"""Unit tests for the instance state machine."""

import pytest

from svcforge_core.domain.states import LEGAL, IllegalTransition, InstanceState, transition


def test_requested_to_provisioning_is_legal() -> None:
    assert transition(InstanceState.REQUESTED, InstanceState.PROVISIONING) is InstanceState.PROVISIONING


def test_deleted_to_ready_raises() -> None:
    with pytest.raises(IllegalTransition):
        transition(InstanceState.DELETED, InstanceState.READY)


def test_failed_to_provisioning_is_legal_retry() -> None:
    assert transition(InstanceState.FAILED, InstanceState.PROVISIONING) is InstanceState.PROVISIONING


@pytest.mark.parametrize("state", list(InstanceState))
def test_every_state_has_a_legal_entry(state: InstanceState) -> None:
    """A new state with no LEGAL entry must fail the suite, not KeyError at runtime."""
    assert state in LEGAL
    assert isinstance(LEGAL[state], frozenset)


@pytest.mark.parametrize("state", list(InstanceState))
def test_every_legal_target_is_an_instance_state(state: InstanceState) -> None:
    for target in LEGAL[state]:
        assert isinstance(target, InstanceState)


def test_deleted_is_terminal_with_an_empty_frozenset() -> None:
    assert LEGAL[InstanceState.DELETED] == frozenset()


def test_strenum_compares_equal_to_its_value() -> None:
    # mypy calls this non-overlapping by declared type. That is exactly what is being
    # tested: StrEnum members ARE their values at runtime, which is why psycopg can
    # adapt them straight to text and model_validate round-trips them for free.
    assert (InstanceState.READY == "ready") is True  # type: ignore[comparison-overlap]