/*
 * Copyright 2002-2019 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.core.style;

import java.lang.reflect.Method;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.StringJoiner;

import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;

Converts objects to String form, generally for debugging purposes, using Spring's toString styling conventions. 
Uses the reflective visitor pattern underneath the hood to nicely
encapsulate styling algorithms for each type of styled object.
Author:
Keith Donald, Juergen Hoeller
Since:
1.2.2/**
 * Converts objects to String form, generally for debugging purposes,
 * using Spring's {@code toString} styling conventions.
 *
 * <p>Uses the reflective visitor pattern underneath the hood to nicely
 * encapsulate styling algorithms for each type of styled object.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @since 1.2.2
 */
public class DefaultValueStyler implements ValueStyler {

	private static final String EMPTY = "[[empty]]";
	private static final String NULL = "[null]";
	private static final String COLLECTION = "collection";
	private static final String SET = "set";
	private static final String LIST = "list";
	private static final String MAP = "map";
	private static final String EMPTY_MAP = MAP + EMPTY;
	private static final String ARRAY = "array";


	@Override
	public String style(@Nullable Object value) {
		if (value == null) {
			return NULL;
		}
		else if (value instanceof String) {
			return "\'" + value + "\'";
		}
		else if (value instanceof Class) {
			return ClassUtils.getShortName((Class<?>) value);
		}
		else if (value instanceof Method) {
			Method method = (Method) value;
			return method.getName() + "@" + ClassUtils.getShortName(method.getDeclaringClass());
		}
		else if (value instanceof Map) {
			return style((Map<?, ?>) value);
		}
		else if (value instanceof Map.Entry) {
			return style((Map.Entry<? ,?>) value);
		}
		else if (value instanceof Collection) {
			return style((Collection<?>) value);
		}
		else if (value.getClass().isArray()) {
			return styleArray(ObjectUtils.toObjectArray(value));
		}
		else {
			return String.valueOf(value);
		}
	}

	private <K, V> String style(Map<K, V> value) {
		if (value.isEmpty()) {
			return EMPTY_MAP;
		}

		StringJoiner result = new StringJoiner(", ", "[", "]");
		for (Map.Entry<K, V> entry : value.entrySet()) {
			result.add(style(entry));
		}
		return MAP + result;
	}

	private String style(Map.Entry<?, ?> value) {
		return style(value.getKey()) + " -> " + style(value.getValue());
	}

	private String style(Collection<?> value) {
		String collectionType = getCollectionTypeString(value);

		if (value.isEmpty()) {
			return collectionType + EMPTY;
		}

		StringJoiner result = new StringJoiner(", ", "[", "]");
		for (Object o : value) {
			result.add(style(o));
		}
		return collectionType + result;
	}

	private String getCollectionTypeString(Collection<?> value) {
		if (value instanceof List) {
			return LIST;
		}
		else if (value instanceof Set) {
			return SET;
		}
		else {
			return COLLECTION;
		}
	}

	private String styleArray(Object[] array) {
		if (array.length == 0) {
			return ARRAY + '<' + ClassUtils.getShortName(array.getClass().getComponentType()) + '>' + EMPTY;
		}

		StringJoiner result = new StringJoiner(", ", "[", "]");
		for (Object o : array) {
			result.add(style(o));
		}
		return ARRAY + '<' + ClassUtils.getShortName(array.getClass().getComponentType()) + '>' + result;
	}

}