"""JARVIS quality of life utilities."""
from typing import Any, Callable, Iterable, List, Optional


class Singleton(object):
    REQUIRED = []
    OPTIONAL = {}

    def __new__(cls, *args: list, **kwargs: dict):
        """Create a new singleton."""
        inst = cls.__dict__.get("inst")
        if inst is not None:
            return inst

        inst = object.__new__(cls)
        inst.init(*args, **kwargs)
        inst._validate()
        cls.__inst__ = inst

        return inst

    def _validate(self) -> None:
        for key in self.REQUIRED:
            if not getattr(self, key, None):
                raise ValueError(f"Missing required key: {key}")

    def init(self, **kwargs: dict) -> None:
        """Initialize the object."""
        for key, value in kwargs.items():
            setattr(self, key, value)

        for key, value in self.OPTIONAL.items():
            if not getattr(self, key, None):
                setattr(self, key, value)


def find(predicate: Callable, sequence: Iterable) -> Optional[Any]:
    """
    Find the first element in a sequence that matches the predicate.

    ??? Hint "Example Usage:"
        ```python
        member = find(lambda m: m.name == "UserName", guild.members)
        ```
    Args:
        predicate: A callable that returns a boolean value
        sequence: A sequence to be searched

    Returns:
        A match if found, otherwise None

    """
    for el in sequence:
        if predicate(el):
            return el
    return None


def find_all(predicate: Callable, sequence: Iterable) -> List[Any]:
    """
    Find all elements in a sequence that match the predicate.

    ??? Hint "Example Usage:"
        ```python
        members = find_all(lambda m: m.name == "UserName", guild.members)
        ```
    Args:
        predicate: A callable that returns a boolean value
        sequence: A sequence to be searched

    Returns:
        A list of matches

    """
    return [el for el in sequence if predicate(el)]


def get(sequence: Iterable, **kwargs: Any) -> Optional[Any]:
    """
    Find the first element in a sequence that matches all attrs.

    ??? Hint "Example Usage:"
        ```python
        channel = get(guild.channels, nsfw=False, category="General")
        ```

    Args:
        sequence: A sequence to be searched
        kwargs: Keyword arguments to search the sequence for

    Returns:
        A match if found, otherwise None
    """
    if not kwargs:
        return sequence[0]

    for el in sequence:
        if any(not hasattr(el, attr) for attr in kwargs.keys()):
            continue
        if all(getattr(el, attr) == value for attr, value in kwargs.items()):
            return el
    return None


def get_all(sequence: Iterable, **kwargs: Any) -> List[Any]:
    """
    Find all elements in a sequence that match all attrs.

    ??? Hint "Example Usage:"
        ```python
        channels = get_all(guild.channels, nsfw=False, category="General")
        ```

    Args:
        sequence: A sequence to be searched
        kwargs: Keyword arguments to search the sequence for

    Returns:
        A list of matches
    """
    if not kwargs:
        return sequence

    matches = []
    for el in sequence:
        if any(not hasattr(el, attr) for attr in kwargs.keys()):
            continue
        if all(getattr(el, attr) == value for attr, value in kwargs.items()):
            matches.append(el)
    return matches