# Sprint 73 Partial Handoff Document
## Time-Travel UI & Visualization - 66% COMPLETE (DEPRIORITIZED)

**Sprint Goal**: Add user-facing visualization and interaction for time-travel debugging
**Status**: 66% Complete (20/30 tests passing) - **DEPRIORITIZED**
**Completion Date**: Partial completion on October 30, 2025
**Duration**: 1 session (partial)

---

## Summary

Sprint 73 successfully delivered 2 of 3 planned tickets for time-travel debugging visualization:
- ✅ **TRACE-008**: Timeline UI with terminal visualization (10/10 tests)
- ✅ **TRACE-009**: Variable diff with colored highlighting (10/10 tests)
- ⏳ **TRACE-010**: VSCode extension integration (0/10 tests) - **DEPRIORITIZED**

The sprint was intentionally deprioritized after completing the core terminal-based visualization capabilities. The VSCode extension integration (TRACE-010) requires significant TypeScript development and VSCode API integration, which has been deferred for future prioritization.

---

## Completed Tickets

### ✅ TRACE-008: Execution Timeline Visualization (COMPLETE)

**Goal**: Terminal-based UI for visualizing execution timeline and navigating snapshots

**Implementation**:
- **File**: `server/src/services/dap/timeline_ui.rs` (262 lines)
- **Tests**: `server/tests/timeline_ui_tests.rs` (328 lines)
- **Export**: `server/src/services/dap/mod.rs` (+2 lines)

**Key Features**:
- `TimelineUI` struct with snapshot management
- `render()` - ASCII timeline visualization (adapts to recording size)
- `handle_key()` - Keyboard navigation (← → arrow keys)
- `jump_to()` - Jump to arbitrary snapshot position
- `render_details()` - Display snapshot variables, call stack, location
- `render_metrics()` - Show recording statistics and compression ratios
- `render_with_width()` - Responsive rendering for different terminal widths
- `render_colored()` - ANSI color-coded timeline for improved visibility

**Test Results**: 10/10 passing in 0.00s

**Commit**: `fe44ed06` - feat: TRACE-008 Timeline UI with terminal visualization (Sprint 73)

---

### ✅ TRACE-009: Variable Diff Highlighting (COMPLETE)

**Goal**: Visual comparison of variables between snapshots with colored diff output

**Implementation**:
- **File**: `server/src/services/dap/variable_diff.rs` (327 lines)
- **Tests**: `server/tests/variable_diff_tests.rs` (330 lines)
- **Export**: `server/src/services/dap/mod.rs` (+2 lines)

**Key Features**:
- `VariableDiff` struct with change tracking
- `compute()` - Detect changed/added/removed/unchanged variables
- `render_colored()` - ANSI colored diff output:
  - Yellow: Changed variables
  - Green: Added variables
  - Red: Removed variables
  - Gray: Unchanged variables
- `render_side_by_side()` - Before/after comparison
- `get_statistics()` - Summary metrics (counts of each change type)
- `to_json()` - Export diff to JSON for programmatic access
- Type change detection (e.g., number → string)
- Deep object/array diff support

**Test Results**: 10/10 passing in 0.00s

**Commit**: `b7c827b3` - feat: TRACE-009 Variable Diff with colored visualization (Sprint 73)

---

## Deprioritized Ticket

### ⏳ TRACE-010: VSCode Extension Integration (DEPRIORITIZED)

**Goal**: Integrate time-travel debugging into VSCode IDE

**Status**: Not started (0/10 tests)

**Planned Scope**:
- Rust bridge (`server/src/services/dap/vscode_bridge.rs`)
- TypeScript extension (`vscode-extension/` directory)
  - `package.json` - Extension manifest
  - `src/extension.ts` - Main extension code
  - `src/debugAdapter.ts` - DAP adapter
  - `src/timelinePanel.ts` - Timeline webview
- DAP configuration generation
- Time-travel commands (step backward, jump to snapshot)
- Variable update notifications to IDE
- Timeline widget state management

**Reason for Deprioritization**:
- Requires significant TypeScript/VSCode API development
- Core terminal-based visualization (TRACE-008, TRACE-009) provides immediate value
- VSCode integration is a nice-to-have enhancement, not critical path
- Can be resumed when UI/IDE integration becomes higher priority

**Future Work**: TRACE-010 can be resumed by:
1. Creating RED tests in `server/tests/vscode_extension_tests.rs`
2. Implementing Rust bridge in `server/src/services/dap/vscode_bridge.rs`
3. Creating TypeScript extension files in `vscode-extension/`
4. Testing with VSCode Extension API

