"""Lifecycle transition chains for kernel event ingress v0.2."""

from __future__ import annotations

from typing import Any, Literal

from steering.lifecycle.slot_maps import SlotStatus

EventKind = Literal[
    "actor_result",
    "gate_verified",
    "gate_reopened",
    "external_event",
    "cadence_due",
    "situational",
]


def _slot_accepts_event(status: SlotStatus, *, event_targets_slot: bool) -> bool:
    if status == "active":
        return True
    if status == "optional" and event_targets_slot:
        return True
    return False


def resolve_lifecycle_chain(
    *,
    primary_method_key: str,
    event_kind: EventKind,
    payload: dict[str, Any] | None = None,
) -> tuple[str, ...]:
    """
    Ordered lifecycle slots to visit for an event (method-aware via slot_map).

    Returns slot keys; caller persists the last applicable state.
    """
    from steering.kernel.lifecycle import resolve_method_slot_map

    payload = payload or {}
    slot_map = resolve_method_slot_map(primary_method_key)

    if event_kind == "actor_result" and payload.get("to_status") == "done":
        candidates = ("result_intake", "adaptation", "action_selection")
        event_slot = "result_intake"
    elif event_kind == "gate_verified":
        candidates = ("validation", "adaptation", "action_selection")
        event_slot = "validation"
    elif event_kind == "gate_reopened":
        candidates = ("adaptation", "planning", "action_selection")
        event_slot = "adaptation"
    elif event_kind == "situational" and payload.get("reason") == "blocker_resolved":
        candidates = ("action_selection",)
        event_slot = "action_selection"
    else:
        return ()

    chain: list[str] = []
    for step in candidates:
        status = slot_map.get(step, "n/a")
        if _slot_accepts_event(
            status,  # type: ignore[arg-type]
            event_targets_slot=(step == event_slot or step in ("adaptation", "action_selection")),
        ):
            chain.append(step)
    return tuple(chain)