from pydantic_settings import BaseSettings
from pydantic import ConfigDict, field_validator
from functools import lru_cache
from urllib.parse import quote_plus


class Settings(BaseSettings):
    # Application
    APP_NAME: str = "ERP AI Assistant"
    APP_ENV: str = "development"
    DEBUG: bool = True
    SECRET_KEY: str

    # Database
    DB_DRIVER: str
    DB_SERVER: str
    DB_PORT: int = 1433
    DB_NAME: str
    DB_USER: str
    DB_PASSWORD: str

    # Claude API
    ANTHROPIC_API_KEY: str
    ANTHROPIC_BASE_URL: str | None = None  # Optional custom base URL for proxy/self-hosted
    CLAUDE_MODEL: str = "claude-sonnet-4-6"
    CLAUDE_MAX_TOKENS: int = 8192
    CLAUDE_TEMPERATURE: float = 0.7

    # Knowledge Base
    KNOWLEDGE_BASE_PATH: str = "./knowledge_base"
    CHROMA_DB_PATH: str = "./knowledge_base/chroma_db"
    EMBEDDING_MODEL: str = "all-MiniLM-L6-v2"
    CHUNK_SIZE: int = 500
    CHUNK_OVERLAP: int = 50

    # HuggingFace
    HF_ENDPOINT: str | None = None  # Optional: HuggingFace mirror endpoint

    @property
    def DATABASE_URL(self) -> str:
        """构建数据库连接 URL（密码安全编码）"""
        password = quote_plus(self.DB_PASSWORD)
        return (
            f"mssql+pyodbc://{self.DB_USER}:{password}"
            f"@{self.DB_SERVER}:{self.DB_PORT}/{self.DB_NAME}"
            f"?driver={quote_plus(self.DB_DRIVER)}"
        )

    @field_validator('CLAUDE_TEMPERATURE')
    @classmethod
    def validate_temperature(cls, v):
        if not 0 <= v <= 2:
            raise ValueError('CLAUDE_TEMPERATURE must be between 0 and 2')
        return v

    @field_validator('CHUNK_OVERLAP')
    @classmethod
    def validate_chunk_overlap(cls, v, info):
        chunk_size = info.data.get('CHUNK_SIZE', 500)
        if v >= chunk_size:
            raise ValueError('CHUNK_OVERLAP must be less than CHUNK_SIZE')
        return v

    model_config = ConfigDict(env_file=".env", case_sensitive=True)


@lru_cache()
def get_settings() -> Settings:
    """获取配置单例"""
    return Settings()