"""Helpers shared by the route modules."""

import io
import os
from functools import lru_cache

from fastapi import HTTPException

from backend import projects as project_store


def project_or_404(project_id: int) -> dict:
    project = project_store.get(project_id)
    if project is None:
        raise HTTPException(404, "No such project")
    return project


@lru_cache(maxsize=512)
def _thumbnail_cached(path: str, width: int, mtime: float) -> bytes:
    from PIL import Image

    with Image.open(path) as image:
        image = image.convert("RGB")
        if image.width > width:
            height = max(1, round(image.height * width / image.width))
            image = image.resize((width, height), Image.BILINEAR)
        buffer = io.BytesIO()
        image.save(buffer, "JPEG", quality=72)
        return buffer.getvalue()


def thumbnail(path: str, width: int) -> bytes:
    # mtime is part of the key so a re-extracted frame never serves a stale one.
    return _thumbnail_cached(path, width, os.path.getmtime(path))