"""Job/item state-machine rules: only declared transitions are legal, and terminal
states are truly terminal (no duplicate terminal transition)."""

import pytest

from photo_pipeline.services.jobs import (
    ALLOWED_TRANSITIONS,
    ITEM_TRANSITIONS,
    TERMINAL_STATES,
    ItemState,
    JobState,
    can_transition,
)


def test_happy_path_transitions_are_allowed():
    assert can_transition(JobState.QUEUED, JobState.RUNNING)
    assert can_transition(JobState.RUNNING, JobState.SUCCEEDED)
    assert can_transition(JobState.RUNNING, JobState.FAILED)
    assert can_transition(JobState.FAILED, JobState.RETRY_QUEUED)
    assert can_transition(JobState.RETRY_QUEUED, JobState.RUNNING)
    assert can_transition(JobState.RUNNING, JobState.CANCELLING)
    assert can_transition(JobState.CANCELLING, JobState.CANCELLED)


@pytest.mark.parametrize(
    "current,target",
    [
        (JobState.QUEUED, JobState.SUCCEEDED),  # can't skip running
        (JobState.SUCCEEDED, JobState.RUNNING),  # terminal, no revive
        (JobState.CANCELLED, JobState.RUNNING),  # terminal
        (JobState.RUNNING, JobState.QUEUED),  # no backward
    ],
)
def test_invalid_transitions_are_rejected(current, target):
    assert not can_transition(current, target)


def test_terminal_states_have_no_outgoing_transition():
    for state in TERMINAL_STATES:
        assert ALLOWED_TRANSITIONS[state] == set()


def test_duplicate_terminal_transition_is_rejected():
    assert not can_transition(JobState.SUCCEEDED, JobState.SUCCEEDED)
    assert not can_transition(JobState.CANCELLED, JobState.CANCELLED)


def test_item_states_are_consistent():
    assert ItemState.SUCCEEDED in ITEM_TRANSITIONS[ItemState.RUNNING]
    assert ITEM_TRANSITIONS[ItemState.SUCCEEDED] == set()  # terminal item