import bpy

class DrawCollectionMixin():
    items: bpy.props.CollectionProperty  # pyright: ignore[reportGeneralTypeIssues]

    def draw_collection(self, items, layout):
        col = layout.column(align=True)
        for item in items:
            item.draw_item(col)

    def _draw_prop(self, text, layout):
        self.draw_collection(self.items, layout)

def update_collection(items: bpy.props.CollectionProperty) -> None:  # pyright: ignore[reportGeneralTypeIssues]
    if len(items) == 0:
        items.add()

    if items[-1].is_active:
        items.add()

    while len(items) >= 2:
        if not items[-1].is_active and not items[-2].is_active:
            items.remove(len(items) - 1)
        else:
            break

class UpdateCollectionMixin():
    items: bpy.props.CollectionProperty  # pyright: ignore[reportGeneralTypeIssues]

    def __init__(self, *args, **kwargs) -> None:
        super().__init__(*args, **kwargs)
        self.update()

    def update(self):
        update_collection(self.items)

class CollectionMixin(DrawCollectionMixin, UpdateCollectionMixin): ...