using System;
using System.Diagnostics;
using System.IO;
using System.Security.Principal;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace D2Multi
{
    /// <summary>
    /// Closes D2R "DiabloII Check For Other Instances" event handles using Sysinternals Handle64
    /// (same approach as Scripts/KillInstanceChecks.ps1). Requires administrator rights for Handle64.
    /// </summary>
    static class D2RInstanceCheckKiller
    {
        static readonly Regex PidLine = new Regex(
            @"^D2R\.exe\s+pid:\s*(?<pid>\d+)",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnoreCase);

        static readonly Regex EventHandleLine = new Regex(
            @"^\s*(?<handle>\S+)\s*:\s*Event.*DiabloII Check For Other Instances",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnoreCase);

        public static bool IsRunningElevated()
        {
            using (var id = WindowsIdentity.GetCurrent())
            {
                var p = new WindowsPrincipal(id);
                return p.IsInRole(WindowsBuiltInRole.Administrator);
            }
        }

        /// <summary>
        /// Resolves Handle64 path: explicit config path if set and exists, else handle64.exe next to D2R folder.
        /// </summary>
        public static string ResolveHandle64Path(string d2rDirectory, string configuredPath)
        {
            if (!string.IsNullOrWhiteSpace(configuredPath))
            {
                var t = configuredPath.Trim();
                if (File.Exists(t))
                    return t;
            }
            if (string.IsNullOrEmpty(d2rDirectory))
                return null;
            var nextToD2r = Path.Combine(d2rDirectory, "handle64.exe");
            return File.Exists(nextToD2r) ? nextToD2r : null;
        }

        /// <summary>
        /// Enumerates D2R.exe handles and closes matching instance-check events. Returns true if Handle64 ran and exited successfully (including when nothing needed closing).
        /// </summary>
        public static bool TryCloseInstanceCheckHandles(string handle64Path, string d2rDirectory, out string detailLog)
        {
            var log = new StringBuilder();
            if (string.IsNullOrEmpty(handle64Path) || !File.Exists(handle64Path))
            {
                detailLog = "handle64.exe not found.";
                return false;
            }

            string listOutput;
            int listExit;
            if (!RunHandle64(handle64Path, d2rDirectory, "-accepteula -a -p D2R.exe", out listOutput, out listExit, log))
            {
                detailLog = log.ToString();
                return false;
            }
            if (listExit != 0)
            {
                log.AppendLine("List pass exit code: " + listExit);
                detailLog = log.ToString();
                if(listOutput.Contains("No matching handles found"))
                {
                    return true;
                }
                return false;
            }

            var currentPid = "";
            var closed = 0;
            using (var reader = new StringReader(listOutput ?? string.Empty))
            {
                string line;
                while ((line = reader.ReadLine()) != null)
                {
                    var pm = PidLine.Match(line);
                    if (pm.Success)
                    {
                        currentPid = pm.Groups["pid"].Value;
                        continue;
                    }

                    var hm = EventHandleLine.Match(line);
                    if (!hm.Success)
                        continue;

                    var handleId = hm.Groups["handle"].Value.Trim();
                    if (string.IsNullOrEmpty(currentPid))
                    {
                        log.AppendLine("Skip handle " + handleId + " (no prior D2R.exe pid line).");
                        continue;
                    }

                    log.AppendLine("Closing pid=" + currentPid + " handle=" + handleId);
                    string closeOut;
                    int closeExit;
                    var closeArgs = "-accepteula -p " + currentPid + " -c " + handleId + " -y";
                    if (!RunHandle64(handle64Path, d2rDirectory, closeArgs, out closeOut, out closeExit, log))
                    {
                        detailLog = log.ToString();
                        return false;
                    }
                    if (closeExit != 0)
                        log.AppendLine("Close exit code: " + closeExit);
                    closed++;
                }
            }

            if (closed == 0)
                log.AppendLine("No 'DiabloII Check For Other Instances' event handles found for D2R.exe.");
            detailLog = log.ToString();
            return true;
        }

        static bool RunHandle64(string handle64Path, string workingDirectory, string arguments,
            out string stdout, out int exitCode, StringBuilder log)
        {
            stdout = null;
            exitCode = -1;
            try
            {
                var psi = new ProcessStartInfo
                {
                    FileName = handle64Path,
                    Arguments = arguments,
                    WorkingDirectory = string.IsNullOrEmpty(workingDirectory) ? Path.GetDirectoryName(handle64Path) : workingDirectory,
                    UseShellExecute = false,
                    RedirectStandardOutput = true,
                    RedirectStandardError = true,
                    CreateNoWindow = true,
                };
                using (var p = Process.Start(psi))
                {
                    if (p == null)
                    {
                        log.AppendLine("Process.Start returned null.");
                        return false;
                    }
                    var outTask = Task.Run(() => p.StandardOutput.ReadToEnd());
                    var errTask = Task.Run(() => p.StandardError.ReadToEnd());
                    if (!p.WaitForExit(120000))
                    {
                        try { p.Kill(); } catch { /* ignore */ }
                        log.AppendLine("Handle64 timed out.");
                        return false;
                    }
                    stdout = outTask.GetAwaiter().GetResult();
                    var err = errTask.GetAwaiter().GetResult();
                    exitCode = p.ExitCode;
                    if (!string.IsNullOrEmpty(err))
                        log.AppendLine("stderr: " + err.Trim());
                }
            }
            catch (Exception ex)
            {
                log.AppendLine(ex.Message);
                return false;
            }
            return true;
        }
    }
}