using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.ServiceProcess;
using System.Text;
using System.IO;
using WMI;
using System.Xml;
using System.Threading;
using Microsoft.Win32;

namespace winsw
{
    /// <summary>
    /// In-memory representation of the configuration file.
    /// </summary>
    public class ServiceDescriptor
    {
        private readonly XmlDocument dom = new XmlDocument();

        /// <summary>
        /// Where did we find the configuration file?
        /// </summary>
        public readonly string BasePath;

        public static string ExecutablePath
        {
            get
            {
                // this returns the executable name as given by the calling process, so
                // it needs to be absolutized.
                string p = Environment.GetCommandLineArgs()[0];
                return Path.Combine(AppDomain.CurrentDomain.BaseDirectory, p);

            }
        }

        public ServiceDescriptor()
        {
            // find co-located configuration xml. We search up to the ancestor directories to simplify debugging,
            // as well as trimming off ".vshost" suffix (which is used during debugging)
            string p = ExecutablePath;
            string baseName = Path.GetFileNameWithoutExtension(p);
            if (baseName.EndsWith(".vshost")) baseName = baseName.Substring(0, baseName.Length - 7);
            while (true)
            {
                p = Path.GetDirectoryName(p);
                if (File.Exists(Path.Combine(p, baseName + ".xml")))
                    break;
            }

            // register the base directory as environment variable so that future expansions can refer to this.
            Environment.SetEnvironmentVariable("BASE", p);

            BasePath = Path.Combine(p, baseName);

            dom.Load(BasePath+".xml");
        }

        private string SingleElement(string tagName)
        {
            var n = dom.SelectSingleNode("//" + tagName);
            if (n == null) throw new InvalidDataException("<" + tagName + "> is missing in configuration XML");
            return Environment.ExpandEnvironmentVariables(n.InnerText);
        }

        /// <summary>
        /// Path to the executable.
        /// </summary>
        public string Executable
        {
            get
            {
                return SingleElement("executable");
            }
        }

        /// <summary>
        /// Arguments
        /// </summary>
        public string Arguments
        {
            get
            {
                return SingleElement("arguments");
            }
        }

        public string Id
        {
            get
            {
                return SingleElement("id");
            }
        }

        public string Caption
        {
            get
            {
                return SingleElement("name");
            }
        }

        public string Description
        {
            get
            {
                return SingleElement("description");
            }
        }

        /// <summary>
        /// True if the service can interact with the desktop.
        /// </summary>
        public bool Interactive
        {
            get
            {
                return dom.SelectSingleNode("//interactive") != null;
            }
        }

        /// <summary>
        /// Environment variable overrides
        /// </summary>
        public Dictionary<string, string> EnvironmentVariables
        {
            get
            {
                Dictionary<string, string> map = new Dictionary<string, string>();
                foreach (XmlNode n in dom.SelectNodes("//env"))
                {
                    map[n.Attributes["name"].Value] = Environment.ExpandEnvironmentVariables(n.Attributes["value"].Value);
                }
                return map;
            }
        }
    }

    public class WrapperService : ServiceBase
    {
        private Process process = new Process();
        private ServiceDescriptor descriptor;

        /// <summary>
        /// Indicates to the watch dog thread that we are going to terminate the process,
        /// so don't try to kill us when the child exits.
        /// </summary>
        private bool orderlyShutdown;

        public WrapperService()
        {
            this.descriptor = new ServiceDescriptor();
            this.ServiceName = descriptor.Id;
            this.CanStop = true;
            this.CanPauseAndContinue = false;
            this.AutoLog = true;
        }

        /// <summary>
        /// Copy stuff from StreamReader to StreamWriter
        /// </summary>
        private void CopyStream(StreamReader i, StreamWriter o)
        {
            char[] buf = new char[1024];
            while (true)
            {
                int sz = i.Read(buf, 0, buf.Length);
                if (sz == 0) break;
                o.Write(buf, 0, sz);
                o.Flush();
            }
            i.Close();
            o.Close();
        }

        /// <summary>
        /// Process the file copy instructions, so that we can replace files that are always in use while
        /// the service runs.
        /// </summary>
        private void HandleFileCopies()
        {
            var file = descriptor.BasePath + ".copies";
            if (!File.Exists(file))
                return; // nothing to handle

            try
            {
                using (var tr = new StreamReader(file,Encoding.UTF8))
                {
                    string line;
                    while ((line = tr.ReadLine()) != null)
                    {
                        try
                        {
                            EventLog.WriteEntry("Handling copy: " + line);
                            string[] tokens = line.Split('>');
                            if (tokens.Length > 2)
                            {
                                EventLog.WriteEntry("Too many delimiters in " + line);
                                continue;
                            }