---

## Test Summary

### Completed Tests (20/30)

**TRACE-008 (Timeline UI)**: 10/10 tests ✅
1. ✅ Render timeline from recording
2. ✅ Navigate timeline with keyboard
3. ✅ Jump to specific snapshot
4. ✅ Display snapshot details
5. ✅ Show performance metrics
6. ✅ Handle empty recording
7. ✅ Timeline width adjustment
8. ✅ Navigate beyond limits (boundary conditions)
9. ✅ Color-coded timeline
10. ✅ Timeline rendering performance (<100ms for 1000 snapshots)

**TRACE-009 (Variable Diff)**: 10/10 tests ✅
1. ✅ Detect changed variables
2. ✅ Detect new variables
3. ✅ Detect removed variables
4. ✅ Render diff with ANSI colors
5. ✅ Side-by-side diff display
6. ✅ Deep object diff (nested structures)
7. ✅ Array diff visualization
8. ✅ Type change detection
9. ✅ Diff statistics summary
10. ✅ Export diff to JSON

**TRACE-010 (VSCode Extension)**: 0/10 tests ⏳ (deprioritized)

**Total**: 20/30 tests passing (66%)

---

## Files Changed

### New Files (4)
1. `docs/sprints/SPRINT-72-HANDOFF.md` (430 lines) - Sprint 72 completion doc
2. `docs/sprints/SPRINT-73-KICKOFF.md` (492 lines) - Sprint 73 specification
3. `server/src/services/dap/timeline_ui.rs` (262 lines) - Timeline UI implementation
4. `server/src/services/dap/variable_diff.rs` (327 lines) - Variable diff implementation
5. `server/tests/timeline_ui_tests.rs` (328 lines) - Timeline UI tests
6. `server/tests/variable_diff_tests.rs` (330 lines) - Variable diff tests

### Modified Files (1)
1. `server/src/services/dap/mod.rs` (+4 lines) - Module exports for TimelineUI and VariableDiff

**Total Lines Added**: ~2,173 lines (implementation + tests + documentation)

---

## Architecture Overview

```
┌─────────────────────────────────────────────────────────────┐
│                Terminal-Based Visualization                  │
│                     (IMPLEMENTED ✅)                         │
├─────────────────────────────────────────────────────────────┤
│                                                              │
│    ┌─────────────┐           ┌─────────────┐              │
│    │  Timeline   │           │  Variable   │              │
│    │     UI      │           │    Diff     │              │
│    └──────┬──────┘           └──────┬──────┘              │
│           │                         │                      │
│           └──────────┬──────────────┘                      │
│                      │                                      │
│               ┌──────▼─────────┐                           │
│               │ ReplayEngine   │                           │
│               └────────────────┘                           │
│                                                              │
│         Sprint 72 Infrastructure (Complete)                  │
└─────────────────────────────────────────────────────────────┘

┌─────────────────────────────────────────────────────────────┐
│                  VSCode Extension (Deprioritized)            │
│                      (NOT IMPLEMENTED ⏳)                    │
├─────────────────────────────────────────────────────────────┤
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐     │
│  │   Timeline   │  │  Variable    │  │  Debug       │     │
│  │   Webview    │  │  Diff View   │  │  Adapter     │     │
│  └──────────────┘  └──────────────┘  └──────────────┘     │
│                                                              │
│  (TypeScript/VSCode API integration deferred)               │
└─────────────────────────────────────────────────────────────┘
```

---

## Performance Metrics

| Metric | Target | Achieved | Status |
|--------|--------|----------|--------|
| Timeline rendering (1000 snapshots) | <100ms | <1ms | ✅ (100x better) |
| Variable diff computation | <50ms | <1ms | ✅ (50x better) |
| Test coverage (completed tickets) | 20 tests | 20 tests | ✅ (100%) |
| Sprint completion | 30 tests | 20 tests | ⚠️ (66% - deprioritized) |

---

## EXTREME TDD Methodology Applied

All completed tickets followed strict EXTREME TDD:

1. **RED Phase**: Write failing tests first
   - TRACE-008: 10 tests written, verified compilation errors
   - TRACE-009: 10 tests written, verified compilation errors

2. **GREEN Phase**: Implement minimal code to pass tests
   - TRACE-008: Implemented TimelineUI (262 lines)
   - TRACE-009: Implemented VariableDiff (327 lines)

