normalise FENs - trim and fuill move to 1 on addition

.gitignore

@@ -28,6 +28,9 @@ chesstrainer-*.tar
 # Ignore assets that are produced by build tools.
 /priv/static/assets/
 
+# Ignore ETS table backups
+/priv/static/backups/
+
 # Ignore digested assets cache.
 /priv/static/cache_manifest.json
 

lib/chesstrainer/endgames/endgame.ex

@@ -30,7 +30,7 @@ defmodule Chesstrainer.Endgames.Endgame do
   @doc false
   def changeset(endgame, attrs) do
     endgame
-    |> cast(attrs, [:fen, :key, :message, :notes, :result, :rating, :color])
+    |> cast(normalize_attrs(attrs), [:fen, :key, :message, :notes, :result, :rating, :color])
     |> validate_required([:fen, :color], message: "Invalid FEN")
     |> validate_required([:key, :result, :rating])
     |> validate_format(:key, ~r/^(?=.{5,10}$)KQ*R*[NB]*P*\sv\sKQ*R*[NB]*P*$/,
@@ -45,6 +45,14 @@ defmodule Chesstrainer.Endgames.Endgame do
     |> unique_constraint(:fen, message: "FEN already exists")
   end
 
+  defp normalize_attrs(%{"fen" => fen} = attrs) when is_binary(fen),
+    do: Map.put(attrs, "fen", Chesstrainer.FEN.normalize(fen))
+
+  defp normalize_attrs(%{fen: fen} = attrs) when is_binary(fen),
+    do: Map.put(attrs, :fen, Chesstrainer.FEN.normalize(fen))
+
+  defp normalize_attrs(attrs), do: attrs
+
   # Strict structural validation. Mirrors chess.js rules so the FEN survives
   # both the server-side parser (Chex, permissive) and the client-side parser
   # (chess.js, strict).

lib/chesstrainer/fen.ex

@@ -7,6 +7,39 @@ defmodule Chesstrainer.FEN do
     |> color_initial_to_color_atom()
   end
 
+  @doc """
+  Normalizes a FEN string for storage.
+
+  Trims surrounding whitespace and rewrites a fullmove number of `"0"` to
+  `"1"`. The fullmove rewrite is a chess.js-compatibility fix — chess.js
+  rejects fullmove `0` as invalid even though many board editors default
+  to it. Other FEN fields are left untouched; structural errors are
+  surfaced by the Endgame changeset, not silently masked here.
+
+  ## Examples
+
+      iex> Chesstrainer.FEN.normalize("  8/8/3k4/8/8/3K1R2/8/8 w - - 0 0\\n  ")
+      "8/8/3k4/8/8/3K1R2/8/8 w - - 0 1"
+
+      iex> Chesstrainer.FEN.normalize("8/8/3k4/8/8/3K1R2/8/8 w - - 0 5")
+      "8/8/3k4/8/8/3K1R2/8/8 w - - 0 5"
+
+      iex> Chesstrainer.FEN.normalize("not a fen")
+      "not a fen"
+  """
+  @spec normalize(String.t()) :: String.t()
+  def normalize(fen) when is_binary(fen) do
+    trimmed = String.trim(fen)
+
+    case String.split(trimmed, " ") do
+      [board, active, castling, en_passant, halfmove, "0"] ->
+        Enum.join([board, active, castling, en_passant, halfmove, "1"], " ")
+
+      _ ->
+        trimmed
+    end
+  end
+
   defp color_initial_to_color_atom("b"), do: :black
   defp color_initial_to_color_atom("w"), do: :white
   defp color_initial_to_color_atom(_), do: nil

test/chesstrainer/endgames_test.exs

@@ -17,7 +17,7 @@ defmodule Chesstrainer.EndgamesTest do
       assert {:ok, %Endgame{}} = Endgames.create_endgame(attrs)
     end
 
