1 files changed, 23 insertions, 0 deletions
diff --git a/src/feed-sync.js b/src/feed-sync.js
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+++ b/src/feed-sync.js
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+// Custom feeds across devices: per feed, the newest edit (`at`) wins, and a
+// deletion is remembered (gone: { id: ms }) so a device still holding the
+// feed doesn't hand it back. Commutative, so snapshots apply in any order.
+// Returns null when the remote copy changes nothing.
+export function mergeFeeds(local, remote) {
+  const gone = { ...(local.gone || {}) };
+  let changed = false;
+  for (const [id, t] of Object.entries(remote.gone || {}))
+    if (typeof t === 'number' && (gone[id] || 0) < t) { gone[id] = t; changed = true; }
+  const feeds = [...(local.feeds || [])];
+  const touched = [];
+  for (const f of Array.isArray(remote.feeds) ? remote.feeds : []) {
+    if (!f || typeof f.id !== 'string' || (gone[f.id] || 0) >= (f.at || 0)) continue;
+    const i = feeds.findIndex((x) => x.id === f.id);
+    if (i < 0) feeds.push(f);
+    else if ((f.at || 0) > (feeds[i].at || 0)) feeds[i] = f;
+    else continue;
+    touched.push(f.id); changed = true;
+  }
+  const kept = feeds.filter((f) => (gone[f.id] || 0) < (f.at || 0));
+  if (kept.length !== feeds.length) changed = true;
+  return changed ? { feeds: kept, gone, touched } : null;
+}