"""统一响应模型。

所有 API 返回统一壳：{code, message, data, trace_id, timestamp}
"""

import uuid
from datetime import datetime, timezone
from typing import Any, Generic, TypeVar

from pydantic import BaseModel, Field

T = TypeVar("T")


class ApiResponse(BaseModel, Generic[T]):
    """统一 API 响应壳。"""

    code: int = Field(default=0, description="业务状态码，0 表示成功")
    message: str = Field(default="success", description="提示信息")
    data: T | None = Field(default=None, description="业务数据")
    trace_id: str = Field(default_factory=lambda: str(uuid.uuid4()), description="链路追踪 ID")
    timestamp: str = Field(
        default_factory=lambda: datetime.now(timezone.utc).isoformat(),
        description="响应时间（UTC ISO 8601）",
    )


def success(data: Any = None, message: str = "success") -> dict[str, Any]:
    """构造成功响应。"""
    return ApiResponse(code=0, message=message, data=data).model_dump()


def error(code: int = -1, message: str = "error", data: Any = None) -> dict[str, Any]:
    """构造错误响应。"""
    return ApiResponse(code=code, message=message, data=data).model_dump()