# React 19 Migration System - Changelog

## [Unreleased]

### Session 1: Foundation + Detection

#### 2024-12-13

**Added:**
- Created CHECKLIST.md for tracking implementation progress
- Created CHANGELOG.md for documenting changes
- Created `packages/noodl-editor/src/editor/src/models/migration/` directory with:
  - `types.ts` - Complete TypeScript interfaces for migration system:
    - Runtime version types (`RuntimeVersion`, `RuntimeVersionInfo`, `ConfidenceLevel`)
    - Migration issue types (`MigrationIssue`, `MigrationIssueType`, `ComponentMigrationInfo`)
    - Session types (`MigrationSession`, `MigrationScan`, `MigrationStep`, `MigrationPhase`)
    - AI types (`AIConfig`, `AIBudget`, `AIPreferences`, `AIMigrationResponse`)
    - Project manifest extensions (`ProjectMigrationMetadata`, `ComponentMigrationNote`)
    - Legacy pattern definitions (`LegacyPattern`, `LegacyPatternScan`)
  - `ProjectScanner.ts` - Version detection and legacy pattern scanning:
    - 5-tier detection system with confidence levels
    - `detectRuntimeVersion()` - Main detection function
    - `scanForLegacyPatterns()` - Scans for React 17 patterns
    - `scanProjectForMigration()` - Full project migration scan
    - 13 legacy React patterns detected (componentWillMount, string refs, etc.)
  - `MigrationSession.ts` - State machine for migration workflow:
    - `MigrationSessionManager` class extending EventDispatcher
    - Step transitions (confirm → scanning → report → configureAi → migrating → complete/failed)
    - Progress tracking and logging
    - Helper functions (`checkProjectNeedsMigration`, `getStepLabel`, etc.)
  - `index.ts` - Clean module exports

**Technical Notes:**
- IFileSystem interface from `@noodl/platform` uses `readFile(path)` with single argument (no encoding)
- IFileSystem doesn't expose file stat/birthtime - creation date heuristic relies on project.json metadata
- Migration phases: copying → automatic → ai-assisted → finalizing
- Default AI budget: $5 max per session, $1 pause increments

**Files Created:**
```
packages/noodl-editor/src/editor/src/models/migration/
├── index.ts
├── types.ts
├── ProjectScanner.ts
└── MigrationSession.ts
```

---

## Overview

This changelog tracks the implementation of the React 19 Migration System feature, which allows users to safely upgrade legacy Noodl projects (React 17) to the new OpenNoodl runtime (React 19), with optional AI-assisted code migration.

### Feature Specs
- [00-OVERVIEW.md](./00-OVERVIEW.md) - Feature summary and architecture
- [01-PROJECT-DETECTION.md](./01-PROJECT-DETECTION.md) - Detecting legacy projects
- [02-MIGRATION-WIZARD.md](./02-MIGRATION-WIZARD.md) - Step-by-step wizard UI
- [03-AI-MIGRATION.md](./03-AI-MIGRATION.md) - AI-assisted code migration
- [04-POST-MIGRATION-UX.md](./04-POST-MIGRATION-UX.md) - Editor experience after migration
- [05-NEW-PROJECT-NOTICE.md](./05-NEW-PROJECT-NOTICE.md) - New project messaging

### Implementation Sessions
1. **Session 1**: Foundation + Detection (types, scanner, models)
2. **Session 2**: Wizard UI (basic flow without AI)
3. **Session 3**: Projects View Integration (legacy badges, buttons)
4. **Session 4**: AI Migration + Polish (Claude integration, UX)