Remove the AI unit growth bonuses and tune the income bonuses for different difficulty levels

src/fheroes2/game/difficulty.cpp

@@ -61,58 +61,45 @@ int Difficulty::GetScoutingBonusForAI( int difficulty )
     default:
         break;
     }
+
     return 0;
 }
 
-double Difficulty::getGoldIncomeBonusForAI( const int difficulty )
+Funds Difficulty::getResourceIncomeBonusForAI( const int difficulty )
 {
     switch ( difficulty ) {
-    case Difficulty::EASY:
-        // It is deduction from the income.
-        return -0.25;
-    case Difficulty::HARD:
-        return 0.29;
     case Difficulty::EXPERT:
-        return 0.45;
+        return { 2, 2, 1, 1, 1, 1, 0 };
     case Difficulty::IMPOSSIBLE:
-        return 0.6;
+        return { 2, 2, 1, 1, 1, 1, 0 };
     default:
         break;
     }
-    return 0;
+
+    return {};
 }
 
-double Difficulty::GetUnitGrowthBonusForAI( const int difficulty, const bool /* isCampaign */, const building_t /* dwelling */ )
+double Difficulty::getGoldIncomeBonusForAI( const int difficulty )
 {
-    // In the original game AI has a cheeky monster growth bonus depending on difficulty:
-    // Easy - 0.0 (no bonus)
-    // Normal - 0.0 (no bonus)
-    // Hard - 0.20 (or 20% extra)
-    // Expert - 0.32 (or 32% extra)
-    // Impossible - 0.44 (or 44% extra)
-    // This bonus was introduced to compensate weak AI in the game.
-    //
-    // However, with introduction of proper AI in this engine AI has become much stronger and some maps are impossible to beat.
-    // Also this bonus can be abused by players while capturing AI castles on a first day of a week.
-    //
-    // Completely removing these bonuses might break some maps and they become unplayable.
-    // Therefore, these bonuses are reduced by 5% which is the value of noise in many processes / systems.
-
     switch ( difficulty ) {
     case Difficulty::EASY:
-    case Difficulty::NORMAL:
-        return 0;
+        // It is deduction from the income.
+        return -0.25;
     case Difficulty::HARD:
-        return 0.14;
+        return 0.5;
     case Difficulty::EXPERT:
-        return 0.254;
+        return 1.0;
     case Difficulty::IMPOSSIBLE:
-        return 0.368;
+        return 2.0;
     default:
-        // Did you add a new difficulty level? Add the logic above!
-        assert( 0 );
         break;
     }
+
+    return 0;
+}
+
+double Difficulty::GetUnitGrowthBonusForAI( const int /* difficulty */, const bool /* isCampaign */, const building_t /* dwelling */ )
+{
     return 0;
 }
 
@@ -125,6 +112,7 @@ int Difficulty::GetHeroMovementBonusForAI( int difficulty )
     default:
         break;
     }
+
     return 0;
 }
 
@@ -156,6 +144,7 @@ double Difficulty::getArmyStrengthRatioForAIRetreat( const int difficulty )
     default:
         break;
     }
+
     return 100.0 / 6.0;
 }
 
@@ -176,6 +165,7 @@ uint32_t Difficulty::GetDimensionDoorLimitForAI( int difficulty )
     default:
         break;
     }
+
     return UINT32_MAX;
 }
 
@@ -227,6 +217,7 @@ bool Difficulty::allowAIToSplitWeakStacks( const int difficulty )
     default:
         break;
     }
+
     return true;
 }
 
@@ -238,6 +229,7 @@ bool Difficulty::allowAIToDevelopCastlesOnDay( const int difficulty, const bool
     default:
         break;
     }
+
     return true;
 }
 
@@ -250,5 +242,6 @@ bool Difficulty::allowAIToBuildCastleBuilding( const int difficulty, const bool
     default:
         break;
     }
+
     return true;
 }

src/fheroes2/game/difficulty.h

@@ -45,7 +45,10 @@ namespace Difficulty
 
     int GetScoutingBonusForAI( int difficulty );
 
-    // Returns an extra gold bonus modifier for AI based on difficulty level.
+    // Returns an extra resource bonus for AI based on difficulty level.
+    Funds getResourceIncomeBonusForAI( const int difficulty );
+
+    // Returns an extra gold bonus modifier for AI based on difficulty level. This modifier is applied after applying the resource income bonus.
     double getGoldIncomeBonusForAI( const int difficulty );
 
     // Returns an extra growth bonus modifier for AI based on difficulty level.

src/fheroes2/kingdom/kingdom.cpp

@@ -85,7 +85,9 @@ namespace
     Funds getHandicapDependentIncome( const Funds & original, const Player::HandicapStatus handicapStatus )
     {
         const int32_t handicapPercentage = getHandicapIncomePercentage( handicapStatus );
+
         Funds corrected( original );
+
         corrected.wood = std::min( corrected.wood, ( corrected.wood * handicapPercentage + 99 ) / 100 );
         corrected.mercury = std::min( corrected.mercury, ( corrected.mercury * handicapPercentage + 99 ) / 100 );
         corrected.ore = std::min( corrected.ore, ( corrected.ore * handicapPercentage + 99 ) / 100 );
@@ -660,7 +662,7 @@ uint32_t Kingdom::GetMaxHeroes()
     return GameStatic::GetKingdomMaxHeroes();
 }
 
-Funds Kingdom::GetIncome( int type /* INCOME_ALL */ ) const
+Funds Kingdom::GetIncome( int type /* = INCOME_ALL */ ) const
 {
     Funds totalIncome;
 
@@ -719,15 +721,28 @@ Funds Kingdom::GetIncome( int type /* INCOME_ALL */ ) const
         }
     }
 
-    if ( isControlAI() && totalIncome.gold > 0 ) {
-        const int32_t bonusGold = static_cast<int32_t>( totalIncome.gold * Difficulty::getGoldIncomeBonusForAI( Game::getDifficulty() ) );
+    if ( isControlAI() ) {
+        const Funds incomeBonus = Difficulty::getResourceIncomeBonusForAI( Game::getDifficulty() );
+        if ( incomeBonus.GetValidItemsCount() != 0 ) {
+            DEBUG_LOG( DBG_AI, DBG_TRACE, "AI bonus to the resource income has been applied to " << Color::String( color ) << ": " << incomeBonus.String() );
+
+            totalIncome += incomeBonus;
+        }
+
+        const int32_t goldBonus = static_cast<int32_t>( totalIncome.gold * Difficulty::getGoldIncomeBonusForAI( Game::getDifficulty() ) );
+        if ( goldBonus != 0 ) {
+            DEBUG_LOG( DBG_AI, DBG_TRACE,
+                       "AI bonus to the gold income has been applied to " << Color::String( color ) << ", original income: " << totalIncome.gold
+                                                                          << ", bonus income: " << goldBonus );
 
-        totalIncome.gold += bonusGold;
+            totalIncome.gold += goldBonus;
+        }
     }
 
-    // Some human players can have handicap for resources.
     const Player * player = Players::Get( color );
     assert( player != nullptr );
+
+    // Some human players can have handicap for resources.
     return getHandicapDependentIncome( totalIncome, player->getHandicapStatus() );
 }