/*
 * Copyright 2002-2017 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.result.method.annotation;

import java.util.Map;
import java.util.Optional;

import org.springframework.core.MethodParameter;
import org.springframework.core.ReactiveAdapterRegistry;
import org.springframework.http.HttpHeaders;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.reactive.BindingContext;
import org.springframework.web.reactive.result.method.HandlerMethodArgumentResolverSupport;
import org.springframework.web.reactive.result.method.SyncHandlerMethodArgumentResolver;
import org.springframework.web.server.ServerWebExchange;

/**
 * Resolves {@link Map} method arguments annotated with {@code @RequestHeader}.
 * For individual header values annotated with {@code @RequestHeader} see
 * {@link RequestHeaderMethodArgumentResolver} instead.
 *
 * <p>The created {@link Map} contains all request header name/value pairs.
 * The method parameter type may be a {@link MultiValueMap} to receive all
 * values for a header, not only the first one.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 * @see RequestHeaderMethodArgumentResolver
 */
public class RequestHeaderMapMethodArgumentResolver extends HandlerMethodArgumentResolverSupport
		implements SyncHandlerMethodArgumentResolver {

	public RequestHeaderMapMethodArgumentResolver(ReactiveAdapterRegistry adapterRegistry) {
		super(adapterRegistry);
	}


	@Override
	public boolean supportsParameter(MethodParameter param) {
		return checkAnnotatedParamNoReactiveWrapper(param, RequestHeader.class, this::allParams);
	}

	private boolean allParams(RequestHeader annotation, Class<?> type) {
		return Map.class.isAssignableFrom(type);
	}


	@Override
	public Optional<Object> resolveArgumentValue(MethodParameter methodParameter,
			BindingContext context, ServerWebExchange exchange) {

		Class<?> paramType = methodParameter.getParameterType();
		boolean isMultiValueMap = MultiValueMap.class.isAssignableFrom(paramType);

		HttpHeaders headers = exchange.getRequest().getHeaders();
		return Optional.of(isMultiValueMap ? headers : headers.toSingleValueMap());
	}

}