from pathlib import Path

from celery import shared_task
from django.utils import timezone

from .algorithms import ProcessingError, average_images, histogram, subtract_images
from .models import ImageSession, ProcessingJob
from .storage import delete_relative_file, load_image_array, save_image_array


@shared_task(bind=True)
def run_batch_job(self, job_id, operation, session_ids):
    job = ProcessingJob.objects.get(id=job_id)
    job.status = ProcessingJob.STATUS_RUNNING
    job.progress = 10
    job.save(update_fields=["status", "progress", "updated_at"])
    try:
        sessions = list(ImageSession.objects.filter(id__in=session_ids))
        if len(sessions) != len(session_ids):
            raise ProcessingError("One or more sessions do not exist.")
        images = [load_image_array(session.processed_image or session.original_image) for session in sessions]
        job.progress = 45
        job.save(update_fields=["progress", "updated_at"])
        if operation == "average":
            result = average_images(images)
        elif operation == "subtract":
            result = subtract_images(images[0], images[1])
        else:
            raise ProcessingError(f"Unsupported batch operation '{operation}'.")
        relative_path = save_image_array(result, f"batch-{operation}")
        job.status = ProcessingJob.STATUS_COMPLETE
        job.progress = 100
        job.result_image = relative_path
        job.result_histogram = histogram(result)
        job.error = ""
        job.save(update_fields=["status", "progress", "result_image", "result_histogram", "error", "updated_at"])
    except Exception as exc:
        job.status = ProcessingJob.STATUS_FAILED
        job.error = str(exc)
        job.progress = 100
        job.save(update_fields=["status", "error", "progress", "updated_at"])
        raise


@shared_task
def cleanup_expired_sessions():
    expired = ImageSession.objects.filter(expires_at__lt=timezone.now())
    for session in expired:
        delete_relative_file(session.original_image)
        delete_relative_file(session.processed_image)
    expired.delete()

    old_jobs = ProcessingJob.objects.filter(created_at__lt=timezone.now() - timezone.timedelta(hours=24))
    for job in old_jobs:
        delete_relative_file(job.result_image)
    old_jobs.delete()