[battle, damage] refactor damage formula to match gen5+

include/battle_util.h

@@ -209,14 +209,12 @@ void BufferStatChange(u8 battlerId, u8 statId, u8 stringId);
 bool32 BlocksPrankster(u16 move, u8 battlerPrankster, u8 battlerDef, bool32 checkTarget);
 u16 GetUsedHeldItem(u8 battler);
 bool32 IsBattlerWeatherAffected(u8 battlerId, u32 weatherFlags);
-u32 ApplyWeatherDamageMultiplier(u8 battlerAtk, u16 move, u8 moveType, u32 dmg, u16 holdEffectAtk, u16 holdEffectDef);
 u32 GetBattlerMoveTargetType(u8 battlerId, u16 move);
 bool32 CanTargetBattler(u8 battlerAtk, u8 battlerDef, u16 move);
 bool8 IsMoveAffectedByParentalBond(u16 move, u8 battlerId);
 void CopyMonLevelAndBaseStatsToBattleMon(u32 battler, struct Pokemon *mon);
 void CopyMonAbilityAndTypesToBattleMon(u32 battler, struct Pokemon *mon);
 void RecalcBattlerStats(u32 battler, struct Pokemon *mon);
-void MulModifier(u16 *modifier, u16 val);
 bool32 IsAlly(u32 battlerAtk, u32 battlerDef);
 
 // Ability checks
@@ -245,9 +243,4 @@ u8 GetBattlerGender(u8 battlerId);
 bool8 AreBattlersOfOppositeGender(u8 battler1, u8 battler2);
 u32 CalcSecondaryEffectChance(u8 battlerId, u8 secondaryEffectChance);
 
-static inline u32 ApplyModifier(uq4_12_t modifier, u32 val)
-{
-    return UQ_4_12_TO_INT((modifier * val) + UQ_4_12_ROUND);
-}
-
 #endif // GUARD_BATTLE_UTIL_H

include/fpmath.h

@@ -52,10 +52,30 @@ static inline uq4_12_t uq4_12_multiply(uq4_12_t a, uq4_12_t b)
     return (product + UQ_4_12_ROUND) >> UQ_4_12_SHIFT;
 }
 
+static inline uq4_12_t uq4_12_multiply_half_down(uq4_12_t a, uq4_12_t b)
+{
+    u32 product = (u32) a * b;
+    return (product + UQ_4_12_ROUND - 1) >> UQ_4_12_SHIFT;
+}
+
 static inline uq4_12_t uq4_12_divide(uq4_12_t dividend, uq4_12_t divisor)
 {
     if (divisor == UQ_4_12(0.0)) return UQ_4_12(0);
     return (dividend << UQ_4_12_SHIFT) / divisor;
 }
 
+// Multiplies value by the UQ_4_12 number modifier.
+// Returns an integer, rounded to nearest (rounding down on n.5)
+static inline u32 uq4_12_multiply_by_int_half_down(uq4_12_t modifier, u32 value)
+{
+    return UQ_4_12_TO_INT((modifier * value) + UQ_4_12_ROUND - 1);
+}
+
+// Multiplies value by the UQ_4_12 number modifier.
+// Returns an integer, rounded to nearest (rounding up on n.5)
+static inline u32 uq4_12_multiply_by_int_half_up(uq4_12_t modifier, u32 value)
+{
+    return UQ_4_12_TO_INT((modifier * value) + UQ_4_12_ROUND);
+}
+
 #endif // FPMATH_H_

src/battle_script_commands.c

@@ -1414,7 +1414,7 @@ static void Cmd_attackcanceler(void)
         return;
     }
 
-    // Z-moves and Max Moves bypass protection, but deal reduced damage (factored in CalcFinalDmg)
+    // Z-moves and Max Moves bypass protection, but deal reduced damage (factored in AccumulateOtherModifiers)
     if (gBattleStruct->zmove.active && IS_BATTLER_PROTECTED(gBattlerTarget))
     {
         BattleScriptPush(cmd->nextInstr);

test/ability_contrary.c

@@ -26,7 +26,7 @@ SINGLE_BATTLE_TEST("Contrary raises Attack when Intimidated", s16 damage)
         HP_BAR(player, captureDamage: &results[i].damage);
     }
     FINALLY {
-        EXPECT_MUL_EQ(results[1].damage, Q_4_12(2.125), results[0].damage);
+        EXPECT_MUL_EQ(results[1].damage, Q_4_12(2.25), results[0].damage);
     }
 }
 

