From b1963967a7a246734b2a216c5e42cef5fdbdfc38 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Ke=C3=9Fler?= <git@maximilian-kessler.de>
Date: Thu, 10 Aug 2023 12:44:09 +0200
Subject: [PATCH] add 8 clue state to backtrack action

---
 game_state.h   | 13 +++++++++++--
 game_state.hpp | 21 +++++++++++----------
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/game_state.h b/game_state.h
index 7aa04a4..8e1451b 100644
--- a/game_state.h
+++ b/game_state.h
@@ -146,13 +146,22 @@ enum class ActionType {
 };
 
 struct BacktrackAction {
-    BacktrackAction(ActionType action_type, Card discarded_or_played, hand_index_t index);
+    explicit BacktrackAction(
+            ActionType action_type,
+            Card discarded_or_played = unknown_card,
+            hand_index_t index = 0,
+            bool was_on_8_clues = false
+            );
 
     ActionType action_type{};
     // The card that was discarded or played
     Card discarded{};
     // Index of card in hand that was discarded or played
     hand_index_t index{};
+
+    // Indicates whether before the action was taken, we had 8 clues.
+    // This is important so that we know if we go back to 7 or 8 clues when we revert playing a 5
+    bool was_on_8_clues {false};
 };
 
 /** Would like to have 2 versions:
@@ -201,7 +210,7 @@ public:
     void discard(hand_index_t index) final;
 
     void revert_clue();
-    void revert_play(bool was_on_8_clues);
+    void revert_play();
     void revert_discard();
 
     [[nodiscard]] hand_index_t find_card_in_hand(const Card& card) const final;
diff --git a/game_state.hpp b/game_state.hpp
index 899977c..bbc92ba 100644
--- a/game_state.hpp
+++ b/game_state.hpp
@@ -62,11 +62,13 @@ namespace Hanabi {
     };
 
     BacktrackAction::BacktrackAction(
-            Hanabi::ActionType action_type, Hanabi::Card discarded_or_played, Hanabi::hand_index_t index
+            Hanabi::ActionType action_type, Hanabi::Card discarded_or_played, Hanabi::hand_index_t index,
+            bool was_on_8_clues
             ):
             action_type(action_type),
             discarded(discarded_or_played),
-            index(index) {
+            index(index),
+            was_on_8_clues(was_on_8_clues) {
     }
 
     template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
@@ -156,6 +158,8 @@ namespace Hanabi {
         const Card played_card = _hands[_turn][index];
         ASSERT(is_playable(played_card));
 
+        _actions_log.emplace(ActionType::play, played_card, index, _num_clues == 8);
+
         --_stacks[played_card.suit];
         _score++;
 
@@ -165,7 +169,6 @@ namespace Hanabi {
         }
 
         unsigned long multiplicity = draw<update_card_positions>(index);
-        _actions_log.emplace(ActionType::play, played_card, index);
 
         incr_turn();
         return multiplicity;
@@ -388,14 +391,14 @@ namespace Hanabi {
 
     template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
     void
-    HanabiState<num_suits, num_players, hand_size>::revert_play(bool was_on_8_clues) {
+    HanabiState<num_suits, num_players, hand_size>::revert_play() {
         const BacktrackAction last_action = _actions_log.top();
         _actions_log.pop();
         ASSERT(last_action.action_type == ActionType::play);
-        ASSERT(!was_on_8_clues or _num_clues == 8);
+        ASSERT(!last_action.was_on_8_clues or _num_clues == 8);
 
         decr_turn();
-        if (last_action.discarded.rank == 0 and not was_on_8_clues) {
+        if (last_action.discarded.rank == 0 and not last_action.was_on_8_clues) {
             _num_clues--;
         }
         revert_draw(last_action.index, last_action.discarded);
@@ -471,20 +474,18 @@ namespace Hanabi {
         for(std::uint8_t index = 0; index < hand_size; index++) {
             if(is_playable(hand[index])) {
                 if (_draw_pile.empty()) {
-                    bool on_8_clues = _num_clues == 8;
                     play_and_potentially_update<true>(index);
                     const probability_t probability_for_this_play = backtrack(depth + 1);
-                    revert_play(on_8_clues);
+                    revert_play();
                     UPDATE_PROBABILITY(probability_for_this_play);
                 } else {
                     probability_t sum_of_probabilities = 0;
                     uint8_t sum_of_mults = 0;
                     for (size_t i = 0; i < _draw_pile.size(); i++) {
-                        bool on_8_clues = _num_clues == 8;
                         const unsigned long multiplicity = play_and_potentially_update<true>(index);
                         sum_of_probabilities += backtrack(depth + 1) * multiplicity;
                         sum_of_mults += multiplicity;
-                        revert_play(on_8_clues);
+                        revert_play();
                         ASSERT(sum_of_mults <= _weighted_draw_pile_size);
                     }
                     ASSERT(sum_of_mults == _weighted_draw_pile_size);