/*
    * Copyright (C) 2009 The Guava Authors
    *
    * 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 com.google.common.util.concurrent;
  
  import com.google.common.base.Supplier;
  import com.google.common.base.Suppliers;
  
  import junit.framework.TestCase;
  
  import java.security.Permission;
  import java.util.concurrent.Callable;
  
  /**
   * Unit tests for {@link Callables}.
   *
   * @author Isaac Shum
   */
  public class CallablesTest extends TestCase {
  
    public void testReturning() throws Exception {
      assertNull(Callables.returning(null).call());
  
      Object value = new Object();
      Callable<Object> callable = Callables.returning(value);
      assertSame(value, callable.call());
      // Expect the same value on subsequent calls
      assertSame(value, callable.call());
    }
  
    public void testRenaming() throws Exception {
      String oldName = Thread.currentThread().getName();
      final Supplier<String> newName = Suppliers.ofInstance("MyCrazyThreadName");
      Callable<Void> callable = new Callable<Void>() {
        @Override public Void call() throws Exception {
          assertEquals(Thread.currentThread().getName(), newName.get());
          return null;
        }
      };
      Callables.threadRenaming(callable, newName).call();
      assertEquals(oldName, Thread.currentThread().getName());
    }
  
    public void testRenaming_exceptionalReturn() throws Exception {
      String oldName = Thread.currentThread().getName();
      final Supplier<String> newName = Suppliers.ofInstance("MyCrazyThreadName");
      class MyException extends Exception {}
      Callable<Void> callable = new Callable<Void>() {
        @Override public Void call() throws Exception {
          assertEquals(Thread.currentThread().getName(), newName.get());
          throw new MyException();
        }
      };
      try {
        Callables.threadRenaming(callable, newName).call();
        fail();
      } catch (MyException expected) {}
      assertEquals(oldName, Thread.currentThread().getName());
    }
  
    public void testRenaming_noPermissions() throws Exception {
      System.setSecurityManager(new SecurityManager() {
        @Override public void checkAccess(Thread t) {
          throw new SecurityException();
        }
        @Override public void checkPermission(Permission perm) {
          // Do nothing so we can clear the security manager at the end
        }
      });
      try {
        final String oldName = Thread.currentThread().getName();
        Supplier<String> newName = Suppliers.ofInstance("MyCrazyThreadName");
        Callable<Void> callable = new Callable<Void>() {
          @Override public Void call() throws Exception {
            assertEquals(Thread.currentThread().getName(), oldName);
            return null;
          }
        };
        Callables.threadRenaming(callable, newName).call();
        assertEquals(oldName, Thread.currentThread().getName());
      } finally {
        System.setSecurityManager(null);
      }
    }
  }