2 files changed, 157 insertions, 2 deletions
diff --git a/engine/events/poisonstep.asm b/engine/events/poisonstep.asm
new file mode 100755
index 00000000..98a6e25a
--- /dev/null
+++ b/engine/events/poisonstep.asm
@@ -0,0 +1,154 @@
+DoPoisonStep::
+	ld a, [wPartyCount]
+	and a
+	jr z, .no_faint
+
+	xor a
+	ld c, wPoisonStepDataEnd - wPoisonStepData
+	ld hl, wPoisonStepData
+.loop_clearPoisonStepData
+	ld [hli], a
+	dec c
+	jr nz, .loop_clearPoisonStepData
+
+	xor a
+	ld [wCurPartyMon], a
+.loop_check_poison
+	call .DamageMonIfPoisoned
+	jr nc, .not_poisoned
+; the output flag is stored in c, copy it to [wPoisonStepPartyFlags + [wCurPartyMon]]
+; and set the corresponding flag in wPoisonStepFlagSum
+	ld a, [wCurPartyMon]
+	ld e, a
+	ld d, 0
+	ld hl, wPoisonStepPartyFlags
+	add hl, de
+	ld [hl], c
+	ld a, [wPoisonStepFlagSum]
+	or c
+	ld [wPoisonStepFlagSum], a
+
+.not_poisoned
+	ld a, [wPartyCount]
+	ld hl, wCurPartyMon
+	inc [hl]
+	cp [hl]
+	jr nz, .loop_check_poison
+
+	ld a, [wPoisonStepFlagSum]
+	and %10
+	jr nz, .someone_has_fainted
+	ld a, [wPoisonStepFlagSum]
+	and %01
+	jr z, .no_faint
+	call .PlayPoisonSFX
+	xor a
+	ret
+
+.someone_has_fainted
+	ld a, BANK(.Script_MonFaintedToPoison)
+	ld hl, .Script_MonFaintedToPoison
+	call CallScript
+	scf
+	ret
+
+.no_faint
+	xor a
+	ret
+
+.DamageMonIfPoisoned:
+; check if mon is poisoned, return if not
+	ld a, MON_STATUS
+	call GetPartyParamLocation
+	ld a, [hl]
+	and 1 << PSN
+	ret z
+
+; check if mon is already fainted, return if so
+	ld a, MON_HP
+	call GetPartyParamLocation
+	ld a, [hli]
+	ld b, a
+	ld c, [hl]
+	or c
+	ret z
+
+; do 1 HP damage
+	dec bc
+	ld [hl], c
+	dec hl
+	ld [hl], b
+
+; check if mon has fainted as a result of poison damage
+	ld a, b
+	or c
+	jr nz, .not_fainted
+
+; the mon has fainted, reset its status, set carry, and return %10
+	ld a, MON_STATUS
+	call GetPartyParamLocation
+	ld [hl], 0
+	ld c, %10
+	scf
+	ret
+
+.not_fainted
+; set carry and return %01
+	ld c, %01
+	scf
+	ret
+
+.PlayPoisonSFX:
+	ld de, SFX_POISON
+	call PlaySFX
+	ld b, $2
+	predef LoadPoisonBGPals
+	call DelayFrame
+	ret
+
+.Script_MonFaintedToPoison:
+	callasm .PlayPoisonSFX
+	opentext
+	callasm .CheckWhitedOut
+	iffalse .whiteout
+	closetext
+	end
+
+.whiteout
+	farsjump Script_OverworldWhiteout
+
+.CheckWhitedOut:
+	xor a
+	ld [wCurPartyMon], a
+	ld de, wPoisonStepPartyFlags
+.party_loop
+	push de
+	ld a, [de]
+	and %10
+	jr z, .mon_not_fainted
+	ld c, HAPPINESS_POISONFAINT
+	farcall ChangeHappiness
+	farcall GetPartyNick
+	ld hl, .PoisonFaintText
+	call PrintText
+
+.mon_not_fainted
+	pop de
+	inc de
+	ld hl, wCurPartyMon
+	inc [hl]
+	ld a, [wPartyCount]
+	cp [hl]
+	jr nz, .party_loop
+	predef CheckPlayerPartyForFitMon
+	ld a, d
+	ld [wScriptVar], a
+	ret
+
+.PoisonFaintText:
+	text_far _PoisonFaintText
+	text_end
+
+.PoisonWhiteoutText:
+	text_far _PoisonWhiteoutText
+	text_end
diff --git a/main.asm b/main.asm
index 60e75e04..7c8a15b5 100644
--- a/main.asm
+++ b/main.asm
@@ -361,8 +361,9 @@ INCLUDE "engine/pokemon/party_menu.asm"
 
 LoadFishingGFX::
 	dr $5054f, $50610
-DoPoisonStep::
-	dr $50610, $506f2
+
+INCLUDE "engine/events/poisonstep.asm"
+
 SweetScentFromMenu::
 	dr $506f2, $50763
 _Squirtbottle::