from pathlib import Path
from typing import Literal
from sqlalchemy.engine import URL
from pydantic import BaseModel
from pydantic_yaml import parse_yaml_raw_as


class SqlServerConfig(BaseModel):
    """SQL Server 连接配置"""
    host: str
    port: int = 1433
    database: str
    username: str
    password: str
    driver: str = "{ODBC Driver 18 for SQL Server}"
    trust_server_certificate: str = "yes"


class PostgreSqlConfig(BaseModel):
    """PostgreSQL 连接配置"""
    host: str
    port: int = 5432
    database: str
    username: str
    password: str


class DatabaseConfig(BaseModel):
    """数据库配置"""
    active: Literal["sql_server", "postgresql"] = "sql_server"
    sql_server: SqlServerConfig
    postgresql: PostgreSqlConfig | None = None


class Settings(BaseModel):
    """应用配置"""
    database: DatabaseConfig

    @property
    def database_url(self) -> URL:
        """构建数据库连接 URL"""
        if self.database.active == "postgresql":
            return self._postgresql_url()
        return self._sql_server_url()

    def _sql_server_url(self) -> URL:
        conf = self.database.sql_server
        return URL.create(
            "mssql+pyodbc",
            username=conf.username,
            password=conf.password,
            host=conf.host,
            port=conf.port,
            database=conf.database,
            query={
                "driver": conf.driver.strip("{}"),
                "TrustServerCertificate": conf.trust_server_certificate,
            },
        )

    def _postgresql_url(self) -> URL:
        conf = self.database.postgresql
        if conf is None:
            raise ValueError("已选择 postgresql，但未配置 database.postgresql")
        return URL.create(
            "postgresql+psycopg",
            username=conf.username,
            password=conf.password,
            host=conf.host,
            port=conf.port,
            database=conf.database,
        )


def load_settings(config_path: str = "config/settings.yaml") -> Settings:
    """加载 YAML 配置文件"""
    # Resolve relative to the project root (where config/ directory exists)
    path = Path(config_path)
    if not path.is_absolute():
        # __file__ is config/settings.py, so parent.parent gives us project root
        project_root = Path(__file__).resolve().parent.parent
        path = project_root / config_path
    if not path.exists():
        raise FileNotFoundError(
            f"配置文件不存在: {config_path}\n"
            f"请确保文件存在于项目根目录或指定正确路径"
        )
    # Use UTF-8 encoding to avoid Windows GBK encoding issues
    with open(path, "r", encoding="utf-8") as f:
        return parse_yaml_raw_as(Settings, f)


# 全局配置单例
settings = load_settings()