backend/app/core/config.py

from pydantic_settings import BaseSettings
from typing import Optional
import os
import tempfile


class Settings(BaseSettings):
    # API Configuration
    API_V1_STR: str = "/api/v1"
    PROJECT_NAME: str = "PDF Q&A Chatbot"
    
    # Security
    SECRET_KEY: str = "your-secret-key-here"
    ACCESS_TOKEN_EXPIRE_MINUTES: int = 60 * 24 * 8  # 8 days
    
    # Database
    DATABASE_URL: str = "sqlite:///./pdf_chatbot.db"
    
    # Vector Database
    CHROMA_PERSIST_DIRECTORY: str = "chroma_db"
    
    # AI Providers
    OPENROUTER_API_KEY: Optional[str] = None
    ANTHROPIC_API_KEY: Optional[str] = None
    
    # File Storage
    UPLOAD_DIR: str = "uploads"
    MAX_FILE_SIZE: int = 10 * 1024 * 1024  # 10MB
    ALLOWED_EXTENSIONS: list = [".pdf"]
    
    # CORS
    BACKEND_CORS_ORIGINS: list = [
        "http://localhost:3000",
        "http://localhost:3001",
        "http://127.0.0.1:3000",
        "http://127.0.0.1:3001",
    ]
    
    class Config:
        env_file = ".env"
        case_sensitive = True


settings = Settings()

# Ensure upload and persistence directories exist, falling back to system temporary
for attr, fallback_subdir in [("UPLOAD_DIR", "uploads"), ("CHROMA_PERSIST_DIRECTORY", "chroma_db")]:
    dir_path = getattr(settings, attr)
    try:
        os.makedirs(dir_path, exist_ok=True)
    except PermissionError:
        # Fall back to a path inside the system temporary directory where writes are usually allowed
        temp_dir = os.path.join(tempfile.gettempdir(), fallback_subdir)
        os.makedirs(temp_dir, exist_ok=True)
        setattr(settings, attr, temp_dir)

# Additional safety: ensure CHROMA_PERSIST_DIRECTORY is writable (fallback to temp dir if not)
try:
    _test_chroma = os.path.join(settings.CHROMA_PERSIST_DIRECTORY, '.write_test')
    with open(_test_chroma, 'w') as _f:
        _f.write('')
    os.remove(_test_chroma)
except (PermissionError, OSError):
    temp_chroma = os.path.join(tempfile.gettempdir(), 'chroma_db')
    os.makedirs(temp_chroma, exist_ok=True)
    settings.CHROMA_PERSIST_DIRECTORY = temp_chroma

# Ensure SQLite database path is writable (fallback to temp dir if not)
if settings.DATABASE_URL.startswith("sqlite"):
    db_uri_prefix = "sqlite:///"
    db_path = settings.DATABASE_URL[len(db_uri_prefix):]
    abs_db_path = os.path.abspath(db_path)
    db_dir = os.path.dirname(abs_db_path)
    try:
        os.makedirs(db_dir, exist_ok=True)
        # Try creating a temporary file to check write access
        test_path = os.path.join(db_dir, ".write_test")
        with open(test_path, "w") as _f:
            _f.write("")
        os.remove(test_path)
    except (PermissionError, OSError):
        # Fallback
        temp_db_path = os.path.join(tempfile.gettempdir(), "pdf_chatbot.db")
        settings.DATABASE_URL = f"sqlite:///{temp_db_path}"