from __future__ import annotations

import unittest

from govoplan_core.core.policy import (
    CAPABILITY_POLICY_IMPACT_SUBJECT_PREFIX,
    PolicyImpactPopulationRequest,
    PolicyImpactSubject,
    PolicyImpactSubjectBatch,
    PolicyImpactSubjectProvider,
    policy_impact_subject_provider,
)


class _Provider:
    provider_id = "example"
    supported_policy_families = ("view",)

    def collect_policy_impact_subjects(
        self,
        session: object | None = None,
        *,
        request: PolicyImpactPopulationRequest,
    ) -> PolicyImpactSubjectBatch:
        del session, request
        return PolicyImpactSubjectBatch(
            provider_id=self.provider_id,
            subjects=(
                PolicyImpactSubject(
                    module_id="example",
                    resource_type="record",
                    resource_id="record-1",
                    action="view",
                ),
            ),
            total_available=1,
        )


class _Registry:
    def __init__(self, capability: object) -> None:
        self._capability = capability

    def has_capability(self, name: str) -> bool:
        return name == f"{CAPABILITY_POLICY_IMPACT_SUBJECT_PREFIX}example"

    def capability(self, name: str) -> object:
        del name
        return self._capability


class PolicyImpactContractTests(unittest.TestCase):
    def test_provider_contract_is_runtime_checkable_and_discoverable(self) -> None:
        provider = _Provider()
        self.assertIsInstance(provider, PolicyImpactSubjectProvider)
        self.assertIs(
            policy_impact_subject_provider(_Registry(provider), "example"),
            provider,
        )

    def test_population_and_provider_batches_are_bounded(self) -> None:
        with self.assertRaisesRegex(ValueError, "between 1 and 500"):
            PolicyImpactPopulationRequest(
                tenant_id="tenant-1",
                policy_family="view",
                limit=501,
            )
        with self.assertRaisesRegex(ValueError, "at most 500"):
            PolicyImpactSubjectBatch(
                provider_id="example",
                subjects=tuple(
                    PolicyImpactSubject(
                        module_id="example",
                        resource_type="record",
                        resource_id=str(index),
                        action="view",
                    )
                    for index in range(501)
                ),
            )

    def test_unavailable_batches_explain_the_gap(self) -> None:
        with self.assertRaisesRegex(ValueError, "need an explanation"):
            PolicyImpactSubjectBatch(
                provider_id="example",
                state="unavailable",
            )


if __name__ == "__main__":
    unittest.main()