from __future__ import annotations

from typing import Callable

from app.core.contracts import RuntimeEvent
from app.events.event_store import SQLiteEventStore


Subscriber = Callable[[RuntimeEvent], None]


class EventBus:
    """Per-task ordered event publishing with durable storage."""

    def __init__(self, event_store: SQLiteEventStore) -> None:
        self._store = event_store
        self._subscribers: list[Subscriber] = []

    def next_sequence(self, task_id: str) -> int:
        return self._store.get_latest_sequence(task_id) + 1

    def publish(self, event: RuntimeEvent) -> RuntimeEvent:
        self._store.append(event)
        for subscriber in self._subscribers:
            subscriber(event)
        return event

    def subscribe(self, subscriber: Subscriber) -> None:
        self._subscribers.append(subscriber)

    def list_for_task(self, task_id: str) -> list[RuntimeEvent]:
        return self._store.list_for_task(task_id)