dsfx/docs/requirements/fr-3-versioning-and-change-tracking.md

# FR-3: Versioning and Change Tracking

## 1. Overview

This document defines the detailed requirements for maintaining a comprehensive versioning system and change tracking mechanism throughout the file storage solution. The objective is to record every file operation—such as creation, modifications, and deletions—in an immutable audit trail. This not only enables users to revert changes and restore previous versions but also provides full transparency and auditability across multi-device interactions. The design leverages an immutable, cryptographically chained manifest (as described in ADR-0006) to ensure that every update is verifiable and resistant to tampering.

## 2. Objectives & Scope

### 2.1 Objectives

- **Comprehensive History:** Record every change made to a file, including creation, updates, and deletions.
- **Auditability & Transparency:** Guarantee that the change history is tamper-evident and fully auditable.
- **Conflict Resolution & Merging:** Enable automatic and deterministic conflict resolution in multi-device scenarios.
- **Reversion:** Allow users to revert to any previous version of a file.
- **Synchronization Support:** Facilitate efficient merging of version histories across devices while preserving the ordering of events.

### 2.2 Scope

- Applies to all file operations across the system, including file modifications on the client and updates propagated through nodes.
- Involves tracking metadata for every operation (e.g., timestamps, author information, and device identifiers).
- Integrates with the immutable manifest (ADR-0006) to leverage cryptographic chaining and snapshots.
- Supports deterministic simulation of versioning and conflict resolution processes under various network and disk conditions.

## 3. Detailed Requirements

### 3.1 Immutable, Append-Only Manifest

- **Manifest Structure:**

  - Every file operation (create, update, delete) must be recorded as an entry in an append-only manifest.
  - Each entry must include essential metadata, such as a unique change identifier, timestamp, device/client identifier, and a description of the operation.
  - Entries are cryptographically chained (e.g., each entry includes a hash of the previous one) to ensure tamper detection.

- **Snapshots:**
  - To prevent performance degradation, periodic snapshots capturing the cumulative state of the manifest must be generated.
  - Future log entries should reference the most recent snapshot, allowing earlier portions of the manifest to be pruned (while remaining verifiable).

### 3.2 Version Tracking and History

- **Version Creation:**

  - Every modification to a file results in a new version being recorded. Metadata such as version number, change description, and timestamp shall be associated with each version.
  - The full version history must be retrievable, allowing users to inspect the progression of changes over time.

- **Multi-Device Versioning:**
  - As files may be modified on multiple devices, each device’s changes must be merged deterministically.
  - Logical timestamps (for example, Lamport timestamps) will be used to order events across devices to ensure that the sequence of modifications is consistent.

### 3.3 Conflict Detection and Resolution

- **Automated Conflict Detection:**

  - When concurrent modifications are detected (e.g., overlapping timestamps or divergent change paths in the manifest), the system must flag the conflict.
  - The system shall initiate a deterministic conflict resolution process by applying predefined rules (e.g., favoring the update with the lower Lamport timestamp or deferring to a primary device designation).

- **User Intervention:**
  - If the automatic resolution algorithm fails to clearly resolve a conflict, the system must flag the conflicted version for manual review.
  - Clear documentation within the user interface should guide users in resolving conflicts when necessary.

### 3.4 Reversion and Rollback Mechanisms

- **Rollback Capability:**

  - Users must be able to revert a file to any previous version recorded in the manifest.
  - Reversion operations should restore the file content and update the manifest to record the rollback as a new change, preserving the audit trail.

- **Verification:**
  - Every reversion must undergo an integrity check (using cryptographic hash comparisons) to ensure that the restored version accurately reflects its original state.

### 3.5 Integration with Deterministic Simulation Testing

- **Simulation of Versioning Under Adverse Conditions:**

  - The complete versioning and conflict resolution logic should be integrated with the deterministic simulation framework.
  - Simulated tests will introduce network and disk delays or failures during file modifications to validate that the versioning mechanism responds predictably.

- **Logging and Monitoring:**
  - All versioning activities (including conflict detection and resolution events) must be logged in detail for reproducibility in simulated failure conditions.

## 4. Measurable Criteria & Test Cases

### 4.1 Automated End-to-End Versioning Tests

- **Manifest Consistency Test:**

  - Create a file and perform a series of modifications.
  - Verify that an immutable manifest accurately records each change and that entries are properly linked via cryptographic chaining.

- **Version History Accuracy Test:**
  - Retrieve the full version history of a file and compare the recorded data with the expected series of changes.
  - Verify that metadata (timestamps, device IDs, operation descriptions) matches the executed operations.

### 4.2 Conflict Resolution Testing

- **Simultaneous Update Simulation:**

  - From multiple simulated devices, perform overlapping modifications on the same file.
  - Validate that conflicts are detected and resolved deterministically according to the predefined rules.
  - Confirm that any unresolved conflicts are flagged for user intervention.

- **Rollback Verification:**
  - Initiate a rollback operation to restore an earlier file version.
  - Verify that the rollback creates a new version entry in the manifest and that the restored file content passes integrity checks.

### 4.3 Performance and Stress Testing

- **Scalability Test:**

  - Simulate rapid, consecutive file modifications to stress-test the versioning system.
  - Monitor performance metrics, including manifest update latency and system responsiveness under heavy load.

- **Deterministic Simulation:**
  - Use the simulation framework to introduce network delays and disk I/O latencies while performing versioning operations.
  - Confirm that the system maintains consistency and the manifest remains verifiable under stressed conditions.

## 5. Dependencies & Integration Points

- **Immutable Manifest System:**

  - This requirement relies heavily on the manifest design (ADR-0006) to store and maintain a tamper-evident history of changes.

- **Conflict Resolution Algorithms:**

  - Integration with the logical timestamp approach (e.g., Lamport timestamps) used in conflict detection and resolution is essential.

- **User Interface:**

  - The UI must present the version history clearly, allow easy navigation of changes, and support rollback/reversion operations.

- **Deterministic Simulation Framework:**
  - Integration ensures that versioning and conflict resolution behave consistently under simulated adverse conditions in accordance with NFR guidelines.

## 6. Security Considerations

- **Integrity of Version Log:**

  - The cryptographic chaining of manifest entries must be secure against tampering to prevent unauthorized alteration of the file history.

- **Auditability:**

  - All versioning operations must be logged in a tamper-evident manner, ensuring that an audit trail is maintained for regulatory compliance and user trust.

- **Access Controls:**
  - Only authorized users should be permitted to view or alter the version history. Appropriate authentication mechanisms must be enforced.

## 7. Conclusion

FR-3 establishes a robust versioning and change tracking system that meets the critical needs for auditability, transparency, and user control in a distributed, multi-device environment. By leveraging an immutable, cryptographically chained manifest, robust conflict resolution algorithms, and reversion capabilities, the system provides a trustworthy mechanism for managing file versions while ensuring resilience even under simulated adverse conditions.