1 files changed, 19 insertions, 0 deletions
diff --git a/src/live.js b/src/live.js
index da18f19..d31c548 100644
--- a/src/live.js
+++ b/src/live.js
@@ -80,3 +80,22 @@ export function zapLine(ev, decode) {
 const zapAddrs = new Map();
 export const setZapAddr = (eventId, addr) => { if (eventId && addr) zapAddrs.set(eventId, addr); };
 export const zapAddrOf = (eventId) => (eventId && zapAddrs.get(eventId)) || null;
+
+// One current reaction per person/message, independent of relay arrival order.
+// A deletion only removes reactions signed by its own author.
+export function liveReactions(events) {
+  const deleted = new Set();
+  for (const ev of events) if (ev.kind === 5)
+    for (const tag of ev.tags || []) if (tag[0] === 'e') deleted.add(ev.pubkey + ':' + tag[1]);
+  const out = new Map();
+  for (const ev of events) {
+    if (ev.kind !== 7 || deleted.has(ev.pubkey + ':' + ev.id)) continue;
+    const target = (ev.tags || []).filter(t => t[0] === 'e').at(-1)?.[1];
+    if (!target) continue;
+    const by = out.get(target) || new Map();
+    const old = by.get(ev.pubkey);
+    if (!old || ev.created_at > old.created_at || (ev.created_at === old.created_at && ev.id > old.id)) by.set(ev.pubkey, ev);
+    out.set(target, by);
+  }
+  return out;
+}