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A type-safe HTTP client for Android and Java.
There is a newer version: 2.11.0
/*
 * Copyright (C) 2013 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package retrofit2;

import static java.util.Arrays.asList;
import static java.util.Collections.emptyList;
import static java.util.Collections.singletonList;

import android.os.Build;
import android.os.Handler;
import android.os.Looper;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.List;
import java.util.concurrent.Executor;
import javax.annotation.Nullable;
import org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement;

class Platform {
  private static final Platform PLATFORM = findPlatform();

  static Platform get() {
    return PLATFORM;
  }

  private static Platform findPlatform() {
    return "Dalvik".equals(System.getProperty("java.vm.name"))
        ? new Android() //
        : new Platform(true);
  }

  private final boolean hasJava8Types;
  private final @Nullable Constructor lookupConstructor;

  Platform(boolean hasJava8Types) {
    this.hasJava8Types = hasJava8Types;

    Constructor lookupConstructor = null;
    if (hasJava8Types) {
      try {
        // Because the service interface might not be public, we need to use a MethodHandle lookup
        // that ignores the visibility of the declaringClass.
        lookupConstructor = Lookup.class.getDeclaredConstructor(Class.class, int.class);
        lookupConstructor.setAccessible(true);
      } catch (NoClassDefFoundError ignored) {
        // Android API 24 or 25 where Lookup doesn't exist. Calling default methods on non-public
        // interfaces will fail, but there's nothing we can do about it.
      } catch (NoSuchMethodException ignored) {
        // Assume JDK 14+ which contains a fix that allows a regular lookup to succeed.
        // See https://bugs.openjdk.java.net/browse/JDK-8209005.
      }
    }
    this.lookupConstructor = lookupConstructor;
  }

  @Nullable
  Executor defaultCallbackExecutor() {
    return null;
  }

  List defaultCallAdapterFactories(
      @Nullable Executor callbackExecutor) {
    DefaultCallAdapterFactory executorFactory = new DefaultCallAdapterFactory(callbackExecutor);
    return hasJava8Types
        ? asList(CompletableFutureCallAdapterFactory.INSTANCE, executorFactory)
        : singletonList(executorFactory);
  }

  int defaultCallAdapterFactoriesSize() {
    return hasJava8Types ? 2 : 1;
  }

  List defaultConverterFactories() {
    return hasJava8Types ? singletonList(OptionalConverterFactory.INSTANCE) : emptyList();
  }

  int defaultConverterFactoriesSize() {
    return hasJava8Types ? 1 : 0;
  }

  @IgnoreJRERequirement // Only called on API 24+.
  boolean isDefaultMethod(Method method) {
    return hasJava8Types && method.isDefault();
  }

  @IgnoreJRERequirement // Only called on API 26+.
  @Nullable
  Object invokeDefaultMethod(Method method, Class declaringClass, Object object, Object... args)
      throws Throwable {
    Lookup lookup =
        lookupConstructor != null
            ? lookupConstructor.newInstance(declaringClass, -1 /* trusted */)
            : MethodHandles.lookup();
    return lookup.unreflectSpecial(method, declaringClass).bindTo(object).invokeWithArguments(args);
  }

  static final class Android extends Platform {
    Android() {
      super(Build.VERSION.SDK_INT >= 24);
    }

    @Override
    public Executor defaultCallbackExecutor() {
      return new MainThreadExecutor();
    }

    @Nullable
    @Override
    Object invokeDefaultMethod(
        Method method, Class declaringClass, Object object, Object... args) throws Throwable {
      if (Build.VERSION.SDK_INT < 26) {
        throw new UnsupportedOperationException(
            "Calling default methods on API 24 and 25 is not supported");
      }
      return super.invokeDefaultMethod(method, declaringClass, object, args);
    }

    static final class MainThreadExecutor implements Executor {
      private final Handler handler = new Handler(Looper.getMainLooper());

      @Override
      public void execute(Runnable r) {
        handler.post(r);
      }
    }
  }
}