MemoHanzi - Implementation Package

Welcome! This package contains everything needed to implement MemoHanzi (记汉字 - "Remember Hanzi"), a self-hosted Chinese character learning application.

📦 What's Included

1. HANZI-LEARNING-APP-SPECIFICATION.md (Main Spec)

Complete technical specification including:

• ✅ System architecture
• ✅ Complete database schema (Prisma)
• ✅ All Server Actions API
• ✅ SM-2 algorithm implementation
• ✅ UI/UX specifications
• ✅ Testing strategy
• ✅ 12-week milestone plan
• ✅ Docker configuration
• ✅ Phase 2 & 3 roadmaps

2. CLAUDE.md (Instructions for Claude Code)

Strict implementation guidelines to prevent deviation from spec:

• Critical rules for following the specification
• Milestone approach
• Common mistakes to avoid
• Progress reporting format

3. PROJECT-NAMING.md (Naming Conventions)

All naming conventions for the MemoHanzi project:

• Application naming (display vs technical)
• Database naming
• Code conventions
• Branding guidelines

🚀 Quick Start

For Claude Code:

1. Read CLAUDE.md first
2. Read HANZI-LEARNING-APP-SPECIFICATION.md
3. Read PROJECT-NAMING.md for naming conventions
4. Start with Milestone 1 (Week 1: Foundation)

For Human Developers:

1. Read HANZI-LEARNING-APP-SPECIFICATION.md - this is your blueprint
2. Check PROJECT-NAMING.md for naming consistency
3. Follow the 12-week milestone plan
4. Use the testing strategy throughout

📋 Project Overview

Name: MemoHanzi (记汉字)
Tagline: Remember Hanzi, effortlessly
Type: Self-hosted web application
Purpose: Learn Chinese characters using spaced repetition (SM-2 algorithm)

Tech Stack:

• Next.js 16 (TypeScript, App Router)
• PostgreSQL 18 + Prisma
• NextAuth.js v5
• Docker Compose + Nginx
• Tailwind CSS

Timeline: 10-12 weeks for MVP

🎯 Key Features (MVP)

For Users:

• Learn Hanzi with spaced repetition
• Multiple choice pinyin quiz (4 options)
• Create custom collections or use HSK levels
• Track progress with charts and statistics
• Search complete Hanzi database

For Admins:

• Import HSK vocabulary (JSON/CSV)
• Manage global collections
• User administration

📁 Project Structure

memohanzi/                          # Your project root
├── src/
│   ├── app/                        # Next.js App Router
│   ├── actions/                    # Server Actions
│   ├── components/                 # React components
│   ├── lib/                        # Utils (SM-2, parsers, etc)
│   └── types/                      # TypeScript types
├── prisma/
│   └── schema.prisma              # Database schema
├── docker/
│   ├── Dockerfile
│   └── nginx.conf
├── docker-compose.yml
└── README.md

🔑 Critical Implementation Notes

1. Follow the Specification EXACTLY

The specification is the single source of truth. Do not deviate without approval.

2. Implement Milestones Sequentially

Complete Week 1 → Week 2 → Week 3... in order.

3. SM-2 Algorithm is Critical

Use the EXACT formulas provided in Section 5 of the spec.

4. Testing is Mandatory

Write tests as you implement. Target: 70%+ coverage.

5. Database Schema is Fixed

Implement ALL models exactly as specified in the Prisma schema.

📊 Development Milestones

Week	Milestone	Focus	Status
1	Foundation	Setup project, Docker, Prisma schema	✅ Complete
2	Authentication	User registration, login, preferences	✅ Complete
3-4	Data Import	Admin imports HSK data (JSON/CSV)	✅ Complete
5	Collections	User collections + global HSK collections	✅ Complete
5	Hanzi Search	Search interface and detail views	✅ Complete
6	SM-2 Algorithm	Core learning algorithm + tests	✅ Complete
7-8	Learning UI	Learning session interface	✅ Complete
9	Dashboard	Progress tracking and visualizations	✅ Complete
10	UI Polish	Responsive design, dark mode	🔄 Next
11	Testing & Docs	Complete test coverage
12	Deployment	Production deployment + data import

✅ Milestone 3 Completed Features

Data Import System:

