ui: raise min SDK to 24HEADmaster

The difference between the usage of 21 and 24 is not big enough to hold
on to all the baggage from API 21

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 2 insertions, 33 deletions

diff --git a/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java b/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
index 46f68b4b..c9a13b2b 100644
--- a/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
+++ b/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
@@ -24,12 +24,10 @@ import com.wireguard.crypto.KeyFormatException;
 import com.wireguard.util.NonNullForAll;
 
 import java.net.InetAddress;
-import java.time.Instant;
 import java.util.Collections;
 import java.util.Set;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
-import java.util.concurrent.FutureTask;
-import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 
@@ -45,7 +43,7 @@ public final class GoBackend implements Backend {
     private static final int DNS_RESOLUTION_RETRIES = 10;
     private static final String TAG = "WireGuard/GoBackend";
     @Nullable private static AlwaysOnCallback alwaysOnCallback;
-    private static GhettoCompletableFuture<VpnService> vpnService = new GhettoCompletableFuture<>();
+    private static CompletableFuture<VpnService> vpnService = new CompletableFuture<>();
     private final Context context;
     @Nullable private Config currentConfig;
     @Nullable private Tunnel currentTunnel;
@@ -377,35 +375,6 @@ public final class GoBackend implements Backend {
         void alwaysOnTriggered();
     }
 
-    // TODO: When we finally drop API 21 and move to API 24, delete this and replace with the ordinary CompletableFuture.
-    private static final class GhettoCompletableFuture<V> {
-        private final LinkedBlockingQueue<V> completion = new LinkedBlockingQueue<>(1);
-        private final FutureTask<V> result = new FutureTask<>(completion::peek);
-
-        public boolean complete(final V value) {
-            final boolean offered = completion.offer(value);
-            if (offered)
-                result.run();
-            return offered;
-        }
-
-        public V get() throws ExecutionException, InterruptedException {
-            return result.get();
-        }
-
-        public V get(final long timeout, final TimeUnit unit) throws ExecutionException, InterruptedException, TimeoutException {
-            return result.get(timeout, unit);
-        }
-
-        public boolean isDone() {
-            return !completion.isEmpty();
-        }
-
-        public GhettoCompletableFuture<V> newIncompleteFuture() {
-            return new GhettoCompletableFuture<>();
-        }
-    }
-
     /**
      * {@link android.net.VpnService} implementation for {@link GoBackend}
      */