Add api for visible system kill information (#133)

* feat: api for zkill information

lib/wanderer_app_web/controllers/util_api_controller.ex

@@ -0,0 +1,41 @@
+defmodule WandererAppWeb.UtilAPIController do
+  @moduledoc """
+  Utility functions for parameter handling, fetch helpers, etc.
+  """
+
+  alias WandererApp.Api
+
+  def fetch_map_id(%{"map_id" => mid}) when is_binary(mid) and mid != "" do
+    {:ok, mid}
+  end
+
+  def fetch_map_id(%{"slug" => slug}) when is_binary(slug) and slug != "" do
+    case Api.Map.get_map_by_slug(slug) do
+      {:ok, map} ->
+        {:ok, map.id}
+
+      {:error, _reason} ->
+        {:error, "No map found for slug=#{slug}"}
+    end
+  end
+
+  def fetch_map_id(_),
+    do: {:error, "Must provide either ?map_id=UUID or ?slug=SLUG"}
+
+  # Require a given param to be present and non-empty
+  def require_param(params, key) do
+    case params[key] do
+      nil -> {:error, "Missing required param: #{key}"}
+      ""  -> {:error, "Param #{key} cannot be empty"}
+      val -> {:ok, val}
+    end
+  end
+
+  # Parse a string into an integer
+  def parse_int(str) do
+    case Integer.parse(str) do
+      {num, ""} -> {:ok, num}
+      _         -> {:error, "Invalid integer for param id=#{str}"}
+    end
+  end
+end