from __future__ import annotations

import unittest

from govoplan_policy.backend.hierarchy import (
    PolicyRestrictionRule,
    simulate_hierarchical_policy_change,
    validate_hierarchical_policy_patch,
)


class PolicyHierarchyTests(unittest.TestCase):
    def test_parent_locks_block_lower_level_field_changes_and_limit_reenable(self) -> None:
        issues = validate_hierarchical_policy_patch(
            parent_policy={"retention_days": 30},
            patch={"retention_days": 20, "allow_lower_level_limits": {"retention_days": True}},
            field_keys=("retention_days",),
            parent_allow_lower_level_limits={"retention_days": False},
        )

        self.assertEqual(["field_locked_by_parent", "lower_level_limit_locked_by_parent"], [issue.code for issue in issues])
        self.assertEqual(["retention_days", "retention_days"], [issue.field for issue in issues])

    def test_restriction_rules_block_less_restrictive_patch(self) -> None:
        issues = validate_hierarchical_policy_patch(
            parent_policy={"retention_days": 30},
            patch={"retention_days": 45},
            field_keys=("retention_days",),
            parent_allow_lower_level_limits={"retention_days": True},
            restriction_rules=(
                PolicyRestrictionRule(
                    field="retention_days",
                    is_more_restrictive_or_equal=lambda parent, requested: int(requested) <= int(parent),
                    less_restrictive_message="retention_days cannot be widened",
                ),
            ),
        )

        self.assertEqual(1, len(issues))
        self.assertEqual("less_restrictive_than_parent", issues[0].code)
        self.assertEqual("retention_days cannot be widened", issues[0].message)

    def test_policy_simulation_returns_decision_payload(self) -> None:
        simulation = simulate_hierarchical_policy_change(
            parent_policy={"retention_days": 30},
            current_policy={"retention_days": 30},
            patch={"retention_days": 45},
            field_keys=("retention_days",),
            parent_allow_lower_level_limits={"retention_days": True},
            restriction_rules=(
                PolicyRestrictionRule(
                    field="retention_days",
                    is_more_restrictive_or_equal=lambda parent, requested: int(requested) <= int(parent),
                    less_restrictive_message="retention_days cannot be widened",
                ),
            ),
        )

        self.assertFalse(simulation.allowed)
        self.assertEqual(("retention_days",), simulation.changed_fields)
        self.assertIsNotNone(simulation.decision)
        self.assertEqual(("retention_days",), simulation.decision.requirements)
        self.assertEqual("Requested policy change is blocked by parent policy constraints.", simulation.decision.reason)


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