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# Shared EXIF identify cache primitive. Promoted out of album-metadata.source.sh
# (task pn0) because the cached `identify -verbose` reader is a low-level
# metadata primitive consumed by BOTH the album (tooltips, details tables) and
# the stats aggregator (leaderboard tallies). Keeping it inside the album module
# forced stats to reach across a module boundary into album internals; moving it
# here gives both consumers a shared, stable dependency that is sourced before
# either of them (see LIB_SOURCES in the Justfile, ordered right after
# metadata-label.source.sh, the sibling shared metadata helper). All library
# modules are sourced before any code runs, so source order documents the
# dependency, it does not affect availability. Behaviour and signatures are
# unchanged by the move.
# Build the cache signature line ("<photo>:<size>:<mtime>") used to decide
# whether a cache entry is still valid for the source file. Kept private to this
# module alongside its only consumers, plus the stats test that pre-seeds caches.
photo_cache_signature() {
local -r photo="$1"; shift
local -r photo_path="$1"; shift
local stat_output
stat_output=$(stat -c '%s:%Y' "$photo_path")
printf '%s:%s\n' "$photo" "$stat_output"
}
# Print a cache file's payload (everything after the leading signature line).
print_cached_photo_identify_output() {
local -r cache_file="$1"; shift
local line
local skipped_signature=no
while IFS= read -r line || [ -n "$line" ]; do
if [ "$skipped_signature" = no ]; then
skipped_signature=yes
continue
fi
printf '%s\n' "$line"
done < "$cache_file"
}
# Return cached ImageMagick `identify -verbose` output for a photo, rebuilding
# the cache when missing or stale. Public shared primitive: album-metadata and
# stats-aggregate both call this rather than running identify themselves.
cached_photo_identify_output() {
local -r photo="$1"; shift
local -r photo_path="$1"; shift
local cache_dir
local cache_file
local cached_signature=''
local current_signature
local identify_status
# Persist the EXIF cache in a volatile ./cache directory parallel to ./dist
# (the staging dir is a sibling of the final dist, so dirname "$DIST_DIR" is
# the working dir in both staging and direct contexts). Keeping it outside
# dist means it survives a fresh/cleared dist and is never deployed, so an
# unchanged photo skips the slow `identify -verbose` on every regenerate.
cache_dir="$(dirname "$DIST_DIR")/cache/exif"
cache_file="$cache_dir/$photo.txt"
current_signature=$(photo_cache_signature "$photo" "$photo_path")
# Reuse the cache when its signature still matches the source file. --force
# is handled once up front by clear_exif_cache (which empties this directory),
# so the first call per photo then rebuilds it and the rest of the run reuses
# it -- exactly one identify per photo even under force.
if [ -f "$cache_file" ]; then
IFS= read -r cached_signature < "$cache_file" || true
if [ "$cached_signature" = "$current_signature" ]; then
print_cached_photo_identify_output "$cache_file"
return
fi
fi
mkdir -p "$cache_dir"
printf '%s\n' "$current_signature" > "$cache_file"
# Capture the identify exit status instead of swallowing it with `|| true`.
# Errors are still hidden from stdout (so a corrupt photo does not pollute
# the EXIF output), but a non-zero status now drives a warning + no-cache
# rather than silently leaving a signature-only cache entry behind.
identify_status=0
imagemagick_identify -verbose "$photo_path" >> "$cache_file" 2>/dev/null \
|| identify_status=$?
if [ "$identify_status" -ne 0 ]; then
# Failed identify (corrupt photo, timeout, missing binary, ...): warn
# naming the photo and remove the cache file. Removing it is essential:
# a file holding only the signature line is a valid-looking cache hit,
# so the next run would silently reuse the empty result forever -- never
# retrying identify and never warning again (the original data-loss bug).
# Deleting it makes the next run retry and warn.
#
# We deliberately do NOT abort: this runs inside backgrounded render jobs
# under `set -euo pipefail`, and one unreadable photo must not kill the
# whole generation. The photo still renders, just with empty tooltip and
# stats, now accompanied by a warning.
rm -f "$cache_file"
log_warning \
"could not read EXIF for $photo (ImageMagick identify failed);" \
"tooltip/stats will be missing"
return 0
fi
print_cached_photo_identify_output "$cache_file"
}
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