1 files changed, 77 insertions, 0 deletions
diff --git a/engine/battle/move_effects/substitute.asm b/engine/battle/move_effects/substitute.asm
new file mode 100644
index 00000000..1bb6c887
--- /dev/null
+++ b/engine/battle/move_effects/substitute.asm
@@ -0,0 +1,77 @@
+SubstituteEffect_:
+	ld c, 50
+	call DelayFrames
+	ld hl, wBattleMonMaxHP
+	ld de, wPlayerSubstituteHP
+	ld bc, wPlayerBattleStatus2
+	ld a, [H_WHOSETURN]
+	and a
+	jr z, .notEnemy
+	ld hl, wEnemyMonMaxHP
+	ld de, wEnemySubstituteHP
+	ld bc, wEnemyBattleStatus2
+.notEnemy
+	ld a, [bc]
+	bit HAS_SUBSTITUTE_UP, a ; user already has substitute?
+	jr nz, .alreadyHasSubstitute
+; quarter health to remove from user
+; assumes max HP is 1023 or lower
+	push bc
+	ld a, [hli]
+	ld b, [hl]
+	srl a
+	rr b
+	srl a
+	rr b ; max hp / 4
+	push de
+	ld de, wBattleMonHP - wBattleMonMaxHP
+	add hl, de ; point hl to current HP low byte
+	pop de
+	ld a, b
+	ld [de], a ; save copy of HP to subtract in wPlayerSubstituteHP/wEnemySubstituteHP
+	ld a, [hld]
+; subtract [max hp / 4] to current HP
+	sub b
+	ld d, a
+	ld a, [hl]
+	sbc 0
+	pop bc
+	jr c, .notEnoughHP ; underflow means user would be left with negative health
+                           ; bug: since it only branches on carry, it will possibly leave user with 0 HP
+.userHasZeroOrMoreHP
+	ldi [hl], a ; save resulting HP after subtraction into current HP
+	ld [hl], d
+	ld h, b
+	ld l, c
+	set HAS_SUBSTITUTE_UP, [hl]
+	ld a, [wOptions]
+	bit 7, a ; battle animation is enabled?
+	ld hl, PlayCurrentMoveAnimation
+	ld b, BANK(PlayCurrentMoveAnimation)
+	jr z, .animationEnabled
+	ld hl, AnimationSubstitute
+	ld b, BANK(AnimationSubstitute)
+.animationEnabled
+	call Bankswitch ; jump to routine depending on animation setting
+	ld hl, SubstituteText
+	call PrintText
+	jpab DrawHUDsAndHPBars
+.alreadyHasSubstitute
+	ld hl, HasSubstituteText
+	jr .printText
+.notEnoughHP
+	ld hl, TooWeakSubstituteText
+.printText
+	jp PrintText
+
+SubstituteText:
+	TX_FAR _SubstituteText
+	db "@"
+
+HasSubstituteText:
+	TX_FAR _HasSubstituteText
+	db "@"
+
+TooWeakSubstituteText:
+	TX_FAR _TooWeakSubstituteText
+	db "@"