/*
 * Copyright 2002-2013 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.web.servlet.tags.form;

import java.util.Map;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;

import org.springframework.beans.PropertyAccessor;
import org.springframework.core.Conventions;
import org.springframework.http.HttpMethod;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.servlet.support.RequestDataValueProcessor;
import org.springframework.web.util.HtmlUtils;

/**
 * Databinding-aware JSP tag for rendering an HTML '{@code form}' whose
 * inner elements are bound to properties on a <em>form object</em>.
 *
 * <p>Users should place the form object into the
 * {@link org.springframework.web.servlet.ModelAndView ModelAndView} when
 * populating the data for their view. The name of this form object can be
 * configured using the {@link #setModelAttribute "modelAttribute"} property.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @author Scott Andrews
 * @author Rossen Stoyanchev
 * @since 2.0
 */
@SuppressWarnings("serial")
public class FormTag extends AbstractHtmlElementTag {

	/**
	 * Resolve the value of the '{@code action}' attribute.
	 * <p>If the user configured an '{@code action}' value then the result of
	 * evaluating this value is used. If the user configured an
	 * '{@code servletRelativeAction}' value then the value is prepended
	 * with the context and servlet paths, and the result is used. Otherwise, the
	 * {@link org.springframework.web.servlet.support.RequestContext#getRequestUri()
	 * originating URI} is used.
	 *
	 * @return the value that is to be used for the '{@code action}' attribute
	 */
	protected String resolveAction() throws JspException {
		String action = getAction();
		String servletRelativeAction = getServletRelativeAction();
		if (StringUtils.hasText(action)) {
			action = getDisplayString(evaluate(ACTION_ATTRIBUTE, action));
			return processAction(action);
		}
		else {
			String requestUri = getRequestContext().getRequestUri();
			requestUri = ((HttpServletResponse) response).encodeURL(requestUri);
			if (StringUtils.hasText(requestUri)) {
				return processAction(requestUri);
			}
		}
	}

	/**
	 * Process the action through a {@link RequestDataValueProcessor} instance
	 * if one is configured or otherwise returns the action unmodified.
	 */
	private String processAction(String action) {
		RequestDataValueProcessor processor = getRequestContext().getRequestDataValueProcessor();
		ServletRequest request = this.pageContext.getRequest();
		if ((processor != null) && (request instanceof HttpServletRequest)) {
			action = processor.processAction((HttpServletRequest) request, action, getHttpMethod());
		}
		return action;
	}
}