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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.flink.util;

import org.apache.flink.annotation.Internal;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;

/**
 * Utility for reflection operations on classes and generic type parametrization.
 */
@Internal
@SuppressWarnings("unused")
public final class ReflectionUtil {

	public static  T newInstance(Class clazz) {
		try {
			return clazz.newInstance();
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	@SuppressWarnings("unchecked")
	public static  Class getTemplateType(Class clazz, int num) {
		return (Class) getSuperTemplateTypes(clazz)[num];
	}

	@SuppressWarnings("unchecked")
	public static  Class getTemplateType(Class clazz, Class classWithParameter, int num) {
		return (Class) getSuperTemplateTypes(clazz)[num];
	}

	public static  Class getTemplateType1(Class clazz) {
		return getTemplateType(clazz, 0);
	}

	@SuppressWarnings("unchecked")
	public static  Class getTemplateType1(Type type) {
		if (type instanceof ParameterizedType) {
			return (Class) getTemplateTypes((ParameterizedType) type)[0];
		} else {
			throw new IllegalArgumentException();
		}
	}

	public static  Class getTemplateType2(Class clazz) {
		return getTemplateType(clazz, 1);
	}

	public static  Class getTemplateType3(Class clazz) {
		return getTemplateType(clazz, 2);
	}

	public static  Class getTemplateType4(Class clazz) {
		return getTemplateType(clazz, 3);
	}

	public static  Class getTemplateType5(Class clazz) {
		return getTemplateType(clazz, 4);
	}

	public static  Class getTemplateType6(Class clazz) {
		return getTemplateType(clazz, 5);
	}

	public static  Class getTemplateType7(Class clazz) {
		return getTemplateType(clazz, 6);
	}

	public static  Class getTemplateType8(Class clazz) {
		return getTemplateType(clazz, 7);
	}

	public static Class[] getSuperTemplateTypes(Class clazz) {
		Type type = clazz.getGenericSuperclass();
		while (true) {
			if (type instanceof ParameterizedType) {
				return getTemplateTypes((ParameterizedType) type);
			}

			if (clazz.getGenericSuperclass() == null) {
				throw new IllegalArgumentException();
			}

			type = clazz.getGenericSuperclass();
			clazz = clazz.getSuperclass();
		}
	}

	public static Class[] getSuperTemplateTypes(Class clazz, Class searchedSuperClass) {
		if (clazz == null || searchedSuperClass == null) {
			throw new NullPointerException();
		}

		Class superClass;
		do {
			superClass = clazz.getSuperclass();
			if (superClass == searchedSuperClass) {
				break;
			}
		}
		while ((clazz = superClass) != null);

		if (clazz == null) {
			throw new IllegalArgumentException("The searched for superclass is not a superclass of the given class.");
		}

		final Type type = clazz.getGenericSuperclass();
		if (type instanceof ParameterizedType) {
			return getTemplateTypes((ParameterizedType) type);
		}
		else {
			throw new IllegalArgumentException("The searched for superclass is not a generic class.");
		}
	}

	public static Class[] getTemplateTypes(ParameterizedType paramterizedType) {
		Class[] types = new Class[paramterizedType.getActualTypeArguments().length];
		int i = 0;
		for (Type templateArgument : paramterizedType.getActualTypeArguments()) {
			assert templateArgument instanceof Class;
			types[i++] = (Class) templateArgument;
		}
		return types;
	}

	public static Class[] getTemplateTypes(Class clazz) {
		Type type = clazz.getGenericSuperclass();
		assert (type instanceof ParameterizedType);
		ParameterizedType paramterizedType = (ParameterizedType) type;
		Class[] types = new Class[paramterizedType.getActualTypeArguments().length];
		int i = 0;
		for (Type templateArgument : paramterizedType.getActualTypeArguments()) {
			assert (templateArgument instanceof Class);
			types[i++] = (Class) templateArgument;
		}
		return types;
	}

	/**
	 * Extract the full template type information from the given type's template parameter at the
	 * given position.
	 *
	 * @param type type to extract the full template parameter information from
	 * @param templatePosition describing at which position the template type parameter is
	 * @return Full type information describing the template parameter's type
	 */
	public static FullTypeInfo getFullTemplateType(Type type, int templatePosition) {
		if (type instanceof ParameterizedType) {
			return getFullTemplateType(((ParameterizedType) type).getActualTypeArguments()[templatePosition]);
		} else {
			throw new IllegalArgumentException();
		}
	}

	/**
	 * Extract the full type information from the given type.
	 *
	 * @param type to be analyzed
	 * @return Full type information describing the given type
	 */
	public static FullTypeInfo getFullTemplateType(Type type) {
		if (type instanceof ParameterizedType) {
			ParameterizedType parameterizedType = (ParameterizedType) type;

			FullTypeInfo[] templateTypeInfos = new FullTypeInfo[parameterizedType.getActualTypeArguments().length];

			for (int i = 0; i < parameterizedType.getActualTypeArguments().length; i++) {
				templateTypeInfos[i] = getFullTemplateType(parameterizedType.getActualTypeArguments()[i]);
			}

			return new FullTypeInfo((Class) parameterizedType.getRawType(), templateTypeInfos);
		} else {
			return new FullTypeInfo((Class) type, null);
		}
	}

	/**
	 * Container for the full type information of a type. This means that it contains the
	 * {@link Class} object and for each template parameter it contains a full type information
	 * describing the type.
	 */
	public static class FullTypeInfo {

		private final Class clazz;
		private final FullTypeInfo[] templateTypeInfos;

		public FullTypeInfo(Class clazz, FullTypeInfo[] templateTypeInfos) {
			this.clazz = Preconditions.checkNotNull(clazz);
			this.templateTypeInfos = templateTypeInfos;
		}

		public Class getClazz() {
			return clazz;
		}

		public FullTypeInfo[] getTemplateTypeInfos() {
			return templateTypeInfos;
		}

		public Iterator> getClazzIterator() {
			UnionIterator> unionIterator = new UnionIterator<>();

			unionIterator.add(Collections.>singleton(clazz).iterator());

			if (templateTypeInfos != null) {
				for (int i = 0; i < templateTypeInfos.length; i++) {
					unionIterator.add(templateTypeInfos[i].getClazzIterator());
				}
			}

			return unionIterator;
		}

		@Override
		public String toString() {
			StringBuilder builder = new StringBuilder();

			builder.append(clazz.getSimpleName());

			if (templateTypeInfos != null) {
				builder.append("<");

				for (int i = 0; i < templateTypeInfos.length - 1; i++) {
					builder.append(templateTypeInfos[i]).append(", ");
				}

				builder.append(templateTypeInfos[templateTypeInfos.length - 1]);
				builder.append(">");
			}

			return builder.toString();
		}

		@Override
		public boolean equals(Object obj) {
			if (obj instanceof FullTypeInfo) {
				FullTypeInfo other = (FullTypeInfo) obj;

				return clazz == other.getClazz() && Arrays.equals(templateTypeInfos, other.getTemplateTypeInfos());
			} else {
				return false;
			}
		}
	}

	/**
	 * Private constructor to prevent instantiation.
	 */
	private ReflectionUtil() {
		throw new RuntimeException();
	}
}