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  package android.taobao.atlas.hack;
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.Field;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  
  import android.taobao.atlas.hack.Hack.HackDeclaration.HackAssertionException;
  import android.taobao.atlas.hack.Interception.InterceptionHandler;
  import android.util.Log;
  
  /** @author Oasis */
  public class Hack {
  
  	/** All hacks should be declared in a centralized point extending this class, typically as static
  	 * method, and call it in your application initialization stage to verify all the hack
  	 * assertions by catching exception thrown:
  	 * <pre>
  	 * class MyHacks extends HackDeclaration {
  	 *
  	 *     static HackedField<Object, PackageManager> ContextImpl_mPackageManager;
  	 *     static HackedField<Object, Map<String, IBinder>> ServiceManager_sCache;
  	 *
  	 *     static void defineAndVerify() {
  	 *         try {
  	 *             ContextImpl_mPackageManager = Hack.into("android.app.ContextImpl").field("mPackageManager").ofType(PackageManager.class);
  	 *             ServiceManager_sCache = Hack.into("android.os.ServiceManager").staticField("sCache").ofGenericType(Map.class)
  	 *             
  	 *             ...
  	 *         } catch (HackAssertionException e) {
  	 *             // Report the failure and activate fall-back strategy.
  	 *             ...
  	 *         }
  	 *     }
  	 * }
  	 * <pre>
  	 * Thus we can verify them all together in an early application initialization stage. If any assertion
  	 * failed, a fall-back strategy is suggested. */
  	public static abstract class HackDeclaration {
  
  		/** This exception is purposely defined as "protected" and not extending Exception to avoid
  		 * developers unconsciously catch it outside the centralized hacks declaration, which results
  		 * in potentially pre-checked usage of hacks. */
  		public static class HackAssertionException extends Throwable {
  
  			private Class<?> mHackedClass;
  			private String mHackedFieldName;			
  			private String mHackedMethodName;
  	
  			public HackAssertionException(final String e) { super(e); }
  			public HackAssertionException(final Exception e) { super(e); }
  			@Override public String toString() {
  				return getCause() != null ? getClass().getName() + ": " + getCause() : super.toString();
  			}			
  			
  			public Class<?> getHackedClass() {
  				return mHackedClass;
  			}
  			
  			public void setHackedClass(Class<?> mHackedClass) {
  				this.mHackedClass = mHackedClass;
  			}		
  			
  			public String getHackedMethodName() {
  				return mHackedMethodName;
  			}
  			
  			public void setHackedMethodName(String methodName) {
  				this.mHackedMethodName = methodName;
  			}
  			
  			public String getHackedFieldName() {
  				return mHackedFieldName;
  			}
  			
  			public void setHackedFieldName(String fieldName) {
  				this.mHackedFieldName = fieldName;
  			}
  
  			private static final long serialVersionUID = 1L;
  		}
  	}
  
  	/** Use {@link Hack#setAssertionFailureHandler(AssertionFailureHandler) } to set the global handler */
  	public interface AssertionFailureHandler {
  		
  		/** @return whether the failure is handled and no need to throw out, return false to let it thrown */
  		boolean onAssertionFailure(HackAssertionException failure);
  	}
  
  	/** @beta */
  	public static class HackedField<C, T> {
  
  		@SuppressWarnings("unchecked")		// TODO: Add more check
  		public <T2> HackedField<C, T2> ofGenericType(final Class<?> type) throws HackAssertionException {
  			if (mField != null && !type.isAssignableFrom(mField.getType()))
  				fail(new HackAssertionException(new ClassCastException(mField + " is not of type " + type)));
  			return (HackedField<C, T2>) this;
  		}
  
  		@SuppressWarnings("unchecked")
  		public <T2> HackedField<C, T2> ofType(final Class<T2> type) throws HackAssertionException {
  			if (mField != null && !type.isAssignableFrom(mField.getType()))
  				fail(new HackAssertionException(new ClassCastException(mField + " is not of type " + type)));
  			return (HackedField<C, T2>) this;
  		}
  		@SuppressWarnings("unchecked")
  		public HackedField<C, T> ofType(final String type_name) throws HackAssertionException {
  			try { return (HackedField<C, T>) ofType(Class.forName(type_name));
  			} catch (final ClassNotFoundException e) { fail(new HackAssertionException(e)); return this; }
  		}
  
  		/** Get current value of this field */
  		public T get(final C instance) {
  			try {
  				@SuppressWarnings("unchecked") final T value = (T) mField.get(instance);
  			return value;
  			} catch (final IllegalAccessException e) {
  				e.printStackTrace();
  				//TBS.Ext.commitEvent("AtlasRuntimeException", AtlasConstant.ATLAS_RUNTIME_EXCEPTION, e.toString());
  				return null; /* Should never happen */ }
  		}
  
  		/**
  		 * Set value of this field
  		 * 
  		 * <p>No type enforced here since most type mismatch can be easily tested and exposed early.</p>
  		 */
  		public void set(final C instance,final Object value) {
  			try {
  			mField.set(instance, value);
  			} catch (final IllegalAccessException e) { 
  				e.printStackTrace();
  				/* Should never happen */
  			}
  		}
  
  		/**
  		 * Hijack the current instance of this field.
  		 *
  		 * <p><b>The instance must not be null at the time of hijacking</b>, or an IllegalStateException will be thrown.
  		 *
  		 * @param handler a invocation handler to implement the hijack logic.
  		 */
  		public void hijack(final C instance,final InterceptionHandler<?> handler) {
  			final Object delegatee = get(instance);
  			if (delegatee == null) throw new IllegalStateException("Cannot hijack null");
  			final Class<?>[] interfaces = delegatee.getClass().getInterfaces();
  			set(instance,Interception.proxy(delegatee, handler, interfaces));
  		}
  
