"""Storage 辅助:tasks 表的 idempotent 创建 / UPSERT / UPDATE。"""
from __future__ import annotations

from typing import Any, Optional
from uuid import UUID

from sqlalchemy import func, select, update
from sqlalchemy.dialects.postgresql import insert

from .engine import session_scope
from .models import SENTINEL_USER_ID, Task


def ensure_local_task_row(
    task_id: UUID,
    task_dir: str = "",
    mode: str = "",
    description: str = "",
    model: str = "",
    model_profile: str = "",
    reasoning_effort: str = "",
    user_id: UUID = SENTINEL_USER_ID,
) -> None:
    """占位 INSERT(ON CONFLICT DO NOTHING)—— 不覆盖已有字段。

    用于 `Session.append` 在首条非 system 消息前打底 tasks 行,避免 messages
    FK 违反。字段是 build_agent 阶段已知的最小集;TaskState.save 之后会通过
    `upsert_task` 把真实字段(desc/status/tokens 等)写进去。
    """
    stmt = (
        insert(Task)
        .values(
            task_id=task_id,
            user_id=user_id,
            task_dir=task_dir,
            mode=mode,
            description=description,
            model=model,
            model_profile=model_profile,
            reasoning_effort=reasoning_effort,
        )
        .on_conflict_do_nothing(index_elements=["task_id"])
    )
    with session_scope() as s:
        s.execute(stmt)


def upsert_task(
    task_id: UUID,
    *,
    user_id: UUID = SENTINEL_USER_ID,
    **fields: Any,
) -> None:
    """INSERT ... ON CONFLICT DO UPDATE —— TaskState.save 的落地点。

    fields 可包含 tasks 表任意可写列(task_dir/mode/description/status/model/
    model_profile/reasoning_effort/tokens_prompt/tokens_completion/cost_usd)。
    不传的字段在 INSERT 时走 ORM 默认值,UPDATE 时不动。
    """
    values = {"task_id": task_id, "user_id": user_id, **fields}
    stmt = insert(Task).values(**values)
    update_cols = {k: stmt.excluded[k] for k in fields}
    if update_cols:
        # ORM 的 onupdate=func.now() 只在 ORM-level UPDATE 触发,DO UPDATE 是 raw DML
        # 不会自动刷 updated_at —— 这里显式追加。
        update_cols["updated_at"] = func.now()
        stmt = stmt.on_conflict_do_update(
            index_elements=["task_id"], set_=update_cols
        )
    else:
        stmt = stmt.on_conflict_do_nothing(index_elements=["task_id"])
    with session_scope() as s:
        s.execute(stmt)


def update_task(task_id: UUID, **fields: Any) -> int:
    """UPDATE 已有 tasks 行;不存在则 no-op(返回 0)。

    ORM-level update 会带 onupdate=func.now() 自动刷 updated_at,无需显式传。
    """
    if not fields:
        return 0
    with session_scope() as s:
        result = s.execute(
            update(Task).where(Task.task_id == task_id).values(**fields)
        )
        return result.rowcount or 0


def get_task(task_id: UUID) -> Optional[Task]:
    """读 tasks 行,不存在返回 None。"""
    with session_scope() as s:
        return s.execute(
            select(Task).where(Task.task_id == task_id)
        ).scalar_one_or_none()