"""Queue document ingestion with a concurrency limit so large batches do not overwhelm the server.

For batch uploads of thousands of files, tasks queue behind the semaphore and
execute as slots free up — the server stays responsive for status polls and new
requests throughout.
"""

import asyncio
import logging
from pathlib import Path

from app.config import settings

logger = logging.getLogger(__name__)

_background_tasks: set[asyncio.Task] = set()  # type: ignore[type-arg]
_sem: asyncio.Semaphore | None = None


def _ingest_semaphore() -> asyncio.Semaphore:
    global _sem
    if _sem is None:
        _sem = asyncio.Semaphore(max(1, settings.max_concurrent_ingests))
    return _sem


async def _ingest_worker(doc_id: str, file_path: Path) -> None:
    async with _ingest_semaphore():
        from app.ingest import pipeline

        await pipeline.ingest_document(doc_id=doc_id, file_path=file_path)


def schedule_ingest(doc_id: str, file_path: Path) -> None:
    """Fire-and-forget background ingestion for a committed Document row."""
    task = asyncio.create_task(_ingest_worker(doc_id, file_path))
    _background_tasks.add(task)

    def _done(t: asyncio.Task) -> None:  # type: ignore[type-arg]
        _background_tasks.discard(t)
        try:
            t.result()
        except Exception:
            logger.exception("Background ingest task failed doc_id=%s", doc_id)

    task.add_done_callback(_done)
    logger.info("Queued ingestion doc=%s path=%s (queue_size=%d)", doc_id, file_path, len(_background_tasks))


def pending_count() -> int:
    """How many ingest tasks are currently queued or running."""
    return len(_background_tasks)