"""Application configuration settings.

This module handles all configuration settings loaded from environment variables.
Settings are validated using Pydantic and cached for performance.
"""

from functools import lru_cache

from pydantic import Field
from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    """Application settings loaded from environment variables."""

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

    # MongoDB Configuration
    mongo_uri: str = Field(
        ...,
        alias="MONGO_URI",
        description="MongoDB connection URI",
    )
    mongo_db: str = Field(
        "expense",
        alias="MONGO_DB",
        description="MongoDB database name",
    )
    mongo_collection: str = Field(
        "headcategories",
        alias="MONGO_COLLECTION",
        description="MongoDB collection name for headcategories",
    )
    mongo_subcategory_collection: str = Field(
        "categories",
        alias="MONGO_SUBCATEGORY_COLLECTION",
        description="MongoDB collection name for categories",
    )
    api_logs_collection: str = Field(
        "api_logs",
        alias="MONGO_API_LOGS_COLLECTION",
        description="MongoDB collection name for API logs",
    )

    # OpenAI Configuration
    openai_api_key: str = Field(
        ...,
        alias="OPENAI_API_KEY",
        description="OpenAI API key for LLM requests",
    )
    openai_model: str = Field(
        "gpt-4o-mini",
        alias="OPENAI_MODEL",
        description="OpenAI model to use for categorization",
    )

    # Performance & Caching Configuration
    category_cache_ttl_seconds: int = Field(
        300,
        alias="CATEGORY_CACHE_TTL",
        description="Time-to-live for category cache in seconds (5 minutes default)",
        ge=60,  # Minimum 1 minute
    )
    db_query_timeout_seconds: float = Field(
        5.0,
        alias="DB_QUERY_TIMEOUT",
        description="Timeout for database queries in seconds",
        ge=1.0,
        le=30.0,
    )
    openai_api_timeout_seconds: float = Field(
        15.0,
        alias="OPENAI_API_TIMEOUT",
        description="Timeout for OpenAI API calls in seconds",
        ge=5.0,
        le=60.0,
    )


@lru_cache
def get_settings() -> Settings:
    """Get cached settings instance.

    Returns:
        Settings: Application settings instance
    """
    return Settings()


# Global settings instance
settings = get_settings()