from dataclasses import dataclass
from typing import Optional

from flet.controls.base_control import control
from flet.controls.control import Control
from flet.controls.control_event import Event, EventHandler
from flet.controls.transform import Offset

__all__ = [
    "DragTarget",
    "DragTargetEvent",
    "DragWillAcceptEvent",
    "DragTargetLeaveEvent",
]


@dataclass
class DragWillAcceptEvent(Event["DragTarget"]):
    accept: bool
    src_id: int


@dataclass
class DragTargetEvent(Event["DragTarget"]):
    src_id: int
    x: float
    y: float

    @property
    def offset(self) -> Offset:
        return Offset(self.x, self.y)


@dataclass
class DragTargetLeaveEvent(Event["DragTarget"]):
    src_id: Optional[int]


@control("DragTarget")
class DragTarget(Control):
    """
    A control that completes drag operation when a [`Draggable`][flet.Draggable] control is dropped.

    When a `Draggable` is dragged on top of a `DragTarget`, the `DragTarget` is asked
    whether it will accept the data the `Draggable` is carrying. The `DragTarget` will
    accept incoming drag if it belongs to the same `group` as `Draggable`. If the user
    does drop the `Draggable` on top of the `DragTarget` (and the `DragTarget` has
    indicated that it will accept the `Draggable`'s data), then the `DragTarget` is
    asked to accept the `Draggable`'s data.

    Raises:
        AssertionError: If [`content`][(c).] is not visible.
    """

    content: Control
    """
    The content of this control.
    """

    group: str = "default"
    """
    The group this target belongs to.

    Note:
        For a `DragTarget` to accept an incoming drop from a [`Draggable`][flet.Draggable],
        they must both be in the same `group`.
    """

    on_will_accept: Optional[EventHandler[DragWillAcceptEvent]] = None
    """
    Called when a draggable is dragged on this target.
    """

    on_accept: Optional[EventHandler[DragTargetEvent]] = None
    """
    Called when the user does drop an acceptable (same [`group`][flet.DragTarget.group]) draggable on
    this target.

    Use `page.get_control(e.src_id)` to retrieve Control reference by its ID.
    """

    on_leave: Optional[EventHandler[DragTargetLeaveEvent]] = None
    """
    Called when a draggable leaves this target.
    """

    on_move: Optional[EventHandler[DragTargetEvent]] = None
    """
    Called when a draggable moves within this target.
    """

    def before_update(self):
        super().before_update()
        assert self.content.visible, "content must be visible"