WTS/game/scripts/inventory/classes.rpy

init python:
    class Inventory(object):
        def __init__(self):
            self.items = set()

        def add(self, item):
            self.items.add(item)

        def remove(self, item):
            self.items.remove(item)

        def get_instances(self):
            return self.items

        def get_instances_of_type(self, type):
            return sorted([x for x in self.get_instances() if x.type == type], key=lambda y: natsort_key(y.name))

        def _get_givables(self, type):
            return any(x.givable for x in self.get_instances_of_type(type))

        def _get_usables(self, type, char):
            return any(char in x.usable_on for x in self.get_instances_of_type(type))

        def is_givable_type(self, type, char=None):
            if not char:
                char = states.active_girl
            return self._get_givables(type) and self._get_usables(type, char)

    class Item(object):
        def __init__(self, id, type, name, price=0, desc="", unlocked=True, use_func=None, use_label=None, give_func=None, give_label=None, limit=100, image="default", givable=False, currency="gold", use_caption=_("Use"), give_caption=_("Give"), owned=0, infinite=False, usable_on=[], use_progression={}, give_progression={}):
            self.id = id
            self.type = type
            self.name = name
            self.price = price
            self.desc = desc
            self.unlocked = unlocked
            self.use_func = use_func
            self.use_label = use_label
            self.use_caption = use_caption
            self.use_progression = use_progression
            self.give_func = give_func
            self.give_label = give_label
            self.give_caption = give_caption
            self.give_progression = give_progression
            self.limit = limit
            self.image = f"interface/icons/{self.id}.webp" if image == "default" else image
            self.currency = currency
            self.used = False
            self.infinite = infinite
            self.usable_on = usable_on
            self.givable = bool(self.give_func or self.give_label or self.usable_on)
            self.usable = bool(self.use_func or self.use_label)

            self._owned = owned

            inventory.add(self)

        def _check_usable(self, func_name):
            if not getattr(self, func_name):
                raise Exception(f"Item {self.name!r} is not marked as {func_name}able.")
            if self.owned == 0:
                raise Exception(f"Item {self.name!r} owned count is equal to zero.")

        def _use_or_give(self, func_name):
            self._check_usable(func_name)
            if not self.type == "quest":
                # Quest items require manual triggers, it's more convenient.
                self.used = True
            func = getattr(self, f"{func_name}_func")
            label = getattr(self, f"{func_name}_label")
            if func:
                func()
            if label:
                enable_game_menu()
                renpy.jump_out_of_context(label) if renpy.context_nesting_level() > 0 else renpy.jump(label)

        def use(self):
            self._use_or_give("use")

        def give(self):
            self._use_or_give("give")

        def get_image(self):
            return self.image() if callable(self.image) else self.image

        @property
        def caption(self):
            return self.use_caption if inventory_mode==0 else self.give_caption # 'inventory_mode' is a global

        @property
        def owned(self):
            return self._owned

        @owned.setter
        def owned(self, value):
            self.unlocked = True
            self._owned = max(min(value, self.limit), 0)

    class Decoration(Item):
        room_scale = 0.5

        def __init__(self, id, type, name, placement, price=0, desc="", unlocked=True, image="default", room_image="default", room_image_hover=None, owned=0, replaces=False, use_action=None, replace_action=None, replace_anchor=None, replace_pos=None):
            super(Decoration, self).__init__(id=id, type=type, name=name, price=price, desc=desc, unlocked=unlocked, limit=1, image=image, givable=False, currency="tokens", use_caption="Apply", owned=owned)

            if room_image == "default":
                room_image = f"images/rooms/main_room/decorations/{self.id}.webp"
            self.room_image = Transform(room_image, zoom=self.room_scale)
            self.room_image_hover = Transform(room_image_hover or room_image, zoom=self.room_scale)
            self.usable = True
            self.placement = placement
            self.in_use = False
            self.replaces = replaces
            self.use_action = use_action
            self.replace_action = replace_action
            self.replace_anchor = replace_anchor
            self.replace_pos = replace_pos

            if not isinstance(self.placement, RoomObject):
                raise TypeError("Placement must be a RoomObject instance reference.")

