ndb: implement eventref building from ndb notes

damus/ContentParsing.swift

@@ -73,3 +73,70 @@ func parse_note_content_ndb(note: NdbNote) -> Blocks {
     return Blocks(words: words, blocks: out)
 }
 
+func interpret_event_refs_ndb(blocks: [Block], tags: TagsSequence) -> [EventRef] {
+    if tags.count == 0 {
+        return []
+    }
+    
+    /// build a set of indices for each event mention
+    let mention_indices = build_mention_indices(blocks, type: .event)
+    
+    /// simpler case with no mentions
+    if mention_indices.count == 0 {
+        let ev_refs = References(tags: tags).ids()
+        return interp_event_refs_without_mentions_ndb(ev_refs)
+    }
+    
+    return interp_event_refs_with_mentions_ndb(tags: tags, mention_indices: mention_indices)
+}
+
+func interp_event_refs_without_mentions_ndb(_ ev_tags: LazyFilterSequence<References>) -> [EventRef] {
+
+    var count = 0
+    var evrefs: [EventRef] = []
+    var first: Bool = true
+    var first_ref: Reference? = nil
+
+    for ref in ev_tags {
+        if first {
+            first_ref = ref
+            evrefs.append(.thread_id(ref.to_referenced_id()))
+            first = false
+        } else {
+
+            evrefs.append(.reply(ref.to_referenced_id()))
+        }
+        count += 1
+    }
+
+    if let first_ref, count == 1 {
+        let r = first_ref.to_referenced_id()
+        return [.reply_to_root(r)]
+    }
+
+    return evrefs
+}
+
+func interp_event_refs_with_mentions_ndb(tags: TagsSequence, mention_indices: Set<Int>) -> [EventRef] {
+    var mentions: [EventRef] = []
+    var ev_refs: [ReferencedId] = []
+    var i: Int = 0
+    
+    for tag in tags {
+        if tag.count >= 2, let t = tag[0], t.matches_char("e"),
+           let ref = tag_to_refid_ndb(tag)
+        {
+            if mention_indices.contains(i) {
+                let mention = Mention(index: i, type: .event, ref: ref)
+                mentions.append(.mention(mention))
+            } else {
+                ev_refs.append(ref)
+            }
+        }
+        i += 1
+    }
+    
+    var replies = interp_event_refs_without_mentions(ev_refs)
+    replies.append(contentsOf: mentions)
+    return replies
+}