Allow undo to reset game at beginning

TODO.md

@@ -2,7 +2,6 @@
 
 - CD: https://fly.io/docs/app-guides/continuous-deployment-with-github-actions/
 - Put everyone's discards in front of their hand (suggested by Mom)
-- If no undoable moves, Undo button should reset the game to get first discarded tile of the game from bot (human went last, missed a discarded tile, can't go back to beginning of game).
 - Bug: Undoing a win after a bot drew a tile hung bot (workaround: paused & unpaused bots)
 - Shrink tile sizes on mobile
 - Lobby not receiving bot player added

lib/mjw/core/game.ex

@@ -43,25 +43,18 @@ defmodule Mjw.Game do
             turn_seatno: 0,
             # Where the deal picking started from. Might be used to count points.
             dealpick_seatno: 0,
-            # Number of times the player has been dealer (wins, draws, DQs all count)
+            # Number of times the player has been dealer (draws, etc, also count)
             dealer_win_count: 0,
             event_log: [],
             undo_seatno: nil,
             undo_state: nil,
             pause_bots: false
 
   @doc """
-  Initialize a game with a random ID and a shuffled deck
+  Initialize a game, defaulting to a random ID and a shuffled deck
   """
-  def new() do
-    new(Uniq.UUID.uuid4())
-  end
-
-  defp new(id) do
-    %__MODULE__{
-      id: id,
-      deck: shuffled_deck()
-    }
+  def new(id \\ Uniq.UUID.uuid4()) do
+    %__MODULE__{id: id, deck: shuffled_deck()}
   end
 
   defp shuffled_deck() do
@@ -193,7 +186,8 @@ defmodule Mjw.Game do
 
   @doc """
   Roll dice and deal the deck. The dealer will have 14 tiles and others will
-  have 13. Set dealpick_seatno and change turn_state to discarding.
+  have 13. Sets dealpick_seatno, changes turn_state to discarding, and sets
+  undo_state to an initial value.
   """
   def roll_dice_and_deal(%__MODULE__{turn_state: :rolling} = game) do
     game
@@ -387,6 +381,7 @@ defmodule Mjw.Game do
     tile = Mjw.BotStrategy.discard(game)
 
     game
+    |> set_undo_state_if_first_discard()
     |> log_discard_event(seatno, tile)
     |> update_seat(seatno, &Mjw.Seat.remove_from_concealed(&1, tile))
     |> Map.merge(%{discards: [tile | game.discards], turn_state: :drawing})
@@ -722,17 +717,26 @@ defmodule Mjw.Game do
     update_seat(game, seatno, fn _seat_being_replaced -> seat end)
   end
 
-  def undo(%__MODULE__{undo_seatno: undo_seatno, undo_state: %__MODULE__{} = undo_state} = game)
-      when undo_seatno != nil do
-    player_name = player_name_at(game, undo_seatno)
+  def undo(
+        %__MODULE__{undo_seatno: undo_seatno, undo_state: %__MODULE__{} = undo_state} = game,
+        player_seatno
+      ) do
+    player_name = player_name_at(game, player_seatno)
+
+    log_event_message =
+      if undo_seatno do
+        "#{player_name} undid their action."
+      else
+        "#{player_name} reset the game."
+      end
 
     undo_state
     # event_log is preserved as a singleton at the top-level game
     |> Map.merge(%{event_log: game.event_log})
     |> merge_seats_for_undo(game)
     # just in case undoing a declared win
     |> clear_all_seat_win_attributes()
-    |> log_event("#{player_name} undid their action.")
+    |> log_event(log_event_message)
   end
 
   # The undo player's hand will change after an undo, but try to preserve their
@@ -764,6 +768,15 @@ defmodule Mjw.Game do
     end)
   end
 
+  @doc """
+  A player can undo when they performed the last human action, OR if the
+  undo_seatno is nil which indicates it's the beginning of the game and we can
+  undo the initial bot discards
+  """
+  def can_undo?(%__MODULE__{undo_seatno: undo_seatno, undo_state: undo_state}, seatno) do
+    undo_state && (!undo_seatno || undo_seatno == seatno)
+  end
+
   @doc """
   Draw a tile from the deck, and temporarily hold it in the seat's peektile
   before deciding whether to keep or discard. Params enforce that this player
@@ -960,11 +973,21 @@ defmodule Mjw.Game do
   # When an undoable change is made, set the undo_state so that the player in
   # undo_seatno can possibly undo it. event_log is not saved in undo states
   # because it exists as a singleton at the top-level game.
-  defp set_undo_state(%__MODULE__{} = game, undo_seatno) do
+  defp set_undo_state(%__MODULE__{} = game, undo_seatno \\ nil) do
     undo_state = game |> Map.delete(:event_log)
     %{game | undo_seatno: undo_seatno, undo_state: undo_state}
   end
 
