Store move when it's made

lib/chess/board.ex

@@ -30,13 +30,20 @@ defmodule Chess.Board do
     board["#{file},#{rank}"]
   end
 
-  def move_piece(board, move_params) do
-    [from_file, from_rank] = move_params["from"]
-    [to_file, to_rank] = move_params["to"]
+  def move_piece(board, %{"from" => from, "to" => to}) do
+    [from_file, from_rank] = from
+    [to_file, to_rank] = to
 
     {piece, board} = Map.pop(board, "#{from_file},#{from_rank}")
+    {piece_captured, board} = Map.pop(board, "#{to_file},#{to_rank}")
 
-    Map.put(board, "#{to_file},#{to_rank}", piece)
+    %{
+      from: %{file: from_file, rank: from_rank},
+      to: %{file: to_file, rank: to_rank},
+      board: Map.put(board, "#{to_file},#{to_rank}", piece),
+      piece: piece,
+      piece_captured: piece_captured,
+    }
   end
 
   def default do

lib/chess/game_state.ex

@@ -61,6 +61,7 @@ defmodule Chess.GameState do
     |> Enum.all?(fn({to_file, to_rank}) ->
       board
       |> Board.move_piece(%{"from" => [file, rank], "to" => [to_file, to_rank]})
+      |> Map.get(:board)
       |> king_in_check?(piece["colour"])
     end)
   end

lib/chess/store/game.ex

@@ -35,11 +35,7 @@ defmodule Chess.Store.Game do
     |> foreign_key_constraint(:opponent_id)
   end
 
-  def move_changeset(struct, move_params) do
-    params = %{
-      board: Board.move_piece(struct.board, move_params),
-    }
-
+  def move_changeset(struct, params) do
     struct
     |> cast(params, required_attrs())
     |> validate_king_in_check(struct, params)

lib/chess_web/channels/game_channel.ex

@@ -3,6 +3,8 @@ defmodule ChessWeb.GameChannel do
 
   use ChessWeb, :channel
 
+  alias Ecto.Multi
+
   alias Chess.Store.Game
   alias Chess.Board
   alias Chess.Moves
@@ -38,14 +40,18 @@ defmodule ChessWeb.GameChannel do
       |> Game.for_user_id()
       |> Repo.get!(socket.assigns.game_id)
 
-    changeset = Game.move_changeset(game, move_params)
+    params = Board.move_piece(game.board, move_params)
 
-    case Repo.update(changeset) do
-      {:ok, game} ->
+    Multi.new
+    |> Multi.update(:game, Game.move_changeset(game, params))
+    |> Multi.insert(:move, Ecto.build_assoc(game, :moves, params))
+    |> Repo.transaction
+    |> case do
+      {:ok, %{game: game}} ->
         send_update(game)
 
         {:noreply, socket}
-      {:error, changeset} ->
+      {:error, :game, changeset, _} ->
         {message, _} = changeset.errors[:board]
 
         {:reply, {:error, %{message: message}}, socket}

test/chess/board_test.exs

@@ -45,7 +45,8 @@ defmodule Chess.BoardTest do
       "3,0" => %{"type" => "queen", "colour" => "white"},
     }
 
-    new_board = Board.move_piece(board, %{"from" => [3, 0], "to" => [5, 2]})
+    %{board: new_board} =
+      Board.move_piece(board, %{"from" => [3, 0], "to" => [5, 2]})
 
     assert new_board == %{
       "5,2" => %{"type" => "queen", "colour" => "white"},

test/chess/store/game_test.exs

@@ -89,7 +89,10 @@ defmodule Chess.GameTest do
 
       move_params = %{"from" => [4, 1], "to" => [4, 3]}
 
-      changeset = Game.move_changeset(game, move_params)
+      changeset = Game.move_changeset(
+        game,
+        Board.move_piece(game.board, move_params)
+      )
 
       assert {:ok, new_game} = Repo.update(changeset)
       assert new_game.turn == "black"