/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.wicket.ajax.markup.html.form;

import java.util.Optional;

import org.apache.wicket.Component;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.ajax.attributes.AjaxRequestAttributes;
import org.apache.wicket.ajax.form.AjaxFormSubmitBehavior;
import org.apache.wicket.markup.ComponentTag;
import org.apache.wicket.markup.html.form.Button;
import org.apache.wicket.markup.html.form.Form;
import org.apache.wicket.model.IModel;

/**
 * An ajax submit button that will degrade to a normal request if ajax is not available or
 * javascript is disabled.
 * 
 * @since 1.3
 * 
 * @author Jeremy Thomerson (jthomerson)
 * @author Alastair Maw
 * 
 * 
 */
public abstract class AjaxFallbackButton extends Button
{
        private static final long serialVersionUID = 1L;

        private final Form<?> mForm;

        /**
         * Construct.
         * 
         * @param id
         * @param form
         */
        public AjaxFallbackButton(String id, Form<?> form)
        {
                this(id, null, form);
        }

        /**
         * Construct.
         * 
         * @param id
         * @param model
         * @param form
         */
        public AjaxFallbackButton(String id, IModel<String> model, Form<?> form)
        {
                super(id, model);
                mForm = form;

                add(newAjaxEventBehavior(form, "click"));
        }

        protected AjaxFormSubmitBehavior newAjaxEventBehavior(Form<?> form, String event)
        {
                return new AjaxFormSubmitBehavior(form, event)
                {
                        private static final long serialVersionUID = 1L;

                        @Override
                        protected void onSubmit(AjaxRequestTarget target)
                        {
                                AjaxFallbackButton.this.onSubmit(Optional.of(target));
                        }

                        @Override
                        protected void onAfterSubmit(AjaxRequestTarget target)
                        {
                                AjaxFallbackButton.this.onAfterSubmit(Optional.of(target));
                        }

                        @Override
                        protected void onError(AjaxRequestTarget target)
                        {
                                AjaxFallbackButton.this.onError(Optional.of(target));
                        }

                        @Override
                        public boolean getDefaultProcessing()
                        {
                                return AjaxFallbackButton.this.getDefaultFormProcessing();
                        }

                        @Override
                        protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
                        {
                                super.updateAjaxAttributes(attributes);

                                // do not allow normal form submit to happen
                                attributes.setPreventDefault(true);

                                AjaxFallbackButton.this.updateAjaxAttributes(attributes);
                        }

                        @Override
                        public boolean getStatelessHint(Component component)
                        {
                                return AjaxFallbackButton.this.getStatelessHint();
                        }
                        
                        @Override
                        protected boolean shouldTriggerJavaScriptSubmitEvent()
                        {
                                return AjaxFallbackButton.this.shouldTriggerJavaScriptSubmitEvent();
                        }
                };
        }

        /**
         * Controls whether or not a JS <code>submit</code> should be triggered on the submitting form.
         * False by default.
         * 
         * @return true if <code>submit</code> should be triggered, false otherwise
         */
        protected boolean shouldTriggerJavaScriptSubmitEvent()
        {
                return false;
        }

        protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
        {
        }

        /**
         * Listener method invoked on form submit with errors. If ajax failed and this event was
         * generated via a normal submission, the target argument will be null.
         * 
         * @param target
         */
        protected void onError(Optional<AjaxRequestTarget> target)
        {
        }

        @Override
        public final void onError()
        {
                if (getRequestCycle().find(AjaxRequestTarget.class).isPresent() == false)
                {
                        onError(Optional.empty());
                }
        }

        @Override
        public final void onSubmit()
        {
                if (getRequestCycle().find(AjaxRequestTarget.class).isPresent() == false)
                {
                        onSubmit(Optional.empty());
                }
        }

        @Override
        public final void onAfterSubmit()
        {
                if (getRequestCycle().find(AjaxRequestTarget.class).isPresent() == false)
                {
                        onAfterSubmit(Optional.empty());
                }
        }

        @Override
        public Form<?> getForm()
        {
                return mForm == null ? super.getForm() : mForm;
        }

        /**
         * Callback for the onClick event. If ajax failed and this event was generated via a normal
         * submission, the target argument will be {@link Optional#empty()}. This method will be called
         * <em>before</em> {@link Form#onSubmit()}.
         * 
         * @param target
         *            ajax target if this linked was invoked using ajax, {@link Optional#empty()}
         *            otherwise
         */
        protected void onSubmit(final Optional<AjaxRequestTarget> target)
        {
        }

        /**
         * Callback for the onClick event. If ajax failed and this event was generated via a normal
         * submission, the target argument will be null. This method will be called <em>after</em>
         * {@link Form#onSubmit()}.
         * 
         * @param target
         *            ajax target if this linked was invoked using ajax, null otherwise
         */
        protected void onAfterSubmit(final Optional<AjaxRequestTarget> target)
        {
        }

        /**
         * Helper methods that both checks whether the link is enabled and whether the action ENABLE is
         * allowed.
         * 
         * @return whether the link should be rendered as enabled
         */
        protected final boolean isButtonEnabled()
        {
                return isEnabledInHierarchy();
        }

        @Override
        protected void onComponentTag(ComponentTag tag)
        {
                String tagName = tag.getName();
                if (!("input".equalsIgnoreCase(tagName) || "button".equalsIgnoreCase(tagName)))
                {
                        String msg = String.format("%s must be used only with <input type=\"submit\"> or <input type=\"submit\"> markup elements. " +
                                        "The fallback functionality doesn't work for other markup elements. " +
                                        "Component path: %s, markup element: <%s>.",
                                        AjaxFallbackButton.class.getSimpleName(), getClassRelativePath(), tagName);
                        findMarkupStream().throwMarkupException(msg);
                }

                super.onComponentTag(tag);
        }
}