/*
    * Copyright (c) 2006 JMockit developers
    * This file is subject to the terms of the MIT license (see LICENSE.txt).
    */
   package mockit;
   
   import static java.lang.reflect.Modifier.isAbstract;
   
   import static mockit.internal.util.GeneratedClasses.isGeneratedImplementationClassName;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  import java.lang.reflect.ParameterizedType;
  import java.lang.reflect.Proxy;
  import java.lang.reflect.Type;
  import java.lang.reflect.TypeVariable;
  
  import mockit.internal.classGeneration.ConcreteSubclass;
  import mockit.internal.faking.CaptureOfFakedImplementations;
  import mockit.internal.faking.FakeClassSetup;
  import mockit.internal.faking.FakeClasses;
  import mockit.internal.faking.FakedImplementationClass;
  import mockit.internal.reflection.ConstructorReflection;
  import mockit.internal.reflection.MockInvocationHandler;
  import mockit.internal.startup.Startup;
  import mockit.internal.state.TestRun;
  
  /**
   * A base class used in the creation of a <em>fake</em> for an <em>external</em> type, which is usually a class from
   * some library or component used from the <em>internal</em> codebase of the system under test (SUT). Such fake classes
   * can be used as <em>fake implementations</em> for use in unit or integration tests. For example:
   *
   * <pre>{@code
   * public final class FakeSystem <strong>extends MockUp&lt;System></strong> {
   *    <strong>&#64;Mock</strong> public static long nanoTime() { return 123L; }
   * }
   * }</pre>
   *
   * One or more <em>fake methods</em> annotated {@linkplain Mock as such} must be defined in the concrete subclass. Each
   * <code>@Mock</code> method should have a matching method or constructor in the faked class. At runtime, the execution
   * of a faked method/constructor will get redirected to the corresponding fake method.
   * <p>
   * When the type to be faked is specified indirectly through a {@linkplain TypeVariable type variable}, then that type
   * is taken as a <em>base</em> type whose concrete implementation classes should <em>also</em> get faked. Example:
   *
   * <pre>{@code
   * &#64;Test
   * public &lt;<strong>BC extends SomeBaseClass</strong>> void someTest() {
   *     new MockUp&lt;<strong>BC</strong>>() {
   *        &#64;Mock int someMethod(int i) { return i + 1; }
   *     };
   *
   *     int i = new AConcreteSubclass().someMethod(1);
   *     assertEquals(2, i);
   * }
   * }</pre>
   *
   * @param <T>
   *            specifies the type to be faked; if a type variable is used, then all implementation classes extending or
   *            implementing that base type are also faked; if the type argument itself is a parameterized type, then only
   *            its raw type is considered
   *
   * @see #MockUp()
   * @see #MockUp(Class)
   * @see #MockUp(Object)
   * @see #getMockInstance()
   * @see #onTearDown()
   * @see #targetType
   * @see <a href="http://jmockit.github.io/tutorial/Faking.html#setUp" target="tutorial">Tutorial</a>
   */
  public abstract class MockUp<T> {
      static {
          Startup.verifyInitialization();
      }
  
      /**
       * Holds the class or generic type targeted by this fake instance.
       */
      protected final Type targetType;
  
      @Nullable
      private final Class<?> mockedClass;
      @Nullable
      private T mockInstance;
      @Nullable
      private T invokedInstance;
  
      /**
       * Applies the {@linkplain Mock fake methods} defined in the concrete subclass to the class or interface specified
       * through the type parameter.
       *
       * @see #MockUp(Class)
       * @see #MockUp(Object)
       */
      protected MockUp() {
          MockUp<?> previousMockUp = findPreviouslyFakedClassIfMockUpAlreadyApplied();
  
          if (previousMockUp != null) {
             targetType = previousMockUp.targetType;
             mockedClass = previousMockUp.mockedClass;
             return;
         }
 
         targetType = getTypeToFake();
         Class<T> classToMock = null;
 
         if (targetType instanceof Class<?>) {
             // noinspection unchecked
             classToMock = (Class<T>) targetType;
         } else if (targetType instanceof ParameterizedType) {
             ParameterizedType parameterizedType = (ParameterizedType) targetType;
             // noinspection unchecked
             classToMock = (Class<T>) parameterizedType.getRawType();
         }
 
         if (classToMock != null) {
             mockedClass = redefineClassOrImplementInterface(classToMock);
         } else {
             Type[] typesToMock = ((TypeVariable<?>) targetType).getBounds();
 
             mockedClass = typesToMock.length > 1
                     ? new FakedImplementationClass<T>(this).createImplementation(typesToMock)
                     : new CaptureOfFakedImplementations(this, typesToMock[0]).apply();
         }
     }
 
     @Nullable
     private MockUp<?> findPreviouslyFakedClassIfMockUpAlreadyApplied() {
         FakeClasses mockClasses = TestRun.getFakeClasses();
         FakeClasses.MockUpInstances mockUpInstances = mockClasses.findPreviouslyAppliedMockUps(this);
 
         if (mockUpInstances != null && mockUpInstances.hasMockUpsForSingleInstances()) {
             return mockUpInstances.initialMockUp;
         }
 
         return null;
     }
 
     /**
      * Gets the type to fake.
      *
      * @return the type to fake
      */
     @NonNull
     private Type getTypeToFake() {
         Class<?> currentClass = getClass();
 
         do {
             Type superclass = currentClass.getGenericSuperclass();
 
             if (superclass instanceof ParameterizedType) {
                 return ((ParameterizedType) superclass).getActualTypeArguments()[0];
             }
 
             if (superclass == MockUp.class) {
                 throw new IllegalArgumentException("No target type");
             }
 
             currentClass = (Class<?>) superclass;
         } while (true);
     }
 
     @NonNull
     private Class<?> redefineClassOrImplementInterface(@NonNull Class<T> classToMock) {
         if (classToMock.isInterface()) {
             return createInstanceOfMockedImplementationClass(classToMock, targetType);
         }
 
