Endgame-Analyzer/include/game_state.hpp

#include <algorithm>

#include "myassert.h"
#include "game_state.h"

namespace Hanabi {

    std::ostream &operator<<(std::ostream &os, HanabiStateIF const &hanabi_state) {
        hanabi_state.print(os);
        return os;
    }

    std::ostream &operator<<(std::ostream &os, Action const& action) {
        switch(action.type) {
            case ActionType::play:
                os << "play " << action.card;
                break;
            case ActionType::discard:
                os << "discard";
                break;
            case ActionType::clue:
                os << "clue";
                break;
            default:
                break;
        }
        return os;
    }

    bool Card::operator==(const Card &other) const {
        return suit == other.suit and rank == other.rank;
    }

    std::ostream &operator<<(std::ostream &os, const Card &card) {
        if (card == Cards::trash) {
            os << "kt";
        } else {
            os << suit_initials[card.suit] << 5 - card.rank;
        }
        return os;
    }

    template<size_t num_suits>
    std::ostream &operator<<(std::ostream &os, const Stacks<num_suits> &stacks) {
        for (size_t i = 0; i < stacks.size(); i++) {
            os << suit_initials[i] << starting_card_rank - stacks[i];
            if(i < stacks.size() - 1) {
                os << ", ";
            }
        }
        return os;
    }

    template<suit_t num_suits, typename T>
    void CardArray<num_suits, T>::fill(T val) {
        for (size_t suit = 0; suit < num_suits; suit++) {
            for (rank_t rank = 0; rank < starting_card_rank; rank++) {
                _array[suit][rank] = val;
            }
        }
    }

    template<suit_t num_suits, typename T>
    CardArray<num_suits, T>::CardArray(T default_val) {
        fill(default_val);
    }

    template<suit_t num_suits, typename T>
    const T &CardArray<num_suits, T>::operator[](const Card &card) const {
        return _array[card.suit][card.rank];
    };

    template<suit_t num_suits, typename T>
    T &CardArray<num_suits, T>::operator[](const Card &card) {
        return _array[card.suit][card.rank];
    };

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    HanabiState<num_suits, num_players, hand_size>::BacktrackAction::BacktrackAction(
            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),
            was_on_8_clues(was_on_8_clues) {
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    HanabiState<num_suits, num_players, hand_size>::HanabiState(const std::vector<Card> &deck):
            _turn(0),
            _num_clues(max_num_clues),
            _weighted_draw_pile_size(deck.size()),
            _stacks(),
            _hands(),
            _draw_pile(),
            _endgame_turns_left(no_endgame),
            _pace(deck.size() - 5 * num_suits - num_players * (hand_size - 1)),
            _score(0),
            _actions_log(),
            _relative_representation(),
            _position_tablebase(),
            _enumerated_states(0) {
        std::ranges::fill(_stacks, starting_card_rank);
        for (const Card &card: deck) {
            _draw_pile.push_back({card, 1});
        }
        for (player_t player = 0; player < num_players; player++) {
            for (std::uint8_t index = 0; index < hand_size; index++) {
                draw(index);
            }
            incr_turn();
        }
        ASSERT(_turn == 0);
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::give_clue() {
        ASSERT(_num_clues > 0);
        --_num_clues;

        _actions_log.emplace(ActionType::clue, Cards::unknown, 0);
        incr_turn();
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::incr_turn() {
        _turn = (_turn + 1) % num_players;
        if (_endgame_turns_left != no_endgame) {
            _endgame_turns_left--;
        }
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::decr_turn() {
        _turn = (_turn + num_players - 1) % num_players;
        if (_endgame_turns_left != no_endgame) {
            _endgame_turns_left++;
        }
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    bool HanabiState<num_suits, num_players, hand_size>::is_playable(const Hanabi::Card &card) const {
        return card.rank == _stacks[card.suit] - 1;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    std::uint64_t HanabiState<num_suits, num_players, hand_size>::enumerated_states() const {
        return _enumerated_states;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    bool HanabiState<num_suits, num_players, hand_size>::is_trash(const Hanabi::Card &card) const {
        return card.rank >= _stacks[card.suit];
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::play(Hanabi::hand_index_t index) {
        play_and_potentially_update(index);
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    unsigned long HanabiState<num_suits, num_players, hand_size>::play_and_potentially_update(hand_index_t index) {
        ASSERT(index < _hands[_turn].size());
        const Card played_card = _hands[_turn][index];
        if (!is_playable(played_card)) {
            const unsigned long multiplicity = draw(index);
            incr_turn();
            return multiplicity;
        }
        ASSERT(is_playable(played_card));

