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package org.apache.juneau.rest.vars;

import org.apache.juneau.*;
import org.apache.juneau.http.response.*;
import org.apache.juneau.rest.*;
import org.apache.juneau.svl.*;

/**
 * URL variable resolver.
 *
 * <p>
 * The format for this var is <js>"$U{uri}"</js>.
 *
 * <p>
 * The advantage of using this variable is that you can resolve URLs with special protocols such as
 * <js>"servlet:/xxx"</js>.
 *
 * <p>
 * See {@link UriResolver} for the kinds of URIs that can be resolved.
 *
 * <p>
 * This variable resolver requires that a {@link RestRequest} bean be available in the session bean store.
 *
 * <p>
 * Uses the URI resolver returned by {@link RestRequest#getUriResolver()}.
 *
 * <ul class='seealso'>
 * 	<li class='link'>{@doc jm.SvlVariables}
 * 	<li class='extlink'>{@source}
 * </ul>
 */
public class UrlVar extends SimpleVar {

	/** The name of this variable. */
	public static final String NAME = "U";

	/**
	 * Constructor.
	 */
	public UrlVar() {
		super(NAME);
	}

	@Override /* Var */
	public String resolve(VarResolverSession session, String key) {
		return session.getBean(RestRequest.class).orElseThrow(InternalServerError::new).getUriResolver().resolve(key);
	}

	@Override /* Var */
	public boolean canResolve(VarResolverSession session) {
		return session.getBean(RestRequest.class).isPresent();
	}
}