"""
Minimal background job runner.

GPU jobs use a shared counter so the Whisper model stays cached between
back-to-back transcriptions and is only released when no more GPU work
is queued.
"""
import threading
import traceback
from concurrent.futures import ThreadPoolExecutor

from . import database as db
from .errors import PipelineError
from .logging_config import get_logger

log = get_logger(__name__)
_executor = ThreadPoolExecutor(max_workers=1)
_gpu_jobs_queued = 0
_gpu_lock = threading.Lock()


def _unload_gpu():
    """Release the cached Whisper model from GPU memory."""
    from .pipeline.transcribe import unload_models
    unload_models()


def submit(job_id: str, fn, *args, requires_gpu=False, **kwargs):
    if requires_gpu:
        with _gpu_lock:
            global _gpu_jobs_queued
            _gpu_jobs_queued += 1

    def _run():
        log.info("Job %s starting", job_id)
        db.update_job(job_id, status="running", progress="Starting...")
        try:
            def progress_cb(msg):
                log.info("Job %s: %s", job_id, msg)
                db.update_job(job_id, progress=msg)
            fn(*args, progress_cb=progress_cb, **kwargs)
            db.update_job(job_id, status="done", progress="Complete")
            log.info("Job %s complete", job_id)
        except PipelineError as e:
            log.error("Job %s failed at stage '%s': %s", job_id, e.stage, e.message)
            db.update_job(
                job_id, status="error",
                error=e.message, error_stage=e.stage,
                error_detail=traceback.format_exc(),
            )
        except Exception as e:
            log.exception("Job %s failed with unexpected error", job_id)
            db.update_job(
                job_id, status="error",
                error=f"Unexpected error: {e}", error_stage="unknown",
                error_detail=traceback.format_exc(),
            )
        finally:
            if requires_gpu:
                with _gpu_lock:
                    global _gpu_jobs_queued
                    _gpu_jobs_queued -= 1
                    if _gpu_jobs_queued <= 0:
                        log.info("No more GPU jobs queued — unloading Whisper model")
                        _unload_gpu()

    _executor.submit(_run)