From 38f8a6aabbfe2378bae1da53ba77344be77f8f56 Mon Sep 17 00:00:00 2001
From: Gunnar Beutner <gbeutner@serenityos.org>
Date: Mon, 31 May 2021 23:56:13 +0200
Subject: [PATCH] Hearts: Pick better lead cards

Previously the AI would prefer playing a lead card for which no other
player had a card with a higher value even though it also had a card
for which a higher value card was still in play.
---
 Userland/Games/Hearts/Game.cpp   |  5 +----
 Userland/Games/Hearts/Player.cpp | 15 ++-------------
 Userland/Games/Hearts/Player.h   |  2 +-
 3 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/Userland/Games/Hearts/Game.cpp b/Userland/Games/Hearts/Game.cpp
index a968fde40f6..7be8d6af17f 100644
--- a/Userland/Games/Hearts/Game.cpp
+++ b/Userland/Games/Hearts/Game.cpp
@@ -327,10 +327,7 @@ size_t Game::pick_card(Player& player)
             auto prefer_card = [this, &player](Card& card) {
                 return !other_player_has_lower_value_card(player, card) && other_player_has_higher_value_card(player, card);
             };
-            auto lower_value_card_in_play = [this, &player](Card& card) {
-                return other_player_has_lower_value_card(player, card);
-            };
-            return player.pick_lead_card(move(valid_card), move(prefer_card), move(lower_value_card_in_play));
+            return player.pick_lead_card(move(valid_card), move(prefer_card));
         }
     }
     auto* high_card = &m_trick[0];
diff --git a/Userland/Games/Hearts/Player.cpp b/Userland/Games/Hearts/Player.cpp
index c42194734e2..a3d86f82cf5 100644
--- a/Userland/Games/Hearts/Player.cpp
+++ b/Userland/Games/Hearts/Player.cpp
@@ -39,8 +39,7 @@ Vector<CardWithIndex> Player::hand_sorted_by_points_and_value() const
     return sorted_hand;
 }
 
-size_t Player::pick_lead_card(Function<bool(Card&)> valid_play, Function<bool(Card&)> prefer_card,
-    Function<bool(Card&)> lower_value_card_in_play)
+size_t Player::pick_lead_card(Function<bool(Card&)> valid_play, Function<bool(Card&)> prefer_card)
 {
     auto sorted_hand = hand_sorted_by_points_and_value();
 
@@ -51,27 +50,17 @@ size_t Player::pick_lead_card(Function<bool(Card&)> valid_play, Function<bool(Ca
         dbgln("----");
     }
 
-    ssize_t fallback_index = -1;
     ssize_t last_index = -1;
     for (auto& cwi : sorted_hand) {
         if (!valid_play(*cwi.card))
             continue;
-        if (lower_value_card_in_play(*cwi.card)) {
-            // Allow falling back to this card if no other suitable card is in play.
-            fallback_index = cwi.index;
-            continue;
-        }
         if (prefer_card(*cwi.card)) {
             dbgln_if(HEARTS_DEBUG, "Preferring card {}", *cwi.card);
             return cwi.index;
         }
         last_index = cwi.index;
     }
-    if (last_index == -1) {
-        dbgln_if(HEARTS_DEBUG, "Falling back to card {}", *hand[fallback_index]);
-        return fallback_index;
-    } else
-        return last_index;
+    return last_index;
 }
 
 Optional<size_t> Player::pick_low_points_high_value_card(Optional<Card::Type> type)
diff --git a/Userland/Games/Hearts/Player.h b/Userland/Games/Hearts/Player.h
index db30a7ef4cd..9f6181e477f 100644
--- a/Userland/Games/Hearts/Player.h
+++ b/Userland/Games/Hearts/Player.h
@@ -34,7 +34,7 @@ public:
     }
 
     NonnullRefPtrVector<Card> pick_cards_to_pass(PassingDirection);
-    size_t pick_lead_card(Function<bool(Card&)>, Function<bool(Card&)>, Function<bool(Card&)>);
+    size_t pick_lead_card(Function<bool(Card&)>, Function<bool(Card&)>);
     Optional<size_t> pick_low_points_high_value_card(Optional<Card::Type> type = {});
     Optional<size_t> pick_lower_value_card(Card& other_card);
     Optional<size_t> pick_slightly_higher_value_card(Card& other_card);