"""Selection previews run on the existing durable job runner, outside request transactions."""

import asyncio
from uuid import uuid4

from sqlalchemy import select

from ..alphas import sanitize
from ..backtests.contracts import fingerprint
from ..models import Job, SuperSelectionSnapshot, now
from .contracts import SelectionPreview
from .evidence import parse_components


async def run_selection(runner, job_id, payload):
    async with runner.sessions() as db:
        existing = await db.scalar(select(SuperSelectionSnapshot).where(SuperSelectionSnapshot.job_id == job_id))
        if existing:
            return  # Restart after snapshot commit must not replace the original observation.
    request = SelectionPreview.model_validate(payload)
    raw = await runner.client.run_super_selection(request.platform_query())
    parsed = parse_components(raw)
    async with runner.sessions.begin() as db:
        job = await db.get(Job, job_id)
        if job.cancel_requested:
            raise asyncio.CancelledError()
        snapshot = SuperSelectionSnapshot(id=str(uuid4()), job_id=job_id, source="preview", request=payload,
            request_hash=fingerprint(request.platform_query()), raw=sanitize(raw), **parsed)
        db.add(snapshot)
        job.processed, job.total, job.updated_at = 1, 1, now()
        job.checkpoint = {"snapshot_id": snapshot.id, "complete": parsed["complete"]}