Allow execution of OneShot tasks

scripts/Common/Scripts/Config.ps1

@@ -3,7 +3,9 @@ using namespace System.Security.AccessControl;
 using namespace System.Security.Principal;
 
 enum SetupStage {
+    Idle
     Initialize
+    OneShot
     Configure
     Install
     CreateUser
@@ -244,7 +246,7 @@ $null = New-Module {
         Gets a value indicating whether the setup has finished.
     #>
     function Get-IsFinished {
-        return [bool] (Get-SetupOption $finishedOption);
+        return [bool] (((Get-Stage) -eq ([SetupStage]::Idle)) -or (Get-SetupOption $finishedOption));
     }
 
     <#

scripts/Common/Scripts/Operations.ps1

@@ -1,4 +1,21 @@
-function Start-Operation {
+. "$PSScriptRoot/Config.ps1";
+. "$PSScriptRoot/../Types/OneShotTask.ps1";
+. "$PSScriptRoot/../../Windows/Scripts/PowerManagement.ps1";
+
+$null = New-Module {
+    . "$PSScriptRoot/../Types/OneShotTask.ps1";
+    $logName = "Application";
+    $oneShotTrigger = 1337;
+    $taskOption = "OneShotTask";
+    # ToDo: Store "ProgramData/PortValhalla" path somewhere as const
+    $errorPath = "$env:ProgramData/PortValhalla/error.txt";
+
+    $taskSetter = {
+        param([Nullable[OneShotTask]] $Task)
+        Set-SetupOption $taskOption ([string]$Task);
+    };
+
+    function Start-Operation {
         param(
             [scriptblock] $Action
         )
@@ -12,4 +29,95 @@ function Start-Operation {
 
         New-Alias "sudo" gsudo;
         & $Action;
-}
+    }
+
+    <#
+        .SYNOPSIS
+        Gets the current OneShot task.
+    #>
+    function Get-OneShotTask {
+        [OneShotTask](Get-SetupOption $taskOption);
+    }
+
+    <#
+        .SYNOPSIS
+        Registers a task for listening to OneShot invocations.
+    #>
+    function Enable-OneShotListener {
+        $tempTask = "PortValhalla Temp";
+        $action = New-ScheduledTaskAction -Execute "pwsh" -Argument (Get-StartupArguments);
+        schtasks /Create /SC ONEVENT /EC $logName /MO "*[System[Provider[@Name='$logName'] and EventID=$($oneShotTrigger)]]" /TR cmd.exe /TN $tempTask;
+        $trigger = (Get-ScheduledTask $tempTask).Triggers;
+        $principal = New-ScheduledTaskPrincipal -UserId (Get-SetupUser) -RunLevel Highest;
+        $task = New-ScheduledTask -Action $action -Principal $principal -Trigger $trigger;
+        $null = Register-ScheduledTask -Force "PortValhalla OneShot" -InputObject $task;
+        $null = Unregister-ScheduledTask -Confirm:$false $tempTask;
+    }
+
+    <#
+        .SYNOPSIS
+        Invokes a one-shot task.
+
+        .PARAMETER Task
+        The task to run.
+    #>
+    function Invoke-OneShot {
+        param(
+            [OneShotTask] $Task
+        )
+
+        $currentStage = Get-Stage;
+        Set-Stage ([SetupStage]::OneShot);
+        & $taskSetter $Task;
+
+        $job = & {
+            $identifier = "EventLog$oneShotTrigger";
+            $log = [System.Diagnostics.EventLog]::new($logName);
+
+            $null = Register-ObjectEvent -InputObject $log -EventName EntryWritten -Action {
+                $entry = $event.SourceEventArgs.Entry;
+
+                if ($entry.EventID -eq $oneShotTrigger) {
+                    $null = New-Event -SourceIdentifier $identifier;
+                }
+            };
+
+            Start-Job {
+                Wait-Event -SourceIdentifier $identifier;
+            };
+        };
+
+        Write-EventLog -LogName $logName -Source $logName -EventId $oneShotTrigger -Message "Starting OneShot task ``$(Get-OneShotTask)``…";
+        $null = Wait-Job $job;
+        Set-Stage $currentStage;
+
+        if (Test-Path $errorPath) {
+            $errorMessage = Get-Content $errorPath;
+            Remove-Item $errorPath;
+            throw $errorMessage;
+        }
+    }
+
+    # ToDo: Store Run-OneShot and Receive-OneShot somewhere else in Windows folder
+
+    <#
+        .SYNOPSIS
+        Executes the specified action and notifies the OneShot task executor.
+    #>
+    function Start-OneShot {
+        param(
+            [scriptblock] $Action
+        )
+
+        try {
+            Start-Operation @PSBoundParameters;
+        }
+        catch {
+            Set-Content -Path $errorPath -Value $Error;
+        }
+        finally {
+            Set-Stage ([SetupStage]::Idle);
+            Write-EventLog -LogName $logName -Source $logName -EventId $oneShotTrigger -Message "The OneShot task ``$(Get-OneShotTask)`` finished.";
+        }
+    }
+};

scripts/Common/Types/OneShotTask.ps1

@@ -0,0 +1,3 @@
+enum OneShotTask {
+    DisableUAC
+}