import time

from django.conf import settings
from django.utils import timezone

from .algorithms import ProcessingError, decode_image, histogram, process_image
from .models import ImageSession, ProcessingJob
from .storage import load_image_array, payload_for_image, save_image_array
from .tasks import run_batch_job


def image_session_create(*, uploaded_file=None, image_base64=None):
    if uploaded_file and uploaded_file.size > settings.MAX_UPLOAD_MB * 1024 * 1024:
        raise ProcessingError(f"Upload exceeds {settings.MAX_UPLOAD_MB} MB.")

    image = decode_image(uploaded_file=uploaded_file, base64_image=image_base64)
    relative_path = save_image_array(image, "original")
    hist = histogram(image)
    session = ImageSession.objects.create(
        original_image=relative_path,
        width=image.shape[1],
        height=image.shape[0],
        channels=image.shape[2] if image.ndim == 3 else 1,
        color_mode="RGB" if image.ndim == 3 else "L",
        original_histogram=hist,
        expires_at=timezone.now() + timezone.timedelta(hours=settings.IMAGE_SESSION_TTL_HOURS),
    )
    payload = {
        "session_id": str(session.id),
        "width": session.width,
        "height": session.height,
        "channels": session.channels,
        "color_mode": session.color_mode,
        "original_histogram": hist,
        "expires_at": session.expires_at.isoformat(),
    }
    payload.update(payload_for_image(image, relative_path))
    return payload


def image_session_process(*, session, operation, params):
    if session.expired:
        raise ProcessingError("Image session has expired.")

    started_at = time.perf_counter()
    source = load_image_array(session.original_image)
    result = process_image(source, operation, params)
    relative_path = save_image_array(result, f"processed-{operation}")
    hist = histogram(result)

    session.processed_image = relative_path
    session.processed_histogram = hist
    session.save(update_fields=["processed_image", "processed_histogram"])

    payload = {
        "session_id": str(session.id),
        "operation": operation,
        "params": params,
        "processed_histogram": hist,
        "elapsed_ms": round((time.perf_counter() - started_at) * 1000, 2),
    }
    payload.update(payload_for_image(result, relative_path))
    return payload


def batch_job_create(*, operation, session_ids, params=None):
    job = ProcessingJob.objects.create(operation=operation, params=params or {})
    run_batch_job.delay(str(job.id), operation, [str(session_id) for session_id in session_ids])
    return job


def processing_job_payload(*, job):
    payload = {
        "job_id": str(job.id),
        "operation": job.operation,
        "status": job.status,
        "progress": job.progress,
        "error": job.error,
        "result_histogram": job.result_histogram,
    }
    if job.result_image:
        image = load_image_array(job.result_image)
        payload.update(payload_for_image(image, job.result_image))
    return payload