Evented Containers#

class EventedDict(TypedMutableMapping[_K, _V]):
    """Mutable mapping that emits events when altered.

    This class is designed to behave exactly like the builtin [`dict`][], but
    will emit events before and after all mutations (addition, removal, and
    changing).

    Parameters
    ----------
    data : Union[Mapping[_K, _V], Iterable[Tuple[_K, _V]], None], optional
        Data suitable of passing to dict(). Mapping of {key: value} pairs, or
        Iterable of two-tuples [(key, value), ...], or None to create an
    basetype : TypeOrSequenceOfTypes, optional
        Type or Sequence of Type objects. If provided, values entered into this Mapping
        must be an instance of one of the provided types. by default ().

    Attributes
    ----------
    events: DictEvents
        The `SignalGroup` object that emits all events available on an `EventedDict`.
    """

    events: DictEvents  # pragma: no cover

    def __init__(
        self,
        data: DictArg | None = None,
        *,
        basetype: TypeOrSequenceOfTypes = (),
        **kwargs: _V,
    ):
        self.events = DictEvents()
        super().__init__(data, basetype=basetype, **kwargs)

    def __setitem__(self, key: _K, value: _V) -> None:
        if key not in self._dict:
            self.events.adding.emit(key)
            super().__setitem__(key, value)
            self.events.added.emit(key, value)
        else:
            old_value = self._dict[key]
            if value is not old_value:
                self.events.changing.emit(key)
                super().__setitem__(key, value)
                self.events.changed.emit(key, old_value, value)

    def __delitem__(self, key: _K) -> None:
        item = self._dict[key]
        self.events.removing.emit(key)
        super().__delitem__(key)
        self.events.removed.emit(key, item)

    def __repr__(self) -> str:
        return f"{self.__class__.__name__}({super().__repr__()})"

class EventedList(MutableSequence[_T]):
    """Mutable Sequence that emits events when altered.

    This class is designed to behave exactly like the builtin `list`, but
    will emit events before and after all mutations (insertion, removal,
    setting, and moving).

    Parameters
    ----------
    data : iterable, optional
        Elements to initialize the list with.
    hashable : bool
        Whether the list should be hashable as id(self). By default `True`.
    child_events: bool
        Whether to re-emit events from emitted from evented items in the list
        (i.e. items that have SignalInstances). If `True`, child events can be connected
        at `EventedList.events.child_event`. By default, `False`.

    Attributes
    ----------
    events : ListEvents
        SignalGroup that with events related to list mutation.  (see ListEvents)
    """

    events: ListEvents  # pragma: no cover

    def __init__(
        self,
        data: Iterable[_T] = (),
        *,
        hashable: bool = True,
        child_events: bool = False,
    ):
        super().__init__()
        self._data: list[_T] = []
        self._hashable = hashable
        self._child_events = child_events
        self.events = ListEvents()
        self.extend(data)

    # WAIT!! ... Read the module docstring before reimplement these methods
    # def append(self, item): ...
    # def clear(self): ...
    # def pop(self, index=-1): ...
    # def extend(self, value: Iterable[_T]): ...
    # def remove(self, value: Any): ...

    def insert(self, index: int, value: _T) -> None:
        """Insert `value` before index."""
        _value = self._pre_insert(value)
        self.events.inserting.emit(index)
        self._data.insert(index, _value)
        self.events.inserted.emit(index, value)
        self._post_insert(value)

    @overload
    def __getitem__(self, key: int) -> _T: ...

    @overload
    def __getitem__(self, key: slice) -> Self: ...

    def __getitem__(self, key: Index) -> _T | Self:
        """Return self[key]."""
        result = self._data[key]
        return self.__newlike__(result) if isinstance(result, list) else result

    @overload
    def __setitem__(self, key: int, value: _T) -> None: ...

