nip-10: fix duplicate replies in feed

some replies rendered twice in different positions, seems to be
related to deprecated positional event tags and a regression
introduced in a596121821

on receiving events it analizes the event tags and stores the id
of the replied event so the client can easily search for replies
later. marked tags are prefered with a fallback to positional tags
as described in nip-10.

mentions are ignored at the moment.

example event that had some replies rendered twice:
22e4ea80161ac591059da611d3ab63c583cb1d47a706826db2fc6955ac0a70b5

src/main.js

@@ -257,7 +257,10 @@ document.body.addEventListener('click', (e) => {
 
 const textNoteList = []; // could use indexDB
 const eventRelayMap = {}; // eventId: [relay1, relay2]
+
 const hasEventTag = tag => tag[0] === 'e';
+const isReply = ([tag, , , marker]) => tag === 'e' && marker !== 'mention';
+const isMention = ([tag, , , marker]) => tag === 'e' && marker === 'mention';
 
 function handleTextNote(evt, relay) {
   if (eventRelayMap[evt.id]) {
@@ -273,7 +276,27 @@ function handleTextNote(evt, relay) {
   }
 }
 
-const replyList = []; // could use textNoteList with isReply field
+const replyList = [];
+const replyDomMap = {};
+const replyToMap = {};
+
+function handleReply(evt, relay) {
+  if (
+    replyDomMap[evt.id] // already rendered probably received from another relay
+    || evt.tags.some(isMention) // ignore mentions for now
+  ) {
+    return;
+  }
+  if (!replyToMap[evt.id]) {
+    replyToMap[evt.id] = getReplyTo(evt);
+  }
+  replyList.push({
+    replyTo: replyToMap[evt.id],
+    ...evt,
+  });
+  renderReply(evt, relay);
+}
+
 const reactionMap = {};
 
 const getReactionList = (id) => {
@@ -313,7 +336,6 @@ function handleReaction(evt, relay) {
 // feed
 const feedContainer = document.querySelector('#homefeed');
 const feedDomMap = {};
-const replyDomMap = {};
 const restoredReplyTo = localStorage.getItem('reply_to');
 
 const sortByCreatedAt = (evt1, evt2) => {
@@ -434,7 +456,8 @@ function linkPreview(href, id, relay) {
 }
 
 function createTextNote(evt, relay) {
-  const {host, img, isReply, name, replies, time, userName} = getMetadata(evt, relay);
+  const {host, img, name, time, userName} = getMetadata(evt, relay);
+  const replies = replyList.filter(({replyTo}) => replyTo === evt.id);
   // const isLongContent = evt.content.trimRight().length > 280;
   // const content = isLongContent ? evt.content.slice(0, 280) : evt.content;
   const hasReactions = reactionMap[evt.id]?.length > 0;
@@ -446,7 +469,6 @@ function createTextNote(evt, relay) {
       className: 'mbox-header',
       title: `User: ${userName}\n${time}\n\nUser pubkey: ${evt.pubkey}\n\nRelay: ${host}\n\nEvent-id: ${evt.id}
       ${evt.tags.length ? `\nTags ${JSON.stringify(evt.tags)}\n` : ''}
-      ${isReply ? `\nReply to ${evt.tags[0][1]}\n` : ''}
       ${evt.content}`
     }, [
       elem('small', {}, [
@@ -473,7 +495,6 @@ function createTextNote(evt, relay) {
         elem('small', {data: {reactions: ''}}, hasReactions ? reactionMap[evt.id].length : ''),
       ]),
     ]),
-    // replies[0] ? elem('div', {className: 'mobx-replies'}, replyFeed.reverse()) : '',
   ]);
   if (restoredReplyTo === evt.id) {
     appendReplyForm(body.querySelector('.buttons'));
@@ -481,22 +502,13 @@ function createTextNote(evt, relay) {
   }
   return renderArticle([
     elem('div', {className: 'mbox-img'}, [img]), body,
-    replies[0] ? elem('div', {className: 'mobx-replies'}, replyFeed.reverse()) : '',
+    replies[0] ? elem('div', {className: 'mobx-replies'}, replyFeed.sort(sortByCreatedAt).reverse()) : '',
   ], {data: {id: evt.id, pubkey: evt.pubkey, relay}});
 }
 
-function handleReply(evt, relay) {
-  if (replyDomMap[evt.id]) {
-    console.log('CALL ME already have reply in replyDomMap', evt, relay);
-    return;
-  }
-  replyList.push(evt);
-  renderReply(evt, relay);
-}
-
 function renderReply(evt, relay) {
-  const eventId = evt.tags.filter(hasEventTag)[0][1]; // TODO: should check for 'reply' marker with fallback to 'root' marker or last 'e' tag, see nip-10
-  const article = feedDomMap[eventId] || replyDomMap[eventId];
+  const replyToId = replyToMap[evt.id];
+  const article = feedDomMap[replyToId] || replyDomMap[replyToId];
   if (!article) { // root article has not been rendered
     return;
   }
@@ -707,10 +719,29 @@ function getMetadata(evt, relay) {
     src: userImg,
     title: `${userName} on ${host} ${userAbout}`,
   }) : elemCanvas(evt.pubkey);
-  const isReply = evt.tags.some(hasEventTag);
-  const replies = replyList.filter(({tags}) => tags.filter(hasEventTag).some(reply => reply[1] === evt.id)); // TODO: nip-10
+  const isReply = !!replyToMap[evt.id];
   const time = new Date(evt.created_at * 1000);
-  return {host, img, isReply, name, replies, time, userName};
+  return {host, img, isReply, name, time, userName};
+}
+
+/**
+ * find reply-to ID according to nip-10, find marked reply or root tag or
+ * fallback to positional (last) e tag or return null
+ * @param {event} evt
+ * @returns replyToID | null
+ */
+function getReplyTo(evt) {
+  const eventTags = evt.tags.filter(isReply);
+  const withReplyMarker = eventTags.filter(([, , , marker]) => marker === 'reply');
+  if (withReplyMarker.length === 1) {
+    return withReplyMarker[0][1];
+  }
+  const withRootMarker = eventTags.filter(([, , , marker]) => marker === 'root');
+  if (withReplyMarker.length === 0 && withRootMarker.length === 1) {
+    return withRootMarker[0][1];
+  }
+  // fallback to deprecated positional 'e' tags (nip-10)
+  return eventTags.length ? eventTags.at(-1)[1] : null;
 }
 
 const writeForm = document.querySelector('#writeForm');