import os
from typing import Optional


class Settings:
    """Centralized application settings"""
    
    # Database
    DATABASE_URL: str = os.getenv("DATABASE_URL", "postgresql://cve_user:cve_password@localhost:5432/cve_sigma_db")
    
    # External API Keys
    NVD_API_KEY: Optional[str] = os.getenv("NVD_API_KEY")
    GITHUB_TOKEN: Optional[str] = os.getenv("GITHUB_TOKEN")
    OPENAI_API_KEY: Optional[str] = os.getenv("OPENAI_API_KEY")
    ANTHROPIC_API_KEY: Optional[str] = os.getenv("ANTHROPIC_API_KEY")
    
    # LLM Configuration
    LLM_PROVIDER: str = os.getenv("LLM_PROVIDER", "ollama")
    LLM_MODEL: str = os.getenv("LLM_MODEL", "llama3.2")
    OLLAMA_BASE_URL: str = os.getenv("OLLAMA_BASE_URL", "http://ollama:11434")
    
    # API Configuration
    NVD_API_BASE_URL: str = "https://services.nvd.nist.gov/rest/json/cves/2.0"
    GITHUB_API_BASE_URL: str = "https://api.github.com"
    
    # Rate Limiting
    NVD_RATE_LIMIT: int = 50 if NVD_API_KEY else 5  # requests per 30 seconds
    GITHUB_RATE_LIMIT: int = 5000 if GITHUB_TOKEN else 60  # requests per hour
    
    # Application Settings
    DEBUG: bool = os.getenv("DEBUG", "false").lower() == "true"
    LOG_LEVEL: str = os.getenv("LOG_LEVEL", "INFO")
    
    # CORS Settings
    CORS_ORIGINS: list = [
        "http://localhost:3000",
        "http://127.0.0.1:3000",
        "http://frontend:3000"
    ]
    
    # Processing Settings
    DEFAULT_BATCH_SIZE: int = 50
    MAX_GITHUB_RESULTS: int = 10
    DEFAULT_START_YEAR: int = 2002
    
    @classmethod
    def get_instance(cls) -> "Settings":
        """Get singleton instance of settings"""
        if not hasattr(cls, "_instance"):
            cls._instance = cls()
        return cls._instance


# Global settings instance
settings = Settings.get_instance()