        _actions_log.emplace(ActionType::play, played_card, index, _num_clues == 8);

        --_stacks[played_card.suit];
        _score++;

        if (played_card.rank == 0 and _num_clues < max_num_clues) {
            // update clues if we played the last played_card of a stack
            _num_clues++;
        }

        const unsigned long multiplicity = draw(index);

        incr_turn();
        return multiplicity;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::discard(hand_index_t index) {
        discard_and_potentially_update(index);
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    unsigned long HanabiState<num_suits, num_players, hand_size>::discard_and_potentially_update(hand_index_t index) {
        ASSERT(index < _hands[_turn].size());
        ASSERT(_num_clues != max_num_clues);

        const Card discarded_card = _hands[_turn][index];
        _num_clues++;
        _pace--;

        unsigned long multiplicity = draw(index);
        _actions_log.emplace(ActionType::discard, discarded_card, index);

        incr_turn();
        return multiplicity;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    std::uint8_t HanabiState<num_suits, num_players, hand_size>::find_card_in_hand(
            const Hanabi::Card &card) const {
        for (std::uint8_t i = 0; i < hand_size; i++) {
            if (_hands[_turn][i].rank == card.rank && _hands[_turn][i].suit == card.suit) {
                return i;
            }
        }
        return -1;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::print(std::ostream &os) const {
        os << "Stacks: " << _stacks << " (score " << +_score << ")";
        os << ", clues: " << +_num_clues << ", turn: " << +_turn;
        if (_endgame_turns_left != no_endgame) {
            os << ", " << +_endgame_turns_left << " turns left";
        }
        os << std::endl;
        os << "Draw pile: ";
        unsigned num_trash = 0;
        for (const auto &[card, mul]: _draw_pile) {
            if (is_trash(card)) {
                num_trash += mul;
                continue;
            }
            os << card;
            if (mul > 1) {
                os << " (" << +mul << ")";
            }
            os << ", ";
        }
        if (num_trash > 0) {
            os << Cards::trash << " (" << num_trash << ") ";
        }
        os << "[size " << +_weighted_draw_pile_size << "]" << std::endl;
        os << "Hands: ";
        for (const auto &hand: _hands) {
            os << "[";
            for(hand_index_t index = 0; index < hand.size(); index++) {
                os << hand[index];
                if (index < hand.size() - 1) {
                    os << " ";
                }
            }
            os << "] ";
        }
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    unsigned HanabiState<num_suits, num_players, hand_size>::draw(uint8_t index) {
        ASSERT(index < _hands[_turn].size());

        // update card position of the card we are about to discard
        if (_relative_representation.initialized) {
            const Card discarded = _hands[_turn][index];
            if (!discarded.initial_trash) {
                if (discarded.in_starting_hand) {
                    ASSERT(_relative_representation.card_positions_hands[discarded.local_index] == true);
                    _relative_representation.card_positions_hands[discarded.local_index] = false;
                } else {
                    auto replaced_card_it = std::ranges::find(_relative_representation.card_positions_draw[discarded.local_index], _turn);
                    ASSERT(replaced_card_it != _relative_representation.card_positions_draw[discarded.local_index].end());
                    *replaced_card_it = trash_or_play_stack;
                    std::ranges::sort(_relative_representation.card_positions_draw[discarded.local_index]);
                }
            }
        }

