/*
 * Copyright 2004-2005 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.springmodules.validation.commons;

import java.util.Locale;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.commons.validator.ValidatorException;
import org.springframework.validation.Errors;
import org.springframework.validation.Validator;

/**
 * @author Rob Harrop
 */
public abstract class AbstractBeanValidator implements Validator {

    private static final Log log = LogFactory.getLog(AbstractBeanValidator.class);

    private ValidatorFactory validatorFactory;

    /**
     * Checks if the validatorFactory is configured to handle this class.  Will
     * convert the class into a form name, suitable for commons validator.
     *
     * @return <code>true</code> if the validatorFactory supports the class,
     *         or <code>false</code> if not
     * @see #getFormName(Class)
     */
    public boolean supports(Class clazz) {
        boolean canSupport = validatorFactory.hasRulesForBean(getFormName(clazz), getLocale());
        if (log.isDebugEnabled()) {
            log.debug("validatorFactory " + (canSupport ? "does" : "does not")
                + " support class " + clazz + " with form name " + getFormName(clazz));
        }
        return canSupport;
    }

    /**
     * Validates the supplied object using a <code>org.apache.commons.validator.Validator</code> loaded from
     * the configured <code>ValidatorFactory</code>.
     *
     * @see ValidatorFactory
     */
    public void validate(Object obj, Errors errors) {
        org.apache.commons.validator.Validator commonsValidator = getValidator(obj, errors);
        initValidator(commonsValidator);
        try {
            commonsValidator.validate();
        }
        catch (ValidatorException e) {
            log.error("Exception while validating object " + obj, e);
        } finally {
            cleanupValidator(commonsValidator);
        }
    }

    public void setValidatorFactory(ValidatorFactory validatorFactory) {
        this.validatorFactory = validatorFactory;
    }

    /**
     * Gets the <code>Locale</code> used to lookup <code>Validator</code> instances. Default implementation
     * returns the value of <code>Locale.getDefault()</code>. Subclasses can override this to change
     * <code>Locale</code>-handling behavior.
     */
    protected Locale getLocale() {
        return Locale.getDefault();
    }

    /**
     * Retrieves an instance of <code>org.apache.commons.validator.Validator</code>
     * for the specified <code>Object</code>
     * from the configured <code>ValidatorFactory</code>.
     *
     * @param obj the <code>Object</code> being validated.
     * @param errors the <code>Errors</code> object to write validation errors to.
     */
    private org.apache.commons.validator.Validator getValidator(Object obj, Errors errors) {
        return this.validatorFactory.getValidator(getFormName(obj.getClass()), obj, errors);
    }

    /**
     * A callback method that is called just before the validate() method is called on the given validator.
     * This can be used to further configure the validator.
     *
     * @param validator
     */
    protected void initValidator(org.apache.commons.validator.Validator validator) {
    }

    /**
     * A callback method that is called just after the validate() method is called on the given validator.
     * This method can be used to clean up all the extra configuration added in the {@link #initValidator(org.apache.commons.validator.Validator)}
     * method.
     *
     * @param validator
     */
    protected void cleanupValidator(org.apache.commons.validator.Validator validator) {
    }

    /**
     * Returns the name of the Commons Validator <code>Form</code> used to
     * validate instances of the supplied class.
     *
     * @param aClass
     * @return the form name that Commons Validator can use to look up a form
     */
    protected abstract String getFormName(Class aClass);
}