"""
=============================================================================
CONFIGURATION MODULE
=============================================================================

This module handles all configuration using Pydantic Settings.

Benefits of using Pydantic Settings:
- Type validation for environment variables
- Auto-loading from .env files
- IDE autocomplete and type hints
- Clear documentation of all required config

Usage:
    from config import settings
    print(settings.OPENAI_API_KEY)
"""

from pydantic_settings import BaseSettings
from functools import lru_cache


class Settings(BaseSettings):
    """
    Application settings loaded from environment variables.
    
    All settings can be overridden via:
    1. Environment variables
    2. .env file in the backend directory
    """
    
    # -------------------------------------------------------------------------
    # Server Configuration
    # -------------------------------------------------------------------------
    PORT: int = 8000
    ENVIRONMENT: str = "development"  # "development", "staging", "production"
    
    # -------------------------------------------------------------------------
    # Supabase Configuration
    # -------------------------------------------------------------------------
    SUPABASE_URL: str = ""
    SUPABASE_SERVICE_KEY: str = ""  # Service key for admin access
    
    # -------------------------------------------------------------------------
    # AI Configuration
    # -------------------------------------------------------------------------
    OPENAI_API_KEY: str = ""
    ANTHROPIC_API_KEY: str = ""
    AI_PROVIDER: str = "openai"  # "openai" or "anthropic"
    AI_MODEL: str = "gpt-3.5-turbo"
    
    # -------------------------------------------------------------------------
    # CORS Configuration
    # -------------------------------------------------------------------------
    CORS_ORIGINS: str = "http://localhost:3000"  # Comma-separated list
    
    @property
    def cors_origins_list(self) -> list[str]:
        """Parse CORS_ORIGINS string into a list."""
        return [origin.strip() for origin in self.CORS_ORIGINS.split(",")]
    
    class Config:
        # Load from .env file
        env_file = ".env"
        env_file_encoding = "utf-8"
        # Make field names case-insensitive
        case_sensitive = False


# Use lru_cache to create a singleton settings instance
@lru_cache
def get_settings() -> Settings:
    """
    Get cached settings instance.
    
    Using lru_cache ensures we only read the .env file once,
    improving performance.
    """
    return Settings()


# Export settings instance for easy import
settings = get_settings()