         Class<T> realClass = classToMock;
 
         if (isAbstract(classToMock.getModifiers())) {
             classToMock = new ConcreteSubclass<T>(classToMock).generateClass();
         }
 
         redefineMethods(realClass, classToMock, targetType);
         return classToMock;
     }
 
     @NonNull
     private Class<T> createInstanceOfMockedImplementationClass(@NonNull Class<T> classToMock,
             @Nullable Type typeToMock) {
         return new FakedImplementationClass<T>(this).createImplementation(classToMock, typeToMock);
     }
 
     private void redefineMethods(@NonNull Class<T> realClass, @NonNull Class<T> classToMock,
             @Nullable Type genericMockedType) {
         new FakeClassSetup(realClass, classToMock, genericMockedType, this).redefineMethods();
     }
 
     /**
      * Applies the {@linkplain Mock mock methods} defined in the mock-up subclass to the given class/interface.
      * <p>
      * In most cases, the constructor with no parameters can be used. This variation should be used only when the type
      * to be faked is not accessible or known from the test code.
      *
      * @param targetClass
      *            the target class
      *
      * @see #MockUp()
      * @see #MockUp(Object)
      */
     protected MockUp(Class<?> targetClass) {
         targetType = targetClass;
         MockUp<?> previousMockUp = findPreviouslyFakedClassIfMockUpAlreadyApplied();
 
         if (previousMockUp != null) {
             mockedClass = previousMockUp.mockedClass;
             return;
         }
 
         if (targetClass.isInterface()) {
             // noinspection unchecked
             mockedClass = createInstanceOfMockedImplementationClass((Class<T>) targetClass, targetClass);
         } else {
             mockedClass = targetClass;
             // noinspection unchecked
             Class<T> realClass = (Class<T>) targetClass;
             redefineMethods(realClass, realClass, null);
             mockInstance = null;
         }
     }
 
     /**
      * Applies the {@linkplain Mock mock methods} defined in the mock-up subclass to the type specified through the type
      * parameter, but only affecting the given instance.
      * <p>
      * In most cases, the constructor with no parameters should be adequate. This variation can be used when mock data
      * or behavior is desired only for a particular instance, with other instances remaining unaffected; or when
      * multiple mock-up objects carrying different states are desired, with one mock-up instance per real instance.
      * <p>
      * If {@link #getMockInstance()} later gets called on this mock-up instance, it will return the instance that was
      * given here.
      *
      * @param targetInstance
      *            a real instance of the type to be faked, meant to be the only one of that type that should be affected
      *            by this mock-up instance
      *
      * @see #MockUp()
      * @see #MockUp(Class)
      */
     protected MockUp(T targetInstance) {
         MockUp<?> previousMockUp = findPreviouslyFakedClassIfMockUpAlreadyApplied();
 
         if (previousMockUp != null) {
             targetType = previousMockUp.targetType;
             mockedClass = previousMockUp.mockedClass;
             setMockInstance(targetInstance);
             return;
         }
 
         @SuppressWarnings("unchecked")
         Class<T> classToMock = (Class<T>) targetInstance.getClass();
         targetType = classToMock;
         mockedClass = classToMock;
         redefineMethods(classToMock, classToMock, classToMock);
 
         setMockInstance(targetInstance);
     }
 
     private void setMockInstance(@NonNull T mockInstance) {
         TestRun.getFakeClasses().addFake(this, mockInstance);
         this.mockInstance = mockInstance;
     }
 
     /**
      * Returns the mock instance exclusively associated with this mock-up instance. If the mocked type was an interface,
      * then said instance is the one that was automatically created when the mock-up was applied. If it was a class, and
      * no such instance is currently associated with this (stateful) mock-up object, then a new <em>uninitialized</em>
      * instance of the faked class is created and returned, becoming associated with the mock-up. If a regular
      * <em>initialized</em> instance was desired, then the {@link #MockUp(Object)} constructor should have been used
      * instead.
      * <p>
      * In any case, for a given mock-up instance this method will always return the same mock instance.
      *
      * @return the mock instance
      *
      * @see <a href="http://jmockit.github.io/tutorial/Faking.html#interfaces" target="tutorial">Tutorial</a>
      */
     public final T getMockInstance() {
         if (invokedInstance == Void.class) {
             return null;
         }
 
         if (invokedInstance != null) {
             return invokedInstance;
         }
 
         if (mockInstance == null && mockedClass != null) {
             @SuppressWarnings("unchecked")
             T newInstance = (T) createMockInstance(mockedClass);
             setMockInstance(newInstance);
         }
 
         return mockInstance;
     }
 
     @NonNull
     private Object createMockInstance(@NonNull Class<?> mockedClass) {
         String mockedClassName = mockedClass.getName();
 
         if (isGeneratedImplementationClassName(mockedClassName)) {
             return ConstructorReflection.newInstanceUsingPublicDefaultConstructor(mockedClass);
         }
 
         if (Proxy.isProxyClass(mockedClass)) {
             return MockInvocationHandler.newMockedInstance(mockedClass);
         }
 
         return ConstructorReflection.newUninitializedInstance(mockedClass);
     }
 
     /**
      * An empty method that can be overridden in a mock-up subclass that wants to be notified whenever the mock-up is
      * automatically torn down. Tear down happens when the mock-up goes out of scope: at the end of the test when
      * applied inside a test, at the end of the test class when applied before the test class, or at the end of the test
      * run when applied through the "<code>mockups</code>" system property.
      * <p>
      * By default, this method does nothing.
      */
     protected void onTearDown() {
     }
 }