"""
使用 Pydantic Settings 的应用程序配置。
"""
from typing import Optional
from pydantic_settings import BaseSettings
from pydantic import Field


class Settings(BaseSettings):
    """
    从环境变量加载的应用程序设置。
    """

    # 应用程序
    app_name: str = Field(default="LangChain Learning Kit", description="Application name")
    environment: str = Field(default="development", description="Environment (development/production)")
    debug: bool = Field(default=False, description="Debug mode")
    log_level: str = Field(default="INFO", description="Logging level")

    # 服务器
    host: str = Field(default="0.0.0.0", description="Server host")
    port: int = Field(default=8000, description="Server port")

    # 数据库
    database_url: str = Field(
        ...,
        description="Database connection URL",
        examples=["mysql+pymysql://root:123456@localhost:3306/langchain_learning"]
    )

    # OpenAI
    openai_api_key: str = Field(..., description="OpenAI API key")
    openai_base_url: Optional[str] = Field(
        default=None,
        description="OpenAI API base URL (for proxy or custom endpoints)"
    )

    # FAISS 存储
    faiss_base_path: str = Field(default="data/faiss", description="Base path for FAISS indexes")

    # 文本分割
    chunk_size: int = Field(default=1000, description="Default chunk size for text splitting")
    chunk_overlap: int = Field(default=200, description="Default chunk overlap")

    model_config = {
        "env_file": ".env",
        "env_file_encoding": "utf-8",
        "case_sensitive": False,
    }


# 全局设置实例
_settings: Optional[Settings] = None


def get_settings() -> Settings:
    """
    获取或创建全局设置实例。

    Returns:
        Settings: 应用程序设置
    """
    global _settings
    if _settings is None:
        _settings = Settings()
    return _settings