1 files changed, 77 insertions, 0 deletions
diff --git a/engine/battle/moveEffects/substitute_effect.asm b/engine/battle/moveEffects/substitute_effect.asm
new file mode 100644
index 00000000..e88def4a
--- /dev/null
+++ b/engine/battle/moveEffects/substitute_effect.asm
@@ -0,0 +1,77 @@
+SubstituteEffect_: ; 17dad (5:7dad)
+	ld c, 50
+	call DelayFrames
+	ld hl, wBattleMonMaxHP
+	ld de, wPlayerSubstituteHP
+	ld bc, W_PLAYERBATTSTATUS2
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .notEnemy
+	ld hl, wEnemyMonMaxHP
+	ld de, wEnemySubstituteHP
+	ld bc, W_ENEMYBATTSTATUS2
+.notEnemy
+	ld a, [bc]                    ;load flags
+	bit HasSubstituteUp, a        ;user already has substitute?
+	jr nz, .alreadyHasSubstitute  ;skip this code if so
+	                              ;user doesn't have a substitute [yet]
+	push bc
+	ld a, [hli]  ;load max hp
+	ld b, [hl]
+	srl a        ;max hp / 4, [quarter health to remove from user]
+	rr b
+	srl a
+	rr b
+	push de
+	ld de, wBattleMonHP - wBattleMonMaxHP
+	add hl, de    ; point hl to current HP
+	pop de
+	ld a, b
+	ld [de], a    ;save copy of HP to subtract in ccd7/ccd8 [how much HP substitute has]
+	ld a, [hld]   ;load current hp
+	sub b         ;subtract [max hp / 4]
+	ld d, a       ;save low byte result in D
+	ld a, [hl]
+	sbc a, 0      ;borrow from high byte if needed
+	pop bc
+	jr c, .notEnoughHP  ;underflow means user would be left with negative health
+                        ;bug: note since it only brances on carry, it will possibly leave user with 0HP
+.userHasZeroOrMoreHP
+	ldi [hl], a  ;store high byte HP
+	ld [hl], d   ;store low byte HP
+	ld h, b
+	ld l, c
+	set HasSubstituteUp, [hl] ;set bit 4 of flags, user now has substitute
+	ld a, [W_OPTIONS]         ;load options
+	bit 7, a                  ;battle animation is enabled?
+	ld hl, PlayCurrentMoveAnimation         ;animation enabled: 0F:7BA8
+	ld b, BANK(PlayCurrentMoveAnimation)
+	jr z, .animationEnabled
+	ld hl, AnimationSubstitute ;animation disabled: 1E:56E0
+	ld b, BANK(AnimationSubstitute)
+.animationEnabled
+	call Bankswitch           ;jump to routine depending on animation setting
+	ld hl, SubstituteText
+	call PrintText
+	ld hl, DrawHUDsAndHPBars
+	ld b, BANK(DrawHUDsAndHPBars)
+	jp Bankswitch
+.alreadyHasSubstitute
+	ld hl, HasSubstituteText
+	jr .printText
+.notEnoughHP
+	ld hl, TooWeakSubstituteText
+.printText
+	jp PrintText
+
+SubstituteText: ; 17e1d (5:7e1d)
+	TX_FAR _SubstituteText
+	db "@"
+
+HasSubstituteText: ; 17e22 (5:7e22)
+	TX_FAR _HasSubstituteText
+	db "@"
+
+TooWeakSubstituteText: ; 17e27 (5:7e27)
+	TX_FAR _TooWeakSubstituteText
+	db "@"