    @overload
    def __setitem__(self, key: slice, value: Iterable[_T]) -> None: ...

    def __setitem__(self, key: Index, value: _T | Iterable[_T]) -> None:
        """Set self[key] to value."""
        old = self._data[key]
        if value is old:
            return

        # sourcery skip: hoist-similar-statement-from-if, hoist-statement-from-if
        if isinstance(key, slice):
            if not isinstance(value, Iterable):
                raise TypeError("Can only assign an iterable to slice")
            value = [self._pre_insert(v) for v in value]  # before we mutate the list
            self._data[key] = value
        else:
            value = self._pre_insert(cast("_T", value))
            self._data[key] = value

        self.events.changed.emit(key, old, value)

    def __delitem__(self, key: Index) -> None:
        """Delete self[key]."""
        # delete from the end
        for parent, index in sorted(self._delitem_indices(key), reverse=True):
            parent.events.removing.emit(index)
            parent._pre_remove(index)
            item = parent._data.pop(index)
            self.events.removed.emit(index, item)

    def _delitem_indices(self, key: Index) -> Iterable[tuple[EventedList[_T], int]]:
        # returning (self, int) allows subclasses to pass nested members
        if isinstance(key, int):
            yield (self, key if key >= 0 else key + len(self))
        elif isinstance(key, slice):
            yield from ((self, i) for i in range(*key.indices(len(self))))
        else:
            n = repr(type(key).__name__)
            raise TypeError(f"EventedList indices must be integers or slices, not {n}")

    def _pre_insert(self, value: _T) -> _T:
        """Validate and or modify values prior to inserted."""
        return value

    def _post_insert(self, new_item: _T) -> None:
        """Modify and or handle values after insertion."""
        if self._child_events:
            self._connect_child_emitters(new_item)

    def _pre_remove(self, index: int) -> None:
        """Modify and or handle values before removal."""
        if self._child_events:
            self._disconnect_child_emitters(self[index])

    def __newlike__(self, iterable: Iterable[_T]) -> Self:
        """Return new instance of same class."""
        return self.__class__(iterable)

    def copy(self) -> Self:
        """Return a shallow copy of the list."""
        return self.__newlike__(self)

    def __copy__(self) -> Self:
        return self.copy()

    def __add__(self, other: Iterable[_T]) -> Self:
        """Add other to self, return new object."""
        copy = self.copy()
        copy.extend(other)
        return copy

    def __iadd__(self, other: Iterable[_T]) -> Self:
        """Add other to self in place (self += other)."""
        self.extend(other)
        return self

    def __radd__(self, other: list) -> list:
        """Reflected add (other + self).  Cast self to list."""
        return other + list(self)

    def __len__(self) -> int:
        """Return len(self)."""
        return len(self._data)

    def __repr__(self) -> str:
        """Return repr(self)."""
        return f"{type(self).__name__}({self._data})"

    def __eq__(self, other: Any) -> bool:
        """Return self==value."""
        return bool(self._data == other)

    def __hash__(self) -> int:
        """Return hash(self)."""
        # it's important to add this to allow this object to be hashable
        # given that we've also reimplemented __eq__
        if self._hashable:
            return id(self)
        name = self.__class__.__name__
        raise TypeError(
            f"unhashable type: {name!r}. "
            f"Create with {name}(..., hashable=True) if you need hashability"
        )

    def reverse(self, *, emit_individual_events: bool = False) -> None:
        """Reverse list *IN PLACE*."""
        if emit_individual_events:
            super().reverse()
        else:
            self._data.reverse()
        self.events.reordered.emit()

    def move(self, src_index: int, dest_index: int = 0) -> bool:
        """Insert object at `src_index` before `dest_index`.

        Both indices refer to the list prior to any object removal
        (pre-move space).
        """
        if dest_index < 0:
            dest_index += len(self) + 1
        if dest_index in (src_index, src_index + 1):
            # this is a no-op
            return False

        self.events.moving.emit(src_index, dest_index)
        item = self._data.pop(src_index)
        if dest_index > src_index:
            dest_index -= 1
        self._data.insert(dest_index, item)
        self.events.moved.emit(src_index, dest_index, item)
        self.events.reordered.emit()
        return True

    def move_multiple(self, sources: Iterable[Index], dest_index: int = 0) -> int:
        """Move a batch of `sources` indices, to a single destination.

