CodeReps

A lightweight, offline-first Progressive Web App (PWA) for tracking LeetCode problem reviews using spaced repetition. Built with clean architecture principles and designed for deliberate practice.

Features

• ✅ Spaced Repetition Algorithm - Smart scheduling based on difficulty
• ✅ Offline-First - Works without internet using IndexedDB
• ✅ Autocomplete Search - Quickly find and review existing problems
• ✅ Review Queue - Prioritized by due date with overdue indicators
• ✅ Progressive Web App - Install on iPhone, Mac, or any device
• ✅ Auto-Archive - Problems automatically archive after 3 successful reviews
• ✅ Clean Architecture - Deep modules with information hiding

Tech Stack

• Framework: Next.js 14 (App Router) + TypeScript
• Styling: Tailwind CSS
• Storage: Dexie.js (IndexedDB wrapper)
• Deployment: Vercel (recommended)

Architecture

This app follows John Ousterhout's Philosophy of Software Design with:

Deep Modules (Simple Interface, Complex Implementation)

src/domain/
├── SRSScheduler.ts       # Handles all scheduling logic
├── ProblemRepository.ts  # Hides IndexedDB complexity
└── ReviewQueue.ts        # Manages review queue sorting

Layers

UI Components (Thin)
      ↓
Application Services (Thin orchestrator)
      ↓
Domain Modules (Deep - business logic)
      ↓
Storage Adapter (Deep - hides IndexedDB)

SRS Algorithm

Initial Intervals

• Easy: 90 days (essentially archived)
• Medium: 7 days
• Hard: 3 days
• Didn't Get: 1 day

Review Progression

After each successful review, intervals multiply:

• Review 1: Base interval
• Review 2: Base × 2
• Review 3: Base × 2
• Review 4+: Base × 3

Max interval: 90 days Auto-archive: After 3 successful reviews (EASY or MEDIUM)

Getting Started

Prerequisites

• Node.js 18+
• npm or yarn

Installation

1. Extract the ZIP file

unzip codereps.zip
cd codereps

2. Install dependencies

npm install

3. Run locally

npm run dev

Open http://localhost:3000 in your browser.

Deployment to Vercel

Option 1: Vercel CLI (Automatic GitHub Repo Creation)

1. Install Vercel CLI

npm install -g vercel

2. Deploy

vercel

Follow the prompts. Vercel will:

• Create a GitHub repository for you
• Deploy your app
• Give you a live URL
• Auto-deploy on every push

Option 2: GitHub + Vercel Dashboard

1. Push to GitHub

git init
git add .
git commit -m "Initial commit"
git remote add origin <your-github-repo-url>
git push -u origin main

2. Connect to Vercel

• Go to vercel.com
• Import your GitHub repository
• Click "Deploy"

That's it! Your app will be live at https://your-app.vercel.app

Install as PWA

iPhone

1. Open the app in Safari
2. Tap the Share button
3. Tap "Add to Home Screen"
4. Tap "Add"

Mac

1. Open the app in Chrome/Edge
2. Click the install icon in the address bar
3. Click "Install"

Android

1. Open the app in Chrome
2. Tap the three dots menu
3. Tap "Add to Home Screen"

Usage Guide

Adding a Problem

1. Enter problem name (autocomplete will suggest existing problems)
2. Optionally enter problem number
3. Select review date (defaults to today)
4. Click a difficulty button:
   • Easy: Won't review again (or 90 days)
   • Medium: Review in 7 days
   • Hard: Review in 3 days
   • Didn't Get: Review tomorrow

Reviewing Problems

1. Today's Reviews section shows all due/overdue problems
2. First 3 reviews are always visible
3. Click "Show X more reviews" to see all
4. Click problem name to open on LeetCode (if number is provided)
5. Use Archive to manually archive a problem
6. Use Delete to permanently remove a problem

Managing Reviews

• Archive: Remove from active reviews (can unarchive later)
• Auto-archive: Happens after 3 successful reviews
• Delete: Permanently remove (cannot undo)

File Structure

codereps/
├── src/
│   ├── app/                    # Next.js App Router
│   │   ├── layout.tsx
│   │   ├── page.tsx
│   │   └── globals.css
│   │
│   ├── domain/                 # Domain layer (deep modules)
│   │   ├── models/
│   │   │   └── Problem.ts
│   │   ├── SRSScheduler.ts
│   │   ├── ProblemRepository.ts
│   │   └── ReviewQueue.ts
│   │
│   ├── storage/                # Storage layer
│   │   └── IndexedDBAdapter.ts
│   │
│   ├── services/               # Application services
│   │   └── ReviewService.ts
│   │
│   └── components/             # UI components
│       ├── ProblemInput.tsx
│       ├── ReviewList.tsx
│       └── Stats.tsx
│
├── public/                     # Static assets
│   └── manifest.json
│
├── package.json
├── tsconfig.json
├── tailwind.config.ts
└── next.config.js

Customization

Adjust SRS Intervals

Edit src/domain/SRSScheduler.ts:

private readonly MAX_INTERVAL_DAYS = 90  // Change max interval
private readonly AUTO_ARCHIVE_THRESHOLD = 3  // Change auto-archive threshold

private getBaseInterval(difficulty: Difficulty): number {
  switch (difficulty) {
    case Difficulty.EASY: return 90  // Change intervals
    case Difficulty.MEDIUM: return 7
    case Difficulty.HARD: return 3
    case Difficulty.DIDNT_GET: return 1
  }
}

Change Review Limit

Edit src/components/ReviewList.tsx:

const REVIEW_LIMIT = 3  // Change number of visible reviews

Customize Colors

Edit tailwind.config.ts to change the color scheme.

Browser Compatibility

• ✅ Chrome/Edge (Desktop & Mobile)
• ✅ Safari (iOS & macOS)
• ✅ Firefox (Desktop & Mobile)

Requires IndexedDB support (all modern browsers).

Data Storage

• Local storage only - All data stored in IndexedDB
• No cloud sync - Works completely offline
• No tracking - Your data never leaves your device
• Clear data: Delete browser data to reset

To add cloud sync in the future, you can integrate Firebase or Supabase with the existing ProblemRepository.

Troubleshooting

App not loading

• Check browser console for errors
• Clear browser cache and reload
• Try in incognito mode

Data not persisting

• Ensure cookies/storage are enabled
• Check if in Private/Incognito mode (IndexedDB disabled)
• Verify browser supports IndexedDB

Build errors

# Clear cache and reinstall
rm -rf node_modules .next
npm install
npm run dev

Future Enhancements

Potential features to add:

• Cloud sync (Firebase/Supabase)
• LeetCode API integration
• Problem difficulty tags
• Review streaks/statistics
• Export/import data
• Dark mode
• Problem notes/solutions

Contributing

This is a personal project, but feel free to fork and customize for your own use!

License

MIT License - Use however you want!