• ✅ HSK JSON parser supporting complete-hsk-vocabulary format
• ✅ CSV parser with flexible column mapping
• ✅ Admin import page with file upload and paste functionality
• ✅ Update existing entries or skip duplicates option
• ✅ Detailed import results with success/failure counts and line-level errors
• ✅ Format validation and error reporting
• ✅ Support for multi-character hanzi (words like 中国)
• ✅ All transcription types (pinyin, numeric, wade-giles, zhuyin, ipa)
• ✅ 14 passing integration tests for both JSON and CSV parsers

Database Initialization System:

• ✅ Multi-file selection for batch initialization
• ✅ Real-time progress updates via Server-Sent Events (SSE)
• ✅ Progress bar showing current operation and percentage
• ✅ Automatic HSK level collection creation
• ✅ Auto-populate collections with hanzi based on level attribute
• ✅ Optional clean data mode (delete all existing data before import)
• ✅ Comprehensive statistics: hanzi imported, collections created, items added
• ✅ Admin initialization page at /admin/initialize
• ✅ SSE API route at /api/admin/initialize for long-running operations

Files Created:

• src/lib/import/json-parser.ts - HSK JSON format parser
• src/lib/import/csv-parser.ts - CSV format parser
• src/lib/import/json-parser.test.ts - JSON parser tests
• src/lib/import/csv-parser.test.ts - CSV parser tests
• src/actions/admin.ts - Admin-only import and initialization actions
• src/actions/admin.integration.test.ts - Admin action tests
• src/app/(admin)/admin/import/page.tsx - Import UI
• src/app/(admin)/admin/initialize/page.tsx - Initialization UI with SSE progress
• src/app/api/admin/initialize/route.ts - SSE API endpoint for real-time progress

✅ Milestone 4 Completed Features

Collections Management:

• ✅ Complete CRUD operations for collections (create, read, update, delete)
• ✅ Global HSK collections (admin-created, read-only for users)
• ✅ User personal collections (full control)
• ✅ Add hanzi to collections via:
  • Search & multi-select with checkboxes
  • Paste list (comma, space, or newline separated)
  • Create collection with hanzi list
• ✅ Remove hanzi (individual and bulk selection)
• ✅ Collection detail view with hanzi list
• ✅ Order preservation for added hanzi
• ✅ Duplicate detection and validation
• ✅ 21 passing integration tests

Files Created:

• src/actions/collections.ts - Collection Server Actions
• src/actions/collections.integration.test.ts - Complete test suite
• src/app/(app)/collections/page.tsx - Collections list page
• src/app/(app)/collections/[id]/page.tsx - Collection detail page
• src/app/(app)/collections/new/page.tsx - Create collection page

✅ Milestone 5 Completed Features

Hanzi Search & Detail Views:

• ✅ Public hanzi search (no authentication required)
• ✅ Search by simplified, traditional, pinyin, or meaning
• ✅ HSK level filtering (12 levels: new-1 through new-6, old-1 through old-6)
• ✅ Pagination with hasMore indicator (20 results per page)
• ✅ Comprehensive detail view showing:
  • All forms (simplified, traditional with isDefault indicator)
  • All transcriptions (pinyin, numeric, wade-giles, etc.)
  • All meanings with language codes
  • HSK level badges
  • Parts of speech
  • Classifiers, radical, frequency
• ✅ Add to collection from detail page
• ✅ 16 passing integration tests

Files Created:

• src/actions/hanzi.ts - Public hanzi search actions
• src/app/(app)/hanzi/page.tsx - Search page with filters
• src/app/(app)/hanzi/[id]/page.tsx - Detail page with all data
• src/actions/hanzi.integration.test.ts - Complete test suite

Key Features:

• searchHanzi(): Fuzzy search across simplified, traditional, pinyin, and meanings
• HSK level filtering for targeted vocabulary
• Pagination with hasMore indicator for infinite scroll support
• Complete hanzi data display including rare transcription types
• Direct integration with collections (add from detail page)

✅ Milestone 6 Completed Features

SM-2 Algorithm Implementation:

