from __future__ import annotations

from backup_tool.execution import (
    ACTIVE_STATES,
    TERMINAL_STATES,
    TransitionError,
    transition,
)


def test_transitions_are_monotonic_and_terminal_states_cannot_change() -> None:
    assert transition("queued", "preparing") == "preparing"
    assert transition("preparing", "running") == "running"
    assert transition("running", "verifying") == "verifying"
    assert transition("verifying", "committed") == "committed"
    assert "committed" in TERMINAL_STATES
    assert "queued" in ACTIVE_STATES
    try:
        transition("committed", "cancelled")
    except TransitionError as error:
        assert error.code == "invalid_transition"
    else:
        raise AssertionError("terminal execution changed state")


def test_cancellation_is_cooperative() -> None:
    assert transition("running", "cancelling") == "cancelling"
    assert transition("cancelling", "cancelled") == "cancelled"