feat: add PSProfile.Prompt.ps1

for #16

PSProfile/PSProfile.Prompt.ps1

@@ -0,0 +1,37 @@
+# -----------------------------------------------------------------------------
+# PowerShell Profile - Prompt
+# -----------------------------------------------------------------------------
+
+Class OMPThemes : System.Management.Automation.IValidateSetValuesGenerator {
+    [String[]] GetValidValues() {
+        $OMPThemes = ((Get-ChildItem -Path "$Env:POSH_THEMES_PATH" -Filter "*.omp.json").Name -replace ".omp.json", "")
+        return [String[]]$OMPThemes
+    }
+}
+
+Function Set-OMPTheme {
+  [CmdletBinding()]
+  Param(
+    [ValidateSet([OMPThemes])]
+    [String]$Theme
+  )
+
+  try {
+    $ConfigPath = Join-Path "$Env:POSH_THEMES_PATH" "$Theme.omp.json"
+    (& oh-my-posh init pwsh --config=$ConfigPath --print) -join "`n" | Invoke-Expression
+  } catch [CommandNotFoundException] {
+    Write-Warning "Failed to set oh-my-posh theme"
+    return
+  } finally {
+    if ($?) {
+      Write-Verbose "oh-my-posh theme set to '$Theme'"
+      $Global:POSH_THEME = $Theme
+    }
+  }
+
+}
+
+if (Get-Command oh-my-posh -ErrorAction SilentlyContinue) {
+    Write-Verbose "Setting oh-my-posh theme..."
+    Set-OMPTheme -Theme space
+}