/*
 * 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.bind;

import java.util.EnumSet;
import java.util.Locale;
import java.util.Set;

import org.springframework.core.convert.ConversionFailedException;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.Converter;
import org.springframework.core.convert.converter.ConverterFactory;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.core.convert.support.GenericConversionService;
import org.springframework.util.Assert;

/**
 * Internal {@link ConversionService} used by {@link RelaxedDataBinder} to support
 * additional relaxed conversion.
 *
 * @author Phillip Webb
 * @author Stephane Nicoll
 */
class RelaxedConversionService implements ConversionService {

	private final ConversionService conversionService;

	private final GenericConversionService additionalConverters;

	/**
	 * Create a new {@link RelaxedConversionService} instance.
	 * @param conversionService and option root conversion service
	 */
	RelaxedConversionService(ConversionService conversionService) {
		this.conversionService = conversionService;
		this.additionalConverters = new GenericConversionService();
		DefaultConversionService.addCollectionConverters(this.additionalConverters);
		this.additionalConverters.addConverterFactory(new StringToEnumIgnoringCaseConverterFactory());
		this.additionalConverters.addConverter(new StringToCharArrayConverter());
	}

	@Override
	public boolean canConvert(Class<?> sourceType, Class<?> targetType) {
		return (this.conversionService != null && this.conversionService.canConvert(sourceType, targetType))
				|| this.additionalConverters.canConvert(sourceType, targetType);
	}

	@Override
	public boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType) {
		return (this.conversionService != null && this.conversionService.canConvert(sourceType, targetType))
				|| this.additionalConverters.canConvert(sourceType, targetType);
	}

	@Override
	@SuppressWarnings("unchecked")
	public <T> T convert(Object source, Class<T> targetType) {
		Assert.notNull(targetType, "The targetType to convert to cannot be null");
		return (T) convert(source, TypeDescriptor.forObject(source), TypeDescriptor.valueOf(targetType));
	}

	@Override
	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
		if (this.conversionService != null) {
			try {
				return this.conversionService.convert(source, sourceType, targetType);
			}
			catch (ConversionFailedException ex) {
				// Ignore and try the additional converters
			}
		}
		return this.additionalConverters.convert(source, sourceType, targetType);
	}

	/**
	 * Clone of Spring's package private StringToEnumConverterFactory, but ignoring the
	 * case of the source.
	 */
	@SuppressWarnings({ "unchecked", "rawtypes" })
	private static class StringToEnumIgnoringCaseConverterFactory implements ConverterFactory<String, Enum> {

		@Override
		public <T extends Enum> Converter<String, T> getConverter(Class<T> 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 StringToEnum(enumType);
		}

		private class StringToEnum<T extends Enum> implements Converter<String, T> {

			private final Class<T> enumType;

			StringToEnum(Class<T> enumType) {
				this.enumType = enumType;
			}

			@Override
			public T convert(String source) {
				if (source.isEmpty()) {
					// It's an empty enum identifier: reset the enum value to null.
					return null;
				}
				source = source.trim();
				for (T candidate : (Set<T>) EnumSet.allOf(this.enumType)) {
					RelaxedNames names = new RelaxedNames(
							candidate.name().replace('_', '-').toLowerCase(Locale.ENGLISH));
					for (String name : names) {
						if (name.equals(source)) {
							return candidate;
						}
					}
					if (candidate.name().equalsIgnoreCase(source)) {
						return candidate;
					}
				}
				throw new IllegalArgumentException(
						"No enum constant " + this.enumType.getCanonicalName() + "." + source);
			}

		}

	}

}
