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Diffstat (limited to 'src/lib/metadata-cache.source.sh')
| -rw-r--r-- | src/lib/metadata-cache.source.sh | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/src/lib/metadata-cache.source.sh b/src/lib/metadata-cache.source.sh new file mode 100644 index 0000000..45edd3c --- /dev/null +++ b/src/lib/metadata-cache.source.sh @@ -0,0 +1,104 @@ +# 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" +} |