        // draw a new card if the draw pile is not empty
        if (!_draw_pile.empty()) {
            --_weighted_draw_pile_size;

            const CardMultiplicity draw = _draw_pile.front();
            _draw_pile.pop_front();
            ASSERT(draw.multiplicity > 0);

            if (draw.multiplicity > 1) {
                _draw_pile.push_back(draw);
                _draw_pile.back().multiplicity--;
            }

            if (_relative_representation.initialized) {
                // update card position of the drawn card
                if (!draw.card.initial_trash) {
                    ASSERT(draw.card.in_starting_hand == false);
                    auto new_card_it = std::ranges::find(_relative_representation.card_positions_draw[draw.card.local_index], draw_pile);
                    ASSERT(new_card_it != _relative_representation.card_positions_draw[draw.card.local_index].end());
                    *new_card_it = _turn;
                    std::ranges::sort(_relative_representation.card_positions_draw[draw.card.local_index]);
                }
            }

            _hands[_turn][index] = draw.card;

            if (_draw_pile.empty()) {
                // Note the +1, since we will immediately decrement this when moving to the next player
                _endgame_turns_left = num_players + 1;
            }
            return draw.multiplicity;
        }
        return 1;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::revert_draw(std::uint8_t index, Card discarded_card) {
        if (_endgame_turns_left == num_players + 1 || _endgame_turns_left == no_endgame) {
            // Put the card that is currently in hand back into the draw pile
            ASSERT(index < _hands[_turn].size());
            const Card &drawn = _hands[_turn][index];

            // put discarded_card back into draw pile (at the back)
            if (!_draw_pile.empty() and _draw_pile.back().card.suit == drawn.suit and
                _draw_pile.back().card.rank == drawn.rank) {
                _draw_pile.back().multiplicity++;
            } else {
                _draw_pile.push_back({drawn, 1});
            }

            if (_relative_representation.initialized && !drawn.initial_trash) {
                ASSERT(drawn.in_starting_hand == false);
                auto drawn_card_it = std::ranges::find(_relative_representation.card_positions_draw[drawn.local_index], _turn);
                ASSERT(drawn_card_it != _relative_representation.card_positions_draw[drawn.local_index].end());
                *drawn_card_it = draw_pile;
                std::ranges::sort(_relative_representation.card_positions_draw[drawn.local_index]);
            }

            _weighted_draw_pile_size++;
            _endgame_turns_left = no_endgame;
        } else {
            ASSERT(_hands[_turn][index] == discarded_card);
        }

        if (_relative_representation.initialized && !discarded_card.initial_trash) {
            if (discarded_card.in_starting_hand) {
                ASSERT(_relative_representation.card_positions_hands[discarded_card.local_index] == false);
                _relative_representation.card_positions_hands[discarded_card.local_index] = true;
            } else {
                auto hand_card_it = std::ranges::find(_relative_representation.card_positions_draw[discarded_card.local_index],
                                                      trash_or_play_stack);
                ASSERT(hand_card_it != _relative_representation.card_positions_draw[discarded_card.local_index].end());
                *hand_card_it = _turn;
                std::ranges::sort(_relative_representation.card_positions_draw[discarded_card.local_index]);
            }
        }

        _hands[_turn][index] = discarded_card;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::init_backtracking_information() {
        // Note that this function does not have to be particularly performant, we only call it once to initialize.
        const Card trash = [this]() -> Card {
            for (suit_t suit = 0; suit < num_suits; suit++) {
                if (_stacks[suit] < starting_card_rank) {
                    return {suit, starting_card_rank - 1, 0, false, true};
                }
            }
            return {0, 0};
        }();

        CardArray<num_suits, std::uint8_t> nums_in_draw_pile;
        for (const auto [card, multiplicity]: _draw_pile) {
            if (_stacks[card.suit] > card.rank) {
                nums_in_draw_pile[card] += multiplicity;
            } else {
                nums_in_draw_pile[trash] += multiplicity;
            }
        }

        // Prepare draw pile
        _draw_pile.clear();
        for (suit_t suit = 0; suit < num_suits; suit++) {
            for (rank_t rank = 0; rank < starting_card_rank; rank++) {
                Card card{suit, rank, static_cast<uint8_t>(_relative_representation.card_positions_draw.size()), false, is_trash(card)};
                if (nums_in_draw_pile[card] > 0) {
                    _draw_pile.push_back({card, nums_in_draw_pile[card]});
                    if (!is_trash(card)) {
                        _relative_representation.card_positions_draw.push_back({});
                        _relative_representation.card_positions_draw.back().resize(nums_in_draw_pile[card], draw_pile);
                        _relative_representation.good_cards_draw.push_back(card);
                    }
                }
            }
        }
        _relative_representation.initial_draw_pile_size = _weighted_draw_pile_size;