+  # When a bot discards first, set the initial undo_state so a human can Undo
+  # to the beginning of the game to pick up a bot's discard they missed
+  defp set_undo_state_if_first_discard(%__MODULE__{} = game) do
+    if Enum.empty?(game.discards) do
+      set_undo_state(game)
+    else
+      game
+    end
+  end
+
   def seat_bot(%__MODULE__{} = game) do
     empty_seatno = Enum.find_index(game.seats, &Mjw.Seat.empty?/1)
 

lib/mjw/core/seat.ex

@@ -26,9 +26,8 @@ defmodule Mjw.Seat do
   end
 
   @bot_id "bot"
-
   def seat_bot(%__MODULE__{} = seat, bot_name) do
-    %{seat | player_id: @bot_id, player_name: bot_name}
+    seat_player(seat, @bot_id, bot_name)
   end
 
   def bot?(%__MODULE__{player_id: @bot_id}), do: true

lib/mjw_web/live/game_live/show.ex

@@ -132,9 +132,8 @@ defmodule MjwWeb.GameLive.Show do
       when socket.assigns.current_user_can_undo do
     game =
       socket.assigns.game
-      |> Mjw.Game.undo()
-      |> optionally_enqueue_bot_roll(socket)
-      |> optionally_enqueue_bot_draw(socket)
+      |> Mjw.Game.undo(socket.assigns.current_user_seatno)
+      |> optionally_enqueue_all_bot_actions
 
     socket = update_game(socket, game, :undo)
 
@@ -912,7 +911,7 @@ defmodule MjwWeb.GameLive.Show do
     |> assign(:deck_remaining, length(game.deck))
     |> assign(:empty_seats_count, Mjw.Game.empty_seats_count(game))
     |> assign(:turn_player_name, Mjw.Game.turn_player_name(game))
-    |> assign(:current_user_can_undo, game.undo_seatno == current_user_seatno)
+    |> assign(:current_user_can_undo, Mjw.Game.can_undo?(game, current_user_seatno))
     |> assign(:bots_present, Mjw.Game.bots_present?(game))
   end
 

test/mjw/core/game_test.exs

@@ -1396,7 +1396,7 @@ defmodule Mjw.GameTest do
       }
 
       {:ok, game} = Mjw.Game.discard(orig_game, 3, "n3-3")
-      game = Mjw.Game.undo(game)
+      game = Mjw.Game.undo(game, 3)
 
       expected_event_log = [{"name3 undid their action.", nil}, {"name3 discarded.", "n3-3"}]
       assert game == %{orig_game | event_log: expected_event_log}
@@ -1423,7 +1423,7 @@ defmodule Mjw.GameTest do
       game =
         orig_game
         |> Mjw.Game.draw_discard(3, ["dp-0"], "dp-0")
-        |> Mjw.Game.undo()
+        |> Mjw.Game.undo(3)
 
       expected_event_log = [
         {"name3 undid their action.", nil},
@@ -1454,7 +1454,7 @@ defmodule Mjw.GameTest do
       game =
         orig_game
         |> Mjw.Game.pong(1, ["dp-0"], "dp-0")
-        |> Mjw.Game.undo()
+        |> Mjw.Game.undo(1)
 
       expected_event_log = [
         {"name1 undid their action.", nil},
@@ -1487,7 +1487,7 @@ defmodule Mjw.GameTest do
         orig_game
         |> Mjw.Game.peek_deck_tile(3)
         |> Mjw.Game.clear_peektile(3)
-        |> Mjw.Game.undo()
+        |> Mjw.Game.undo(3)
 
       expected_event_log = [
         {"name3 undid their action.", nil},
@@ -1519,7 +1519,7 @@ defmodule Mjw.GameTest do
       {game, "b1-0"} =
         orig_game |> Mjw.Game.draw_correction_tile(3, ["n1-3", "n2-3", "n3-3", "decktile"])
 
