from typing import Annotated
from pydantic import BaseModel, ConfigDict, Field, model_validator
from datetime import datetime


class TaskAssignmentCreate(BaseModel):
    model_config = ConfigDict(extra="forbid")

    user_ids: list[Annotated[int, Field(ge=1, le=2147483647)]] = Field(min_length=1, max_length=20)


class TaskAssignmentResponse(BaseModel):
    id: int
    task_id: int
    user_id: int
    assigned_by: int
    user_name: str | None = None
    created_at: datetime

    model_config = ConfigDict(from_attributes=True)

    @model_validator(mode="before")
    @classmethod
    def resolve_user_name(cls, data):  # type: ignore[override]
        """Populate user_name from eagerly loaded user relationship."""
        if hasattr(data, "user") and data.user is not None and not getattr(data, "user_name", None):
            # Build dict from ORM columns so new fields are auto-included
            cols = {c.key: getattr(data, c.key) for c in data.__table__.columns}
            cols["user_name"] = data.user.username
            return cols
        return data