        // Prepare cards in hands
        for (player_t player = 0; player < num_players; player++) {
            for (Card &card: _hands[player]) {
                card.initial_trash = is_trash(card);
                card.in_starting_hand = true;
                // Needed to check for dupes in same hand
                boost::container::static_vector<Card, hand_size> good_cards_in_hand;
                if (!is_trash(card)) {
                    if (std::count(good_cards_in_hand.begin(), good_cards_in_hand.end(), card) > 0) {
                        // This card is already in hand, so just replace the second copy by some trash
                        card = trash;
                    } else {
                        card.local_index = _relative_representation.num_useful_cards_in_starting_hands;
                        _relative_representation.num_useful_cards_in_starting_hands++;

                        good_cards_in_hand.push_back(card);
                    }
                }
            }
        }
        _relative_representation.card_positions_hands.reset();
        for (size_t i = 0; i < _relative_representation.num_useful_cards_in_starting_hands; i++) {
            _relative_representation.card_positions_hands[i] = true;
        }
        _relative_representation.initialized = true;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void
    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(!last_action.was_on_8_clues or _num_clues == 8);

        decr_turn();
        if (last_action.discarded.rank == 0 and not last_action.was_on_8_clues) {
            _num_clues--;
        }
        revert_draw(last_action.index, last_action.discarded);
        if(_stacks[last_action.discarded.suit] == last_action.discarded.rank) {
            _stacks[last_action.discarded.suit]++;
        }
        _score--;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::revert_discard() {
        const BacktrackAction last_action = _actions_log.top();
        _actions_log.pop();

        ASSERT(last_action.action_type == ActionType::discard);

        decr_turn();
        ASSERT(_num_clues > 0);

        _num_clues--;
        _pace++;

        revert_draw(last_action.index, last_action.discarded);
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::revert_clue() {
        const BacktrackAction last_action = _actions_log.top();
        _actions_log.pop();

        ASSERT(last_action.action_type == ActionType::clue);

        decr_turn();
        ASSERT(_num_clues < max_num_clues);

        _num_clues++;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::revert() {
        switch(_actions_log.top().action_type) {
            case ActionType::clue:
                revert_clue();
                break;
            case ActionType::discard:
                revert_discard();
                break;
            case ActionType::play:
                revert_play();
                break;
            default:
                return;
        }
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    player_t HanabiState<num_suits, num_players, hand_size>::turn() const {
        return _turn;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    clue_t HanabiState<num_suits, num_players, hand_size>::num_clues() const {
        return _num_clues;
    };

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    std::vector<std::vector<Card>> HanabiState<num_suits, num_players, hand_size>::hands() const {
        std::vector<std::vector<Card>> hands;
        for(player_t player = 0; player < num_players; player++) {
            hands.push_back({});
            for(const Card& card: _hands[player]) {
                hands.back().push_back(card);
            }
        }
        return hands;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    std::vector<Card> HanabiState<num_suits, num_players, hand_size>::cur_hand() const {
        std::vector<Card> hand;
        for(const Card& card: _hands[_turn]) {
            hand.push_back(card);
        }
        return hand;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    std::vector<std::pair<CardMultiplicity, std::optional<probability_t>>> HanabiState<num_suits, num_players, hand_size>::possible_next_states(hand_index_t index, bool play) {
        std::vector<std::pair<CardMultiplicity, std::optional<probability_t>>> next_states;
        do_for_each_potential_draw(index, play, [this, &next_states, &index](unsigned multiplicity){
            auto prob = lookup();

            // bit hacky to get drawn card here
            decr_turn();
            const CardMultiplicity drawn_card = {_hands[_turn][index], multiplicity};
            incr_turn();

            next_states.emplace_back(drawn_card, prob);
        });
        return next_states;
    }

    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(index, true, [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(index, false, [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) {
            give_clue();
            const std::optional<probability_t> prob = lookup();
            const Action action = {ActionType::clue, Cards::unknown};
            reasonable_actions.emplace_back(action, prob);
            revert_clue();
        }
        return reasonable_actions;
    }

