Optimize date parsing by reusing the last successful date format

Author: nmdias

Sources/FeedKit/FeedDateFormatter.swift

@@ -55,6 +55,15 @@ class PermissiveDateFormatter: DateFormatter, @unchecked Sendable {
   /// Attempts to parse a string into a Date using available formats.
   override func date(from string: String) -> Date? {
     let trimmedString = string.trimmingCharacters(in: .whitespacesAndNewlines)
+
+    // Attempts parsing with the last successful format first to avoid
+    // unnecessary iterations over all formats.
+    if dateFormat != nil && !dateFormat.isEmpty {
+        if let date = super.date(from: trimmedString) {
+            return date
+        }
+    }
+
     for format in dateFormats + permissiveDateFormats {
       dateFormat = format
       if let date = super.date(from: trimmedString) {