"""Configuration management using Pydantic Settings.

This module provides centralized configuration management for the
OpenRouter API Key Monitor application.
"""
from functools import lru_cache
from pydantic_settings import BaseSettings, SettingsConfigDict
from pydantic import Field


class Settings(BaseSettings):
    """Application settings loaded from environment variables.
    
    Required environment variables:
        - SECRET_KEY: JWT signing key (min 32 chars)
        - ENCRYPTION_KEY: AES-256 encryption key (32 bytes)
    
    Optional environment variables with defaults:
        - DATABASE_URL: SQLite database path
        - OPENROUTER_API_URL: OpenRouter API base URL
        - SYNC_INTERVAL_MINUTES: Background sync interval
        - MAX_API_KEYS_PER_USER: API key limit per user
        - RATE_LIMIT_REQUESTS: API rate limit
        - RATE_LIMIT_WINDOW: Rate limit window (seconds)
        - JWT_EXPIRATION_HOURS: JWT token lifetime
        - DEBUG: Debug mode flag
        - LOG_LEVEL: Logging level
    """
    
    # Database
    database_url: str = Field(
        default="sqlite:///./data/app.db",
        description="SQLite database URL"
    )
    
    # Security - REQUIRED
    secret_key: str = Field(
        description="JWT signing key (min 32 characters)"
    )
    encryption_key: str = Field(
        description="AES-256 encryption key (32 bytes)"
    )
    jwt_expiration_hours: int = Field(
        default=24,
        description="JWT token expiration in hours"
    )
    
    # OpenRouter Integration
    openrouter_api_url: str = Field(
        default="https://openrouter.ai/api/v1",
        description="OpenRouter API base URL"
    )
    
    # Task scheduling
    sync_interval_minutes: int = Field(
        default=60,
        description="Background sync interval in minutes"
    )
    usage_stats_retention_days: int = Field(
        default=365,
        description="Retention period for usage stats in days"
    )
    
    # Limits
    max_api_keys_per_user: int = Field(
        default=10,
        description="Maximum API keys per user"
    )
    max_api_tokens_per_user: int = Field(
        default=5,
        description="Maximum API tokens per user"
    )
    rate_limit_requests: int = Field(
        default=100,
        description="API rate limit requests"
    )
    rate_limit_window: int = Field(
        default=3600,
        description="Rate limit window in seconds"
    )
    
    # App settings
    debug: bool = Field(
        default=False,
        description="Debug mode"
    )
    log_level: str = Field(
        default="INFO",
        description="Logging level"
    )

    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        case_sensitive=False
    )


@lru_cache()
def get_settings() -> Settings:
    """Get cached settings instance.
    
    Returns:
        Settings: Application settings instance
        
    Example:
        >>> from openrouter_monitor.config import get_settings
        >>> settings = get_settings()
        >>> print(settings.database_url)
    """
    return Settings()