/*
 * Copyright 2002-2018 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
 *
 *      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.springframework.expression.spel.ast;

import java.util.ArrayList;
import java.util.List;

import org.springframework.expression.PropertyAccessor;
import org.springframework.lang.Nullable;

Utilities methods for use in the Ast classes.
Author:
Andy Clement
Since:
3.0.2/**
 * Utilities methods for use in the Ast classes.
 *
 * @author Andy Clement
 * @since 3.0.2
 */
public abstract class AstUtils {

	
Determines the set of property resolvers that should be used to try and access a
property on the specified target type. The resolvers are considered to be in an
ordered list, however in the returned list any that are exact matches for the input
target type (as opposed to 'general' resolvers that could work for any type) are
placed at the start of the list. In addition, there are specific resolvers that
exactly name the class in question and resolvers that name a specific class but it
is a supertype of the class we have. These are put at the end of the specific resolvers
set and will be tried after exactly matching accessors but before generic accessors.
Params:
targetType – the type upon which property access is being attempted
Returns:
a list of resolvers that should be tried in order to access the property/**
	 * Determines the set of property resolvers that should be used to try and access a
	 * property on the specified target type. The resolvers are considered to be in an
	 * ordered list, however in the returned list any that are exact matches for the input
	 * target type (as opposed to 'general' resolvers that could work for any type) are
	 * placed at the start of the list. In addition, there are specific resolvers that
	 * exactly name the class in question and resolvers that name a specific class but it
	 * is a supertype of the class we have. These are put at the end of the specific resolvers
	 * set and will be tried after exactly matching accessors but before generic accessors.
	 * @param targetType the type upon which property access is being attempted
	 * @return a list of resolvers that should be tried in order to access the property
	 */
	public static List<PropertyAccessor> getPropertyAccessorsToTry(
			@Nullable Class<?> targetType, List<PropertyAccessor> propertyAccessors) {

		List<PropertyAccessor> specificAccessors = new ArrayList<>();
		List<PropertyAccessor> generalAccessors = new ArrayList<>();
		for (PropertyAccessor resolver : propertyAccessors) {
			Class<?>[] targets = resolver.getSpecificTargetClasses();
			if (targets == null) {  // generic resolver that says it can be used for any type
				generalAccessors.add(resolver);
			}
			else {
				if (targetType != null) {
					int pos = 0;
					for (Class<?> clazz : targets) {
						if (clazz == targetType) {  // put exact matches on the front to be tried first?
							specificAccessors.add(pos++, resolver);
						}
						else if (clazz.isAssignableFrom(targetType)) {  // put supertype matches at the end of the
							// specificAccessor list
							generalAccessors.add(resolver);
						}
					}
				}
			}
		}
		List<PropertyAccessor> resolvers = new ArrayList<>(specificAccessors.size() + generalAccessors.size());
		resolvers.addAll(specificAccessors);
		resolvers.addAll(generalAccessors);
		return resolvers;
	}

}