feat(rover): bulk elevation lookup wrapper

lib/microwaveprop/rover/elevation.ex

@@ -0,0 +1,23 @@
+defmodule Microwaveprop.Rover.Elevation do
+  @moduledoc """
+  Bulk SRTM elevation lookup for a list of `{lat, lon}` points.
+
+  Wraps `Microwaveprop.Terrain.Srtm.lookup/3`, which already opens and
+  reads each tile per call. Cells whose tile is missing or whose value
+  is the SRTM void sentinel are mapped to `nil`.
+  """
+
+  alias Microwaveprop.Terrain.Srtm
+
+  @spec lookup_many([{float(), float()}]) :: %{{float(), float()} => integer() | nil}
+  def lookup_many(points) when is_list(points) do
+    tiles_dir = Application.get_env(:microwaveprop, :srtm_tiles_dir, "/data/srtm")
+
+    Map.new(points, fn {lat, lon} = key ->
+      case Srtm.lookup(lat, lon, tiles_dir) do
+        {:ok, elev} -> {key, elev}
+        {:error, _} -> {key, nil}
+      end
+    end)
+  end
+end

test/microwaveprop/rover/elevation_test.exs

@@ -0,0 +1,41 @@
+defmodule Microwaveprop.Rover.ElevationTest do
+  use ExUnit.Case, async: false
+
+  alias Microwaveprop.Rover.Elevation
+
+  setup do
+    tmp = Path.join(System.tmp_dir!(), "rover_elev_#{System.unique_integer([:positive])}")
+    File.mkdir_p!(tmp)
+    prev = Application.get_env(:microwaveprop, :srtm_tiles_dir)
+    Application.put_env(:microwaveprop, :srtm_tiles_dir, tmp)
+
+    on_exit(fn ->
+      File.rm_rf!(tmp)
+
+      if prev do
+        Application.put_env(:microwaveprop, :srtm_tiles_dir, prev)
+      else
+        Application.delete_env(:microwaveprop, :srtm_tiles_dir)
+      end
+    end)
+
+    :ok
+  end
+
+  describe "lookup_many/1" do
+    test "returns map keyed by {lat, lon}, nil values when no tiles available" do
+      points = [{33.0, -96.0}, {30.0, -97.0}]
+      result = Elevation.lookup_many(points)
+
+      assert is_map(result)
+      assert Map.has_key?(result, {33.0, -96.0})
+      assert Map.has_key?(result, {30.0, -97.0})
+      assert result[{33.0, -96.0}] == nil
+      assert result[{30.0, -97.0}] == nil
+    end
+
+    test "empty list returns empty map" do
+      assert Elevation.lookup_many([]) == %{}
+    end
+  end
+end