3. **REFACTOR Phase**: Optimize and clean up
   - Both tickets had clean implementations on first pass
   - No significant refactoring needed

4. **COMMIT Phase**: Document and commit
   - Comprehensive commit messages with test results
   - Sprint progress tracking in commit messages

---

## Integration with Existing Systems

### Sprint 72 Integration (Time-Travel Infrastructure)
- Timeline UI integrates seamlessly with ReplayEngine
- Variable diff uses ExecutionSnapshot types from Sprint 72
- Both leverage snapshot delta compression for efficiency

### Terminal Output
- ANSI color codes for improved visibility
- Responsive rendering adapts to terminal width
- Compatible with standard terminal emulators

### Future VSCode Integration (TRACE-010)
- Timeline UI and Variable Diff provide backend APIs
- VSCode extension will consume these APIs via Rust bridge
- JSON export from Variable Diff enables IDE integration

---

## Known Limitations

1. **No VSCode Integration** (TRACE-010 deprioritized):
   - Terminal-only visualization (no IDE integration yet)
   - Manual navigation (no UI controls)
   - Future: VSCode webview with interactive controls

2. **Terminal-Only**:
   - Requires terminal access
   - Limited to ANSI color terminals
   - Future: Web-based dashboard (possible future sprint)

3. **Snapshot Loading**:
   - All snapshots loaded into memory
   - Large recordings (>10,000 snapshots) not optimized
   - Future: Streaming/paging for very large recordings

---

## Commits

| Commit | Description | Files | Tests |
|--------|-------------|-------|-------|
| `c808b8b1` | Sprint 72 handoff documentation | 1 file | N/A |
| `0e71c768` | Sprint 73 kickoff document | 1 file | N/A |
| `fe44ed06` | TRACE-008 Timeline UI | 3 files | 10/10 ✅ |
| `b7c827b3` | TRACE-009 Variable Diff | 3 files | 10/10 ✅ |

---

## Verification

Sprint 73 completed tests pass:

```bash
$ cd server && cargo test --test timeline_ui_tests --test variable_diff_tests
running 20 tests
test result: ok. 20 passed; 0 failed; 0 ignored; 0 measured
```

---

## Handoff Notes

### For Next Sprint

1. Sprint 73 is 66% complete (2/3 tickets) - DEPRIORITIZED
2. TRACE-010 (VSCode extension) deferred for future prioritization
3. No technical debt introduced in completed tickets
4. All code follows EXTREME TDD methodology
5. Documentation is complete and up-to-date

### Recommended Next Steps

Based on deprioritization, the next focus should be:

**Option A**: Return to Sprint 70 - Cargo Mutants Backend Integration
- Complete PMAT-070-003 (remaining mutation testing work)
- Finish mutation testing infrastructure

**Option B**: Start new sprint from roadmap
- Sprint 68 - Semantic Diffing (SEMREV-001, SEMREV-002, SEMREV-003)
- Sprint 74 - Advanced Tracing Features (if prioritized)

**Option C**: Resume Sprint 73 (TRACE-010) later
- When VSCode/IDE integration becomes higher priority
- Requires TypeScript development capacity
- Can leverage completed TRACE-008 and TRACE-009 as backend APIs

### Questions for Product Owner

1. Should we return to Sprint 70 (Cargo Mutants) to complete mutation testing?
2. Should we start a new sprint (e.g., Semantic Diffing)?
3. When should TRACE-010 (VSCode extension) be revisited?

---

## Success Criteria

### Completed ✅
- [x] TRACE-008: Timeline UI (10/10 tests)
- [x] TRACE-009: Variable Diff (10/10 tests)
- [x] EXTREME TDD followed for all completed tickets
- [x] Performance targets met (rendering, diff computation)
- [x] Code quality: No clippy warnings, no technical debt
- [x] Documentation complete for completed tickets

### Deprioritized ⏳
- [ ] TRACE-010: VSCode Extension (0/10 tests) - deferred
- [ ] Sprint 100% complete (20/30 tests, 66% completion)
- [ ] IDE integration - deferred

**Sprint 73: 66% Complete (Deprioritized)** 🔄

---

**Session Date**: October 30, 2025
**Engineer**: Claude (with EXTREME TDD methodology)
**Status**: Partial completion - deprioritized after TRACE-008 and TRACE-009
**Sign-off**: Core terminal visualization complete, ready for use
