add method to list reasonable moves

game_state.h

@@ -143,6 +143,10 @@ enum class ActionType {
     vote_terminate = 10,
 };
 
+class Action {
+    ActionType type {};
+    Card card {};
+};
 
 /** Would like to have 2 versions:
  * All:
@@ -185,8 +189,6 @@ public:
     HanabiState() = default;
     explicit HanabiState(const std::vector<Card>& deck);
 
-    probability_t evaluate_state() final;
-
     void clue() final;
     void discard(hand_index_t index) final;
     void play(hand_index_t index) final;
@@ -203,6 +205,11 @@ public:
     [[nodiscard]] const std::unordered_map<unsigned long, probability_t>& position_tablebase() const final;
 
     void init_backtracking_information() final;
+    probability_t evaluate_state() final;
+
+    std::optional<probability_t> lookup() const;
+
+    std::vector<std::pair<Action, std::optional<probability_t>>> get_reasonable_actions();
 
     auto operator<=>(const HanabiState &) const = default;
 

game_state.hpp

@@ -451,6 +451,90 @@ namespace Hanabi {
         }
     }
 
+    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
+    std::vector<std::pair<Action, std::optional<probability_t>>> HanabiState<num_suits, num_players, hand_size>::get_reasonable_actions() {
+        std::vector<std::pair<Action, std::optional<probability_t>>> reasonable_actions {};
+
+        if(_score == 5 * num_suits or _pace < 0 or _endgame_turns_left == 0) {
+            return reasonable_actions;
+        }
+
+        const std::array<Card, hand_size>& hand = _hands[_turn];
+        // First, check for playable cards
+        for(std::uint8_t index = 0; index < hand_size; index++) {
+            if(is_playable(hand[index])) {
+                const Action action = {ActionType::play, hand[index]};
+                bool known = true;
+                probability_t sum_of_probabilities = 0;
+
+                do_for_each_potential_draw<true>(index, [this, &sum_of_probabilities, &known](const unsigned long multiplicity){
+                    const std::optional<probability_t> prob = lookup();
+                    if (prob.has_value()) {
+                        sum_of_probabilities += prob.value() * multiplicity;
+                    } else {
+                        known = false;
+                    }
+                });
+
+                if (known) {
+                    const unsigned long total_weight = std::max(static_cast<unsigned long>(_weighted_draw_pile_size), 1ul);
+                    const probability_t probability_play = sum_of_probabilities / total_weight;
+                    reasonable_actions.emplace_back(action, probability_play);
+                } else {
+                    reasonable_actions.emplace_back(action, std::nullopt);
+                }
+            }
+        }
+
+        if(_pace > 0 and _num_clues < max_num_clues) {
+            for(std::uint8_t index = 0; index < hand_size; index++) {
+                if (is_trash(hand[index])) {
+                    const Action action = {ActionType::discard, hand[index]};
+                    bool known = true;
+                    probability_t sum_of_probabilities = 0;
+
+                    do_for_each_potential_draw<false>(index, [this, &sum_of_probabilities, &known](const unsigned long multiplicity){
+                        const std::optional<probability_t> prob = lookup();
+                        if (prob.has_value()) {
+                            sum_of_probabilities += prob.value() * multiplicity;
+                        } else {
+                            known = false;
+                        }
+                    });
+
+                    if (known) {
+                        const unsigned long total_weight = std::max(static_cast<unsigned long>(_weighted_draw_pile_size), 1ul);
+                        const probability_t probability_discard = sum_of_probabilities / total_weight;
+                        reasonable_actions.emplace_back(action, probability_discard);
+                    } else {
+                        reasonable_actions.emplace_back(action, std::nullopt);
+                    }
+
+                    // All discards are equivalent, do not continue searching for different trash
+                    break;
+                }
+            }
+        }
+
+        if(_num_clues > 0) {
+            clue();
+            const std::optional<probability_t> prob = lookup();
+            const Action action = {ActionType::clue, unknown_card};
+            reasonable_actions.emplace_back(action, prob);
+            const probability_t probability_stall = evaluate_state();
+            revert_clue();
+        }
+    }
+
+    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
+    std::optional<probability_t> HanabiState<num_suits, num_players, hand_size>::lookup() const {
+        const auto id = unique_id();
+        if(_position_tablebase.contains(id)) {
+            return _position_tablebase[id];
+        } else {
+            return std::nullopt;
+        }
+    }
 
     template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
     probability_t HanabiState<num_suits, num_players, hand_size>::evaluate_state() {