AzureAuth Windows uninstall script (#340)

* First commit uninstall script

* Improved comments and variable names

* Added message about whether something was uninstalled or not

* Removed file accidentally created

* Redesigned workflow

* Close running instances of azureauth before deleting

* Fixed bug, not removing from path

* Added warning in case AZUREAUTH_INSTALL_DIRECTORY is not empty

* Applied feedback from code review

* Warn user about custom locations at the end

* Changed order of functions

* Fixed error, verbose not printing

* Changed checks to see if parent of path is the default location

* Improved messaging

install/uninstall.ps1

@@ -0,0 +1,132 @@
+# Enable a default -Verbose flag for debug output.
+[CmdletBinding()]
+$VerbosePreference = "Continue"
+
+# Halt script execution at the first failed command.
+$script:ErrorActionPreference='Stop'
+
+$azureauthDefaultLocation = ([System.IO.Path]::Combine($Env:LOCALAPPDATA, "Programs", "AzureAuth"))
+
+function Get-CustomLocationsFromPath {
+    $customLocations = [System.Collections.ArrayList]@()
+    $azureauthsInPath = (Get-Command -Name azureauth -ErrorAction SilentlyContinue -CommandType Application -All).Source
+
+    ForEach($az in $azureauthsInPath) {
+        $azureauthParent = (Get-Item $az).Directory.FullName
+        if (!(Is-ChildOfDefaultLocation($azureauthParent))) {
+            $_ = $customLocations.Add($azureauthParent)
+        }
+    }
+
+    return $customLocations
+}
+
+function Write-WarningForCustomLocations {
+    # We only warn the user of any custom locations that are found in the PATH.
+    # Installations in custom locations that are not listed in PATH cannot
+    # be found and uninstalled.
+    $customLocations = Get-CustomLocationsFromPath
+    $customLocationsCount = $customLocations.Count 
+
+    if ($customLocationsCount -ne 0) {
+        $warning = "Uninstallation from custom locations is unsupported. Custom locations must be removed manually. 
+                    `rFound ${customLocationsCount} potential installations outside of the default location:"
+        ForEach($location in $customLocations) {
+            $warning += "`n   ${location}"
+        }
+        Write-Warning $warning
+    }
+}
+
+# Send WM_SETTINGCHANGE after changing Environment variables.
+# Refer to https://gist.github.com/alphp/78fffb6d69e5bb863c76bbfc767effda
+function Send-SettingChange {
+    Add-Type -Namespace Win32 -Name NativeMethods -MemberDefinition @"
+    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
+    public static extern IntPtr SendMessageTimeout(IntPtr hWnd, uint Msg, UIntPtr wParam, string lParam, uint fuFlags, uint uTimeout, out UIntPtr lpdwResult);
+"@
+    $HWND_BROADCAST = [IntPtr] 0xffff;
+    $WM_SETTINGCHANGE = 0x1a;
+    $result = [UIntPtr]::Zero
+
+    [void] ([Win32.Nativemethods]::SendMessageTimeout($HWND_BROADCAST, $WM_SETTINGCHANGE, [UIntPtr]::Zero, "Environment", 2, 5000, [ref] $result))
+}
+
+function Is-ChildOfDefaultLocation {
+    param ([string]$path) 
+
+    $parent = (Split-Path $path -Parent)
+    return ($parent -eq $azureauthDefaultLocation)
+}
+
+function Remove-FromPath {
+    $registryPath = 'Registry::HKEY_CURRENT_USER\Environment'
+    $currentPath = (Get-ItemProperty -Path $registryPath -Name PATH -ErrorAction SilentlyContinue).Path
+
+    # Reconstruct the $PATH without any azureauth directories.
+    $updatedPath = "";
+    if (($null) -ne $currentPath) {
+        $paths = $currentPath.Split(";")
+        $pathArr = @()
+        ForEach($path in $paths){
+            if(!$path.Equals("") -And !(Is-ChildOfDefaultLocation($path))) {
+                $pathArr += "${path}"
+            }
+            elseif (!$path.Equals("")) {
+                Write-Verbose "Removing PATH entry '${path}'"
+            }
+        }
+        $updatedPath = ($pathArr -join ";") + ";"
+    }
+
+    Set-ItemProperty -Path $registryPath -Name PATH -Value $updatedPath
+    Send-SettingChange
+}
+
+function Remove-InstallationFolder {
+    param ([string]$directory)
+
+    if (Test-Path -Path $directory) {
+        Write-Verbose "Removing all installations at '${directory}'"
+        Remove-Item -Force -Recurse $directory
+    } else {
+        Write-Verbose "There were no installations found at '${directory}'"
+    }
+}
+
+function Remove-Directories {
+    Remove-InstallationFolder $azureauthDefaultLocation
+}
+
+function Kill-Process {
+    # Uninstall will fail if there are instances of AzureAuth running. 
+    # We suppress taskkill output here because this is a best effort attempt and we don't want the user to see its output.
+    # Here, Get-Process is used to first determine whether there is an existing azureauth process. If there is, kill the existing process first.
+    $ProcessCheck = Get-Process -Name azureauth -ErrorAction SilentlyContinue -ErrorVariable ProcessError
+    if ($null -ne $ProcessCheck) {
+        Write-Verbose "Stopping any currently running azureauth instances"
+        taskkill /f /im azureauth.exe 2>&1 | Out-Null
+
+        # After killing the process it is still possible for there there to be locks on the files it was using (including
+        # its own DLLs). The OS may take an indeterminate amount of time to clean those up, but so far we've observed 1
+        # second to be enough.
+        Start-Sleep -Seconds 1
+    }
+}
+
+function Uninstall {
+    if (![string]::IsNullOrEmpty($Env:AZUREAUTH_INSTALL_DIRECTORY) `
+            -And $Env:AZUREAUTH_INSTALL_DIRECTORY -ne $azureauthDefaultLocation) {
+        Write-Warning "Ignoring AZUREAUTH_INSTALL_DIRECTORY environment variable. Uninstallation for custom locations is not supported."
+    }
+
+    Kill-Process
+
+    Remove-Directories
+    Remove-FromPath
+
+    Write-WarningForCustomLocations
+    Write-Output "Uninstalled AzureAuth!"
+}
+
+Uninstall