import os
import sys
import pytest

# Ensure top-level package directory takes precedence over any on-src compatibility
ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), ".."))
if ROOT not in sys.path:
    sys.path.insert(0, ROOT)

from guardrail_space.contract import SafetyContract, Precondition, Budget
from guardrail_space.engine import evaluate_action


def test_precondition_veto():
    contract = SafetyContract(
        id="c1",
        preconditions=[Precondition(key="state.battery", op=">=", value=10)],
        budgets={"energy": Budget(name="energy", limit=100.0)},
    )

    state = {"battery": 5}
    action = {"name": "drive", "costs": {"energy": 5}, "speed": 1.0}

    verdict, payload = evaluate_action(contract, state, action)
    assert verdict == "veto"
    assert "precondition failed" in payload["reason"]


def test_budget_rewrite_to_safe_action():
    contract = SafetyContract(
        id="c2",
        preconditions=[Precondition(key="state.battery", op=">=", value=1)],
        budgets={"energy": Budget(name="energy", limit=2.0)},
    )

    state = {"battery": 50}
    action = {"name": "drive", "costs": {"energy": 4.0}, "speed": 2.0}

    verdict, payload = evaluate_action(contract, state, action)
    # With rewrite, engine should accept a scaled-down action
    assert verdict == "accept"
    assert payload["speed"] == pytest.approx(1.0)
    assert payload["costs"]["energy"] == pytest.approx(2.0)


def test_accept_action_and_charge_budget():
    contract = SafetyContract(
        id="c3",
        preconditions=[Precondition(key="state.battery", op=">=", value=1)],
        budgets={"energy": Budget(name="energy", limit=10.0)},
    )

    state = {"battery": 50}
    action = {"name": "drive", "costs": {"energy": 3.0}, "speed": 1.0}

    verdict, payload = evaluate_action(contract, state, action)
    assert verdict == "accept"
    assert contract.budgets["energy"].used == pytest.approx(3.0)