LexPlain

LexPlain is a web app that helps you understand legal documents in plain language. Upload a contract or paste text, and get an AI-powered summary, key clauses, and risk highlights—plus ask follow-up questions about your document.

Features

• Document analysis — Upload a file (PDF, DOC, DOCX, TXT) or paste text. AI summarizes the document, extracts key clauses, and flags risk levels.
• Plain-language results — Summary, clause breakdowns, and risk indicators (high/medium/low) in an easy-to-scan report.
• Ask questions — After analysis, ask questions about your document and get short, practical answers (with a reminder to consult a lawyer for serious matters).
• Multi-language — English and Simplified Chinese (简体中文) via the locale switcher.
• Privacy-focused — No document storage; analysis runs on your input and results stay in your session.
• Rate limiting — AI endpoints (analyze, ask) are limited per IP per hour (Redis-backed); when Redis is unavailable, requests are allowed.

Tech Stack

• Framework: Next.js 16 (App Router)
• UI: React 19, Tailwind CSS 4, lucide-react
• i18n: next-intl
• AI: DeepSeek (OpenAI-compatible API) for analysis and Q&A
• Storage & limits: Redis for stats, ratings, and per-IP rate limiting (set REDIS_URL)

Getting Started

Prerequisites

• Node.js 18+
• npm, yarn, pnpm, or bun

Install and run

# Install dependencies (pnpm preferred; npm/yarn/bun work too)
pnpm install

# Copy environment variables
cp .env.example .env

# Edit .env with your LLM API credentials and optional REDIS_URL

# Run the development server
pnpm dev

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

Scripts

Command	Description
pnpm dev	Start development server
pnpm build	Production build
pnpm start	Start production server
pnpm lint	Run ESLint
pnpm check	Run Biome check (format + lint)
pnpm release	Generate changelog and release

Project Structure

• src/app/ — App Router: [locale]/ (home, results), api/ (analyze, ask, rate, stats)
• src/components/ — Reusable UI (ClauseCard, RiskIndicators, RatingWidget, LocaleSwitcher, HeroTypewriter)
• src/lib/ — Utilities, AI helpers (utils.ts), Redis DB (db.ts), rate limiting (ratelimit.ts)
• src/types/ — Shared types (Risk, Clause, AnalysisResult)
• src/i18n/ — next-intl config and messages; proxy.ts for locale middleware
• messages/ — Locale JSON files (en, zh-CN)

See ARCHITECTURE.md for detailed architecture and data flow.

Environment Variables

Variable	Description
LLM_API_URL	LLM API base URL (e.g. DeepSeek)
LLM_API_KEY	LLM API key
LLM_MODEL	Model name (e.g. DeepSeek-chat)
REDIS_URL	Optional. Redis for stats, ratings, and per-IP rate limiting (20 AI requests/hour). If unset, stats/rate APIs fail and rate limiting is skipped (requests allowed).

Copy .env.example to .env and fill in your credentials.

Deployment

Deploy to Vercel or any Node.js platform. See Next.js deployment docs for more.