backend/config/settings.py

import os
from pathlib import Path
from datetime import timedelta
import dotenv

# Build paths inside the project like this: BASE_DIR / 'subdir'.
BASE_DIR = Path(__file__).resolve().parent.parent

# Load environment variables from parent directory .env
ENV_PATH = BASE_DIR.parent / '.env'
if ENV_PATH.exists():
    dotenv.load_dotenv(ENV_PATH)

# Security settings
SECRET_KEY = os.getenv('SECRET_KEY')
if not SECRET_KEY:
    raise ValueError(
        "SECRET_KEY environment variable is required. "
        "Generate one with: python -c \"from django.core.management.utils import get_random_secret_key; print(get_random_secret_key())\""
    )
DEBUG = os.getenv('DEBUG', 'False') == 'True'
ALLOWED_HOSTS = [h.strip() for h in os.getenv('ALLOWED_HOSTS', 'localhost,127.0.0.1').split(',') if h.strip()]

# Production security hardening (only when DEBUG=False)
if not DEBUG:
    SECURE_BROWSER_XSS_FILTER = True
    SECURE_CONTENT_TYPE_NOSNIFF = True
    SESSION_COOKIE_SECURE = True
    CSRF_COOKIE_SECURE = True
    X_FRAME_OPTIONS = 'DENY'
    SECURE_SSL_REDIRECT = False  # Set True if behind TLS termination proxy
    SECURE_HSTS_SECONDS = 0       # Set to 31536000 once HTTPS is confirmed
    SECURE_HSTS_INCLUDE_SUBDOMAINS = False
    SECURE_HSTS_PRELOAD = False

# Application definition
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    
    # Third party apps
    'rest_framework',
    'rest_framework_simplejwt.token_blacklist',
    'corsheaders',
    
    # Custom apps
    'graphrag',
]

MIDDLEWARE = [
    'corsheaders.middleware.CorsMiddleware',  # Must be placed high up
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

ROOT_URLCONF = 'config.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'config.wsgi.application'

# Database configuration
# Supports: sqlite (default) or postgres
DB_ENGINE = os.getenv('DB_ENGINE', 'sqlite')

if DB_ENGINE == 'postgres':
    DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.postgresql',
            'NAME': os.getenv('DB_NAME', 'graphrag'),
            'USER': os.getenv('DB_USER', 'postgres'),
            'PASSWORD': os.getenv('DB_PASSWORD', ''),
            'HOST': os.getenv('DB_HOST', 'localhost'),
            'PORT': os.getenv('DB_PORT', '5432'),
        }
    }
else:
    DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.sqlite3',
            'NAME': BASE_DIR / 'db' / 'db.sqlite3',
        }
    }

# Custom User Model
AUTH_USER_MODEL = 'graphrag.User'

AUTHENTICATION_BACKENDS = [
    'graphrag.views.EmailOrUsernameModelBackend',
    'django.contrib.auth.backends.ModelBackend',
]

# Password validation
AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
        'OPTIONS': {
            'min_length': 8,
        }
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]

# Internationalization
LANGUAGE_CODE = 'en-us'
TIME_ZONE = 'UTC'
USE_I18N = True
USE_TZ = True

# Static files (CSS, JavaScript, Images)
STATIC_URL = 'static/'

# Media files (User uploads)
MEDIA_URL = '/media/'
MEDIA_ROOT = BASE_DIR / 'uploaded_documents'

DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'

# CORS configuration
CORS_ALLOW_ALL_ORIGINS = False
CORS_ALLOWED_ORIGINS = [
    origin.strip()
    for origin in os.getenv(
        'CORS_ALLOWED_ORIGINS',
        'http://localhost:3000,http://0.0.0.0:3000,http://127.0.0.1:3000'
    ).split(',')
    if origin.strip()
]

# Django REST Framework configuration
REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'rest_framework_simplejwt.authentication.JWTAuthentication',
    ),
    'DEFAULT_PERMISSION_CLASSES': (
        'rest_framework.permissions.IsAuthenticated',
    ),
    'DEFAULT_THROTTLE_CLASSES': (
        'rest_framework.throttling.AnonRateThrottle',
        'rest_framework.throttling.UserRateThrottle',
    ),
    'DEFAULT_THROTTLE_RATES': {
        'anon': '30/minute',
        'user': '100/minute',
    },
}

# Simple JWT settings
SIMPLE_JWT = {
    'ACCESS_TOKEN_LIFETIME': timedelta(minutes=30),
    'REFRESH_TOKEN_LIFETIME': timedelta(days=7),
    'ROTATE_REFRESH_TOKENS': True,
    'BLACKLIST_AFTER_ROTATION': True,
    'ALGORITHM': 'HS256',
    'SIGNING_KEY': SECRET_KEY,
    'VERIFYING_KEY': None,
    'AUDIENCE': None,
    'ISSUER': None,
    'AUTH_HEADER_TYPES': ('Bearer',),
    'USER_ID_FIELD': 'id',
    'USER_ID_CLAIM': 'user_id',
    'AUTH_TOKEN_CLASSES': ('rest_framework_simplejwt.tokens.AccessToken',),
}

# File Upload Settings
ALLOWED_EXTENSIONS = {'.pdf', '.txt', '.md', '.docx', '.doc', '.csv', '.json', '.html', '.xml'}
MAX_UPLOAD_SIZE_MB = 10

# Ingestion Concurrency
MAX_INGESTION_WORKERS = 3

# Graph Database (Neo4j) settings
NEO4J_URI = os.getenv('NEO4J_URI', 'bolt://localhost:7687')
NEO4J_USERNAME = os.getenv('NEO4J_USERNAME', 'neo4j')
NEO4J_PASSWORD = os.getenv('NEO4J_PASSWORD', 'password')

# ChromaDB settings
# Supports: local (default) or cloud
CHROMADB_MODE = os.getenv('CHROMADB_MODE', 'local')
CHROMADB_HOST = os.getenv('CHROMADB_HOST', '')
CHROMADB_PORT = int(os.getenv('CHROMADB_PORT', '0'))
CHROMADB_DIR = os.path.join(BASE_DIR, os.getenv('CHROMADB_DIR', 'chroma_db'))

# Logging Configuration
LOG_DIR = BASE_DIR / 'logs'
LOG_DIR.mkdir(exist_ok=True)

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': {
        'detailed': {
            'format': '%(asctime)s [%(levelname)s] %(name)s:%(lineno)d - %(message)s'
        },
        'simple': {
            'format': '[%(levelname)s] %(message)s'
        },
    },
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
            'formatter': 'detailed',
        },
        'file': {
            'class': 'logging.handlers.RotatingFileHandler',
            'filename': LOG_DIR / 'graphrag.log',
            'maxBytes': 10 * 1024 * 1024,  # 10MB
            'backupCount': 5,
            'formatter': 'detailed',
        },
    },
    'loggers': {
        '': {
            'handlers': ['console', 'file'],
            'level': 'INFO',
        },
        'django': {
            'handlers': ['console', 'file'],
            'level': 'INFO',
            'propagate': False,
        },
        'graphrag': {
            'handlers': ['console', 'file'],
            'level': 'INFO',
            'propagate': False,
        },
    },
}