test/ability_dry_skin.c

@@ -36,15 +36,24 @@ SINGLE_BATTLE_TEST("Dry Skin increases damage taken from Fire-type moves by 25%"
     PARAMETRIZE { ability = ABILITY_DRY_SKIN; }
     GIVEN {
         ASSUME(gBattleMoves[MOVE_EMBER].type == TYPE_FIRE);
-        PLAYER(SPECIES_WOBBUFFET);
-        OPPONENT(SPECIES_PARASECT) { Ability(ability); }
+        ASSUME(gBattleMoves[MOVE_EMBER].power == 40);
+        ASSUME(gSpeciesInfo[SPECIES_PARASECT].types[0] == TYPE_BUG);
+        ASSUME(gSpeciesInfo[SPECIES_PARASECT].types[1] == TYPE_GRASS);
+        ASSUME(gSpeciesInfo[SPECIES_WOBBUFFET].types[0] == TYPE_PSYCHIC);
+        ASSUME(gSpeciesInfo[SPECIES_WOBBUFFET].types[1] == TYPE_PSYCHIC);
+        PLAYER(SPECIES_WOBBUFFET) { SpAttack(71); }
+        OPPONENT(SPECIES_PARASECT) { Ability(ability); SpDefense(165); }
     } WHEN {
         TURN { MOVE(player, MOVE_EMBER); }
     } SCENE {
         MESSAGE("Wobbuffet used Ember!");
         HP_BAR(opponent, captureDamage: &results[i].damage);
     } FINALLY {
-        EXPECT_MUL_EQ(results[0].damage, Q_4_12(1.25), results[1].damage);
+        // Due to numerics related to rounding on each applied multiplier,
+        // the ability effect doesn't manifest as a 25% damage increase, but as a ~31% damage increase in this case.
+        // Values obtained from https://calc.pokemonshowdown.com (Neutral nature and 0 IVs on both sides)
+        EXPECT_EQ(results[0].damage, 52);
+        EXPECT_EQ(results[1].damage, 68);
     }
 }
 

test/ability_fluffy.c

@@ -0,0 +1,66 @@
+#include "global.h"
+#include "test_battle.h"
+
+ASSUMPTIONS
+{
+    ASSUME(gBattleMoves[MOVE_TACKLE].makesContact);
+    ASSUME(gBattleMoves[MOVE_EMBER].type == TYPE_FIRE);
+    ASSUME(gBattleMoves[MOVE_TACKLE].makesContact);
+    ASSUME(gBattleMoves[MOVE_FIRE_PUNCH].makesContact);
+    ASSUME(gBattleMoves[MOVE_FIRE_PUNCH].type == TYPE_FIRE);
+    ASSUME(P_GEN_7_POKEMON == TRUE);
+}
+
+SINGLE_BATTLE_TEST("Fluffy halves damage taken from moves that make direct contact", s16 damage)
+{
+    u32 ability;
+    PARAMETRIZE { ability = ABILITY_KLUTZ; }
+    PARAMETRIZE { ability = ABILITY_FLUFFY; }
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_STUFFUL) { Ability(ability); }
+    } WHEN {
+        TURN { MOVE(player, MOVE_TACKLE); }
+    } SCENE {
+        MESSAGE("Wobbuffet used Tackle!");
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(0.5), results[1].damage);
+    }
+}
+
+SINGLE_BATTLE_TEST("Fluffy doubles damage taken from fire type moves", s16 damage)
+{
+    u32 ability;
+    PARAMETRIZE { ability = ABILITY_KLUTZ; }
+    PARAMETRIZE { ability = ABILITY_FLUFFY; }
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_STUFFUL) { Ability(ability); }
+    } WHEN {
+        TURN { MOVE(player, MOVE_EMBER); }
+    } SCENE {
+        MESSAGE("Wobbuffet used Ember!");
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(2.0), results[1].damage);
+    }
+}
+
+SINGLE_BATTLE_TEST("Fluffy does not alter damage of fire-type moves that make direct contact", s16 damage)
+{
+    u32 ability;
+    PARAMETRIZE { ability = ABILITY_KLUTZ; }
+    PARAMETRIZE { ability = ABILITY_FLUFFY; }
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_STUFFUL) { Ability(ability); }
+    } WHEN {
+        TURN { MOVE(player, MOVE_FIRE_PUNCH); }
+    } SCENE {
+        MESSAGE("Wobbuffet used Fire Punch!");
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_EQ(results[0].damage, results[1].damage);
+    }
+}