    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 {
        if (_score == 5 * num_suits) {
            return 1;
        }
        if (_pace < 0 or _endgame_turns_left == 0) {
            return 0;
        }
        const auto id = unique_id();
        if(_position_tablebase.contains(id)) {
            return _position_tablebase.at(id);
        } else {
            return std::nullopt;
        }
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::rotate_next_draw(const Card& card) {
        auto card_it = std::find_if(_draw_pile.begin(), _draw_pile.end(), [&card](const CardMultiplicity& card_multiplicity){
            return card_multiplicity.card.rank == card.rank and card_multiplicity.card.suit == card.suit;
        });
        ASSERT(card_it != _draw_pile.end());
        std::swap(*card_it, _draw_pile.front());
    }

    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() {
        ASSERT(_relative_representation.initialized);
        _enumerated_states++;
        const unsigned long id_of_state = unique_id();

        if (_score == 5 * num_suits) {
            return 1;
        }
        if(_pace < 0 || _endgame_turns_left == 0) {
            return 0;
        }
        if (_position_tablebase.contains(id_of_state)) {
            return _position_tablebase[id_of_state];
        }

        // TODO: Have some endgame analysis here?

        probability_t best_probability = 0;
        const std::array<Card, hand_size>& hand = _hands[_turn];

        // First, check for playables
        for(std::uint8_t index = 0; index < hand_size; index++) {
            if(is_playable(hand[index])) {
                probability_t sum_of_probabilities = 0;

                do_for_each_potential_draw(index, true, [this, &sum_of_probabilities](const unsigned long multiplicity){
                    sum_of_probabilities += evaluate_state() * multiplicity;
                });

                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;

                best_probability = std::max(best_probability, probability_play);
                if (best_probability == 1) {
                    update_tablebase(id_of_state, best_probability);
                    return best_probability;
                };
            }
        }

        // Check for discards now
        if(_pace > 0 and _num_clues < max_num_clues) {
            for(std::uint8_t index = 0; index < hand_size; index++) {
                if (is_trash(hand[index])) {
                    probability_t sum_of_probabilities = 0;

                    do_for_each_potential_draw(index, false, [this, &sum_of_probabilities](const unsigned long multiplicity){
                        sum_of_probabilities += evaluate_state() * multiplicity;
                    });

                    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;
                    best_probability = std::max(best_probability, probability_discard);

                    best_probability = std::max(best_probability, probability_discard);
                    if (best_probability == 1) {
                        update_tablebase(id_of_state, best_probability);
                        return best_probability;
                    };

                    // All discards are equivalent, do not continue searching for different trash
                    break;
                }
            }
        }

        // Last option is to stall
        if(_num_clues > 0) {
            give_clue();
            const probability_t probability_stall = evaluate_state();
            revert_clue();
            best_probability = std::max(best_probability, probability_stall);
            if (best_probability == 1) {
                update_tablebase(id_of_state, best_probability);
                return best_probability;
            };
        }

        update_tablebase(id_of_state, best_probability);
        return best_probability;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    template<class Function>
    void HanabiState<num_suits, num_players, hand_size>::do_for_each_potential_draw(hand_index_t index, bool play, Function f) {
        auto do_action = [this, index, play](){
            if (play) {
                return play_and_potentially_update(index);
            } else {
                return discard_and_potentially_update(index);
            }
        };

        auto revert_action = [this, play](){
            if (play) {
                revert_play();
            } else {
                revert_discard();
            }
        };

        if(_draw_pile.empty()) {
            do_action();
            f(1);
            revert_action();
        } else {
            unsigned sum_of_multiplicities = 0;
            for(size_t i = 0; i < _draw_pile.size(); i++) {
                const unsigned long multiplicity = do_action();
                sum_of_multiplicities += multiplicity;
                f(multiplicity);
                revert_action();
            }
            ASSERT(sum_of_multiplicities == _weighted_draw_pile_size);
        }
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    std::uint64_t HanabiState<num_suits, num_players, hand_size>::unique_id() const {
        unsigned long id = 0;

