"""Requirement evaluation shared by patrons, objectives, outposts, and AI."""

from __future__ import annotations

from .models import Requirement, RequirementKind


def requirements_met(requirements: list[Requirement], bonuses: dict[str, int]) -> bool:
    """Return whether one assignment satisfies all fixed and wildcard clauses."""
    chosen: dict[str, str] = {}

    def visit(index: int) -> bool:
        if index == len(requirements):
            return True
        requirement = requirements[index]
        if requirement.kind == RequirementKind.COLOR:
            if bonuses.get(requirement.resource or "", 0) < requirement.count:
                return False
            chosen[requirement.id] = requirement.resource or ""
            return visit(index + 1)

        forbidden = set(requirement.exclude)
        forbidden.update(chosen[item] for item in requirement.distinct_from if item in chosen)
        for resource, amount in bonuses.items():
            if resource in forbidden or amount < requirement.count:
                continue
            chosen[requirement.id] = resource
            if visit(index + 1):
                return True
            chosen.pop(requirement.id, None)
        return False

    fixed = [item for item in requirements if item.kind == RequirementKind.COLOR]
    flexible = [item for item in requirements if item.kind == RequirementKind.ANY_COLOR]
    return visit_ordered([*fixed, *flexible], bonuses, chosen)


def visit_ordered(requirements: list[Requirement], bonuses: dict[str, int], chosen: dict[str, str]) -> bool:
    """Backtracking evaluator kept separate for straightforward unit testing."""
    if not requirements:
        return True
    requirement, *rest = requirements
    if requirement.kind == RequirementKind.COLOR:
        resource = requirement.resource or ""
        if bonuses.get(resource, 0) < requirement.count:
            return False
        chosen[requirement.id] = resource
        return visit_ordered(rest, bonuses, chosen)
    forbidden = set(requirement.exclude)
    forbidden.update(chosen[item] for item in requirement.distinct_from if item in chosen)
    for resource, amount in bonuses.items():
        if resource in forbidden or amount < requirement.count:
            continue
        chosen[requirement.id] = resource
        if visit_ordered(rest, bonuses, chosen):
            return True
        chosen.pop(requirement.id, None)
    return False