/*
 * Copyright 2011-2020 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.util.Map;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;

import org.springframework.data.mapping.Alias;
import org.springframework.data.util.ClassTypeInformation;
import org.springframework.data.util.TypeInformation;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;

Basic TypeInformationMapper implementation that interprets the alias handles as fully qualified class name and tries to load a class with the given name to build TypeInformation. Returns the fully qualified class name for alias creation. 
Author:
Oliver Gierke, Mark Paluch/**
 * Basic {@link TypeInformationMapper} implementation that interprets the alias handles as fully qualified class name
 * and tries to load a class with the given name to build {@link TypeInformation}. Returns the fully qualified class
 * name for alias creation.
 *
 * @author Oliver Gierke
 * @author Mark Paluch
 */
public class SimpleTypeInformationMapper implements TypeInformationMapper {

	private final Map<String, Optional<ClassTypeInformation<?>>> CACHE = new ConcurrentHashMap<>();

	
Returns the TypeInformation that shall be used when the given String value is found as type hint. The implementation will simply interpret the given value as fully-qualified class name and try to load the class. Will return null in case the given String is empty. 
Params:
alias – the type to load, must not be null.
Returns:
the type to be used for the given String representation or null if nothing found or the class cannot be loaded./**
	 * Returns the {@link TypeInformation} that shall be used when the given {@link String} value is found as type hint.
	 * The implementation will simply interpret the given value as fully-qualified class name and try to load the class.
	 * Will return {@literal null} in case the given {@link String} is empty.
	 *
	 * @param alias the type to load, must not be {@literal null}.
	 * @return the type to be used for the given {@link String} representation or {@literal null} if nothing found or the
	 *         class cannot be loaded.
	 */
	@Nullable
	@Override
	public TypeInformation<?> resolveTypeFrom(Alias alias) {

		String stringAlias = alias.mapTyped(String.class);

		if (stringAlias != null) {
			return CACHE.computeIfAbsent(stringAlias, SimpleTypeInformationMapper::loadClass).orElse(null);
		}

		return null;
	}

	
Turn the given type information into the String representation that shall be stored. Default implementation simply
returns the fully-qualified class name.
Params:
type – must not be null.
Returns:
the String representation to be stored or null if no type information shall be stored./**
	 * Turn the given type information into the String representation that shall be stored. Default implementation simply
	 * returns the fully-qualified class name.
	 *
	 * @param type must not be {@literal null}.
	 * @return the String representation to be stored or {@literal null} if no type information shall be stored.
	 */
	public Alias createAliasFor(TypeInformation<?> type) {
		return Alias.of(type.getType().getName());
	}

	private static Optional<ClassTypeInformation<?>> loadClass(String typeName) {

		try {
			return Optional.of(ClassTypeInformation.from(ClassUtils.forName(typeName, null)));
		} catch (ClassNotFoundException e) {
			return Optional.empty();
		}
	}
}