Adds a cache layer for citations in Notes

app/src/main/java/com/vitorpamplona/amethyst/service/model/BaseTextNoteEvent.kt

@@ -19,6 +19,7 @@ open class BaseTextNoteEvent(
     open fun replyTos() = tags.filter { it.firstOrNull() == "e" }.mapNotNull { it.getOrNull(1) }
 
     private var citedUsersCache: Set<HexKey>? = null
+    private var citedNotesCache: Set<HexKey>? = null
 
     fun citedUsers(): Set<HexKey> {
         citedUsersCache?.let { return it }
@@ -61,8 +62,10 @@ open class BaseTextNoteEvent(
         return returningList
     }
 
-    fun findCitations(): Set<String> {
-        var citations = mutableSetOf<String>()
+    fun findCitations(): Set<HexKey> {
+        citedNotesCache?.let { return it }
+
+        val citations = mutableSetOf<HexKey>()
         // Removes citations from replies:
         val matcher = tagSearch.matcher(content)
         while (matcher.find()) {
@@ -102,6 +105,7 @@ open class BaseTextNoteEvent(
             }
         }
 
+        citedNotesCache = citations
         return citations
     }