        def use(self):
            if self.owned == 0:
                raise Exception(f"Decoration {self.name!r} owned count is equal to zero.")

            achievements.unlock("decorator")

            target = self.placement

            if not target.decoration is None:
                target.decoration.in_use = False

            if self.use_action:
                self.use_action()

            # Toggle
            if not target.decoration == self:
                target.set_decoration(self)
                self.in_use = True
            else:
                target.set_decoration(None)
                self.in_use = False

    class Potion(Item):
        def __init__(self, id, type, name, price=0, desc="", unlocked=True, label=None, limit=100, image="default", currency="gold", use_caption=_("Use"), give_caption=_("Give"), owned=0, recipe=None, usable_on=[], levels={}):
            super(Potion, self).__init__(id, type=type, name=name, price=price, desc=desc, unlocked=unlocked, give_label=label, limit=limit, image=image, givable=True, currency=currency, use_caption=use_caption, give_caption=give_caption, owned=owned)

            # self.givable = bool(self.give_label)
            self.label = label
            self.recipe = recipe
            self.usable_on = usable_on
            self.levels = levels

            self.make_intro = False
            self.in_progress = {i: False for i in usable_on}

            self.usable = bool(renpy.has_label(f"{self.label}_use"))

            if self.recipe is None:
                raise Exception(f"Potion {self.name!r} recipe is empty!")

        def has_ingredients(self):
            return all(x.owned > 0 for x in self.recipe)

        def set_active(self, who):
            """Marks the event as 'in progress' and will trigger a return event in the morning/evening."""
            if not who in list(self.in_progress.keys()):
                raise Exception(f"Potion {self.name!r} is not marked as usable on {who!r}.")

            self.in_progress[who] = True

        def make(self):
            if not self.has_ingredients():
                return

            for i in self.recipe:
                if not i.infinite:
                    i.owned -= 1

            self.owned += 1
            label = f"{self.label}_make"

            if renpy.has_label(label) and not self.make_intro:
                self.make_intro = True
                self.jump(label)

        def check_progression(self, who):
            """Check if progression is eligible to play this event"""
            progression = get_character_progression(who)

            return (progression >= self.levels.get(who))

        def give(self, who):
            """Use potion on <active_girl>"""

            give_label = f"{who[:3]}_{self.label}_give"
            check_label = f"{who[:3]}_potion_check"

            if not renpy.has_label(give_label):
                raise Exception(f"Potion {self.name!r} give label doesn't exist.")

            if not renpy.has_label(check_label):
                raise Exception(f"Potion {self.name!r} check label doesn't exist for {who!r}.")

            if self.owned == 0:
                raise Exception(f"Potion {self.name!r} owned count is equal to zero.")

            if not self.check_progression(who):
                self.jump(check_label)

            self.owned -= 1
            self.jump(give_label)

        def use(self):
            """Use potion on Genie"""

            label = f"{self.label}_use"

            if not renpy.has_label(label):
                raise Exception(f"Potion {self.name!r} has no use label.")

            if self.owned == 0:
                raise Exception(f"Potion {self.name!r} owned count is equal to zero.")

            self.owned -= 1
            self.jump(label)

        def ret(self, who):
            """Play the return event for <girl>"""

            if not self.in_progress[who]:
                raise Exception(f"Potion {self.name!r} is not marked as in progress.")

            label = f"{who[:3]}_{self.label}_return"

            if not renpy.has_label(label):
                raise Exception(f"Potion {self.name!r} has no return label.")

            self.in_progress[who] = False
            self.jump(label)

        def jump(self, label):
            if renpy.context_nesting_level() > 0:
                renpy.jump_out_of_context(label)
            else:
                renpy.jump(label)

init offset = -5

default inventory = Inventory()