shared/events/handlers/ap_delivery_handler.py

"""Deliver AP activities to remote followers.

On ``federation.activity_created`` → load activity + actor + followers →
sign with HTTP Signatures → POST to each follower inbox.
"""
from __future__ import annotations

import logging

import httpx
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from shared.events.bus import register_handler, DomainEvent
from shared.models.federation import ActorProfile, APActivity, APFollower
from shared.services.registry import services

log = logging.getLogger(__name__)

AP_CONTENT_TYPE = "application/activity+json"
DELIVERY_TIMEOUT = 15  # seconds per request


def _build_activity_json(activity: APActivity, actor: ActorProfile, domain: str) -> dict:
    """Build the full AP activity JSON-LD for delivery."""
    username = actor.preferred_username
    actor_url = f"https://{domain}/users/{username}"

    obj = dict(activity.object_data or {})

    # Object id MUST be on the actor's domain (Mastodon origin check).
    # The post URL (e.g. coop.rose-ash.com/slug/) goes in "url" only.
    object_id = activity.activity_id + "/object"

    if activity.activity_type == "Delete":
        # Delete: object is a Tombstone with just id + type
        obj.setdefault("id", object_id)
        obj.setdefault("type", "Tombstone")
    else:
        # Create/Update: full object with attribution
        obj["id"] = object_id
        obj.setdefault("type", activity.object_type)
        obj.setdefault("attributedTo", actor_url)
        obj.setdefault("published", activity.published.isoformat() if activity.published else None)
        obj.setdefault("to", ["https://www.w3.org/ns/activitystreams#Public"])
        obj.setdefault("cc", [f"{actor_url}/followers"])

    return {
        "@context": [
            "https://www.w3.org/ns/activitystreams",
            "https://w3id.org/security/v1",
        ],
        "id": activity.activity_id,
        "type": activity.activity_type,
        "actor": actor_url,
        "published": activity.published.isoformat() if activity.published else None,
        "to": ["https://www.w3.org/ns/activitystreams#Public"],
        "cc": [f"{actor_url}/followers"],
        "object": obj,
    }


async def _deliver_to_inbox(
    client: httpx.AsyncClient,
    inbox_url: str,
    body: dict,
    actor: ActorProfile,
    domain: str,
) -> bool:
    """POST signed activity to a single inbox. Returns True on success."""
    from shared.utils.http_signatures import sign_request
    from urllib.parse import urlparse
    import json

    body_bytes = json.dumps(body).encode()
    key_id = f"https://{domain}/users/{actor.preferred_username}#main-key"

    parsed = urlparse(inbox_url)
    headers = sign_request(
        private_key_pem=actor.private_key_pem,
        key_id=key_id,
        method="POST",
        path=parsed.path,
        host=parsed.netloc,
        body=body_bytes,
    )
    headers["Content-Type"] = AP_CONTENT_TYPE

    try:
        resp = await client.post(
            inbox_url,
            content=body_bytes,
            headers=headers,
            timeout=DELIVERY_TIMEOUT,
        )
        if resp.status_code < 300:
            log.info("Delivered to %s → %d", inbox_url, resp.status_code)
            return True
        else:
            log.warning("Delivery to %s → %d: %s", inbox_url, resp.status_code, resp.text[:200])
            return False
    except Exception:
        log.exception("Delivery failed for %s", inbox_url)
        return False


async def on_activity_created(event: DomainEvent, session: AsyncSession) -> None:
    """Deliver a newly created activity to all followers."""
    import os

    if not services.has("federation"):
        return

    payload = event.payload
    activity_id_uri = payload.get("activity_id")
    if not activity_id_uri:
        return

    domain = os.getenv("AP_DOMAIN", "rose-ash.com")

    # Load the activity
    activity = (
        await session.execute(
            select(APActivity).where(APActivity.activity_id == activity_id_uri)
        )
    ).scalar_one_or_none()
    if not activity:
        log.warning("Activity not found: %s", activity_id_uri)
        return

    # Load actor with private key
    actor = (
        await session.execute(
            select(ActorProfile).where(ActorProfile.id == activity.actor_profile_id)
        )
    ).scalar_one_or_none()
    if not actor or not actor.private_key_pem:
        log.warning("Actor not found or missing key for activity %s", activity_id_uri)
        return

    # Load followers
    followers = (
        await session.execute(
            select(APFollower).where(APFollower.actor_profile_id == actor.id)
        )
    ).scalars().all()

    if not followers:
        log.debug("No followers to deliver to for %s", activity_id_uri)
        return

    # Build activity JSON
    activity_json = _build_activity_json(activity, actor, domain)

    # Deliver to each follower inbox
    # Deduplicate inboxes (multiple followers might share a shared inbox)
    inboxes = {f.follower_inbox for f in followers if f.follower_inbox}

    log.info(
        "Delivering %s to %d inbox(es) for @%s",
        activity.activity_type, len(inboxes), actor.preferred_username,
    )

    async with httpx.AsyncClient() as client:
        for inbox_url in inboxes:
            await _deliver_to_inbox(client, inbox_url, activity_json, actor, domain)


register_handler("federation.activity_created", on_activity_created)