Issue #12: Use proper DNS library instead of handcrafted DNS query to fetch statistics.

dns/BlockedCount.swift

@@ -1,9 +1,13 @@
 
 import SwiftUI
 import Foundation
+import AsyncDNSResolver
 
 struct BlockedCount: View {
 
+    @Environment(\.scenePhase)
+    private var scenePhase
+
     @EnvironmentObject
     private var viewModel: ViewModel
 
@@ -21,46 +25,32 @@ struct BlockedCount: View {
     var body: some View {
         Text(txtRecord)
         .onAppear {
-            fetchTXTRecord()
+            fetchTxtRecord()
         }
         .onChange(of: viewModel.blocklist) { _ in
-            fetchTXTRecord()
+            fetchTxtRecord()
+        }
+        .onChange(of: scenePhase) { newPhase in
+            if newPhase == .active {
+                fetchTxtRecord()
+            }
         }
     }
 
-    func parseResponse(data: Data) -> String? {
-        // This is a DNS wire format response and we make a lot of assumptions
-        // It is not critical functionality so just let it fail if it fails
-
-        guard data.count > Self.startIndex else {
-            return nil
-        }
-
-        // Find the first space character (ASCII 32).
-        guard let endIndex = data.suffix(from: Self.startIndex).firstIndex(of: 32) else {
-            return nil
-        }
-
-        guard let numberString = String(data: data[Self.startIndex ..< endIndex], encoding: .utf8)
-        else {
-            return nil
-        }
-
-        return Self.formatter.string(for: Int(numberString))
-    }
-    
-    func fetchTXTRecord() {
-        let dohURL = URL(string: "https://\(viewModel.blocklist.server)/dns-query?dns=DoQBAAABAAAAAAAABXN0YXRzB2ludmFsaWQAABAAAQ")!
-        let request = URLRequest(url: dohURL)
-
-        txtRecord = "…"
-
+    private func fetchTxtRecord() {
         Task {
             do {
-                let (data, _) = try await URLSession.shared.data(for: request)
+                let resolver = try AsyncDNSResolver()
 
-                if let count = parseResponse(data: data) {
-                    txtRecord = count
+                let records = try await resolver.queryTXT(name: "stats.invalid")
+
+                let text = records.map { $0.txt }.joined()
+
+                if let number = text.split(separator: " ").first,
+                   let intValue = Int(number),
+                   let formatted = Self.formatter.string(for: intValue)
+                {
+                    txtRecord = formatted
                 }
                 else {
                     txtRecord = NSLocalizedString("Error", comment: "")