        Note, if `dest_index` is higher than any of the `sources`, then
        the resulting position of the moved objects after the move operation
        is complete will be lower than `dest_index`.

        Parameters
        ----------
        sources : Iterable[Union[int, slice]]
            A sequence of indices
        dest_index : int, optional
            The destination index.  All sources will be inserted before this
            index (in pre-move space), by default 0... which has the effect of
            "bringing to front" everything in `sources`, or acting as a
            "reorder" method if `sources` contains all indices.

        Returns
        -------
        int
            The number of successful move operations completed.

        Raises
        ------
        TypeError
            If the destination index is a slice, or any of the source indices
            are not `int` or `slice`.
        """
        # calling list here makes sure that there are no index errors up front
        move_plan = list(self._move_plan(sources, dest_index))

        # don't assume index adjacency ... so move objects one at a time
        # this *could* be simplified with an intermediate list ... but this way
        # allows any views (such as QtViews) to update themselves more easily.
        # If this needs to be changed in the future for performance reasons,
        # then the associated QtListView will need to changed from using
        # `beginMoveRows` & `endMoveRows` to using `layoutAboutToBeChanged` &
        # `layoutChanged` while *manually* updating model indices with
        # `changePersistentIndexList`.  That becomes much harder to do with
        # nested tree-like models.
        with self.events.reordered.blocked():
            for src, dest in move_plan:
                self.move(src, dest)

        self.events.reordered.emit()
        return len(move_plan)

    def _move_plan(
        self, sources: Iterable[Index], dest_index: int
    ) -> Iterable[tuple[int, int]]:
        """Yield prepared indices for a multi-move.

        Given a set of `sources` from anywhere in the list,
        and a single `dest_index`, this function computes and yields
        `(from_index, to_index)` tuples that can be used sequentially in
        single move operations.  It keeps track of what has moved where and
        updates the source and destination indices to reflect the model at each
        point in the process.

        This is useful for a drag-drop operation with a QtModel/View.

        Parameters
        ----------
        sources : Iterable[tuple[int, ...]]
            An iterable of tuple[int] that should be moved to `dest_index`.
        dest_index : Tuple[int]
            The destination for sources.
        """
        if isinstance(dest_index, slice):
            raise TypeError("Destination index may not be a slice")  # pragma: no cover

        to_move: list[int] = []
        for idx in sources:
            if isinstance(idx, slice):
                to_move.extend(list(range(*idx.indices(len(self)))))
            elif isinstance(idx, int):
                to_move.append(idx)
            else:
                raise TypeError(
                    "Can only move integer or slice indices"
                )  # pragma: no cover

        to_move = list(dict.fromkeys(to_move))

        if dest_index < 0:
            dest_index += len(self) + 1

        d_inc = 0
        popped: list[int] = []
        for i, src in enumerate(to_move):
            if src != dest_index:
                # we need to decrement the src_i by 1 for each time we have
                # previously pulled items out from in front of the src_i
                src -= sum(x <= src for x in popped)
                # if source is past the insertion point, increment src for each
                # previous insertion
                if src >= dest_index:
                    src += i
                yield src, dest_index + d_inc

            popped.append(src)
            # if the item moved up, increment the destination index
            if dest_index <= src:
                d_inc += 1

    def _connect_child_emitters(self, child: _T) -> None:
        """Connect all events from the child to be reemitted."""
        for emitter in iter_signal_instances(child):
            emitter.connect(self._reemit_child_event)

    def _disconnect_child_emitters(self, child: _T) -> None:
        """Disconnect all events from the child from the reemitter."""
        for emitter in iter_signal_instances(child):
            emitter.disconnect(self._reemit_child_event)

    def _reemit_child_event(self, *args: Any) -> None:
        """Re-emit event from child with index."""
        emitter = Signal.current_emitter()
        if emitter is None:
            return  # pragma: no cover
        obj = emitter.instance
        try:
            idx = self.index(obj)
        except ValueError:  # pragma: no cover
            return

        if (
            args
            and isinstance(emitter, SignalRelay)
            and isinstance(args[0], EmissionInfo)
        ):
            emitter, args = args[0]

        self.events.child_event.emit(idx, obj, emitter, args)