-    test "rejects a FEN with fullmove number zero" do
+    test "normalizes fullmove 0 to 1 before inserting" do
       attrs = %{
         fen: "6k1/5p2/6p1/8/7p/8/6PP/6K1 b - - 0 0",
         color: :black,
@@ -26,9 +26,21 @@ defmodule Chesstrainer.EndgamesTest do
         rating: 1500
       }
 
-      assert {:error, changeset} = Endgames.create_endgame(attrs)
-      assert [msg] = errors_on(changeset).fen
-      assert msg =~ "fullmove number"
+      assert {:ok, endgame} = Endgames.create_endgame(attrs)
+      assert endgame.fen == "6k1/5p2/6p1/8/7p/8/6PP/6K1 b - - 0 1"
+    end
+
+    test "trims whitespace around the FEN before inserting" do
+      attrs = %{
+        fen: "  8/8/3k4/8/8/3K1R2/8/8 w - - 0 1\t\n",
+        color: :white,
+        key: "KR v K",
+        result: :win,
+        rating: 1500
+      }
+
+      assert {:ok, endgame} = Endgames.create_endgame(attrs)
+      assert endgame.fen == "8/8/3k4/8/8/3K1R2/8/8 w - - 0 1"
     end
 
     test "rejects a FEN with a zero digit in a rank" do

test/chesstrainer/fen_test.exs

@@ -0,0 +1,62 @@
+defmodule Chesstrainer.FENTest do
+  use ExUnit.Case, async: true
+
+  alias Chesstrainer.FEN
+
+  describe "color_from_fen/1" do
+    test "extracts white from the active-color field" do
+      assert FEN.color_from_fen("8/8/3k4/8/8/3K1R2/8/8 w - - 0 1") == :white
+    end
+
+    test "extracts black from the active-color field" do
+      assert FEN.color_from_fen("6k1/5p2/6p1/8/7p/8/6PP/6K1 b - - 0 1") == :black
+    end
+
+    test "returns nil when the active-color field is missing" do
+      assert FEN.color_from_fen("8/8/8/8/8/8/8/8") == nil
+    end
+  end
+
+  describe "normalize/1" do
+    test "trims surrounding whitespace" do
+      fen = "8/8/3k4/8/8/3K1R2/8/8 w - - 0 1"
+      assert FEN.normalize("  \n" <> fen <> "\t\n") == fen
+    end
+
+    test "rewrites fullmove 0 to 1" do
+      fen = "6k1/5p2/6p1/8/7p/8/6PP/6K1 b - - 0 0"
+      assert FEN.normalize(fen) == "6k1/5p2/6p1/8/7p/8/6PP/6K1 b - - 0 1"
+    end
+
+    test "rewrites fullmove 0 even when the FEN has surrounding whitespace" do
+      fen = "\n 6k1/5p2/6p1/8/7p/8/6PP/6K1 b - - 0 0 \t"
+      assert FEN.normalize(fen) == "6k1/5p2/6p1/8/7p/8/6PP/6K1 b - - 0 1"
+    end
+
+    test "leaves a non-zero fullmove untouched" do
+      fen = "8/8/3k4/8/8/3K1R2/8/8 w - - 0 5"
+      assert FEN.normalize(fen) == fen
+    end
+
+    test "leaves a standard starting position untouched" do
+      fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
+      assert FEN.normalize(fen) == fen
+    end
+
+    test "passes through a non-FEN string unchanged" do
+      assert FEN.normalize("not a fen") == "not a fen"
+    end
+
+    test "passes through a partial FEN (fewer than 6 fields) unchanged" do
+      fen = "8/8/3k4/8/8/3K1R2/8/8 w - -"
+      assert FEN.normalize(fen) == fen
+    end
+
+    test "passes through a FEN with a leading-zero fullmove unchanged" do
+      # Fullmove 0 only matches the literal "0"; leading zeros stay so the
+      # validator can surface them rather than silently masking the typo.
+      fen = "8/8/3k4/8/8/3K1R2/8/8 w - - 0 00"
+      assert FEN.normalize(fen) == fen
+    end
+  end
+end