/*
 * Copyright 2002-2016 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.reactive;

import reactor.core.publisher.Mono;

import org.springframework.web.server.ServerWebExchange;

/**
 * Interface to be implemented by objects that define a mapping between
 * requests and handler objects.
 *
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @since 5.0
 */
public interface HandlerMapping {

	/**
	 * Name of the {@link ServerWebExchange} attribute that contains the
	 * best matching pattern within the handler mapping.
	 * <p>Note: This attribute is not required to be supported by all
	 * HandlerMapping implementations. URL-based HandlerMappings will
	 * typically support it, but handlers should not necessarily expect
	 * this request attribute to be present in all scenarios.
	 */
	String BEST_MATCHING_PATTERN_ATTRIBUTE = HandlerMapping.class.getName() + ".bestMatchingPattern";

	/**
	 * Name of the {@link ServerWebExchange} attribute that contains the path
	 * within the handler mapping, in case of a pattern match, or the full
	 * relevant URI (typically within the DispatcherServlet's mapping) else.
	 * <p>Note: This attribute is not required to be supported by all
	 * HandlerMapping implementations. URL-based HandlerMappings will
	 * typically support it, but handlers should not necessarily expect
	 * this request attribute to be present in all scenarios.
	 */
	String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class.getName() + ".pathWithinHandlerMapping";

	/**
	 * Name of the {@link ServerWebExchange} attribute that contains the URI
	 * templates map, mapping variable names to values.
	 * <p>Note: This attribute is not required to be supported by all
	 * HandlerMapping implementations. URL-based HandlerMappings will
	 * typically support it, but handlers should not necessarily expect
	 * this request attribute to be present in all scenarios.
	 */
	String URI_TEMPLATE_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".uriTemplateVariables";

	/**
	 * Name of the {@link ServerWebExchange} attribute that contains a map with
	 * URI matrix variables.
	 * <p>Note: This attribute is not required to be supported by all
	 * HandlerMapping implementations and may also not be present depending on
	 * whether the HandlerMapping is configured to keep matrix variable content
	 * in the request URI.
	 */
	String MATRIX_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".matrixVariables";

	/**
	 * Name of the {@link ServerWebExchange} attribute that contains the set of
	 * producible MediaTypes applicable to the mapped handler.
	 * <p>Note: This attribute is not required to be supported by all
	 * HandlerMapping implementations. Handlers should not necessarily expect
	 * this request attribute to be present in all scenarios.
	 */
	String PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE = HandlerMapping.class.getName() + ".producibleMediaTypes";


	/**
	 * Return a handler for this request.
	 * @param exchange current server exchange
	 * @return a {@link Mono} that emits one value or none in case the request
	 * cannot be resolved to a handler
	 */
	Mono<Object> getHandler(ServerWebExchange exchange);

}