                            File.Delete(tokens[1]);
                            File.Move(tokens[0], tokens[1]);
                        }
                        catch(IOException e)
                        {
                            EventLog.WriteEntry("Failed to copy :"+line+" because "+e.Message);
                        }
                    }
                }
            }
            finally
            {
                File.Delete(file);
            }

        }

        protected override void OnStart(string[] args)
        {
            HandleFileCopies();

            EventLog.WriteEntry("Starting "+descriptor.Executable+' '+descriptor.Arguments);
            string baseName = descriptor.BasePath;

            var ps = process.StartInfo;
            ps.FileName = descriptor.Executable;
            ps.Arguments = descriptor.Arguments;
            ps.CreateNoWindow = false;
            ps.UseShellExecute = false;
            ps.RedirectStandardInput = true; // this creates a pipe for stdin to the new process, instead of having it inherit our stdin.
            ps.RedirectStandardOutput = true;
            ps.RedirectStandardError = true;

            var envs = descriptor.EnvironmentVariables;
            foreach (string key in envs.Keys)
                ps.EnvironmentVariables[key] = envs[key];

            process.Start();

            // send stdout and stderr to its respective output file.
            new Thread(delegate() { CopyStream(process.StandardOutput, new StreamWriter(new FileStream(baseName + ".out.log", FileMode.Append))); }).Start();
            new Thread(delegate() { CopyStream(process.StandardError, new StreamWriter(new FileStream(baseName + ".err.log", FileMode.Append))); }).Start();

            // monitor the completion of the process
            new Thread(delegate()
            {
                process.WaitForExit();
                if (!orderlyShutdown)
                {
                    EventLog.WriteEntry("Child process terminated with " + process.ExitCode,EventLogEntryType.Warning);
                    Environment.Exit(process.ExitCode);
                }
            }).Start();

            process.StandardInput.Close(); // nothing for you to read!
        }

        protected override void OnStop()
        {
            try
            {
                EventLog.WriteEntry("Stopping "+descriptor.Id);
                orderlyShutdown = true;
                process.Kill();
            }
            catch (InvalidOperationException)
            {
                // already terminated
            }
            process.Dispose();
        }



        public static int Main(string[] args)
        {
            try
            {
                Run(args);
                return 0;
            }
            catch (WmiException e)
            {
                Console.Error.WriteLine(e);
                return (int)e.ErrorCode;
            }
            catch (Exception e)
            {
                Console.Error.WriteLine(e);
                return -1;
            }
        }

        private static void ThrowNoSuchService()
        {
            throw new WmiException(ReturnValue.NoSuchService);
        }

        public static void Run(string[] args)
        {
            if (args.Length > 0)
            {
                var d = new ServiceDescriptor();
                Win32Services svc = new WmiRoot().GetCollection<Win32Services>();
                Win32Service s = svc.Select(d.Id);

                args[0] = args[0].ToLower();
                if (args[0] == "install")
                {
                    svc.Create(
                        d.Id,
                        d.Caption,
                        ServiceDescriptor.ExecutablePath,
                        WMI.ServiceType.OwnProcess,
                        ErrorControl.UserNotified,
                        StartMode.Automatic,
                        d.Interactive);
                    // update the description
                    /* Somehow this doesn't work, even though it doesn't report an error
                    Win32Service s = svc.Select(d.Id);
                    s.Description = d.Description;
                    s.Commit();
                     */

                    // so using a classic method to set the description. Ugly.
                    Registry.LocalMachine.OpenSubKey("System").OpenSubKey("CurrentControlSet").OpenSubKey("Services")
                        .OpenSubKey(d.Id, true).SetValue("Description", d.Description);
                }
                if (args[0] == "uninstall")
                {
                    if (s == null)
                        return; // there's no such service, so consider it already uninstalled
                    try
                    {
                        s.Delete();
                    }
                    catch (WmiException e)
                    {
                        if (e.ErrorCode == ReturnValue.ServiceMarkedForDeletion)
                            return; // it's already uninstalled, so consider it a success
                        throw e;
                    }
                }
                if (args[0] == "start")
                {
                    if (s == null) ThrowNoSuchService();
                    s.StartService();
                }
                if (args[0] == "stop")
                {
                    if (s == null) ThrowNoSuchService();
                    s.StopService();
                }
                if (args[0] == "restart")
                {
                    if (s == null) ThrowNoSuchService();
                    if(s.Started)
                        s.StopService();
                    s.StartService();
                }
                if (args[0] == "status")
                {
                    if (s == null)
                        Console.WriteLine("NonExistent");
                    else if (s.Started)
                        Console.WriteLine("Started");
                    else
                        Console.WriteLine("Stopped");
                }
                if (args[0] == "test")
                {
                    WrapperService wsvc = new WrapperService();
                    wsvc.OnStart(args);
                    Thread.Sleep(1000);
                    wsvc.OnStop();
                }
                return;
            }
            ServiceBase.Run(new WrapperService());
        }
    }
}