Conversation & message service layer (Python)

[mehalyna]

Task 3 — Conversation & message service layer (Python)

Title: service: implement server-side conversation/message service (persistence + helpers)

Description

• Implement a Python service module (e.g., messaging.services) that:

  • Creates/loads conversations (create if not exists on first message).
  • Persists messages to Mongo.
  • Updates conversations.last_message_at.
  • Provides recent message fetch (pagination), unread count per conversation, and mark-as-read helper.

• Expose simple functions used by REST endpoints and Channels consumers:

  • create_message(conversation_id, sender_id, body, attachments, meta) -> message_doc
  • get_conversation(conversation_id, page, page_size)
  • list_conversations_for_user(user_id, page, page_size)
  • mark_messages_read(conversation_id, user_id)

Acceptance

• Unit tests for each function using a test Mongo fixture.
• Service functions documented and used later by REST & Channels layers.

Dependencies

• Task 2 Mongo schema, Auth, Uploads.

Notes

• Validate participant membership in conversation before persisting messages.