/*
 * Copyright 2012-2020 the original author or 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
 *
 *      https://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.springframework.data.convert;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

import org.springframework.beans.BeanInstantiationException;
import org.springframework.beans.BeanUtils;
import org.springframework.data.mapping.PersistentEntity;
import org.springframework.data.mapping.PersistentProperty;
import org.springframework.data.mapping.PreferredConstructor;
import org.springframework.data.mapping.PreferredConstructor.Parameter;
import org.springframework.data.mapping.model.MappingInstantiationException;
import org.springframework.data.mapping.model.ParameterValueProvider;

EntityInstantiator that uses the PersistentEntity's PreferredConstructor to instantiate an instance of the entity via reflection. 
Author:
Oliver Gierke, Mark Paluch/**
 * {@link EntityInstantiator} that uses the {@link PersistentEntity}'s {@link PreferredConstructor} to instantiate an
 * instance of the entity via reflection.
 *
 * @author Oliver Gierke
 * @author Mark Paluch
 */
public enum ReflectionEntityInstantiator implements EntityInstantiator {

	INSTANCE;

	private static final Object[] EMPTY_ARGS = new Object[0];

	@SuppressWarnings("unchecked")
	public <T, E extends PersistentEntity<? extends T, P>, P extends PersistentProperty<P>> T createInstance(E entity,
			ParameterValueProvider<P> provider) {

		PreferredConstructor<? extends T, P> constructor = entity.getPersistenceConstructor();

		if (constructor == null) {

			try {
				Class<?> clazz = entity.getType();
				if (clazz.isArray()) {
					Class<?> ctype = clazz;
					int dims = 0;
					while (ctype.isArray()) {
						ctype = ctype.getComponentType();
						dims++;
					}
					return (T) Array.newInstance(clazz, dims);
				} else {
					return BeanUtils.instantiateClass(entity.getType());
				}
			} catch (BeanInstantiationException e) {
				throw new MappingInstantiationException(entity, Collections.emptyList(), e);
			}
		}
		int parameterCount = constructor.getConstructor().getParameterCount();

		Object[] params = parameterCount == 0 ? EMPTY_ARGS : new Object[parameterCount];
		int i = 0;
		for (Parameter<?, P> parameter : constructor.getParameters()) {
			params[i++] = provider.getParameterValue(parameter);
		}

		try {
			return BeanUtils.instantiateClass(constructor.getConstructor(), params);
		} catch (BeanInstantiationException e) {
			throw new MappingInstantiationException(entity, new ArrayList<>(Arrays.asList(params)), e);
		}
	}
}