//  Copyright 2004 The Apache Software Foundation
//
// 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.apache.tapestry.engine;

/**
 *  Define a link that may be generated as part of a page render.  The vast majority
 *  of links are tied to {@link IEngineService services} and are, in
 *  fact, callbacks.  A small number, such as those generated by
 *  {@link org.apache.tapestry.link.GenericLink} component, are to arbitrary locations.
 *  In addition, ILink differentiates between the path portion of the link, and any
 *  query parameters encoded into a link, primarily to benefit {@link org.apache.tapestry.form.Form},
 *  which needs to encode the query parameters as hidden form fields.
 *
 *  <p>
 *  In addition, an ILink is responsible for
 *  passing constructed URLs through
 *  {@link org.apache.tapestry.IRequestCycle#encodeURL(String)}
 *  as needed.
 * 
 *  @author Howard Lewis Ship
 *  @version $Id$
 *  @since 3.0
 * 
 **/

public interface ILink
{
	/**
	 *  Returns the relative URL as a String.  A relative
	 *  URL may include a leading slash, but omits
	 *  the scheme, host and port portions of a full URL.
	 *  
	 *  @return the relative URL, with no anchor, but including
	 *  query parameters.
	 * 
	 **/
	
	public String getURL();
	
    /**
     *  Returns the relative URL as a String.  This is used
     *  for most links.
     * 
     *  @param anchor if not null, appended to the URL
     *  @param includeParameters if true, parameters are included
     * 
     **/

    public String getURL(String anchor, boolean includeParameters);

	/**
	 *  Returns the absolute URL as a String, using
	 *  default scheme, server and port, including
	 *  parameters, and no anchor.
	 * 
	 **/
	
	public String getAbsoluteURL();

    /**
     *  Returns the absolute URL as a String.  
     * 
     *  @param scheme if not null, overrides the default scheme.
     *  @param server if not null, overrides the default server
     *  @param port if non-zero, overrides the default port
     *  @param anchor if not null, appended to the URL
     *  @param includeParameters if true, parameters are included
     * 
     **/

    public String getAbsoluteURL(
        String scheme,
        String server,
        int port,
        String anchor,
        boolean includeParameters);

    /**
     * 
     *  Returns an array of parameters names (in
     *  no specified order).
     * 
     *  @see #getParameterValues(String)
     * 
     **/

    public String[] getParameterNames();

    /**
     *  Returns the values for the named parameter.
     *  
     *  @throws IllegalArgumentException if the
     *  link does not define values for the
     *  specified name.
     * 
     **/

    public String[] getParameterValues(String name);
}