test/ability_swarm.c

@@ -8,13 +8,21 @@ SINGLE_BATTLE_TEST("Swarm boosts Bug-type moves in a pinch", s16 damage)
     PARAMETRIZE { hp = 33; }
     GIVEN {
         ASSUME(gBattleMoves[MOVE_BUG_BITE].type == TYPE_BUG);
-        PLAYER(SPECIES_LEDYBA) { Ability(ABILITY_SWARM); MaxHP(99); HP(hp); }
-        OPPONENT(SPECIES_WOBBUFFET);
+        ASSUME(gBattleMoves[MOVE_BUG_BITE].power == 60);
+        ASSUME(gSpeciesInfo[SPECIES_LEDYBA].types[0] == TYPE_BUG);
+        ASSUME(gSpeciesInfo[SPECIES_WOBBUFFET].types[0] == TYPE_PSYCHIC);
+        ASSUME(gSpeciesInfo[SPECIES_WOBBUFFET].types[1] == TYPE_PSYCHIC);
+        PLAYER(SPECIES_LEDYBA) { Ability(ABILITY_SWARM); MaxHP(99); HP(hp); Attack(45); }
+        OPPONENT(SPECIES_WOBBUFFET) { Defense(121); }
     } WHEN {
         TURN { MOVE(player, MOVE_BUG_BITE); }
     } SCENE {
         HP_BAR(opponent, captureDamage: &results[i].damage);
     } FINALLY {
-        EXPECT_MUL_EQ(results[0].damage, Q_4_12(1.5), results[1].damage);
+        // Due to numerics related to rounding on each applied multiplier,
+        // the 50% move power increase doesn't manifest as a 50% damage increase, but as a 44% damage increase in this case.
+        // Values obtained from https://calc.pokemonshowdown.com (Neutral nature and 0 IVs on both sides)
+        EXPECT_EQ(results[0].damage, 50);
+        EXPECT_EQ(results[1].damage, 72);
     }
 }

test/damage_formula.c

@@ -0,0 +1,78 @@
+#include "global.h"
+#include "test_battle.h"
+
+// From https://bulbapedia.bulbagarden.net/wiki/Damage#Example
+
+SINGLE_BATTLE_TEST("Damage calculation matches Gen5+")
+{
+    s16 dmg;
+    s16 expectedDamage;
+    PARAMETRIZE { expectedDamage = 196; }
+    PARAMETRIZE { expectedDamage = 192; }
+    PARAMETRIZE { expectedDamage = 192; }
+    PARAMETRIZE { expectedDamage = 192; }
+    PARAMETRIZE { expectedDamage = 184; }
+    PARAMETRIZE { expectedDamage = 184; }
+    PARAMETRIZE { expectedDamage = 184; }
+    PARAMETRIZE { expectedDamage = 180; }
+    PARAMETRIZE { expectedDamage = 180; }
+    PARAMETRIZE { expectedDamage = 180; }
+    PARAMETRIZE { expectedDamage = 172; }
+    PARAMETRIZE { expectedDamage = 172; }
+    PARAMETRIZE { expectedDamage = 172; }
+    PARAMETRIZE { expectedDamage = 168; }
+    PARAMETRIZE { expectedDamage = 168; }
+    PARAMETRIZE { expectedDamage = 168; }
+    GIVEN {
+        PLAYER(SPECIES_GLACEON) { Level(75); Attack(123); }
+        OPPONENT(SPECIES_GARCHOMP) { Defense(163); }
+    } WHEN {
+        TURN {
+            MOVE(player, MOVE_ICE_FANG, WITH_RNG(RNG_DAMAGE_MODIFIER, i));
+        }
+    }
+    SCENE{
+        MESSAGE("Glaceon used Ice Fang!");
+        HP_BAR(opponent, captureDamage: &dmg);
+    }
+    THEN{
+        EXPECT_EQ(expectedDamage, dmg);
+    }
+}
+
+SINGLE_BATTLE_TEST("Damage calculation matches Gen5+ (Muscle Band, crit)")
+{
+    s16 dmg;
+    s16 expectedDamage;
+    PARAMETRIZE { expectedDamage = 324; }
+    PARAMETRIZE { expectedDamage = 316; }
+    PARAMETRIZE { expectedDamage = 312; }
+    PARAMETRIZE { expectedDamage = 312; }
+    PARAMETRIZE { expectedDamage = 304; }
+    PARAMETRIZE { expectedDamage = 304; }
+    PARAMETRIZE { expectedDamage = 300; }
+    PARAMETRIZE { expectedDamage = 300; }
+    PARAMETRIZE { expectedDamage = 292; }
+    PARAMETRIZE { expectedDamage = 292; }
+    PARAMETRIZE { expectedDamage = 288; }
+    PARAMETRIZE { expectedDamage = 288; }
+    PARAMETRIZE { expectedDamage = 280; }
+    PARAMETRIZE { expectedDamage = 276; }
+    PARAMETRIZE { expectedDamage = 276; }
+    PARAMETRIZE { expectedDamage = 268; }
+    GIVEN {
+        PLAYER(SPECIES_GLACEON) { Level(75); Attack(123); Item(ITEM_MUSCLE_BAND); }
+        OPPONENT(SPECIES_GARCHOMP) { Defense(163); }
+    } WHEN {
+        TURN {
+            MOVE(player, MOVE_ICE_FANG, WITH_RNG(RNG_DAMAGE_MODIFIER, i), criticalHit: TRUE);
+        }
+    }
+    SCENE{
+        MESSAGE("Glaceon used Ice Fang!");
+        HP_BAR(opponent, captureDamage: &dmg);
+    }
+    THEN{
+        EXPECT_EQ(expectedDamage, dmg);
+    }
+}

