feat: added blog selection for existing blog

lib/bds/desktop/folder_picker.ex

@@ -0,0 +1,35 @@
+defmodule BDS.Desktop.FolderPicker do
+  @moduledoc false
+
+  def choose_directory(prompt) when is_binary(prompt) do
+    case :os.type() do
+      {:unix, :darwin} -> choose_directory_macos(prompt)
+      _other -> {:error, %{message: "Folder selection is only supported on macOS desktop"}}
+    end
+  end
+
+  defp choose_directory_macos(prompt) do
+    script = "POSIX path of (choose folder with prompt \"#{escape_applescript(prompt)}\")"
+
+    case System.cmd("osascript", ["-e", script], stderr_to_stdout: true) do
+      {output, 0} -> {:ok, String.trim(output)}
+      {output, _status} -> normalize_picker_failure(output)
+    end
+  end
+
+  defp normalize_picker_failure(output) do
+    message = String.trim(output)
+
+    if message == "" or String.contains?(String.downcase(message), "canceled") do
+      :cancel
+    else
+      {:error, %{message: message}}
+    end
+  end
+
+  defp escape_applescript(value) do
+    value
+    |> String.replace("\\", "\\\\")
+    |> String.replace("\"", "\\\"")
+  end
+end