Merge pull request #759 from Infomaniak/largeComplexMailSlowToDisplay

Large complex mails are slow to display

Mail/Views/Thread/MessageView.swift

@@ -16,6 +16,7 @@
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+import CocoaLumberjackSwift
 import InfomaniakCore
 import InfomaniakCoreUI
 import InfomaniakDI
@@ -92,11 +93,29 @@ struct MessageView: View {
     private func prepareBody() {
         guard let messageBody = message.body else { return }
         presentableBody.body = messageBody.detached()
+        let bodyValue = messageBody.value ?? ""
+
+        // Heuristic to give up on mail too large for "perfect" preprocessing.
+        // 5 Meg looks like a fine threshold
+        guard bodyValue.lengthOfBytes(using: String.Encoding.utf8) < 5_000_000 else {
+            DDLogInfo("give up on processing, file too large")
+            mutate(compactBody: bodyValue, quote: nil)
+            return
+        }
+
+        Task.detached {
+            guard let messageBodyQuote = MessageBodyUtils.splitBodyAndQuote(messageBody: bodyValue) else {
+                return
+            }
+
+            await mutate(compactBody: messageBodyQuote.messageBody, quote: messageBodyQuote.quote)
+        }
+    }
 
-        guard let messageBodyQuote = MessageBodyUtils.splitBodyAndQuote(messageBody: messageBody.value ?? "")
-        else { return }
-        presentableBody.compactBody = messageBodyQuote.messageBody
-        presentableBody.quote = messageBodyQuote.quote
+    /// Update the DOM in the main thread
+    @MainActor func mutate(compactBody: String?, quote: String?) {
+        presentableBody.compactBody = compactBody
+        presentableBody.quote = quote
     }
 
     private func insertInlineAttachments() async throws {