A Python library for processing Activity Streams 2.0 activities via a rule-based engine. Activity Bus is designed to work in concert with Activity Store and provides a high-level pipeline for submitting, validating, storing, and processing activities using dynamic, declarative behaviors.

pip install activity-bus

• Build on Activity Store for storage, caching, and dereferencing
• Easy creation and management of behaviors
• Clean, async-first interface
• Compatible with ActivityPub delivery semantics
• Agent-friendly, auditable, and introspectable
• Support for asynchronous and dynamic rule processing

import asyncio
from activity_bus import ActivityBus, when

# Define a behavior
@when({"type": "Create", "object": {"type": "Note"}})
def create_note(activity):
    print(f"Note created with content: {activity['object']['content']}")
    # You can return new activities to be submitted
    return [{
        "type": "Notification",
        "summary": "New note created",
        "actor": activity["actor"]
    }]

async def main():
    # Create a new ActivityBus instance
    bus = ActivityBus()
    
    # Submit an activity
    activity = {
        "type": "Create",
        "actor": "https://example.com/users/user1",
        "object": {
            "type": "Note",
            "content": "Hello, world!"
        }
    }
    
    await bus.submit(activity)
    
    # Process the next activity in the queue
    processed = await bus.process_next()
    
    # Process any new activities that were created
    notification = await bus.process_next()
    
    print(f"Processed: {processed}")
    print(f"Notification: {notification}")

# Run the example
asyncio.run(main())

• Must contain at minimum: actor, type, and optionally id
• If id is not present, it is generated: /users/<user-id>/outbox/<nanoid>
• Must be scoped under actor's URI; otherwise, rejected
• On submission, published timestamp is set

await bus.submit(activity)

1. Validate required fields
2. Set ID if missing
3. Validate ID scope
4. Store activity in ActivityStore
5. Enqueue activity in in-memory asyncio.Queue

await bus.process_next()

1. Dequeue activity
2. Fetch all behaviors from /sys/behaviors
3. Match each behavior using frame(activity, behavior["when"], require_match=True)
4. Execute function for each matching behavior
5. If activity["result"] includes new activities, submit each with context = activity["id"]
6. On any exception:
   • Append an error to activity["result"]
   • Convert activity to a Tombstone
   • Store updated activity

For more detailed documentation, see the comments in the source code and the SPEC.md file.

# Install test dependencies
pip install -e ".[test]"

# Run all tests
pytest

# Run with coverage
pytest --cov=activity_bus

MIT