split code out of main.asm

engine/items/inventory.asm

@@ -0,0 +1,150 @@
+; function to add an item (in varying quantities) to the player's bag or PC box
+; INPUT:
+; hl = address of inventory (either wNumBagItems or wNumBoxItems)
+; [wcf91] = item ID
+; [wItemQuantity] = item quantity
+; sets carry flag if successful, unsets carry flag if unsuccessful
+AddItemToInventory_:
+	ld a,[wItemQuantity] ; a = item quantity
+	push af
+	push bc
+	push de
+	push hl
+	push hl
+	ld d,PC_ITEM_CAPACITY ; how many items the PC can hold
+	ld a,wNumBagItems & $FF
+	cp l
+	jr nz,.checkIfInventoryFull
+	ld a,wNumBagItems >> 8
+	cp h
+	jr nz,.checkIfInventoryFull
+; if the destination is the bag
+	ld d,BAG_ITEM_CAPACITY ; how many items the bag can hold
+.checkIfInventoryFull
+	ld a,[hl]
+	sub d
+	ld d,a
+	ld a,[hli]
+	and a
+	jr z,.addNewItem
+.loop
+	ld a,[hli]
+	ld b,a ; b = ID of current item in table
+	ld a,[wcf91] ; a = ID of item being added
+	cp b ; does the current item in the table match the item being added?
+	jp z,.increaseItemQuantity ; if so, increase the item's quantity
+	inc hl
+	ld a,[hl]
+	cp a,$ff ; is it the end of the table?
+	jr nz,.loop
+.addNewItem ; add an item not yet in the inventory
+	pop hl
+	ld a,d
+	and a ; is there room for a new item slot?
+	jr z,.done
+; if there is room
+	inc [hl] ; increment the number of items in the inventory
+	ld a,[hl] ; the number of items will be the index of the new item
+	add a
+	dec a
+	ld c,a
+	ld b,0
+	add hl,bc ; hl = address to store the item
+	ld a,[wcf91]
+	ld [hli],a ; store item ID
+	ld a,[wItemQuantity]
+	ld [hli],a ; store item quantity
+	ld [hl],$ff ; store terminator
+	jp .success
+.increaseItemQuantity ; increase the quantity of an item already in the inventory
+	ld a,[wItemQuantity]
+	ld b,a ; b = quantity to add
+	ld a,[hl] ; a = existing item quantity
+	add b ; a = new item quantity
+	cp a,100
+	jp c,.storeNewQuantity ; if the new quantity is less than 100, store it
+; if the new quantity is greater than or equal to 100,
+; try to max out the current slot and add the rest in a new slot
+	sub a,99
+	ld [wItemQuantity],a ; a = amount left over (to put in the new slot)
+	ld a,d
+	and a ; is there room for a new item slot?
+	jr z,.increaseItemQuantityFailed
+; if so, store 99 in the current slot and store the rest in a new slot
+	ld a,99
+	ld [hli],a
+	jp .loop
+.increaseItemQuantityFailed
+	pop hl
+	and a
+	jr .done
+.storeNewQuantity
+	ld [hl],a
+	pop hl
+.success
+	scf
+.done
+	pop hl
+	pop de
+	pop bc
+	pop bc
+	ld a,b
+	ld [wItemQuantity],a ; restore the initial value from when the function was called
+	ret
+
+; function to remove an item (in varying quantities) from the player's bag or PC box
+; INPUT:
+; hl = address of inventory (either wNumBagItems or wNumBoxItems)
+; [wWhichPokemon] = index (within the inventory) of the item to remove
+; [wItemQuantity] = quantity to remove
+RemoveItemFromInventory_:
+	push hl
+	inc hl
+	ld a,[wWhichPokemon] ; index (within the inventory) of the item being removed
+	sla a
+	add l
+	ld l,a
+	jr nc,.noCarry
+	inc h
+.noCarry
+	inc hl
+	ld a,[wItemQuantity] ; quantity being removed
+	ld e,a
+	ld a,[hl] ; a = current quantity
+	sub e
+	ld [hld],a ; store new quantity
+	ld [wMaxItemQuantity],a
+	and a
+	jr nz,.skipMovingUpSlots
+; if the remaining quantity is 0,
+; remove the emptied item slot and move up all the following item slots
+.moveSlotsUp
+	ld e,l
+	ld d,h
+	inc de
+	inc de ; de = address of the slot following the emptied one
+.loop ; loop to move up the following slots
+	ld a,[de]
+	inc de
+	ld [hli],a
+	cp a,$ff
+	jr nz,.loop
+; update menu info
+	xor a
+	ld [wListScrollOffset],a
+	ld [wCurrentMenuItem],a
+	ld [wBagSavedMenuItem],a
+	ld [wSavedListScrollOffset],a
+	pop hl
+	ld a,[hl] ; a = number of items in inventory
+	dec a ; decrement the number of items
+	ld [hl],a ; store new number of items
+	ld [wListCount],a
+	cp a,2
+	jr c,.done
+	ld [wMaxMenuItem],a
+	jr .done
+.skipMovingUpSlots
+	pop hl
+.done
+	ret