content: /*
   * Copyright 2012-2019 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.boot.convert;
  
  import java.util.Collections;
  import java.util.EnumSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  import org.springframework.core.convert.converter.Converter;
  import org.springframework.core.convert.converter.ConverterFactory;
  import org.springframework.util.Assert;
  import org.springframework.util.LinkedMultiValueMap;
  import org.springframework.util.MultiValueMap;
  
  /**
   * Abstract base class for converting from a type to a {@link java.lang.Enum}.
   *
   * @param <T> the source type
   * @author Phillip Webb
   * @author Madhura Bhave
   */
  @SuppressWarnings("rawtypes")
  abstract class LenientObjectToEnumConverterFactory<T> implements ConverterFactory<T, Enum<?>> {
  
  	private static Map<String, List<String>> ALIASES;
  
  	static {
  		MultiValueMap<String, String> aliases = new LinkedMultiValueMap<>();
  		aliases.add("true", "on");
  		aliases.add("false", "off");
  		ALIASES = Collections.unmodifiableMap(aliases);
  	}
  
  	@Override
  	@SuppressWarnings("unchecked")
  	public <E extends Enum<?>> Converter<T, E> getConverter(Class<E> targetType) {
  		Class<?> enumType = targetType;
  		while (enumType != null && !enumType.isEnum()) {
  			enumType = enumType.getSuperclass();
  		}
  		Assert.notNull(enumType, () -> "The target type " + targetType.getName() + " does not refer to an enum");
  		return new LenientToEnumConverter<>((Class<E>) enumType);
  	}
  
  	@SuppressWarnings("unchecked")
  	private class LenientToEnumConverter<E extends Enum> implements Converter<T, E> {
  
  		private final Class<E> enumType;
  
  		LenientToEnumConverter(Class<E> enumType) {
  			this.enumType = enumType;
  		}
  
  		@Override
  		public E convert(T source) {
  			String value = source.toString().trim();
  			if (value.isEmpty()) {
  				return null;
  			}
  			try {
  				return (E) Enum.valueOf(this.enumType, value);
  			}
  			catch (Exception ex) {
  				return findEnum(value);
  			}
  		}
  
  		private E findEnum(String value) {
  			String name = getCanonicalName(value);
  			List<String> aliases = ALIASES.getOrDefault(name, Collections.emptyList());
  			for (E candidate : (Set<E>) EnumSet.allOf(this.enumType)) {
  				String candidateName = getCanonicalName(candidate.name());
  				if (name.equals(candidateName) || aliases.contains(candidateName)) {
  					return candidate;
  				}
  			}
  			throw new IllegalArgumentException("No enum constant " + this.enumType.getCanonicalName() + "." + value);
  		}
  
  		private String getCanonicalName(String name) {
  			StringBuilder canonicalName = new StringBuilder(name.length());
  			name.chars().filter(Character::isLetterOrDigit).map(Character::toLowerCase)
  					.forEach((c) -> canonicalName.append((char) c));
  			return canonicalName.toString();
  		}
  
  	}
  
  }
  