1 files changed, 118 insertions, 0 deletions
diff --git a/engine/events/pikachu_happiness.asm b/engine/events/pikachu_happiness.asm
new file mode 100644
index 00000000..0d79e32b
--- /dev/null
+++ b/engine/events/pikachu_happiness.asm
@@ -0,0 +1,118 @@
+ModifyPikachuHappiness::
+	ld a, d
+	cp PIKAHAPPY_GYMLEADER
+	jr z, .checkanywhereinparty
+	cp PIKAHAPPY_WALKING
+	jr z, .checkanywhereinparty
+	push de
+	callfar IsThisPartymonStarterPikachu_Party
+	pop de
+	ret nc
+	jr .proceed
+
+.checkanywhereinparty
+	push de
+	callfar IsStarterPikachuInOurParty
+	pop de
+	ret nc
+
+.proceed
+	push de
+	; Divide [wPikachuHappiness] by 100.  Hold the integer part in e.
+	ld e, $0
+	ld a, [wPikachuHappiness]
+	cp 100
+	jr c, .wPikachuHappiness_div_100
+	inc e
+	cp 200
+	jr c, .wPikachuHappiness_div_100
+	inc e
+.wPikachuHappiness_div_100
+	; Get the (d, e) entry from HappinessChangeTable.
+	ld c, d
+	dec c
+	ld b, $0
+	ld hl, HappinessChangeTable
+	add hl, bc
+	add hl, bc
+	add hl, bc
+	ld d, $0
+	add hl, de
+	ld a, [hl]
+	; If [hl] is positive, take min(0xff, [hl] + [wPikachuHappiness]).
+	; If [hl] is negative, take max(0x00, [hl] + [wPikachuHappiness]).
+	; Inexplicably, we're using 100 as the threshold for comparison.
+	cp 100
+	ld a, [wPikachuHappiness]
+	jr nc, .negative
+	add [hl]
+	jr nc, .okay
+	ld a, -1
+	jr .okay
+
+.negative
+	add [hl]
+	jr c, .okay
+	xor a
+.okay
+	ld [wPikachuHappiness], a
+
+	; Restore d and get the d'th entry in PikachuMoods.
+	pop de
+	dec d
+	ld hl, PikachuMoods
+	ld e, d
+	ld d, $0
+	add hl, de
+	ld a, [hl]
+	ld b, a
+	; Modify Pikachu's mood
+	cp $80
+	jr z, .done
+	ld a, [wPikachuMood]
+	jr c, .decreased
+	cp b
+	jr nc, .done
+	ld a, [wd49c]
+	and a
+	jr nz, .done
+	jr .update_mood
+
+.decreased
+	cp b
+	jr c, .done
+.update_mood
+	ld a, b
+	ld [wPikachuMood], a
+.done
+	ret
+
+HappinessChangeTable:
+	; Increase
+	db   5, 3, 2 ; Gained a level
+	db   5, 3, 2 ; HP restore
+	db   1, 1, 0 ; Used X item
+	db   3, 2, 1 ; Challenged Gym Leader
+	db   1, 1, 0 ; Teach TM/HM
+	db   2, 1, 1 ; Walking around
+	; Decrease
+	db  -3, -3, -5 ; Deposited
+	db  -1, -1, -1 ; Fainted in battle
+	db  -5, -5, -10 ; Fainted due to Poison outside of battle
+	db  -5, -5, -10 ; Fainted to opponent at least 30 levels higher
+	db -10, -10, -20 ; Traded away
+
+PikachuMoods:
+	; Increase
+	db $8a           ; Gained a level
+	db $83           ; HP restore
+	db $80           ; Teach TM/HM
+	db $80           ; Challenged Gym Leader
+	db $94           ; Unknown (d = 5)
+	db $80           ; Unknown (d = 6)
+	; Decrease
+	db $62           ; Deposited
+	db $6c           ; Fainted
+	db $62           ; Unknown (d = 9)
+	db $6c           ; Unknown (d = 10)
+	db $00           ; Unknown (d = 11)