Highlights

This patch adds highlights (NIP-84) to Damus.

Kind 9802 are handled by all the necessary models.
We show highlighted events, longform events, and url references.
Url references also leverage text fragments to take the user to the highlighted text.

Testing
——
iPhone 15 Pro Max (17.0) Dark Mode:
https://v.nostr.build/oM6DW.mp4

iPhone 15 Pro Max (17.0) Light Mode:
https://v.nostr.build/BRrmP.mp4

iPhone SE (3rd generation) (16.4) Light Mode:
https://v.nostr.build/6GzKa.mp4
——

Closes: https://github.com/damus-io/damus/issues/2172
Closes: https://github.com/damus-io/damus/issues/1772
Closes: https://github.com/damus-io/damus/issues/1773
Closes: https://github.com/damus-io/damus/issues/2173
Closes: https://github.com/damus-io/damus/issues/2175
Changelog-Added: Highlights (NIP-84)

PATCH CHANGELOG:
V1 -> V2: addressed review comments highlights are now truncated and highlight label shown in Thread view
V2 -> V3: handle case where highlight context is smaller than the highlight content

Signed-off-by: ericholguin <ericholguin@apache.org>

damus/Models/HighlightEvent.swift

@@ -0,0 +1,34 @@
+//
+//  HighlightEvent.swift
+//  damus
+//
+//  Created by eric on 4/22/24.
+//
+
+import Foundation
+
+struct HighlightEvent {
+    let event: NostrEvent
+
+    var event_ref: String? = nil
+    var url_ref: URL? = nil
+    var context: String? = nil
+
+    static func parse(from ev: NostrEvent) -> HighlightEvent {
+        var highlight = HighlightEvent(event: ev)
+
+        for tag in ev.tags {
+            guard tag.count >= 2 else { continue }
+            switch tag[0].string() {
+            case "e":   highlight.event_ref = tag[1].string()
+            case "a":   highlight.event_ref = tag[1].string()
+            case "r":   highlight.url_ref = URL(string: tag[1].string())
+            case "context": highlight.context = tag[1].string()
+            default:
+                break
+            }
+        }
+
+        return highlight
+    }
+}

damus/Models/HomeModel.swift

@@ -184,7 +184,7 @@ class HomeModel: ContactsDelegate {
         }
 
         switch kind {
-        case .chat, .longform, .text:
+        case .chat, .longform, .text, .highlight:
             handle_text_event(sub_id: sub_id, ev)
         case .contacts:
             handle_contact_event(sub_id: sub_id, relay_id: relay_id, ev: ev)
@@ -586,7 +586,7 @@ class HomeModel: ContactsDelegate {
     func subscribe_to_home_filters(friends fs: [Pubkey]? = nil, relay_id: RelayURL? = nil) {
         // TODO: separate likes?
         var home_filter_kinds: [NostrKind] = [
-            .text, .longform, .boost
+            .text, .longform, .boost, .highlight
         ]
         if !damus_state.settings.onlyzaps_mode {
             home_filter_kinds.append(.like)

damus/Models/ProfileModel.swift

@@ -60,11 +60,11 @@ class ProfileModel: ObservableObject, Equatable {
         damus.pool.unsubscribe(sub_id: sub_id)
         damus.pool.unsubscribe(sub_id: prof_subid)
     }
-    
+
     func subscribe() {
-        var text_filter = NostrFilter(kinds: [.text, .longform])
+        var text_filter = NostrFilter(kinds: [.text, .longform, .highlight])
         var profile_filter = NostrFilter(kinds: [.contacts, .metadata, .boost])
-        
+
         profile_filter.authors = [pubkey]
         
         text_filter.authors = [pubkey]

damus/Models/SearchModel.swift

@@ -36,7 +36,7 @@ class SearchModel: ObservableObject {
     func subscribe() {
         // since 1 month
         search.limit = self.limit
-        search.kinds = [.text, .like, .longform]
+        search.kinds = [.text, .like, .longform, .highlight]
 
         //likes_filter.ids = ref_events.referenced_ids!