implement updating of picture metadata on publish

[petrjasek]

SDCP-737

[MarkLark86]

Should this be 2.8?

[MarkLark86]

Using this library may be troublesome on devices with ARM CPUs (LeoHsiao1/pyexiv2#108) such as the Apple M1.

[petrjasek]

yep true, haven't really seen any alternatives, and as this won't be used by default might make it import the library only when calling those methods so it won't break anything by default

[MarkLark86]

This is just a personal preference.
To avoid nested if statements, and along the idea of fail fast / return early, this method could be re-written as:

def _update_picture_metadata(self, updates, original, updated):
    renditions = updated.get("renditions") or {}
    mapping = app.config.get("PHOTO_METADATA_MAPPING")
    if not mapping or not renditions:
        return

    try:
        media_id = renditions["original"]["media"]
    except (KeyError, TypeError):
        return

    if not media_id:
        return

    picture = app.media.get(media_id)
    binary = picture.read()
    metadata = get_metadata_from_item(updated, mapping)
    updated_binary = write_metadata(binary, metadata)

    if updated_binary == binary:
        return

    updated_media_id = app.media.put(
        updated_binary, content_type=picture.content_type, filename=picture.filename
    )
    updates.setdefault("renditions", deepcopy(renditions))["original"].update(
        {
            "media": updated_media_id,
            "href": app.media.url_for_media(updated_media_id, picture.content_type),
        }
    )
    updated["renditions"] = updates["renditions"]