"""State machine unit tests — verify exactly the allowed transition families.

Ported from trex-orbit (dcy-001 FR-3). Covers REQ-002 / REQ-003.
"""
from __future__ import annotations

import pytest

from trex_core.domain.slot.state import (
    ALLOWED_TRANSITIONS,
    SLOT_ADVISORY_LOCK_ID,
    SlotState,
    is_allowed_transition,
)


def test_slot_state_has_six_members():
    """6 states per dcy-001 5.3.5.1."""
    assert {s.value for s in SlotState} == {
        "idle",
        "pending_buy",
        "holding",
        "pending_sell",
        "closed",
        "error",
    }


def test_advisory_lock_id_is_stable_constant():
    """SLOT_ADVISORY_LOCK_ID must not change between releases (REQ-002 NFR-1)."""
    assert isinstance(SLOT_ADVISORY_LOCK_ID, int)
    assert SLOT_ADVISORY_LOCK_ID == 0x5107_4D31


@pytest.mark.parametrize(
    "from_state,to_state",
    [
        # 1-7. dcy-001 FR-2 base transitions
        (SlotState.IDLE, SlotState.PENDING_BUY),
        (SlotState.PENDING_BUY, SlotState.HOLDING),
        (SlotState.PENDING_BUY, SlotState.IDLE),
        (SlotState.HOLDING, SlotState.PENDING_SELL),
        (SlotState.PENDING_SELL, SlotState.CLOSED),
        (SlotState.PENDING_SELL, SlotState.HOLDING),
        (SlotState.CLOSED, SlotState.IDLE),
        # 8. * -> error
        (SlotState.IDLE, SlotState.ERROR),
        (SlotState.PENDING_BUY, SlotState.ERROR),
        (SlotState.HOLDING, SlotState.ERROR),
        (SlotState.PENDING_SELL, SlotState.ERROR),
        (SlotState.CLOSED, SlotState.ERROR),
        # operator manual resolve (REQ-004)
        (SlotState.ERROR, SlotState.IDLE),
        (SlotState.ERROR, SlotState.HOLDING),
    ],
)
def test_allowed_transition(from_state: SlotState, to_state: SlotState):
    assert is_allowed_transition(from_state, to_state)


@pytest.mark.parametrize(
    "from_state,to_state",
    [
        # explicitly disallowed: skipping intermediate states
        (SlotState.IDLE, SlotState.HOLDING),
        (SlotState.IDLE, SlotState.PENDING_SELL),
        (SlotState.IDLE, SlotState.CLOSED),
        (SlotState.HOLDING, SlotState.IDLE),
        (SlotState.HOLDING, SlotState.CLOSED),
        (SlotState.PENDING_BUY, SlotState.CLOSED),
        (SlotState.PENDING_BUY, SlotState.PENDING_SELL),
        (SlotState.PENDING_SELL, SlotState.IDLE),
        (SlotState.PENDING_SELL, SlotState.PENDING_BUY),
        (SlotState.CLOSED, SlotState.HOLDING),
        (SlotState.CLOSED, SlotState.PENDING_BUY),
        (SlotState.CLOSED, SlotState.PENDING_SELL),
        # error has restricted exits — only idle and holding allowed (REQ-004)
        (SlotState.ERROR, SlotState.PENDING_BUY),
        (SlotState.ERROR, SlotState.PENDING_SELL),
        (SlotState.ERROR, SlotState.CLOSED),
        (SlotState.ERROR, SlotState.ERROR),
    ],
)
def test_disallowed_transition(from_state: SlotState, to_state: SlotState):
    assert not is_allowed_transition(from_state, to_state)


def test_self_loops_are_not_allowed():
    """No state may transition to itself."""
    for s in SlotState:
        assert not is_allowed_transition(s, s)


def test_allowed_transitions_set_size():
    """7 base + 5 to-error + 2 operator-resolve = 14 transitions."""
    assert len(ALLOWED_TRANSITIONS) == 14