add teaching feature

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+**OnlineJudge** is the backend for an Online Judge platform. Built with Django 5 + Django REST Framework, PostgreSQL, Redis, Django Channels (WebSocket), and Dramatiq (async task queue). Python 3.12+, managed with `uv`.
+
+## Commands
+
+```bash
+# Development
+python dev.py                    # Start dev server (Daphne ASGI + Django runserver)
+python manage.py runserver       # HTTP only (no WebSocket support)
+python manage.py migrate         # Apply database migrations
+python manage.py makemigrations  # Create new migrations
+
+# Dependencies
+uv sync                          # Install dependencies from uv.lock
+uv add <package>                 # Add a dependency
+
+# Testing
+python manage.py test            # Run Django test suite
+coverage run manage.py test      # Run with coverage
+coverage report                  # Show coverage report
+```
+
+## Architecture
+
+### App Modules
+
+Each Django app follows the same structure:
+```
+<app>/
+├── models.py         # Django models
+├── serializers.py    # DRF serializers
+├── views/
+│   ├── oj.py         # User-facing API views
+│   └── admin.py      # Admin API views
+└── urls/
+    ├── oj.py         # User-facing URL patterns
+    └── admin.py      # Admin URL patterns
+```
+
+Apps: `account`, `problem`, `submission`, `contest`, `ai`, `flowchart`, `problemset`, `class_pk`, `announcement`, `tutorial`, `message`, `comment`, `conf`, `options`, `judge`
+
+### URL Routing
+
+All routes are registered in `oj/urls.py`:
+- `api/` — user-facing endpoints
+- `api/admin/` — admin-only endpoints
+
+WebSocket routing is in `oj/routing.py`.
+
+### Settings Structure
+
+- `oj/settings.py` — base configuration
+- `oj/dev_settings.py` — development overrides (imported when `OJ_ENV != "production"`)
+- `oj/production_settings.py` — production overrides
+
+### Base APIView
+
+`utils/api/api.py` provides a custom `APIView` base class used by all views. It provides:
+- `self.success(data)` — returns `{"error": null, "data": data}`
+- `self.error(msg)` — returns `{"error": "error", "data": msg}`
+
+All views inherit from this, not Django's generic views or DRF's `APIView` directly.
+
+### Authentication & Permissions
+
+`account/decorators.py` provides decorators used on view methods:
+- `@login_required`
+- `@super_admin_required`
+- `@check_contest_permission`
+
+### Judge System
+
+- `judge/dispatcher.py` — dispatches submissions to the judge sandbox
+- `judge/tasks.py` — Dramatiq async tasks for judging
+- `judge/languages.py` — language configurations (compile/run commands, limits)
+
+Judge status codes are defined in `utils/constants.py` and must match the frontend's `utils/constants.ts`.
+
+### WebSocket (Channels)
+
+`submission/consumers.py` — WebSocket consumer for real-time submission status updates. Uses `channels-redis` as the channel layer backend.
+
+### Caching
+
+Redis-backed via `django-redis`. Cache keys use MD5 hashing for consistency. See `utils/cache.py`.
+
+### AI Integration
+
+`utils/openai.py` — OpenAI client wrapper configured to work with OpenAI-compatible APIs (e.g., DeepSeek). Used by `ai/` app for submission analysis.
+
+### Data Directory
+
+Test cases and submission outputs are stored in a separate data directory (configured in settings, not in the repo). The `data/` directory in the repo contains configuration templates.
+
+## Key Domain Concepts
+
+| Concept | Details |
+|---|---|
+| Problem types | ACM (binary accept/reject) vs OI (partial scoring) |
+| Judge statuses | Numeric codes -2 to 9 (defined in `utils/constants.py`) |
+| User roles | Regular / Admin / Super Admin |
+| Contest types | Public vs Password Protected |
+| Supported languages | C, C++, Python2, Python3, Java, JavaScript, Golang, Flowchart |
+
+## Related Repository
+
+The frontend is at `D:\Projects\ojnext` — a Vue 3 + Rsbuild project. See its CLAUDE.md for frontend details.