"""Flag Thumb:/Background: fields whose file did not survive the recovery.

The recovered articles kept their original image references even where the file
is unrecoverable -- deliberately, since the reference records what was there
(see IMAGES.md in the working material). 29 of 90 thumbnails and a similar share of heroes point at
files that no archive holds.

Resolving that in the browser via an <img> error handler means a visible flash
of broken image on a third of the grid. Checking at build time instead lets the
templates render a typographic card from the start, and keeps the metadata
intact rather than stripping it.
"""
import os

from pelican import signals

FIELDS = ("thumb", "background")


def _flag(content):
    base = content.settings.get("PATH", "content")
    for field in FIELDS:
        ref = content.metadata.get(field)
        if not ref:
            continue
        path = os.path.join(base, str(ref).lstrip("/"))
        if not os.path.exists(path):
            content.metadata[field + "_missing"] = True


def register():
    signals.content_object_init.connect(_flag)