1 files changed, 151 insertions, 0 deletions
diff --git a/engine/items/inventory.asm b/engine/items/inventory.asm
new file mode 100644
index 00000000..58bcf7e9
--- /dev/null
+++ b/engine/items/inventory.asm
@@ -0,0 +1,151 @@
+; 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
+.notAtEndOfInventory
+	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
+.loop
+	ld a, [hl]
+	cp a, $ff ; is it the end of the table?
+	jr nz, .notAtEndOfInventory
+.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 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 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
+	add 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 $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 2
+	jr c, .done
+	ld [wMaxMenuItem], a
+	jr .done
+.skipMovingUpSlots
+	pop hl
+.done
+	ret