create endgame play section

lib/chesstrainer/endgames/endgame.ex

@@ -36,6 +36,78 @@ defmodule Chesstrainer.Endgames.Endgame do
     |> validate_format(:key, ~r/^(?=.{5,10}$)KQ*R*[NB]*P*\sv\sKQ*R*[NB]*P*$/,
       message: "Key must follow pattern KQ.. v KQR.., max pieces 7"
     )
+    |> validate_change(:fen, fn :fen, fen ->
+      case fen_issues(fen) do
+        [] -> []
+        issues -> [fen: "is not a valid FEN: #{Enum.join(issues, "; ")}"]
+      end
+    end)
     |> unique_constraint(:fen, message: "FEN already exists")
   end
+
+  # 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).
+  defp fen_issues(fen) do
+    case String.split(fen, " ") do
+      [board, active, _castling, _en_passant, halfmove, fullmove] ->
+        issues = []
+
+        issues =
+          if valid_board?(board),
+            do: issues,
+            else: ["board must be 8 ranks of 8 squares each"]
+
+        issues =
+          if active in ["w", "b"],
+            do: issues,
+            else: ["active color must be 'w' or 'b'"]
+
+        issues =
+          if non_negative_integer?(halfmove),
+            do: issues,
+            else: ["halfmove clock must be a non-negative integer"]
+
+        issues =
+          if positive_integer?(fullmove),
+            do: issues,
+            else: ["fullmove number must be a positive integer"]
+
+        issues
+
+      _ ->
+        ["must have 6 space-separated fields"]
+    end
+  end
+
+  defp valid_board?(board) do
+    ranks = String.split(board, "/")
+
+    length(ranks) == 8 and Enum.all?(ranks, &valid_rank?/1)
+  end
+
+  defp valid_rank?(rank) do
+    squares =
+      rank
+      |> String.graphemes()
+      |> Enum.reduce(0, fn
+        g, acc when byte_size(g) == 1 ->
+          c = :binary.first(g)
+
+          if c >= ?1 and c <= ?8 do
+            acc + (c - ?0)
+          else
+            acc + 1
+          end
+      end)
+
+    squares == 8
+  end
+
+  defp non_negative_integer?(str), do: integer_string?(str) and String.to_integer(str) >= 0
+  defp positive_integer?(str), do: integer_string?(str) and String.to_integer(str) >= 1
+
+  defp integer_string?(str) do
+    Regex.match?(~r/^[0-9]+$/, str)
+  end
 end

lib/chesstrainer/tags.ex

@@ -101,4 +101,23 @@ defmodule Chesstrainer.Tags do
   def change_tag(%Tag{} = tag, attrs \\ %{}) do
     Tag.changeset(tag, attrs)
   end
+
+  def search("", _category), do: []
+
+  def search(query, category) when is_binary(query) do
+    pattern = "%#{query}%"
+
+    Tag
+    |> where([t], ilike(t.name, ^pattern) and t.category == ^category)
+    |> order_by([t], asc: t.name)
+    |> limit(20)
+    |> Repo.all()
+  end
+
+  def get_or_create(name, category) when is_binary(name) do
+    case Repo.get_by(Tag, name: name, category: category) do
+      nil -> create_tag(%{name: name, category: category})
+      tag -> {:ok, tag}
+    end
+  end
 end

lib/chesstrainer_web/live/endgame_live/index.ex

@@ -34,6 +34,7 @@ defmodule ChesstrainerWeb.EndgameLive.Index do
           <div class="sr-only">
             <.link navigate={~p"/admin/endgames/#{endgame}"}>Show</.link>
           </div>
+          <.link navigate={~p"/endgames/#{endgame}/play"}>Play</.link>
           <.link navigate={~p"/admin/endgames/#{endgame}/edit"}>Edit</.link>
         </:action>
         <:action :let={{id, endgame}}>

