1 files changed, 149 insertions, 0 deletions
diff --git a/engine/pokemon/experience.asm b/engine/pokemon/experience.asm
new file mode 100755
index 00000000..3ee4b2a8
--- /dev/null
+++ b/engine/pokemon/experience.asm
@@ -0,0 +1,149 @@
+; calculates the level a mon should be based on its current exp
+CalcLevelFromExperience::
+	ld a, [wLoadedMonSpecies]
+	ld [wd0b5], a
+	call GetMonHeader
+	ld d, $1 ; init level to 1
+.loop
+	inc d ; increment level
+	call CalcExperience
+	push hl
+	ld hl, wLoadedMonExp + 2 ; current exp
+; compare exp needed for level d with current exp
+	ld a, [hExperience + 2]
+	ld c, a
+	ld a, [hld]
+	sub c
+	ld a, [hExperience + 1]
+	ld c, a
+	ld a, [hld]
+	sbc c
+	ld a, [hExperience]
+	ld c, a
+	ld a, [hl]
+	sbc c
+	pop hl
+	jr nc, .loop ; if exp needed for level d is not greater than exp, try the next level
+	dec d ; since the exp was too high on the last loop iteration, go back to the previous value and return
+	ret
+
+; calculates the amount of experience needed for level d
+CalcExperience::
+	ld a, [wMonHGrowthRate]
+	add a
+	add a
+	ld c, a
+	ld b, 0
+	ld hl, GrowthRateTable
+	add hl, bc
+	call CalcDSquared
+	ld a, d
+	ld [H_MULTIPLIER], a
+	call Multiply
+	ld a, [hl]
+	and $f0
+	swap a
+	ld [H_MULTIPLIER], a
+	call Multiply
+	ld a, [hli]
+	and $f
+	ld [H_DIVISOR], a
+	ld b, $4
+	call Divide
+	ld a, [H_QUOTIENT + 1]
+	push af
+	ld a, [H_QUOTIENT + 2]
+	push af
+	ld a, [H_QUOTIENT + 3]
+	push af
+	call CalcDSquared
+	ld a, [hl]
+	and $7f
+	ld [H_MULTIPLIER], a
+	call Multiply
+	ld a, [H_PRODUCT + 1]
+	push af
+	ld a, [H_PRODUCT + 2]
+	push af
+	ld a, [H_PRODUCT + 3]
+	push af
+	ld a, [hli]
+	push af
+	xor a
+	ld [H_MULTIPLICAND], a
+	ld [H_MULTIPLICAND + 1], a
+	ld a, d
+	ld [H_MULTIPLICAND + 2], a
+	ld a, [hli]
+	ld [H_MULTIPLIER], a
+	call Multiply
+	ld b, [hl]
+	ld a, [H_PRODUCT + 3]
+	sub b
+	ld [H_PRODUCT + 3], a
+	ld b, $0
+	ld a, [H_PRODUCT + 2]
+	sbc b
+	ld [H_PRODUCT + 2], a
+	ld a, [H_PRODUCT + 1]
+	sbc b
+	ld [H_PRODUCT + 1], a
+; The difference of the linear term and the constant term consists of 3 bytes
+; starting at H_PRODUCT + 1. Below, hExperience (an alias of that address) will
+; be used instead for the further work of adding or subtracting the squared
+; term and adding the cubed term.
+	pop af
+	and $80
+	jr nz, .subtractSquaredTerm ; check sign
+	pop bc
+	ld a, [hExperience + 2]
+	add b
+	ld [hExperience + 2], a
+	pop bc
+	ld a, [hExperience + 1]
+	adc b
+	ld [hExperience + 1], a
+	pop bc
+	ld a, [hExperience]
+	adc b
+	ld [hExperience], a
+	jr .addCubedTerm
+.subtractSquaredTerm
+	pop bc
+	ld a, [hExperience + 2]
+	sub b
+	ld [hExperience + 2], a
+	pop bc
+	ld a, [hExperience + 1]
+	sbc b
+	ld [hExperience + 1], a
+	pop bc
+	ld a, [hExperience]
+	sbc b
+	ld [hExperience], a
+.addCubedTerm
+	pop bc
+	ld a, [hExperience + 2]
+	add b
+	ld [hExperience + 2], a
+	pop bc
+	ld a, [hExperience + 1]
+	adc b
+	ld [hExperience + 1], a
+	pop bc
+	ld a, [hExperience]
+	adc b
+	ld [hExperience], a
+	ret
+
+; calculates d*d
+CalcDSquared:
+	xor a
+	ld [H_MULTIPLICAND], a
+	ld [H_MULTIPLICAND + 1], a
+	ld a, d
+	ld [H_MULTIPLICAND + 2], a
+	ld [H_MULTIPLIER], a
+	jp Multiply
+
+INCLUDE "data/growth_rates.asm"