/*
 * Copyright 2002-2008 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.validation;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import org.springframework.util.StringUtils;

/**
 * Default implementation of the {@link MessageCodesResolver} interface.
 *
 * <p>Will create two message codes for an object error, in the following order:
 * <ul>
 * <li>1.: code + "." + object name
 * <li>2.: code
 * </ul>
 *
 * <p>Will create four message codes for a field specification, in the following order:
 * <ul>
 * <li>1.: code + "." + object name + "." + field
 * <li>2.: code + "." + field
 * <li>3.: code + "." + field type
 * <li>4.: code
 * </ul>
 *
 * <p>For example, in case of code "typeMismatch", object name "user", field "age":
 * <ul>
 * <li>1. try "typeMismatch.user.age"
 * <li>2. try "typeMismatch.age"
 * <li>3. try "typeMismatch.int"
 * <li>4. try "typeMismatch"
 * </ul>
 *
 * <p>This resolution algorithm thus can be leveraged for example to show
 * specific messages for binding errors like "required" and "typeMismatch":
 * <ul>
 * <li>at the object + field level ("age" field, but only on "user");
 * <li>at the field level (all "age" fields, no matter which object name);
 * <li>or at the general level (all fields, on any object).
 * </ul>
 *
 * <p>In case of array, {@link List} or {@link java.util.Map} properties,
 * both codes for specific elements and for the whole collection are
 * generated. Assuming a field "name" of an array "groups" in object "user":
 * <ul>
 * <li>1. try "typeMismatch.user.groups[0].name"
 * <li>2. try "typeMismatch.user.groups.name"
 * <li>3. try "typeMismatch.groups[0].name"
 * <li>4. try "typeMismatch.groups.name"
 * <li>5. try "typeMismatch.name"
 * <li>6. try "typeMismatch.java.lang.String"
 * <li>7. try "typeMismatch"
 * </ul>
 *
 * <p>In order to group all codes into a specific category within your resource bundles,
 * e.g. "validation.typeMismatch.name" instead of the default "typeMismatch.name",
 * consider specifying a {@link #setPrefix prefix} to be applied.
 *
 * @author Juergen Hoeller
 * @since 1.0.1
 */
public class DefaultMessageCodesResolver implements MessageCodesResolver, Serializable {

	/**
	 * The separator that this implementation uses when resolving message codes.
	 */
	public static final String CODE_SEPARATOR = ".";


	private String prefix = "";


	/**
	 * Specify a prefix to be applied to any code built by this resolver.
	 * <p>Default is none. Specify, for example, "validation." to get
	 * error codes like "validation.typeMismatch.name".
	 */
	public void setPrefix(String prefix) {
		this.prefix = (prefix != null ? prefix : "");
	}

	/**
	 * Return the prefix to be applied to any code built by this resolver.
	 * <p>Returns an empty String in case of no prefix.
	 */
	protected String getPrefix() {
		return this.prefix;
	}


	public String[] resolveMessageCodes(String errorCode, String objectName) {
		return new String[] {
				postProcessMessageCode(errorCode + CODE_SEPARATOR + objectName),
				postProcessMessageCode(errorCode)};
	}

	/**
	 * Build the code list for the given code and field: an
	 * object/field-specific code, a field-specific code, a plain error code.
	 * <p>Arrays, Lists and Maps are resolved both for specific elements and
	 * the whole collection.
	 * <p>See the {@link DefaultMessageCodesResolver class level Javadoc} for
	 * details on the generated codes.
	 * @return the list of codes
	 */
	public String[] resolveMessageCodes(String errorCode, String objectName, String field, Class fieldType) {
		List<String> codeList = new ArrayList<String>();
		List<String> fieldList = new ArrayList<String>();
		buildFieldList(field, fieldList);
		for (String fieldInList : fieldList) {
			codeList.add(postProcessMessageCode(errorCode + CODE_SEPARATOR + objectName + CODE_SEPARATOR + fieldInList));
		}
		int dotIndex = field.lastIndexOf('.');
		if (dotIndex != -1) {
			buildFieldList(field.substring(dotIndex + 1), fieldList);
		}
		for (String fieldInList : fieldList) {
			codeList.add(postProcessMessageCode(errorCode + CODE_SEPARATOR + fieldInList));
		}
		if (fieldType != null) {
			codeList.add(postProcessMessageCode(errorCode + CODE_SEPARATOR + fieldType.getName()));
		}
		codeList.add(postProcessMessageCode(errorCode));
		return StringUtils.toStringArray(codeList);
	}

	/**
	 * Add both keyed and non-keyed entries for the supplied <code>field</code>
	 * to the supplied field list.
	 */
	protected void buildFieldList(String field, List<String> fieldList) {
		fieldList.add(field);
		String plainField = field;
		int keyIndex = plainField.lastIndexOf('[');
		while (keyIndex != -1) {
			int endKeyIndex = plainField.indexOf(']', keyIndex);
			if (endKeyIndex != -1) {
				plainField = plainField.substring(0, keyIndex) + plainField.substring(endKeyIndex + 1);
				fieldList.add(plainField);
				keyIndex = plainField.lastIndexOf('[');
			}
			else {
				keyIndex = -1;
			}
		}
	}

	/**
	 * Post-process the given message code, built by this resolver.
	 * <p>The default implementation applies the specified prefix, if any.
	 * @param code the message code as built by this resolver
	 * @return the final message code to be returned
	 * @see #setPrefix
	 */
	protected String postProcessMessageCode(String code) {
		return getPrefix() + code;
	}

}