• ✅ Core SM-2 spaced repetition algorithm following SuperMemo specification
• ✅ Exact formulas for correct and incorrect answer calculations
• ✅ Initial values: easeFactor=2.5, interval=1, consecutiveCorrect=0
• ✅ Correct answer logic:
  • First correct: interval = 1 day
  • Second correct: interval = 6 days
  • Third+ correct: interval = Math.round(interval × easeFactor)
  • Increase easeFactor by 0.1 with each correct answer
• ✅ Incorrect answer logic:
  • Reset interval to 1 day
  • Reset consecutiveCorrect to 0
  • Decrease easeFactor by 0.2 (minimum 1.3)
  • Increment incorrectCount
• ✅ Card selection algorithm:
  • Filter out SUSPENDED cards
  • Select due cards (nextReviewDate ≤ now)
  • Priority: HARD > NORMAL > EASY
  • Sort by: nextReviewDate ASC, incorrectCount DESC, consecutiveCorrect ASC
  • Limit to cardsPerSession
• ✅ Wrong answer generation with Fisher-Yates shuffle
• ✅ 38 passing unit tests with 100% statement and line coverage
• ✅ 94.11% branch coverage (exceeds 90% requirement)

Files Created:

• src/lib/learning/sm2.ts - Core algorithm implementation
• src/lib/learning/sm2.test.ts - Comprehensive unit tests

Functions Implemented:

• calculateCorrectAnswer() - Update progress for correct answers
• calculateIncorrectAnswer() - Update progress for incorrect answers
• selectCardsForSession() - Select due cards with priority sorting
• generateWrongAnswers() - Generate 3 incorrect options from same HSK level
• shuffleOptions() - Fisher-Yates shuffle for randomizing answer positions

✅ Milestone 7-8 Completed Features

Learning Interface:

• ✅ Learning session page (/learn/[collectionId]) with dynamic routing
• ✅ Large hanzi display (text-9xl) for easy reading
• ✅ 4 pinyin answer options in 2x2 grid layout
• ✅ Auto-submit after answer selection (100ms delay)
• ✅ Progress bar showing "Card X of Y" with percentage
• ✅ Green/red feedback overlay with checkmark/X icons
• ✅ Correct answer display for incorrect responses
• ✅ English meaning display after answer submission
• ✅ Session summary screen with statistics:
  • Total cards, correct/incorrect counts
  • Accuracy percentage
  • Session duration in minutes
• ✅ Keyboard shortcuts:
  • Press 1-4 to select answer options
  • Press Space to continue after feedback
• ✅ Loading and error states
• ✅ Responsive mobile-first design

Learning Server Actions:

• ✅ startLearningSession() - Initialize session with card selection and answer generation
• ✅ submitAnswer() - Record answer and update SM-2 progress
• ✅ endSession() - Mark session complete and return summary
• ✅ getDueCards() - Count cards due today/this week
• ✅ updateCardDifficulty() - Manual difficulty override (EASY/MEDIUM/HARD/SUSPENDED)
• ✅ removeFromLearning() - Suspend card from learning

SM-2 Integration:

• ✅ Automatic progress tracking with SM-2 algorithm
• ✅ Due card selection with priority sorting
• ✅ New card introduction when insufficient due cards
• ✅ Two-stage card randomization:
  • Random tiebreaker for equal-priority cards during selection
  • Final shuffle of selected cards for presentation
• ✅ Wrong answer generation from same HSK level
• ✅ Session tracking in database (LearningSession, SessionReview)

Navigation Integration:

• ✅ "Start Learning" button on collection detail pages
• ✅ "Learn All" option on dashboard
• ✅ Routes: /learn/all and /learn/[collectionId]

Files Created:

• src/actions/learning.ts - Learning session Server Actions (700+ lines)
• src/app/(app)/learn/[collectionId]/page.tsx - Learning session UI (340+ lines)

Enhancements:

• ✅ English meaning display for vocabulary reinforcement
• ✅ Randomized card presentation to prevent demoralization
• ✅ All 38 SM-2 algorithm tests passing with 98.92% coverage

✅ Milestone 9 Completed Features

Dashboard Enhancements:

• ✅ Real-time statistics widgets replacing hardcoded zeros
• ✅ Due cards counter (now, today, this week)
• ✅ Total learned cards count
• ✅ Daily goal progress tracker (reviewed today / daily goal)
• ✅ Learning streak calculation (consecutive days with reviews)
• ✅ Recent activity section showing last 5 learning sessions
• ✅ Session cards with accuracy percentages and collection names
• ✅ Navigation link to progress page

Progress Page:

