Feature Specification: Version Control & History

1. Overview & Vision

Version Control is the Document module's safety net. it provides a complete, chronological record of every change made to a document, allowing authors to experiment with confidence and admins to audit the evolution of organizational policies over time.

2. Personas & Stakeholders

Persona	Goal
Author	Review previous drafts and restore content after accidental deletion.
Admin	Audit specific changes made to corporate policies.
Reviewer	Compare the current version with previous feedback cycles.

3. User Stories

• As an author, I want to see a list of previous versions so I can restore a paragraph I deleted yesterday.
• As an admin, I want to see who made specific changes to the "Remote Work Policy".
• As a user, I want to name a specific version (e.g., "Board Approved") for easy reference.

4. Functional Requirements (FR)

• REQ-VC-001: Automated version snapshot creation on every manual save.
• REQ-VC-002: Visual version history list with timestamps and actor names.
• REQ-VC-003: Point-in-time "Restore" capability for any historical version.
• REQ-VC-004: Side-by-side version comparison (planned for v1.2).

5. Non-Functional Requirements (NFR)

• Scalability: Support for up to 1000 versions per document without performance loss.
• Storage: JSON delta storage (planned) to minimize database footprint.

6. Business Logic & Rules

• Immutability: Historical versions CANNOT be modified once created.
• Restoration: Restoring a version creates a NEW version (cloned from the old one) to maintain a linear history.
• Cleanup: (Optional) Auto-pruning of minor autosave versions older than 30 days.

7. User Interface (UI/UX)

• History Sidebar: Scrollable list of versions with "Preview" and "Restore" actions.
• Metadata: Each version entry shows: Version #, Date/Time, and Author Avatar.
• Preview Mode: Read-only rendering of the selected historical version.

8. Information Architecture

• "Version History" accessible via the editor's "File" or "Clock" menu.

9. Data Model & Persistence

• Table: document_versions.
• Fields: id, document_id, version_number, content, saved_by.

10. API & Service Layer

• GET /documents/:id/versions
• POST /documents/:id/versions/:versionId/restore

11. Integration Patterns

• User Service: Links saved_by IDs to full Shell user profiles for avatar rendering.

12. Security & Permissions

• RBAC: documents:read required to view history; documents:write required to restore.
• Integrity: Versions are linked to the parent document's org_id for isolation.

13. Error Handling & Resilience

• Restore Confirmation: Mandatory double-confirmation before overwriting the current draft.
• Conflict detection: Standard logic applies if multiple users try to restore different versions simultaneously.

14. Performance & Scalability

• Versions are paginated in the history sidebar.
• Large JSON payloads are compressed before storage (planned).

15. Globalization & i18n

• Timestamps are formatted according to the user's browser locale.

16. Accessibility (a11y)

• Accessible version list (focus management when opening/closing history).

17. Observability & Analytics

• Tracking of "Restore Frequency" to identify document volatility.

18. Testing & Quality

• Integration tests for the version numbering sequence.
• Unit tests for the restoration logic (cloning vs overwriting).

19. Constraints & Assumptions

• Assumes that jsonb storage in PostgreSQL is sufficient for v1 history needs.

20. Future Enhancements

• Visual diffing (highlights added/deleted text in red/green).
• "Milestone" versions (Permanently kept versions that bypass cleanup).