test/status3.c

@@ -0,0 +1,90 @@
+#include "global.h"
+#include "test_battle.h"
+
+ASSUMPTIONS {
+    ASSUME(gBattleMoves[MOVE_MINIMIZE].effect == EFFECT_MINIMIZE);
+    ASSUME(gBattleMoves[MOVE_STEAMROLLER].minimizeDoubleDamage);
+    ASSUME(gBattleMoves[MOVE_EARTHQUAKE].damagesUnderground);
+    ASSUME(gBattleMoves[MOVE_SURF].damagesUnderwater);
+    ASSUME(gBattleMoves[MOVE_TWISTER].damagesAirborneDoubleDamage);
+}
+
+SINGLE_BATTLE_TEST("Minimize causes the target to take double damage from certain moves", s16 damage)
+{
+    bool32 useMinimize;
+    PARAMETRIZE { useMinimize = FALSE; }
+    PARAMETRIZE { useMinimize = TRUE; }
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET) { Speed(1); }
+        OPPONENT(SPECIES_WOBBUFFET) { Speed(2); }
+    } WHEN {
+        if (useMinimize)
+            TURN { MOVE(opponent, MOVE_MINIMIZE); MOVE(player, MOVE_STEAMROLLER); }
+        else
+            TURN { MOVE(player, MOVE_STEAMROLLER); }
+    } SCENE {
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(2.0), results[1].damage);
+    }
+}
+
+SINGLE_BATTLE_TEST("Being underground causes the target to take double damage from certain moves", s16 damage)
+{
+    bool32 useDig;
+    PARAMETRIZE { useDig = FALSE; }
+    PARAMETRIZE { useDig = TRUE; }
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET) { Speed(1); }
+        OPPONENT(SPECIES_WOBBUFFET) { Speed(2); }
+    } WHEN {
+        if (useDig)
+            TURN { MOVE(opponent, MOVE_DIG); MOVE(player, MOVE_EARTHQUAKE); }
+        else
+            TURN { MOVE(player, MOVE_EARTHQUAKE); }
+    } SCENE {
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(2.0), results[1].damage);
+    }
+}
+
+SINGLE_BATTLE_TEST("Being underwater causes the target to take double damage from certain moves", s16 damage)
+{
+    bool32 useDive;
+    PARAMETRIZE { useDive = FALSE; }
+    PARAMETRIZE { useDive = TRUE; }
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET) { Speed(1); }
+        OPPONENT(SPECIES_WOBBUFFET) { Speed(2); }
+    } WHEN {
+        if (useDive)
+            TURN { MOVE(opponent, MOVE_DIVE); MOVE(player, MOVE_SURF); }
+        else
+            TURN { MOVE(player, MOVE_SURF); }
+    } SCENE {
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(2.0), results[1].damage);
+    }
+}
+
+SINGLE_BATTLE_TEST("Being airborne causes the target to take double damage from certain moves", s16 damage)
+{
+    bool32 useDive;
+    PARAMETRIZE { useDive = FALSE; }
+    PARAMETRIZE { useDive = TRUE; }
+    GIVEN {
+        PLAYER(SPECIES_WOBBUFFET) { Speed(1); }
+        OPPONENT(SPECIES_WOBBUFFET) { Speed(2); }
+    } WHEN {
+        if (useDive)
+            TURN { MOVE(opponent, MOVE_FLY); MOVE(player, MOVE_TWISTER); }
+        else
+            TURN { MOVE(player, MOVE_TWISTER); }
+    } SCENE {
+        HP_BAR(opponent, captureDamage: &results[i].damage);
+    } FINALLY {
+        EXPECT_MUL_EQ(results[0].damage, UQ_4_12(2.0), results[1].damage);
+    }
+}

test/weather_snow.c

@@ -81,7 +81,6 @@ SINGLE_BATTLE_TEST("Snow halves the power of Solar Beam", s16 damage)
 SINGLE_BATTLE_TEST("Snow halves the power of Solar Blade", s16 damage)
 {
     u16 move;
-    KNOWN_FAILING; // fails bc the bp of solar blade gets rounded up which leads to slightly incorrect calcs down the line
     PARAMETRIZE{ move = MOVE_CELEBRATE; }
     PARAMETRIZE{ move = MOVE_SNOWSCAPE; }
     GIVEN {