-      game = game |> Mjw.Game.undo()
+      game = game |> Mjw.Game.undo(3)
 
       expected_event_log = [
         {"name3 undid their action.", nil},
@@ -1550,7 +1550,7 @@ defmodule Mjw.GameTest do
       game =
         orig_game
         |> Mjw.Game.declare_win_from_discards(1, "dp-0")
-        |> Mjw.Game.undo()
+        |> Mjw.Game.undo(1)
 
       expected_event_log = [{"name1 undid their action.", nil}, {"name1 went out!", "dp-0"}]
       assert game == %{orig_game | event_log: expected_event_log}
@@ -1577,7 +1577,7 @@ defmodule Mjw.GameTest do
       game =
         orig_game
         |> Mjw.Game.declare_win_from_hand(1, "n3-1")
-        |> Mjw.Game.undo()
+        |> Mjw.Game.undo(1)
 
       expected_event_log = [{"name1 undid their action.", nil}, {"name1 went out!", "n3-1"}]
       assert game == %{orig_game | event_log: expected_event_log}
@@ -1615,7 +1615,7 @@ defmodule Mjw.GameTest do
       {:ok, game} = Mjw.Game.discard(orig_game, 0, "b5-0")
 
       {:draw_discard, game} = Mjw.Game.bot_draw(game)
-      game = Mjw.Game.undo(game)
+      game = Mjw.Game.undo(game, 0)
 
       expected_event_log = [
         {"name0 undid their action.", nil},
@@ -2039,4 +2039,71 @@ defmodule Mjw.GameTest do
       assert game.turn_state == :discarding
     end
   end
+
+  describe "can_undo?" do
+    test "is false for all players before the first discard" do
+      game =
+        Mjw.Game.new()
+        |> Mjw.Game.seat_player("id0", "name0")
+        |> Mjw.Game.seat_player("id1", "name1")
+        |> Mjw.Game.seat_player("id2", "name2")
+        |> Mjw.Game.seat_bot()
+        |> Mjw.Game.pick_random_available_wind(0)
+        |> Mjw.Game.pick_random_available_wind(1)
+        |> Mjw.Game.pick_random_available_wind(2)
+        |> Mjw.Game.pick_random_available_wind(3)
+        |> Mjw.Game.roll_dice_and_reseat_players()
+        |> Mjw.Game.roll_dice_and_deal()
+
+      refute Mjw.Game.can_undo?(game, 0)
+      refute Mjw.Game.can_undo?(game, 1)
+      refute Mjw.Game.can_undo?(game, 2)
+      refute Mjw.Game.can_undo?(game, 3)
+    end
+
+    test "is true for all human players after the first bot discard" do
+      {:ok, game} =
+        Mjw.Game.new()
+        |> Mjw.Game.seat_player("id0", "name0")
+        |> Mjw.Game.seat_player("id1", "name1")
+        |> Mjw.Game.seat_player("id2", "name2")
+        |> Mjw.Game.seat_bot()
+        |> Mjw.Game.pick_random_available_wind(0)
+        |> Mjw.Game.pick_random_available_wind(1)
+        |> Mjw.Game.pick_random_available_wind(2)
+        |> Mjw.Game.pick_random_available_wind(3)
+        |> Mjw.Game.roll_dice_and_reseat_players()
+        |> Mjw.Game.roll_dice_and_deal()
+        |> Map.merge(%{turn_seatno: 3})
+        |> Mjw.Game.bot_discard()
+
+      assert Mjw.Game.can_undo?(game, 0)
+      assert Mjw.Game.can_undo?(game, 1)
+      assert Mjw.Game.can_undo?(game, 2)
+    end
+
+    test "when undo_seatno is set, is true only for the undo_seatno player id" do
+      orig_game =
+        Mjw.Game.new()
+        |> Mjw.Game.seat_player("id0", "name0")
+        |> Mjw.Game.seat_player("id1", "name1")
+        |> Mjw.Game.seat_player("id2", "name2")
+        |> Mjw.Game.seat_bot()
+        |> Mjw.Game.pick_random_available_wind(0)
+        |> Mjw.Game.pick_random_available_wind(1)
+        |> Mjw.Game.pick_random_available_wind(2)
+        |> Mjw.Game.pick_random_available_wind(3)
+        |> Mjw.Game.roll_dice_and_reseat_players()
+        |> Mjw.Game.roll_dice_and_deal()
+        |> Map.merge(%{turn_seatno: 0})
+
+      tile = orig_game.seats |> Enum.at(0) |> Map.get(:concealed) |> Enum.random()
+      {:ok, game} = orig_game |> Mjw.Game.discard(0, tile)
+
+      assert Mjw.Game.can_undo?(game, 0)
+      refute Mjw.Game.can_undo?(game, 1)
+      refute Mjw.Game.can_undo?(game, 2)
+      refute Mjw.Game.can_undo?(game, 3)
+    end
+  end
 end