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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.html;

import org.apache.juneau.svl.*;

/**
 * Defines an interface for resolvers of <js>"$W{...}"</js> string variables.
 *
 * <p>
 * Widgets must provide one of the following public constructors:
 * <ul>
 * 	<li><code><jk>public</jk> Widget();</code>
 * </ul>
 *
 * <p>
 * Widgets can be defined as inner classes of REST resource classes.
 *
 * <ul class='seealso'>
 * 	<li class='link'>{@doc juneau-rest-server.HtmlDocAnnotation.Widgets}
 * </ul>
 */
public interface HtmlWidget {

	/**
	 * The name for this widget.
	 *
	 * @return A unique identifying name for this widget.
	 */
	public String getName();

	/**
	 * Resolves the HTML content for this widget.
	 *
	 * <p>
	 * A returned value of <jk>null</jk> will cause nothing to be added to the page.
	 *
	 * @param session The current serializer session.
	 * @return The HTML content of this widget.
	 * @throws Exception Error occurred.
	 */
	public String getHtml(VarResolverSession session) throws Exception;

	/**
	 * Resolves any Javascript that should be added to the <xt>&lt;head&gt;/&lt;script&gt;</xt> element.
	 *
	 * <p>
	 * A returned value of <jk>null</jk> will cause nothing to be added to the page.
	 *
	 * @param session The current serializer session.
	 * @return The Javascript needed by this widget.
	 * @throws Exception Error occurred.
	 */
	public String getScript(VarResolverSession session) throws Exception;

	/**
	 * Resolves any CSS styles that should be added to the <xt>&lt;head&gt;/&lt;style&gt;</xt> element.
	 *
	 * <p>
	 * A returned value of <jk>null</jk> will cause nothing to be added to the page.
	 *
	 * @param session The current serializer session.
	 * @return The CSS styles needed by this widget.
	 * @throws Exception Error occurred.
	 */
	public String getStyle(VarResolverSession session) throws Exception;
}