        // encode all positions of cards that started in draw pile
        ASSERT(_relative_representation.card_positions_draw.size() == _relative_representation.good_cards_draw.size());
        for(size_t i = 0; i < _relative_representation.card_positions_draw.size(); i++) {
            for(player_t player : _relative_representation.card_positions_draw[i]) {
                id *= num_players + 2;
                // We normalize here: If a card is already played, then the positions of its other copies
                // do not matter, so we can just pretend that they are all in the trash already.
                // The resulting states will be equivalent.
                if (!is_trash(_relative_representation.good_cards_draw[i])) {
                    id += player;
                } else {
                    id += trash_or_play_stack;
                }
            }
        }

        // encode number of clues
        id *= max_num_clues + 1;
        id += _num_clues;

        // we can encode draw pile size and extra turn in one metric, since we only have extra turns if draw pile is empty
        const std::uint8_t draw_pile_size_and_extra_turns = [this]() -> uint8_t {
            if(_endgame_turns_left == no_endgame) {
                return _weighted_draw_pile_size + num_players;
            }
            else {
                return _endgame_turns_left;
            }
        }();

        id *= _relative_representation.initial_draw_pile_size + num_players;
        id += draw_pile_size_and_extra_turns;

        // encode positions of cards that started in hands
        id = id << _relative_representation.num_useful_cards_in_starting_hands;
        id += _relative_representation.card_positions_hands.to_ulong();

        id *= num_players;
        id += _turn;

        // The id is unique now, since for all relevant cards, we know their position (including if they are played),
        // the number of clues, the draw pile size and whose turn it is.
        // This already uniquely determines the current players position, assuming that we never discard good cards
        // (and only play them)

        return id;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    std::pair<std::vector<std::uint64_t>, std::vector<Card>> HanabiState<num_suits, num_players, hand_size>::dump_unique_id_parts() const {
        std::vector<std::uint64_t> ret;
        std::vector<Card> cards;

        // encode all positions of cards that started in draw pile
        ASSERT(_relative_representation.card_positions_draw.size() == _relative_representation.good_cards_draw.size());
        for(size_t i = 0; i < _relative_representation.card_positions_draw.size(); i++) {
            for(player_t player : _relative_representation.card_positions_draw[i]) {
                // We normalize here: If a card is already played, then the positions of its other copies
                // do not matter, so we can just pretend that they are all in the trash already.
                // The resulting states will be equivalent.
                if (!is_trash(_relative_representation.good_cards_draw[i])) {
                    ret.push_back(player);
                } else {
                    ret.push_back(trash_or_play_stack);
                }
                cards.push_back(_relative_representation.good_cards_draw[i]);
            }
        }

        // encode number of clues
        ret.push_back(_num_clues);

        // we can encode draw pile size and extra turn in one metric, since we only have extra turns if draw pile is empty
        const std::uint8_t draw_pile_size_and_extra_turns = [this]() -> uint8_t {
            if(_endgame_turns_left == no_endgame) {
                return _weighted_draw_pile_size + num_players;
            }
            else {
                return _endgame_turns_left;
            }
        }();

        ret.push_back(draw_pile_size_and_extra_turns);

        // encode positions of cards that started in hands
        ret.push_back(_relative_representation.card_positions_hands.to_ulong());

        ret.push_back(_turn);

        // The id is unique now, since for all relevant cards, we know their position (including if they are played),
        // the number of clues, the draw pile size and whose turn it is.
        // This already uniquely determines the current players position, assuming that we never discard good cards
        // (and only play them)

        return {ret, cards};
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    const std::unordered_map<unsigned long, probability_t>& HanabiState<num_suits, num_players, hand_size>::position_tablebase() const {
        return _position_tablebase;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    size_t HanabiState<num_suits, num_players, hand_size>::draw_pile_size() const {
        return _weighted_draw_pile_size;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    bool HanabiState<num_suits, num_players, hand_size>::is_relative_state_initialized() const {
        return _relative_representation.initialized;
    }

    template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
    void HanabiState<num_suits, num_players, hand_size>::update_tablebase(
            unsigned long id,
            Hanabi::probability_t probability) {
        if (_position_tablebase.contains(id)) {
            ASSERT(_position_tablebase[id] == probability);
        }
        _position_tablebase[id] = probability;
    }

} // namespace Hanabi