/*
 * Copyright 2002-2020 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.web.server.handler;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import reactor.core.publisher.Mono;

import org.springframework.http.HttpMethod;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.util.StringUtils;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebExceptionHandler;
import org.springframework.web.server.WebHandler;

WebHandler decorator that invokes one or more WebExceptionHandlers after the delegate WebHandler. 
Author:
Rossen Stoyanchev
Since:
5.0/**
 * WebHandler decorator that invokes one or more {@link WebExceptionHandler WebExceptionHandlers}
 * after the delegate {@link WebHandler}.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class ExceptionHandlingWebHandler extends WebHandlerDecorator {

	private final List<WebExceptionHandler> exceptionHandlers;


	
Create an ExceptionHandlingWebHandler for the given delegate. 
Params:
delegate – the WebHandler delegate
handlers – the WebExceptionHandlers to apply/**
	 * Create an {@code ExceptionHandlingWebHandler} for the given delegate.
	 * @param delegate the WebHandler delegate
	 * @param handlers the WebExceptionHandlers to apply
	 */
	public ExceptionHandlingWebHandler(WebHandler delegate, List<WebExceptionHandler> handlers) {
		super(delegate);
		List<WebExceptionHandler> handlersToUse = new ArrayList<>();
		handlersToUse.add(new CheckpointInsertingHandler());
		handlersToUse.addAll(handlers);
		this.exceptionHandlers = Collections.unmodifiableList(handlersToUse);
	}


	
Return a read-only list of the configured exception handlers.
/**
	 * Return a read-only list of the configured exception handlers.
	 */
	public List<WebExceptionHandler> getExceptionHandlers() {
		return this.exceptionHandlers;
	}


	@Override
	public Mono<Void> handle(ServerWebExchange exchange) {
		Mono<Void> completion;
		try {
			completion = super.handle(exchange);
		}
		catch (Throwable ex) {
			completion = Mono.error(ex);
		}

		for (WebExceptionHandler handler : this.exceptionHandlers) {
			completion = completion.onErrorResume(ex -> handler.handle(exchange, ex));
		}
		return completion;
	}


	
WebExceptionHandler to insert a checkpoint with current URL information.
Must be the first in order to ensure we catch the error signal before
the exception is handled and e.g. turned into an error response.
Since:
5.2/**
	 * WebExceptionHandler to insert a checkpoint with current URL information.
	 * Must be the first in order to ensure we catch the error signal before
	 * the exception is handled and e.g. turned into an error response.
	 * @since 5.2
 	 */
	private static class CheckpointInsertingHandler implements WebExceptionHandler {

		@Override
		public Mono<Void> handle(ServerWebExchange exchange, Throwable ex) {
			ServerHttpRequest request = exchange.getRequest();
			String rawQuery = request.getURI().getRawQuery();
			String query = StringUtils.hasText(rawQuery) ? "?" + rawQuery : "";
			HttpMethod httpMethod = request.getMethod();
			String description = "HTTP " + httpMethod + " \"" + request.getPath() + query + "\"";
			return Mono.<Void>error(ex).checkpoint(description + " [ExceptionHandlingWebHandler]");
		}
	}

}