from typing import TYPE_CHECKING
from typing import Any
from typing import Optional

from poetry.mixology.term import Term


if TYPE_CHECKING:
    from poetry.core.packages.dependency import Dependency
    from poetry.core.packages.package import Package
    from poetry.mixology.incompatibility import Incompatibility


class Assignment(Term):
    """
    A term in a PartialSolution that tracks some additional metadata.
    """

    def __init__(
        self,
        dependency: "Dependency",
        is_positive: bool,
        decision_level: int,
        index: int,
        cause: Optional["Incompatibility"] = None,
    ) -> None:
        super().__init__(dependency, is_positive)

        self._decision_level = decision_level
        self._index = index
        self._cause = cause

    @property
    def decision_level(self) -> int:
        return self._decision_level

    @property
    def index(self) -> int:
        return self._index

    @property
    def cause(self) -> "Incompatibility":
        return self._cause

    @classmethod
    def decision(
        cls, package: "Package", decision_level: int, index: int
    ) -> "Assignment":
        return cls(package.to_dependency(), True, decision_level, index)

    @classmethod
    def derivation(
        cls,
        dependency: Any,
        is_positive: bool,
        cause: "Incompatibility",
        decision_level: int,
        index: int,
    ) -> "Assignment":
        return cls(dependency, is_positive, decision_level, index, cause)

    def is_decision(self) -> bool:
        return self._cause is None
