Consolidate MangaCircus app, scraper, and Compose baseline

scraper/lib/metadata-merge.js

@@ -0,0 +1,34 @@
+'use strict';
+
+const IMPORTED_FIELDS = ['title', 'altTitles', 'authors', 'status', 'year', 'tags', 'description'];
+const same = (a, b) => JSON.stringify(a) === JSON.stringify(b);
+
+// The effective fields remain at the top of manga.json. A snapshot of the last
+// imported values lets later imports refresh unchanged fields without replacing
+// values somebody edited in the library. Legacy files have no snapshot, so their
+// existing values are conservatively treated as intentional.
+function mergeImportedMetadata(prior, imported, fallbackTitle) {
+  const previous = prior['x-metadata']?.imported || {};
+  const result = { ...prior };
+  for (const field of IMPORTED_FIELDS) {
+    if (!Object.hasOwn(imported, field)) continue;
+    if (result[field] === undefined || result[field] === null || result[field] === ''
+      || (Object.hasOwn(previous, field) && same(result[field], previous[field]))) {
+      result[field] = imported[field];
+    }
+  }
+  if (!result.title) result.title = fallbackTitle;
+
+  const oldId = prior['x-anilist']?.id;
+  const newId = imported['x-anilist']?.id;
+  if (oldId != null && newId != null && String(oldId) !== String(newId)) {
+    throw new Error(`AniList identity conflict: existing ${oldId}, imported ${newId}; review the manga match`);
+  }
+  if (imported['x-anilist']) result['x-anilist'] = { ...(prior['x-anilist'] || {}), ...imported['x-anilist'] };
+  const snapshot = { ...previous };
+  for (const field of IMPORTED_FIELDS) if (Object.hasOwn(imported, field)) snapshot[field] = imported[field];
+  if (Object.keys(snapshot).length) result['x-metadata'] = { ...(prior['x-metadata'] || {}), imported: snapshot };
+  return result;
+}
+
+module.exports = { mergeImportedMetadata, IMPORTED_FIELDS };