using NtApiDotNet;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Management.Automation;
using System.Text;
using System.Threading.Tasks;

namespace NtObjectManager.Cmdlets.Accessible
{
    /// <summary>
    /// <para type="description">Specify check mode.</para>
    /// </summary>
    public enum WindowStationCheckMode
    {
        /// <summary>
        /// Only check Window Stations.
        /// </summary>
        WindowStationOnly,
        /// <summary>
        /// Only check Desktops.
        /// </summary>
        DesktopOnly,
        /// <summary>
        /// Check Window Stations and Desktops.
        /// </summary>
        WindowStationAndDesktop
    }

    /// <summary>
    /// <para type="synopsis">Get a list of Window Station an/or Desktops accessible by a specified token.</para>
    /// <para type="description">This cmdlet checks all Window Stations/Desktops and tries to determine
    /// if one or more specified tokens can access them. If no tokens are specified then the 
    /// current process token is used. Note, this will only check the current session.</para>
    /// </summary>
    /// <example>
    ///   <code>Get-AccessibleWindowStation</code>
    ///   <para>Check all accessible Window Stations for the current process token.</para>
    /// </example>
    /// <example>
    ///   <code>Get-AccessibleWindowStation -CheckMode WindowStationAndDesktop</code>
    ///   <para>Check all accessible Window Stations and Desktops for the current process token.</para>
    /// </example>
    /// <example>
    ///   <code>Get-AccessibleWindowStation -ProcessIds 1234,5678</code>
    ///   <para>>Check all accessible Window Stations for the process tokens of PIDs 1234 and 5678</para>
    /// </example>
    /// <example>
    ///   <code>$token = Get-NtToken -Primary -Duplicate -IntegrityLevel Low&#x0A;Get-AccessibleWindowStation -Tokens $token</code>
    ///   <para>Get all Window Stations which can be accessed by a low integrity copy of current token.</para>
    /// </example>
    [Cmdlet(VerbsCommon.Get, "AccessibleWindowStation")]
    [OutputType(typeof(CommonAccessCheckResult))]
    public class GetAccessibleWindowStation : CommonAccessBaseWithAccessCmdlet<WindowStationAccessRights>
    {
        /// <summary>
        /// <para type="description">Specify check mode.</para>
        /// </summary>
        [Parameter]
        public WindowStationCheckMode CheckMode { get; set; }

        /// <summary>
        /// <para type="description">Specify desktop access rights when checking Desktops.</para>
        /// </summary>
        [Parameter]
        [Alias("DesktopAccessRights")]
        public DesktopAccessRights DesktopAccess { get; set; }

        private void RunAccessCheckDesktop(IEnumerable<TokenEntry> tokens, NtWindowStation winsta)
        {
            NtType desktop_type = NtType.GetTypeByType<NtDesktop>();
            AccessMask desktop_access_rights = desktop_type.GenericMapping.MapMask(DesktopAccess);
            using (var desktops = winsta.GetAccessibleDesktops().ToDisposableList())
            {
                foreach (var desktop in desktops)
                {
                    if (desktop.IsAccessGranted(DesktopAccessRights.ReadControl))
                    {
                        var sd = desktop.SecurityDescriptor;
                        foreach (TokenEntry token in tokens)
                        {
                            AccessMask granted_access = NtSecurity.GetMaximumAccess(sd,
                                token.Token, desktop_type.GenericMapping);
                            if (IsAccessGranted(granted_access, desktop_access_rights))
                            {
                                WriteAccessCheckResult($"{winsta.FullPath}{desktop.FullPath}", desktop_type.Name, granted_access, desktop_type.GenericMapping,
                                    sd, desktop_type.AccessRightsType, true, token.Information);
                            }
                        }
                    }
                }
            }
        }

        private protected override void RunAccessCheck(IEnumerable<TokenEntry> tokens)
        {
            NtType winsta_type = NtType.GetTypeByType<NtWindowStation>();
            
            AccessMask winsta_access_rights = winsta_type.GenericMapping.MapMask(Access);
            bool check_winsta = CheckMode == WindowStationCheckMode.WindowStationOnly || CheckMode == WindowStationCheckMode.WindowStationAndDesktop;
            bool check_desktop = CheckMode == WindowStationCheckMode.DesktopOnly || CheckMode == WindowStationCheckMode.WindowStationAndDesktop;

            using (var winstas = NtWindowStation.GetAccessibleWindowStations().ToDisposableList())
            {
                foreach (var winsta in winstas)
                {
                    if (check_winsta && winsta.IsAccessGranted(WindowStationAccessRights.ReadControl))
                    {
                        var sd = winsta.SecurityDescriptor;
                        foreach (TokenEntry token in tokens)
                        {
                            AccessMask granted_access = NtSecurity.GetMaximumAccess(sd,
                                token.Token, winsta_type.GenericMapping);
                            if (IsAccessGranted(granted_access, winsta_access_rights))
                            {
                                WriteAccessCheckResult(winsta.FullPath, winsta_type.Name, granted_access, winsta_type.GenericMapping,
                                    sd, winsta_type.AccessRightsType, true, token.Information);
                            }
                        }
                    }

                    if (check_desktop && winsta.IsAccessGranted(WindowStationAccessRights.EnumDesktops))
                    {
                        RunAccessCheckDesktop(tokens, winsta);
                    }
                }
            }
        }
    }
}
