hostAddress = tag.Substring(f + 1);
                    if (hostAddress.IndexOf(" ") > -1)
                    {
                        hostAddress = hostAddress.Substring(hostAddress.IndexOf(" ")).Trim();
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error in GetHostAddress: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
             
            return hostAddress;
        }

        private void UpdateHosts(string ipHost)
        {
            try
            {
                StringBuilder sbHostsNew = new StringBuilder();

                // Read hosts file
                FileInfo fileInfo = new FileInfo(GetHostsFilename());
                StreamReader sr = fileInfo.OpenText();
                while (sr.EndOfStream == false)
                {
                    string line = sr.ReadLine();

                    // Check if we found selected host commented out
                    if (string.IsNullOrEmpty(ipHost) == false &&
                        line.Contains(ipHost) &&
                        line.StartsWith("#" + ipHost))
                    {
                        // Uncomment selected host
                        line = line.Substring(1);
                    }
                    else if (((string.IsNullOrEmpty(ipHost) == false) && (line.Contains(ipHost) == false)) ||
                               string.IsNullOrEmpty(ipHost) == true)
                    {
                        // Comment out other entries except already uncommend host entry
                        if (StartWithNumber(line))
                        {
                            line = "#" + line;
                        }
                    }
                    sbHostsNew.Append(line + "\r\n");
                }
                sr.Close();

                // Saves new host file and prevent file watcher from raising event
                fileWatcher.EnableRaisingEvents = false;
                TextWriter tw = new StreamWriter(GetHostsFilename());
                tw.Write(sbHostsNew.ToString());
                tw.Flush();
                tw.Close();
                fileWatcher.EnableRaisingEvents = true;
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error updating hosts file: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        #endregion

        #region Host File Watcher

        private void CreateHostsFileWatcher()
        {
            try
            {
                // Make sure to monitor hosts file for changes
                fileWatcher = new FileSystemWatcher();
                fileWatcher = new FileSystemWatcher(GetHostsPath());
                fileWatcher.Changed += new FileSystemEventHandler(fileWatcher_Changed);
                fileWatcher.NotifyFilter = NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName;
                fileWatcher.EnableRaisingEvents = true;
                fileWatcher.Filter = "hosts";
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error monitoring hosts file: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private void fileWatcher_Changed(object sender, FileSystemEventArgs e)
        {
            try
            {
                // Wait a bit for file to be saved and reload
                // hosts menu when file is changed externally
                //
                System.Threading.Thread.Sleep(700);
                if (InvokeRequired == false)
                {
                    BuildHostsTray();
                }
                else
                {
                    Invoke(new FileSystemEventHandler(fileWatcher_Changed), sender, e);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error monitoring hosts file: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        #endregion

        #region View Hosts File

        private void viewHostsToolStripMenuItem_Click(object sender, EventArgs e)
        {
            try
            {
                // Shows notepad with hosts file
                ProcessStartInfo psi = new ProcessStartInfo("notepad.exe");
                psi.Arguments = GetHostsFilename();
                Process.Start(psi);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error showing hosts file: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        #endregion

        #region Exit

        private void exitToolStripMenuItem_Click(object sender, EventArgs e)
        {
            try
            {
                //
                // When exitting and No Hosts is not selected
                // ask user if he would like to keep host configuration
                // otherwise clear hosts
                //
                if (((ToolStripMenuItem)cmsHosts.Items[0]).Checked == false)
                {
                    DialogResult dialogResult = MessageBox.Show("Keep current host configuration ?", "Question", MessageBoxButtons.YesNo, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2);
                    if (dialogResult == DialogResult.No)
                    {
                        UpdateHosts(string.Empty);
                    }
                }
                Application.Exit();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error exitting application: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        #endregion

        #region General Methods

        private string GetHostsPath()
        {
            // Gets dynamic hosts path from system folder
            string systemPath = Environment.GetFolderPath(Environment.SpecialFolder.System);
            string hostsPath = Path.Combine(systemPath, @"drivers\etc");
            return hostsPath;
        }

        private string GetHostsFilename()
        {
            // Creates full host filename
            string hostsFileName = Path.Combine(GetHostsPath(), "hosts");
            return hostsFileName;
        }

        private bool StartWithNumber(string str)
        {
            // Check if string starts with an ip number
            Regex regex = new Regex(@"^\d{1}");
            return regex.IsMatch(str);
        }

        private bool StartWithNumberCommented(string str)
        {
            // Check if strings starts with a commented ip number
            Regex regex = new Regex(@"^#{1}\d{1}");
            return regex.IsMatch(str);
        }

        #endregion
    }
}