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"""Computation space definitions controlling logical basis selection."""

from enum import Enum


class ComputationSpace(str, Enum):
    """Enumeration of supported computational subspaces."""

    FOCK = "fock"
    UNBUNCHED = "unbunched"
    DUAL_RAIL = "dual_rail"

    @classmethod
    def default(cls, *, no_bunching: bool) -> "ComputationSpace":
        """Derive the default computation space from the legacy `no_bunching` flag."""
        return cls.UNBUNCHED if no_bunching else cls.FOCK

    @classmethod
    def coerce(cls, value: "ComputationSpace | str") -> "ComputationSpace":
        """Normalize user-provided values (enum instances or case-insensitive strings)."""
        if isinstance(value, cls):
            return value
        if isinstance(value, str):
            normalized = value.lower()
            for space in cls:
                if normalized == space.value:
                    return space
        supported = sorted(space.value for space in cls)
        raise ValueError(
            f"Invalid computation_space '{value}'. Supported values are {supported}."
        )