    # PYDANTIC SUPPORT

    @classmethod
    def __get_pydantic_core_schema__(
        cls, source_type: Any, handler: Callable
    ) -> Mapping[str, Any]:
        """Return the Pydantic core schema for this object."""
        from pydantic_core import core_schema

        args = get_args(source_type)
        return core_schema.no_info_after_validator_function(
            function=cls,
            schema=core_schema.list_schema(
                items_schema=handler(args[0]) if args else None,
            ),
        )

class EventedSet(_BaseMutableSet[_T]):
    """A set with an `items_changed` signal that emits when items are added/removed.

    Parameters
    ----------
    iterable : Iterable[_T]
        Data to populate the set.  If omitted, an empty set is created.

    Attributes
    ----------
    events : SetEvents
        SignalGroup that with events related to set mutation.  (see SetEvents)

    Examples
    --------
    >>> from psygnal.containers import EventedSet
    >>>
    >>> my_set = EventedSet([1, 2, 3])
    >>> my_set.events.items_changed.connect(
    >>>     lambda a, r: print(f"added={a}, removed={r}")
    >>> )
    >>> my_set.update({3, 4, 5})
    added=(4, 5), removed=()

    Multi-item events will be reduced into a single emission:
    >>> my_set.symmetric_difference_update({4, 5, 6, 7})
    added=(6, 7), removed=(4, 5)

    >>> my_set
    EventedSet({1, 2, 3, 6, 7})
    """

    events: SetEvents  # pragma: no cover

    def __init__(self, iterable: Iterable[_T] = ()):
        self.events = self._get_events_class()
        super().__init__(iterable)

    def update(self, *others: Iterable[_T]) -> None:
        """Update this set with the union of this set and others."""
        with self.events.items_changed.paused(_reduce_events):
            super().update(*others)

    def clear(self) -> None:
        """Remove all elements from this set."""
        with self.events.items_changed.paused(_reduce_events):
            super().clear()

    def difference_update(self, *s: Iterable[_T]) -> None:
        """Remove all elements of another set from this set."""
        with self.events.items_changed.paused(_reduce_events):
            super().difference_update(*s)

    def intersection_update(self, *s: Iterable[_T]) -> None:
        """Update this set with the intersection of itself and another."""
        with self.events.items_changed.paused(_reduce_events):
            super().intersection_update(*s)

    def symmetric_difference_update(self, __s: Iterable[_T]) -> None:
        """Update this set with the symmetric difference of itself and another.

        This will remove any items in this set that are also in `other`, and
        add any items in others that are not present in this set.
        """
        with self.events.items_changed.paused(_reduce_events, ((), ())):
            super().symmetric_difference_update(__s)

    def _pre_add_hook(self, item: _T) -> _T | BailType:
        return BAIL if item in self else item

    def _post_add_hook(self, item: _T) -> None:
        self._emit_change((item,), ())

    def _pre_discard_hook(self, item: _T) -> _T | BailType:
        return BAIL if item not in self else item

    def _post_discard_hook(self, item: _T) -> None:
        self._emit_change((), (item,))

    def _pre_clear_hook(self) -> tuple[_T, ...] | BailType:
        return BAIL if len(self) == 0 else tuple(self)

    def _post_clear_hook(self, item: tuple[_T, ...]) -> None:
        self._emit_change((), item)

    def _emit_change(self, added: tuple[_T, ...], removed: tuple[_T, ...]) -> None:
        """Emit a change event."""
        self.events.items_changed.emit(added, removed)

    def _get_events_class(self) -> SetEvents:
        return SetEvents()

class EventedOrderedSet(EventedSet, OrderedSet[_T]):
    """A ordered variant of EventedSet that maintains insertion order.