• ✅ Comprehensive progress page at /progress
• ✅ Date range selector (7/30/90/365 days)
• ✅ Summary statistics cards:
  • Cards reviewed in selected period
  • Overall accuracy percentage
  • Total cards in learning
  • Average session length (minutes)
• ✅ Daily Activity bar chart (Recharts):
  • Stacked correct/incorrect reviews by date
  • Interactive tooltips with detailed counts
• ✅ Accuracy Trend line chart:
  • Daily accuracy percentage over time
  • Smooth line visualization
• ✅ Session history table:
  • Sortable by date
  • Shows collection, cards reviewed, accuracy, session length
  • Responsive design
• ✅ Dark mode compatible color schemes

Progress Server Actions:

• ✅ getStatistics() - Returns due cards, total learned, daily goal, streak
• ✅ getUserProgress() - Returns overview stats and daily activity breakdown
• ✅ getLearningSessions() - Returns paginated session history
• ✅ getHanziProgress() - Individual hanzi progress details
• ✅ resetHanziProgress() - Reset card to initial state

Statistics Calculations:

• ✅ Streak calculation algorithm (consecutive days with reviews)
• ✅ Daily activity aggregation using Map for efficient grouping
• ✅ Accuracy calculations (correct / total reviews)
• ✅ Average session length (total duration / session count)
• ✅ Date range filtering for historical data

Recharts Integration:

• ✅ Installed and configured Recharts library
• ✅ Line chart component for trends
• ✅ Bar chart component with stacking for activity
• ✅ Responsive containers for mobile/desktop
• ✅ Custom tooltips and legends

Files Created:

• src/actions/progress.ts - Progress tracking Server Actions (550+ lines)
• src/app/(app)/progress/page.tsx - Progress visualization page (380+ lines)

Files Modified:

• src/app/(app)/dashboard/page.tsx - Added real statistics and recent activity
• Navigation updated across dashboard and progress pages

🎨 Naming Conventions

User-Facing:

• Always: "MemoHanzi" (capitalized)
• Tagline: "Remember Hanzi, effortlessly"
• Include Chinese: 记汉字

Technical:

• Directory: memohanzi/
• Database: memohanzi_db
• User: memohanzi_user
• Container: memohanzi-app, memohanzi-postgres

See PROJECT-NAMING.md for complete guidelines.

📚 Data Source

HSK Vocabulary: https://github.com/drkameleon/complete-hsk-vocabulary/

This repository contains comprehensive HSK (Chinese proficiency test) vocabulary data that will be imported into MemoHanzi.

🔐 Security Highlights

• ✅ Passwords hashed with bcrypt
• ✅ NextAuth.js session management
• ✅ HTTPS via Nginx
• ✅ Rate limiting
• ✅ Input validation (Zod)
• ✅ SQL injection prevention (Prisma)

🧪 Testing Strategy

• Unit Tests (70%): Business logic, SM-2 algorithm, parsers
• Integration Tests (20%): Server Actions, database operations
• E2E Tests (10%): Critical user flows

Tools: Vitest (unit/integration), Playwright (E2E)

📖 Additional Resources

• Next.js Docs: https://nextjs.org/docs
• Prisma Docs: https://www.prisma.io/docs
• NextAuth Docs: https://authjs.dev
• SM-2 Algorithm: https://www.supermemo.com/en/archives1990-2015/english/ol/sm2

🎯 Success Criteria (MVP)

Technical:

• All tests passing (70%+ coverage)
• Can import complete HSK vocabulary
• Page load <2s
• Mobile responsive

Functional:

• Complete learning session works end-to-end
• SM-2 algorithm accurate
• Progress tracking working
• Collections management functional
• Search efficient

User Experience:

• Can learn 20+ cards in 5-10 minutes
• Interface intuitive
• Daily use sustainable

🚦 Getting Started Checklist

Before beginning implementation:

• Read complete specification document
• Understand the tech stack
• Review the milestone approach
• Check naming conventions
• Set up development environment
• Confirm understanding of SM-2 algorithm

💡 Important Reminders

1. Read the spec before implementing anything
2. Ask questions if anything is unclear
3. Don't make up alternatives or "improvements"
4. Write tests as you go
5. Follow the milestone sequence
6. Use consistent naming (check PROJECT-NAMING.md)

📞 Next Steps

For Claude Code: Start by saying: "I've read CLAUDE.md and HANZI-LEARNING-APP-SPECIFICATION.md. Ready to begin Milestone 1: Project Foundation."

For Human Developers:

1. Set up your development environment
2. Create project directory: memohanzi/
3. Begin Milestone 1 tasks
4. Reference the specification frequently

---

Good luck building MemoHanzi! 🎯

记汉字 - Remember Hanzi, effortlessly.