from __future__ import annotations

from collections.abc import Iterable, Mapping, Sequence
from typing import Any, Generic, TypeVar

from .base import Source

T = TypeVar("T")
UNDEFINED = object()

ListSourceT = TypeVar("ListSourceT", bound=Source)
"""
A type describing any object adhering to the same interface as
[ListSource][toga.sources.ListSource].
"""


def _find_item(
    candidates: Sequence[T],
    data: object,
    accessors: Sequence[str],
    start: T | None,
    error: str,
) -> T:
    """Find-by-value implementation helper; find an item matching `data` in
    `candidates`, starting with item `start`."""
    if start is not None:
        start_index = candidates.index(start) + 1
    else:
        start_index = 0

    for item in candidates[start_index:]:
        try:
            if isinstance(data, Mapping):
                found = all(
                    getattr(item, attr) == value for attr, value in data.items()
                )
            elif hasattr(data, "__iter__") and not isinstance(data, str):
                found = all(
                    getattr(item, attr) == value
                    for value, attr in zip(data, accessors, strict=False)
                )
            else:
                found = getattr(item, accessors[0]) == data

            if found:
                return item
        except AttributeError:
            # Attribute didn't exist, so it's not a match
            pass

    raise ValueError(error)


class Row(Generic[T]):
    def __init__(self, **data: T):
        """Create a new Row object.

        The keyword arguments specified in the constructor will be converted into
        attributes on the new Row object.

        When any public attributes of the Row are modified (i.e., any attribute whose
        name doesn't start with `_`), the source to which the row belongs will be
        notified.
        """
        self._source: Source | None = None
        for name, value in data.items():
            setattr(self, name, value)

    def __repr__(self) -> str:
        descriptor = " ".join(
            f"{attr}={getattr(self, attr)!r}"
            for attr in sorted(self.__dict__)
            if not attr.startswith("_")
        )
        return f"<Row {id(self):x} {descriptor if descriptor else '(no attributes)'}>"

    ######################################################################
    # Utility wrappers
    ######################################################################

    def __setattr__(self, attr: str, value: T) -> None:
        """Set an attribute on the Row object, notifying the source of the change.

        :param attr: The attribute to change.
        :param value: The new attribute value.
        """
        super().__setattr__(attr, value)
        if not attr.startswith("_"):
            if self._source is not None:
                self._source.notify("change", item=self)

    def __getattr__(self, attr: str) -> T:
        return super().__getattr__(attr)

    def __delattr__(self, attr: str) -> None:
        """Remove an attribute from the Row object, notifying the source of the change.

        :param attr: The attribute to change.
        """
        super().__delattr__(attr)
        if not attr.startswith("_"):
            if self._source is not None:
                self._source.notify("change", item=self)


class ListSource(Source):
    _data: list[Row]

    def __init__(self, accessors: Iterable[str], data: Iterable | None = None):
        """A data source to store an ordered list of multiple data values.

        :param accessors: A list of attribute names for accessing the value
            in each column of the row.
        :param data: The initial list of items in the source. Items are converted as
            shown [above][listsource-item].
        """
        super().__init__()
        if isinstance(accessors, str) or not hasattr(accessors, "__iter__"):
            raise ValueError("accessors should be a list of attribute names")

        # Copy the list of accessors
        self._accessors = list(accessors)
        if len(self._accessors) == 0:
            raise ValueError("ListSource must be provided a list of accessors")

        # Convert the data into row objects
        if data is not None:
            self._data = [self._create_row(value) for value in data]
        else:
            self._data = []

    ######################################################################
    # Methods required by the ListSource interface
    ######################################################################

    def __len__(self) -> int:
        """Returns the number of items in the list."""
        return len(self._data)

    def __getitem__(self, index: int | slice) -> Row:
        """Returns the item at position `index` of the list."""
        return self._data[index]

    def __delitem__(self, index: int) -> None:
        """Deletes the item at position `index` of the list."""
        row = self._data[index]
        del self._data[index]
        self.notify("remove", index=index, item=row)

    ######################################################################
    # Factory methods for new rows
    ######################################################################

    # This behavior is documented in list_source.rst.
    def _create_row(self, data: object) -> Row:
        if isinstance(data, Mapping):
            row = Row(**data)
        elif hasattr(data, "__iter__") and not isinstance(data, str):
            row = Row(**dict(zip(self._accessors, data, strict=False)))
        else:
            row = Row(**{self._accessors[0]: data})
        row._source = self
        return row

    ######################################################################
    # Utility methods to make ListSources more list-like
    ######################################################################

    def __setitem__(self, index: int, value: object) -> None:
        """Set the value of a specific item in the data source.

        :param index: The item to change
        :param value: The data for the updated item. This data will be converted
            into a Row object.
        """
        row = self._create_row(value)
        self._data[index] = row
        self.notify("insert", index=index, item=row)

    def clear(self) -> None:
        """Clear all data from the data source."""
        self._data = []
        self.notify("clear")

    def insert(self, index: int, data: object) -> Row:
        """Insert a row into the data source at a specific index.

        :param index: The index at which to insert the item.
        :param data: The data to insert into the ListSource. This data will be converted
            into a Row object.
        :returns: The newly constructed Row object.
        """
        row = self._create_row(data)
        self._data.insert(index, row)
        self.notify("insert", index=index, item=row)
        return row

    def append(self, data: object) -> Row:
        """Insert a row at the end of the data source.

        :param data: The data to append to the ListSource. This data will be converted
            into a Row object.
        :returns: The newly constructed Row object.
        """
        return self.insert(len(self), data)

    def remove(self, row: Row) -> None:
        """Remove a row from the data source.

        :param row: The row to remove from the data source.
        """
        del self[self._data.index(row)]

    def index(self, row: Row) -> int:
        """The index of a specific row in the data source.

        This search uses Row instances, and searches for an *instance* match.
        If two Row instances have the same values, only the Row that is the
        same Python instance will match. To search for values based on equality,
        use [`ListSource.find()`][toga.sources.ListSource.find].

        :param row: The row to find in the data source.
        :returns: The index of the row in the data source.
        :raises ValueError: If the row cannot be found in the data source.
        """
        return self._data.index(row)

    def find(
        self, data: object, start: Row | None = None, default: Any = UNDEFINED
    ) -> Row:
        """Find the first item in the data that matches all the provided
        attributes.

        This is a value based search, rather than an instance search. If two Row
        instances have the same values, the first instance that matches will be
        returned. To search for a second instance, provide the first found instance
        as the `start` argument. To search for a specific Row instance, use the
        [`ListSource.index()`][toga.sources.ListSource.index].

        :param data: The data to search for. Only the values specified in data will be
            used as matching criteria; if the row contains additional data attributes,
            they won't be considered as part of the match.
        :param start: The instance from which to start the search. Defaults to `None`,
            indicating that the first match should be returned.
        :param default: If provided, this value will be returned if no match is found.
        :return: The matching Row object if found, or the value of `default` if
            provided.
        :raises ValueError: If no match is found and `default` is not provided.
        """
        try:
            return _find_item(
                candidates=self._data,
                data=data,
                accessors=self._accessors,
                start=start,
                error=f"No row matching {data!r} in data",
            )
        except ValueError:
            if default is UNDEFINED:
                raise
            else:
                return default
