"""模型网关 endpoint 覆盖数据访问（api-spec §4.4）。

按 (logical_model_name, endpoint_name) 唯一；upsert 手动 find+update，兼容 SQLite。
字段 None 表示不覆盖该字段（回退 yaml/env）。
"""

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.governance import ModelEndpointOverride


async def list_overrides(session: AsyncSession) -> list[ModelEndpointOverride]:
    result = await session.execute(select(ModelEndpointOverride))
    return list(result.scalars().all())


async def get_override(
    session: AsyncSession,
    logical_model_name: str,
    endpoint_name: str,
) -> ModelEndpointOverride | None:
    result = await session.execute(
        select(ModelEndpointOverride).where(
            ModelEndpointOverride.logical_model_name == logical_model_name,
            ModelEndpointOverride.endpoint_name == endpoint_name,
        )
    )
    return result.scalars().first()


async def upsert_override(
    session: AsyncSession,
    override: ModelEndpointOverride,
) -> ModelEndpointOverride:
    """存在则更新非 None 字段，否则新建。返回最终实体（未 commit）。"""
    existing = await get_override(session, override.logical_model_name, override.endpoint_name)
    if existing is not None:
        existing.base_url = override.base_url
        existing.api_key = override.api_key
        existing.status = override.status
        existing.weight = override.weight
        existing.priority = override.priority
        return existing
    session.add(override)
    await session.flush()
    return override