/*
 * Copyright 2010 Google Inc.
 * 
 * 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 com.google.gwt.validation.client;

import com.google.gwt.core.client.GWT;
import com.google.gwt.validation.client.impl.AbstractGwtValidator;
import com.google.gwt.validation.client.impl.GwtValidatorContext;

import javax.validation.ConstraintValidatorFactory;
import javax.validation.MessageInterpolator;
import javax.validation.TraversableResolver;
import javax.validation.Validator;
import javax.validation.ValidatorContext;
import javax.validation.ValidatorFactory;
import javax.validation.spi.ConfigurationState;

/**
 * Abstract {@link ValidatorFactory} that delegates to a GWT generated
 * {@link Validator}.
 * <p>
 * Extend this class create and implement createValidator
 * 
 * <pre>
 * public class MyValidatorFactory extends AbstractGwtValidatorFactory {
 *   @GwtValidation(value = {Pojo.class,Other.class})
 *   public static interface GwtValidator extends Validator {
 *   }
 *
 *   public AbstractGwtValidator createValidator (){
 *     return GWT.create(GwtValidator.class));
 *   }
 * }
 * </pre>
 * <p>
 * Then add a line like this to your Gwt Module config (gwt.xml) file.
 * 
 * <pre>
 * <replace-with class="com.example.MyValidatorFactory">
 *   <when-type-is class="javax.validation.ValidatorFactory"/>
 * </replace-with>
 * </pre>
 */
public abstract class AbstractGwtValidatorFactory implements ValidatorFactory {
  private ConstraintValidatorFactory constraintValidatorFactory;
  private MessageInterpolator messageInterpolator;
  private TraversableResolver traversableResolver;

  /**
   * Implement this method to return a {@link GWT#create}d {@link Validator}
   * annotated with {@link GwtValidation}.
   * 
   * @return newly created Validator
   */
  public abstract AbstractGwtValidator createValidator();

  /**
   * GWT does not support {@link ConstraintValidatorFactory}, so the object returned by this method
   * will not work.
   */
  @Override
  public final ConstraintValidatorFactory getConstraintValidatorFactory() {
    return constraintValidatorFactory;
  }

  @Override
  public final MessageInterpolator getMessageInterpolator() {
    return messageInterpolator;
  }

  @Override
  public final TraversableResolver getTraversableResolver() {
    return traversableResolver;
  }

  @Override
  public final Validator getValidator() {
    AbstractGwtValidator validator = createValidator();
    validator.init(getConstraintValidatorFactory(), getMessageInterpolator(),
        getTraversableResolver());
    return validator;
  }

  public final void init(ConfigurationState configState) {
    ConstraintValidatorFactory configConstraintValidatorFactory =
        configState.getConstraintValidatorFactory();
    this.constraintValidatorFactory = configConstraintValidatorFactory != null ?
        configConstraintValidatorFactory : 
        GWT.<ConstraintValidatorFactory>create(ConstraintValidatorFactory.class);
    TraversableResolver configTraversableResolver = configState.getTraversableResolver();
    this.traversableResolver = configTraversableResolver != null ?
        configTraversableResolver : new DefaultTraversableResolver();
    MessageInterpolator configMessageInterpolator = configState.getMessageInterpolator();
    this.messageInterpolator = configMessageInterpolator != null ?
        configMessageInterpolator : new GwtMessageInterpolator();
  }

  /**
   * Unsupported. Always throws an {@link UnsupportedOperationException}.
   * 
   * @throws UnsupportedOperationException
   */
  @Override
  public final <T> T unwrap(Class<T> type) {
    throw new UnsupportedOperationException("GWT Validation does not support upwrap()");
  }

  @Override
  public final ValidatorContext usingContext() {
    return new GwtValidatorContext(this);
  }
}