  		/** @param modifiers the modifiers this field must have */
  		HackedField(final Class<C> clazz, final String name, int modifiers) throws HackAssertionException {
  			Field field = null;
  			try {
  				if (clazz == null) return;
  				field = clazz.getDeclaredField(name);
  				if (modifiers > 0 && (field.getModifiers() & modifiers) != modifiers)
  					fail(new HackAssertionException(field + " does not match modifiers: " + modifiers));
  				field.setAccessible(true);
  			} catch (final NoSuchFieldException e) {
  				HackAssertionException hae = new HackAssertionException(e);
  				hae.setHackedClass(clazz);
  				hae.setHackedFieldName(name);
  				fail(hae);
  			} finally { mField = field; }
  		}
  		private final Field mField;
  		
  		public Field getField() {
  			return mField;
  		}
  	}
  
  	public static class HackedMethod {
          private static final String TAG = "HackedMethod";
  
  		public Object invoke(final Object receiver, final Object... args) throws IllegalArgumentException, InvocationTargetException {
  			Object obj = null;
  			try {
  				obj = mMethod.invoke(receiver, args);
  				return obj;
  			} catch (final IllegalAccessException e) { /* Should never happen */
  				e.printStackTrace();
  			}
  			return obj;
  		}
  
  		HackedMethod(final Class<?> clazz, final String name, final Class<?>[] arg_types, int modifiers) throws HackAssertionException {
  			Method method = null;
  			try {
  				if (clazz == null) return;
  				method = clazz.getDeclaredMethod(name, arg_types);
  				if (modifiers > 0 && (method.getModifiers() & modifiers) != modifiers)
  					fail(new HackAssertionException(method + " does not match modifiers: " + modifiers));
  				method.setAccessible(true);
  			} catch (final NoSuchMethodException e) {
                  Log.e(TAG, "No such method: " + e.getMessage());
                  HackAssertionException hae = new HackAssertionException(e);
  				hae.setHackedClass(clazz);
  				hae.setHackedMethodName(name);
  				fail(hae);
  			} finally { mMethod = method; }
  		}
  
  		protected final Method mMethod;
  
  		public Method getMethod() {
  			return mMethod;
  		}		
  	}
  
  	public static class HackedConstructor {
  
  		protected Constructor<?> mConstructor;
  
  		HackedConstructor(final Class<?> clazz, final Class<?>[] arg_types) throws HackAssertionException {
  			try {
  				if (clazz == null) return;
  				mConstructor = clazz.getDeclaredConstructor(arg_types);
  			} catch (NoSuchMethodException e) {
  				HackAssertionException hae = new HackAssertionException(e);
  				hae.setHackedClass(clazz);
  				fail(hae);
  			}
  		}
  
  		public Object getInstance(final Object... arg_types) throws IllegalArgumentException {
  			Object obj = null;
  			mConstructor.setAccessible(true);
  			try {
  			obj = mConstructor.newInstance(arg_types);
  			} catch (Exception e) {
  				e.printStackTrace();
  			} 
  			return obj;
  		}
  	}
  	
  	public static class HackedClass<C> {
  
  		public HackedField<C, Object> staticField(final String name) throws HackAssertionException {
  			return new HackedField<C, Object>(mClass, name, Modifier.STATIC);
  		}
  
  		public HackedField<C, Object> field(final String name) throws HackAssertionException {
  			return new HackedField<C, Object>(mClass, name, 0);
  		}
  
  		public HackedMethod staticMethod(final String name, final Class<?>... arg_types) throws HackAssertionException {
  			return new HackedMethod(mClass, name, arg_types, Modifier.STATIC);
  		}
  
  		public HackedMethod method(final String name, final Class<?>... arg_types) throws HackAssertionException {
  			return new HackedMethod(mClass, name, arg_types, 0);
  		}
  
  		public HackedConstructor constructor(final Class<?>... arg_types) throws HackAssertionException {
  			return new HackedConstructor(mClass, arg_types);
  		}
  		
  		public HackedClass(final Class<C> clazz) { mClass = clazz; }
  
  		protected Class<C> mClass;
  
  		public Class<C> getmClass() {
  			return mClass;
  		}
  	}
  
  	public static <T> HackedClass<T> into(final Class<T> clazz) {
  		return new HackedClass<T>(clazz);
  	}
  
  	@SuppressWarnings({ "rawtypes", "unchecked" })
  	public static <T> HackedClass<T> into(final String class_name) throws HackAssertionException {
  		try {
  			return new HackedClass(Class.forName(class_name));
  		} catch (final ClassNotFoundException e) {
  			fail(new HackAssertionException(e));
  			return new HackedClass(null);	// TODO: Better solution to avoid null?
  		}
  	}
  	
  	private static void fail(HackAssertionException e) throws HackAssertionException {
  		if (sFailureHandler == null || ! sFailureHandler.onAssertionFailure(e)) throw e;
  	}
  
  	/** Specify a handler to deal with assertion failure, and decide whether the failure should be thrown. */
  	public static void setAssertionFailureHandler(AssertionFailureHandler handler) {
  		sFailureHandler = handler;
  	}
  
  	private Hack() {}
  
  	private static AssertionFailureHandler sFailureHandler;
  }
  