Fixes #1270 - Parse the latest room message instead of directly using the body. Add an app wide attributed string caching layer.

ElementX/Sources/Other/HTMLParsing/AttributedStringBuilder.swift

@@ -16,6 +16,7 @@
 
 import DTCoreText
 import Foundation
+import LRUCache
 
 struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     private let temporaryBlockquoteMarkingColor = UIColor.magenta
@@ -23,6 +24,8 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     private let linkColor = UIColor.blue
     private let permalinkBaseURL: URL
     
+    private static var cache = LRUCache<String, AttributedString>(countLimit: 1000)
+    
     init(permalinkBaseURL: URL) {
         self.permalinkBaseURL = permalinkBaseURL
     }
@@ -31,12 +34,18 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
         guard let string else {
             return nil
         }
+        
+        if let cached = Self.cache.value(forKey: string) {
+            return cached
+        }
 
         let mutableAttributedString = NSMutableAttributedString(string: string)
         addLinks(mutableAttributedString)
         removeLinkColors(mutableAttributedString)
         
-        return try? AttributedString(mutableAttributedString, including: \.elementX)
+        let result = try? AttributedString(mutableAttributedString, including: \.elementX)
+        Self.cache.setValue(result, forKey: string)
+        return result
     }
         
     // Do not use the default HTML renderer of NSAttributedString because this method
@@ -52,6 +61,10 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
             return nil
         }
         
+        if let cached = Self.cache.value(forKey: htmlString) {
+            return cached
+        }
+        
         let defaultFont = UIFont.preferredFont(forTextStyle: .body)
         
         let parsingOptions: [String: Any] = [
@@ -83,7 +96,9 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
         replaceMarkedCodeBlocks(mutableAttributedString)
         removeDTCoreTextArtifacts(mutableAttributedString)
         
-        return try? AttributedString(mutableAttributedString, including: \.elementX)
+        let result = try? AttributedString(mutableAttributedString, including: \.elementX)
+        Self.cache.setValue(result, forKey: htmlString)
+        return result
     }
     
     // MARK: - Private