    Parameters
    ----------
    iterable : Iterable[_T]
        Data to populate the set.  If omitted, an empty set is created.

    Attributes
    ----------
    events : SetEvents
        SignalGroup that with events related to set mutation.  (see SetEvents)
    """

    # reproducing init here to avoid a mkdocs warning:
    # "Parameter 'iterable' does not appear in the function signature"
    def __init__(self, iterable: Iterable[_T] = ()):
        super().__init__(iterable)

class Selection(EventedOrderedSet[_T]):
    """An model of selected items, with a `active` and `current` item.

    There can only be one `active` and one `current` item, but there can be
    multiple selected items.  An "active" item is defined as a single selected
    item (if multiple items are selected, there is no active item).  The
    "current" item is mostly useful for (e.g.) keyboard actions: even with
    multiple items selected, you may only have one current item, and keyboard
    events (like up and down) can modify that current item.  It's possible to
    have a current item without an active item, but an active item will always
    be the current item.

    An item can be the current item and selected at the same time. Qt views
    will ensure that there is always a current item as keyboard navigation,
    for example, requires a current item.
    This pattern mimics current/selected items from Qt:
    https://doc.qt.io/qt-5/model-view-programming.html#current-item-and-selected-items

    Parameters
    ----------
    data : iterable, optional
        Elements to initialize the set with.
    parent : Container, optional
        The parent container, if any. This is used to provide validation upon
        mutation in common use cases.

    Attributes
    ----------
    events : SelectionEvents
        SignalGroup that with events related to selection changes. (see SelectionEvents)
    active : Any, optional
        The active item, if any. An "active" item is defined as a single selected
        item (if multiple items are selected, there is no active item)
    _current : Any, optional
        The current item, if any. This is used primarily by GUI views when
        handling mouse/key events.
    """

    events: SelectionEvents  # pragma: no cover

    def __init__(self, data: Iterable[_T] = (), parent: Container | None = None):
        self._active: _T | None = None
        self._current_: _T | None = None
        self._parent: Container | None = parent
        super().__init__(iterable=data)
        self._update_active()

    @property
    def _current(self) -> _T | None:  # pragma: no cover
        """Get current item."""
        return self._current_

    @_current.setter
    def _current(self, value: _T | None) -> None:  # pragma: no cover
        """Set current item."""
        if value == self._current_:
            return
        self._current_ = value
        self.events._current.emit(value)

    @property
    def active(self) -> _T | None:  # pragma: no cover
        """Return the currently active item or None."""
        return self._active

    @active.setter
    def active(self, value: _T | None) -> None:  # pragma: no cover
        """Set the active item.

        This makes `value` the only selected item, and makes it current.
        """
        if value == self._active:
            return
        self._active = value
        self.clear() if value is None else self.select_only(value)
        self._current = value
        self.events.active.emit(value)

    def clear(self, keep_current: bool = False) -> None:
        """Clear the selection.

        Parameters
        ----------
        keep_current : bool
            If `False` (the default), the "current" item will also be set to None.
        """
        if not keep_current:
            self._current = None
        super().clear()

    def toggle(self, obj: _T) -> None:
        """Toggle selection state of obj."""
        self.symmetric_difference_update({obj})

    def select_only(self, obj: _T) -> None:
        """Unselect everything but `obj`. Add to selection if not currently selected."""
        self.intersection_update({obj})
        self.add(obj)

    def _update_active(self) -> None:
        """On a selection event, update the active item based on selection.