lib/chesstrainer_web/live/endgame_live/play.ex

@@ -0,0 +1,119 @@
+defmodule ChesstrainerWeb.EndgameLive.Play do
+  use ChesstrainerWeb, :live_view
+
+  alias Chesstrainer.Endgames
+
+  @impl true
+  def render(assigns) do
+    ~H"""
+    <Layouts.app flash={@flash}>
+      <.header>
+        Play endgame {@endgame.key}
+        <:subtitle>
+          {@endgame.color} to move · Result: {@endgame.result} · Rating: {@endgame.rating}
+        </:subtitle>
+        <:actions>
+          <.button navigate={~p"/endgames"}>
+            <.icon name="hero-arrow-left" /> Back to endgames
+          </.button>
+        </:actions>
+      </.header>
+
+      <div class="bg-gray-100 p-4 rounded mb-4 flex justify-between items-center shadow-sm">
+        <div>
+          <p class="text-sm text-gray-600 font-semibold">Last Played Move:</p>
+          <p class="text-lg font-mono text-blue-600">{@last_from_to}</p>
+          <p class="text-lg font-mono text-blue-600">{@last_san}</p>
+          <p class="text-lg font-mono text-emerald-600">
+            {if @move_list == [] do
+              "No Moves"
+            else
+              Enum.reverse(@move_list) |> Enum.join(", ")
+            end}
+          </p>
+        </div>
+        <div>
+          <.button phx-click="reset" variant="primary">
+            <.icon name="hero-arrow-path" /> Reset
+          </.button>
+        </div>
+      </div>
+
+      <div class="flex justify-center bg-gray-200 p-4 rounded-xl shadow-inner">
+        <div
+          id="endgame-board"
+          phx-hook="ChessBoard"
+          phx-update="ignore"
+          data-endgame-id={@endgame.id}
+          class="w-[400px] h-[400px]"
+        >
+        </div>
+      </div>
+
+      <.list>
+        <:item title="Fen">{@endgame.fen}</:item>
+        <:item title="Key">{@endgame.key}</:item>
+        <:item title="Color">{@endgame.color}</:item>
+        <:item title="Result">{@endgame.result}</:item>
+        <:item title="Rating">{@endgame.rating}</:item>
+      </.list>
+    </Layouts.app>
+    """
+  end
+
+  @impl true
+  def mount(%{"id" => id}, _session, socket) do
+    endgame = Endgames.get_endgame!(id)
+
+    socket =
+      socket
+      |> assign(:page_title, "Play endgame")
+      |> assign(:endgame, endgame)
+      |> assign(:move_list, [])
+      |> assign(:last_san, "None yet")
+      |> assign(:last_from_to, "None yet")
+      |> push_event("init_board", %{
+        fen: endgame.fen,
+        orientation: Atom.to_string(endgame.color),
+        player_color: Atom.to_string(endgame.color)
+      })
+
+    {:ok, socket}
+  end
+
+  @impl true
+  def handle_event(
+        "endgame_move_played",
+        %{"from" => from, "to" => to, "san" => san},
+        socket
+      ) do
+    # TODO: server-side legality check + tablebase evaluation when wired
+    {:noreply,
+     socket
+     |> assign(:last_from_to, "#{from} ➔ #{to}")
+     |> assign(:last_san, san)
+     |> assign(:move_list, [san | socket.assigns.move_list])}
+  end
+
+  def handle_event("chess_fen_invalid", %{"fen" => fen, "message" => message}, socket) do
+    {:noreply,
+     put_flash(
+       socket,
+       :error,
+       "Endgame FEN is invalid and the board cannot be loaded: #{message} (#{fen})"
+     )}
+  end
+
+  def handle_event("reset", _params, socket) do
+    {:noreply,
+     socket
+     |> assign(:move_list, [])
+     |> assign(:last_san, "None yet")
+     |> assign(:last_from_to, "None yet")
+     |> push_event("init_board", %{
+       fen: socket.assigns.endgame.fen,
+       orientation: Atom.to_string(socket.assigns.endgame.color),
+       player_color: Atom.to_string(socket.assigns.endgame.color)
+     })}
+  end
+end

lib/chesstrainer_web/live/endgame_live/player_index.ex

@@ -0,0 +1,38 @@
+defmodule ChesstrainerWeb.EndgameLive.PlayerIndex do
+  use ChesstrainerWeb, :live_view
+
+  alias Chesstrainer.Endgames
+
+  @impl true
+  def render(assigns) do
+    ~H"""
+    <Layouts.app flash={@flash}>
+      <.header>
+        Endgames
+        <:subtitle>Pick an endgame to play.</:subtitle>
+      </.header>
+
+      <.table
+        id="player-endgames"
+        rows={@streams.endgames}
+      >
+        <:col :let={{_id, endgame}} label="Key">{endgame.key}</:col>
+        <:col :let={{_id, endgame}} label="Color">{endgame.color}</:col>
+        <:col :let={{_id, endgame}} label="Result">{endgame.result}</:col>
+        <:col :let={{_id, endgame}} label="Rating">{endgame.rating}</:col>
+        <:action :let={{_id, endgame}}>
+          <.link navigate={~p"/endgames/#{endgame}/play"}>Play</.link>
+        </:action>
+      </.table>
+    </Layouts.app>
+    """
+  end
+
+  @impl true
+  def mount(_params, _session, socket) do
+    {:ok,
+     socket
+     |> assign(:page_title, "Endgames")
+     |> stream(:endgames, Endgames.list_endgames())}
+  end
+end

lib/chesstrainer_web/live/endgame_live/show.ex

@@ -31,6 +31,9 @@ defmodule ChesstrainerWeb.EndgameLive.Show do
           <.button navigate={~p"/admin/endgames"}>
             <.icon name="hero-arrow-left" />
           </.button>
+          <.button navigate={~p"/endgames/#{@endgame}/play"}>
+            <.icon name="hero-play" /> Play (opens trainer)
+          </.button>
           <.button variant="primary" navigate={~p"/admin/endgames/#{@endgame}/edit?return_to=show"}>
             <.icon name="hero-pencil-square" /> Edit endgame
           </.button>

lib/chesstrainer_web/router.ex

@@ -20,6 +20,9 @@ defmodule ChesstrainerWeb.Router do
     get "/", PageController, :home
 
     live "/chess-test", ChessTestLive
+
+    live "/endgames", EndgameLive.PlayerIndex, :index
+    live "/endgames/:id/play", EndgameLive.Play, :play
   end
 
   scope "/admin", ChesstrainerWeb do