/*
 * Copyright 2017-2020 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
 *
 *      https://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.data.web;

import javax.annotation.Nonnull;

import org.springframework.core.MethodParameter;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.util.Assert;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.BindingContext;
import org.springframework.web.reactive.result.method.SyncHandlerMethodArgumentResolver;
import org.springframework.web.server.ServerWebExchange;

Extracts paging information from web requests and thus allows injecting Pageable instances into WebFlux controller methods. Request properties to be parsed can be configured. Default configuration uses request parameters beginning with DEFAULT_PAGE_PARAMETERDEFAULT_QUALIFIER_DELIMITER. 
Author:
Mark Paluch
Since:
2.2/**
 * Extracts paging information from web requests and thus allows injecting {@link Pageable} instances into WebFlux
 * controller methods. Request properties to be parsed can be configured. Default configuration uses request parameters
 * beginning with {@link #DEFAULT_PAGE_PARAMETER}{@link #DEFAULT_QUALIFIER_DELIMITER}.
 *
 * @since 2.2
 * @author Mark Paluch
 */
public class ReactivePageableHandlerMethodArgumentResolver extends PageableHandlerMethodArgumentResolverSupport
		implements SyncHandlerMethodArgumentResolver {

	private static final ReactiveSortHandlerMethodArgumentResolver DEFAULT_SORT_RESOLVER = new ReactiveSortHandlerMethodArgumentResolver();

	private ReactiveSortHandlerMethodArgumentResolver sortResolver;

	
Constructs an instance of this resolved with a default ReactiveSortHandlerMethodArgumentResolver. /**
	 * Constructs an instance of this resolved with a default {@link ReactiveSortHandlerMethodArgumentResolver}.
	 */
	public ReactivePageableHandlerMethodArgumentResolver() {
		this(DEFAULT_SORT_RESOLVER);
	}

	
Constructs an instance of this resolver with the specified SortArgumentResolver. 
Params:
sortResolver – the sort resolver to use./**
	 * Constructs an instance of this resolver with the specified {@link SortArgumentResolver}.
	 *
	 * @param sortResolver the sort resolver to use.
	 */
	public ReactivePageableHandlerMethodArgumentResolver(ReactiveSortHandlerMethodArgumentResolver sortResolver) {

		Assert.notNull(sortResolver, "ReactiveSortHandlerMethodArgumentResolver must not be null!");

		this.sortResolver = sortResolver;
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.web.reactive.result.method.HandlerMethodArgumentResolver#supportsParameter(org.springframework.core.MethodParameter)
	 */
	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return Pageable.class.equals(parameter.getParameterType());
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.web.reactive.result.method.SyncHandlerMethodArgumentResolver#resolveArgumentValue(org.springframework.core.MethodParameter, org.springframework.web.reactive.BindingContext, org.springframework.web.server.ServerWebExchange)
	 */
	@Nonnull
	@Override
	public Pageable resolveArgumentValue(MethodParameter parameter, BindingContext bindingContext,
			ServerWebExchange exchange) {

		MultiValueMap<String, String> queryParams = exchange.getRequest().getQueryParams();
		String page = queryParams.getFirst(getParameterNameToUse(getPageParameterName(), parameter));
		String pageSize = queryParams.getFirst(getParameterNameToUse(getSizeParameterName(), parameter));

		Sort sort = sortResolver.resolveArgumentValue(parameter, bindingContext, exchange);

		Pageable pageable = getPageable(parameter, page, pageSize);

		return sort.isSorted() ? PageRequest.of(pageable.getPageNumber(), pageable.getPageSize(), sort) : pageable;
	}
}