"""
Unified activity bus.

emit_activity() writes an APActivity row with process_state='pending' within
the caller's existing DB transaction — atomic with the domain change.

register_activity_handler() registers async handler functions that the
EventProcessor dispatches when processing pending activities.
"""
from __future__ import annotations

import logging
import uuid
from collections import defaultdict
from typing import Awaitable, Callable, Dict, List, Tuple

from sqlalchemy.ext.asyncio import AsyncSession

from shared.models.federation import APActivity

log = logging.getLogger(__name__)

# ---------------------------------------------------------------------------
# Activity-handler registry
# ---------------------------------------------------------------------------
# Handler signature: async def handler(activity: APActivity, session: AsyncSession) -> None
ActivityHandlerFn = Callable[[APActivity, AsyncSession], Awaitable[None]]

# Keyed by (activity_type, object_type). object_type="*" is wildcard.
_activity_handlers: Dict[Tuple[str, str], List[ActivityHandlerFn]] = defaultdict(list)


def register_activity_handler(
    activity_type: str,
    fn: ActivityHandlerFn,
    *,
    object_type: str | None = None,
) -> None:
    """Register an async handler for an activity type + optional object type.

    Use ``activity_type="*"`` as a wildcard that fires for every activity
    (e.g. federation delivery handler).
    """
    key = (activity_type, object_type or "*")
    _activity_handlers[key].append(fn)
    log.info("Registered activity handler %s.%s for key %s", fn.__module__, fn.__qualname__, key)


def get_activity_handlers(
    activity_type: str,
    object_type: str | None = None,
) -> List[ActivityHandlerFn]:
    """Return all matching handlers for an activity.

    Matches in order:
    1. Exact (activity_type, object_type)
    2. (activity_type, "*")  — type-level wildcard
    3. ("*", "*")            — global wildcard (e.g. delivery)
    """
    handlers: List[ActivityHandlerFn] = []
    ot = object_type or "*"

    # Exact match
    if ot != "*":
        handlers.extend(_activity_handlers.get((activity_type, ot), []))
    # Type-level wildcard
    handlers.extend(_activity_handlers.get((activity_type, "*"), []))
    # Global wildcard
    if activity_type != "*":
        handlers.extend(_activity_handlers.get(("*", "*"), []))

    return handlers


# ---------------------------------------------------------------------------
# emit_activity — the primary way to emit events
# ---------------------------------------------------------------------------
async def emit_activity(
    session: AsyncSession,
    *,
    activity_type: str,
    actor_uri: str,
    object_type: str,
    object_data: dict | None = None,
    source_type: str | None = None,
    source_id: int | None = None,
    visibility: str = "internal",
    actor_profile_id: int | None = None,
    origin_app: str | None = None,
) -> APActivity:
    """
    Write an AP-shaped activity to ap_activities with process_state='pending'.

    Called inside a service function using the same session that performs the
    domain change.  The activity and the change commit together.
    """
    if not origin_app:
        try:
            from quart import current_app
            origin_app = current_app.name
        except (ImportError, RuntimeError):
            pass

    activity_uri = f"internal:{uuid.uuid4()}" if visibility == "internal" else f"urn:uuid:{uuid.uuid4()}"

    activity = APActivity(
        activity_id=activity_uri,
        activity_type=activity_type,
        actor_profile_id=actor_profile_id,
        actor_uri=actor_uri,
        object_type=object_type,
        object_data=object_data or {},
        is_local=True,
        source_type=source_type,
        source_id=source_id,
        visibility=visibility,
        process_state="pending",
        origin_app=origin_app,
    )
    session.add(activity)
    await session.flush()
    return activity