/*
 * Copyright 2013-2020 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.cloud.gateway.filter.factory;

import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;

import reactor.core.publisher.Mono;

import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.util.Assert;
import org.springframework.web.server.ServerWebExchange;

import static org.springframework.cloud.gateway.support.GatewayToStringStyler.filterToStringCreator;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.addOriginalRequestUrl;

/**
 * @author Spencer Gibb
 */
public class RewritePathGatewayFilterFactory
		extends AbstractGatewayFilterFactory<RewritePathGatewayFilterFactory.Config> {

	/**
	 * Regexp key.
	 */
	public static final String REGEXP_KEY = "regexp";

	/**
	 * Replacement key.
	 */
	public static final String REPLACEMENT_KEY = "replacement";

	public RewritePathGatewayFilterFactory() {
		super(Config.class);
	}

	@Override
	public List<String> shortcutFieldOrder() {
		return Arrays.asList(REGEXP_KEY, REPLACEMENT_KEY);
	}

	@Override
	public GatewayFilter apply(Config config) {
		String replacement = config.replacement.replace("$\\", "$");
		Pattern pattern = Pattern.compile(config.regexp);
		return new GatewayFilter() {
			@Override
			public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
				ServerHttpRequest req = exchange.getRequest();
				addOriginalRequestUrl(exchange, req.getURI());
				String path = req.getURI().getRawPath();
				String newPath = pattern.matcher(path).replaceAll(replacement);

				ServerHttpRequest request = req.mutate().path(newPath).build();

				exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, request.getURI());

				return chain.filter(exchange.mutate().request(request).build());
			}

			@Override
			public String toString() {
				return filterToStringCreator(RewritePathGatewayFilterFactory.this)
						.append(config.getRegexp(), replacement).toString();
			}
		};
	}

	public static class Config {

		private String regexp;

		private String replacement;

		public String getRegexp() {
			return regexp;
		}

		public Config setRegexp(String regexp) {
			Assert.hasText(regexp, "regexp must have a value");
			this.regexp = regexp;
			return this;
		}

		public String getReplacement() {
			return replacement;
		}

		public Config setReplacement(String replacement) {
			Assert.notNull(replacement, "replacement must not be null");
			this.replacement = replacement;
			return this;
		}

	}

}
