fix(microprints): limit page to 2 most recently modified files

- Sort source files by mtime (newest first) and take only the first 2
- This limits the page scope for easier testing/investigation
- Temporary limit; will be 10 most recently changed files later
- Updated tests to work with the 2-file limit

app/lib/firehose_web/live/microprints_live.ex

@@ -123,25 +123,33 @@ defmodule FirehoseWeb.MicroprintsLive do
 
   # Private helpers
 
+  defp sort_by_mtime(files) do
+    app_root = Mix.Project.project_file() |> Path.dirname()
+
+    files
+    |> Enum.map(fn file ->
+      abs_path = Path.join(app_root, file)
+      {file, File.stat!(abs_path).mtime}
+    end)
+    |> Enum.sort_by(fn {_file, mtime} -> mtime end, :desc)
+    |> Enum.map(fn {file, _mtime} -> file end)
+  end
+
   @doc false
   def scan_source_files do
     @source_dirs
     |> Enum.flat_map(&collect_elixir_files/1)
     |> Enum.uniq()
     |> Enum.sort()
+    |> sort_by_mtime()
+    |> Enum.take(2)
   end
 
   defp resolve_absolute_paths(files) do
     app_root = Mix.Project.project_file() |> Path.dirname()
 
     Enum.map(files, fn path ->
-      case Path.split(path) do
-        [".." | _rest] ->
-          Path.join(app_root, path)
-
-        _ ->
-          Path.expand(path)
-      end
+      Path.join(app_root, path)
     end)
   end
 

app/test/firehose_web/live/microprints_live_test.exs

@@ -2,11 +2,20 @@ defmodule FirehoseWeb.MicroprintsLiveTest do
   use ExUnit.Case, async: true
 
   describe "scan_source_files/0" do
+    test "returns exactly 2 files" do
+      files = FirehoseWeb.MicroprintsLive.scan_source_files()
+
+      assert length(files) == 2
+    end
+
     test "returns only .ex files from app/ and blogex/ directories" do
       files = FirehoseWeb.MicroprintsLive.scan_source_files()
 
-      # Should include app/lib files
-      assert "lib/firehose.ex" in files
+      # With the 2-file limit, check that returned files are valid .ex paths
+      Enum.each(files, fn file ->
+        assert String.ends_with?(file, ".ex")
+        assert String.starts_with?(file, "lib/") or String.starts_with?(file, "../blogex/")
+      end)
     end
 
     test "does not include files from _build/ directory" do
@@ -50,7 +59,9 @@ defmodule FirehoseWeb.MicroprintsLiveTest do
       files = FirehoseWeb.MicroprintsLive.scan_source_files()
 
       blogex_files = Enum.filter(files, &String.starts_with?(&1, "../blogex/"))
-      refute blogex_files == []
+      # With the 2-file limit, blogex files may or may not be included
+      # depending on which files are most recently modified
+      assert is_list(blogex_files)
     end
   end
 end