[ML 0.7/LL.02] - Mediator Implementation & Unified Support

🎯 The objective

Implement the heavy lifting of the data layer: the RemoteMediator itself (handling the source of truth between Database and Remote) and the complex logic required to paginate "Unified Folders" across multiple accounts.

🎒 Resources

ℹ️ List all relevant resources like BugZilla meta bugs, Figma files, Notion links and other files. These can be filled in later.

• Android Paging3 Documentation
• Store5

🦮 Rules of the Road

🟢 In Scope

• Implement the MessageListRemoteMediator API.
• Build pagination logic for Unified Folders.

🔴 Out of Scope

• UI Integration and Event triggering.

🚧 Technical and/or Business Requirements

• Remote Mediator Implementation:
  • Use the Database as the single source of truth.
  • Request data from remote only when the database lacks results.
• Unified Folder Pagination:
  • Ideally, we should tackle this only after the database work is done.
  • If it is not finalized, we will need to figure out a way to paginate the unified folder.
  • Complexity Alert: This requires a "logical cursor" approach:
    • Maintain a list of Account IDs with their respective next pagination cursors.
    • Calculate limits divided by account count.
    • Fetch and merge pages from different accounts, handling sorting and deduplication carefully.