/*
    Copyright (c) 2017 Marcin Szeniak (https://github.com/Klocman/)
    Apache License Version 2.0
*/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Management;
using System.Runtime.InteropServices;
using System.Security;
using Klocman.Extensions;
using Klocman.Native;
using Klocman.Tools;

namespace UninstallTools.Startup.Service
{
    internal class ServiceEntryFactory
    {
        internal enum StartMode
        {
            Auto,
            Manual,
            Disabled
        }

        /* ServiceType
        Kernel Driver 
        File System Driver 
        Adapter 
        Recognizer Driver 
        Own Process 
        Share Process 
        Interactive Process 
        */

        public static IEnumerable<ServiceEntry> GetServiceEntries()
        {
            var searcher = new ManagementObjectSearcher("root\\CIMV2",
                "SELECT * FROM Win32_Service");

            var results = new List<ServiceEntry>();
            try
            {
                foreach (var queryObj in searcher.Get())
                {
                    // Skip drivers and adapters
                    var serviceType = queryObj["ServiceType"] as string;
                    if (serviceType == null || !serviceType.Contains("Process"))
                        continue;

                    var filename = queryObj["PathName"] as string;
                    // Don't show system services
                    if (filename == null || filename.Contains(
                        WindowsTools.GetEnvironmentPath(CSIDL.CSIDL_WINDOWS),
                        StringComparison.InvariantCultureIgnoreCase))
                        continue;

                    var e = new ServiceEntry((string)queryObj["Name"],
                        queryObj["DisplayName"] as string, filename);

                    //queryObj["Caption"]);
                    //queryObj["Description"]);
                    //queryObj["ProcessId"]

                    results.Add(e);
                }
            }
            catch (COMException ex)
            {
                Console.WriteLine(@"Error while gathering services");
                Console.WriteLine(ex);
            }

            return results.ToArray();
        }

        private static bool GetEnabledState(ManagementBaseObject queryObj)
        {
            return queryObj["StartMode"] as string != nameof(StartMode.Auto);
        }

        public static void EnableService(string serviceName, bool newState)
        {
            var classInstance = GetServiceObject(serviceName);

            // Obtain in-parameters for the method
            var inParams = classInstance.GetMethodParameters("ChangeStartMode");

            // Add the input parameters.
            inParams["StartMode"] = newState ? "Automatic" : "Disabled";

            // Execute the method and obtain the return values.
            var outParams = classInstance.InvokeMethod("ChangeStartMode", inParams, null);
            CheckReturnValue(outParams);
        }

        public static bool CheckServiceEnabled(string serviceName)
        {
            var classInstance = GetServiceObject(serviceName);

            return GetEnabledState(classInstance);
        }

        public static void DeleteService(string serviceName)
        {
            try { EnableService(serviceName, false); }
            catch (ManagementException) { }

            var classInstance = GetServiceObject(serviceName);

            // Execute the method and obtain the return values.
            var outParams = classInstance.InvokeMethod("Delete", null, null);
            CheckReturnValue(outParams, 16); // 16 - Service Marked For Deletion
        }

        private static void CheckReturnValue(ManagementBaseObject outParams, params UInt32[] ignoredCodes)
        {
            if (outParams == null) return;

            var exitCode = (UInt32)outParams["ReturnValue"];
            if (exitCode == 0 || ignoredCodes.Any(x => x == exitCode)) return;

            if (exitCode == 2) // 2 - Access Denied
                throw new SecurityException("The user does not have the necessary access.");

            throw new ManagementException("Action failed with return value " + outParams["ReturnValue"] + 
                ". Check return codes of Win32_Service class methods for more information.");
        }

        private static ManagementObject GetServiceObject(string serviceName)
        {
            return new ManagementObject("root\\CIMV2", 
                $"Win32_Service.Name='{serviceName}'", null);
        }
    }
}