        An active item is a single selected item.
        """
        if len(self) == 1:
            self.active = next(iter(self))
        elif self._active is not None:
            self._active = None
            self.events.active.emit(None)

    def _get_events_class(self) -> SelectionEvents:
        """Override SetEvents with SelectionEvents."""
        return SelectionEvents()

    def _emit_change(self, added: tuple[_T, ...], removed: tuple[_T, ...]) -> None:
        """Emit a change event."""
        super()._emit_change(added, removed)
        self._update_active()

    def _pre_add_hook(self, item: _T) -> _T | BailType:
        if self._parent is not None and item not in self._parent:
            raise ValueError(
                "Cannot select an item that is not in the parent container."
            )
        return super()._pre_add_hook(item)

    def __hash__(self) -> int:
        """Make selection hashable."""
        return id(self)

class SelectableEventedList(Selectable[_T], EventedList[_T]):
    """`EventedList` subclass with a built in selection model.

    In addition to all `EventedList` properties, this class also has a `selection`
    attribute that manages a set of selected items in the list.

    Parameters
    ----------
    data : iterable, optional
        Elements to initialize the list with.
    hashable : bool
        Whether the list should be hashable as id(self). By default `True`.
    child_events: bool
        Whether to re-emit events from emitted from evented items in the list
        (i.e. items that have SignalInstances). If `True`, child events can be connected
        at `EventedList.events.child_event`. By default, `False`.

    Attributes
    ----------
    events : ListEvents
        SignalGroup that with events related to list mutation.  (see ListEvents)
    selection : Selection
        An evented set containing the currently selected items, along with an `active`
        and `current` item.  (See `Selection`)
    """

    events: ListEvents  # pragma: no cover

    def __init__(
        self,
        data: Iterable[_T] = (),
        *,
        hashable: bool = True,
        child_events: bool = False,
    ):
        self._activate_on_insert: bool = True
        super().__init__(data=data, hashable=hashable, child_events=child_events)
        self.events.removed.connect(self._on_item_removed)

    def _on_item_removed(self, idx: int, obj: Any) -> None:
        self.selection.discard(obj)

    def insert(self, index: int, value: _T) -> None:
        """Insert item(s) into the list and update the selection."""
        super().insert(index, value)
        if self._activate_on_insert:
            self.selection.active = value

    def select_all(self) -> None:
        """Select all items in the list."""
        self.selection.update(self)

    def deselect_all(self) -> None:
        """Deselect all items in the list."""
        self.selection.clear()

    def select_next(
        self, step: int = 1, expand_selection: bool = False, wraparound: bool = False
    ) -> None:
        """Select the next item in the list.

        Parameters
        ----------
        step : int
            The step size to take when picking the next item, by default 1
        expand_selection : bool
            If True, will expand the selection to contain the both the current item and
            the next item, by default False
        wraparound : bool
            Whether to return to the beginning of the list of the end has been reached,
            by default False
        """
        if len(self) == 0:
            return
        elif not self.selection:
            idx = -1 if step > 0 else 0
        else:
            idx = self.index(self.selection._current) + step
        idx_in_sequence = len(self) > idx >= 0
        if wraparound:
            idx = idx % len(self)
        elif not idx_in_sequence:
            idx = -1 if step > 0 else 0
        next_item = self[idx]
        if expand_selection:
            self.selection.add(next_item)
            self.selection._current = next_item
        else:
            self.selection.active = next_item

    def select_previous(
        self, expand_selection: bool = False, wraparound: bool = False
    ) -> None:
        """Select the previous item in the list."""
        self.select_next(
            step=-1, expand_selection=expand_selection, wraparound=wraparound
        )

    def remove_selected(self) -> tuple[_T, ...]:
        """Remove selected items from the list and the selection.

        Returns
        -------
        Tuple[_T, ...]
            The items that were removed.
        """
        selected_items = tuple(self.selection)
        idx = 0
        for item in list(self.selection):
            idx = self.index(item)
            self.remove(item)
        new_idx = max(0, idx - 1)
        if len(self) > new_idx:
            self.selection.add(self[new_idx])
        return selected_items