/*-
 * ========================LICENSE_START=================================
 * O-RAN-SC
 * %%
 * Copyright (C) 2019 AT&T Intellectual Property
 * Modifications Copyright (C) 2020 Nordix Foundation
 * %%
 * 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.
 * ========================LICENSE_END===================================
 */
package org.oransc.portal.nonrtric.controlpanel.controller;

import java.lang.invoke.MethodHandles;

import org.oransc.portal.nonrtric.controlpanel.model.ErrorTransport;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.client.HttpStatusCodeException;
import org.springframework.web.client.RestClientResponseException;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;

/**
 * Catches certain exceptions. This controller advice factors out try-catch
 * blocks in many controller methods.
 *
 * Also see:<br>
 * https://www.baeldung.com/exception-handling-for-rest-with-spring
 * https://www.springboottutorial.com/spring-boot-exception-handling-for-rest-services
 */
@ControllerAdvice
public class CustomResponseEntityExceptionHandler extends ResponseEntityExceptionHandler {

    // Superclass has "logger" that is exposed here, so use a different name
    private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

    /**
     * Logs the error and generates a JSON response when a REST controller method
     * takes a RestClientResponseException. This is thrown by the Http client when a
     * remote method returns a non-2xx code. All the controller methods are proxies
     * in that they just forward the request along to a remote system, so if that
     * remote system fails, return 502 plus some details about the failure, rather
     * than the generic 500 that Spring-Boot will return on an uncaught exception.
     *
     * Why 502? I quote: <blockquote>HTTP server received an invalid response from a
     * server it consulted when acting as a proxy or gateway.</blockquote>
     *
     * @param ex
     *        The exception
     *
     * @param request
     *        The original request
     *
     * @return A response entity with status code 502 plus some details in the body.
     */
    @ExceptionHandler({RestClientResponseException.class})
    public final ResponseEntity<ErrorTransport> handleProxyMethodException(Exception ex, WebRequest request) {
        // Capture the full stack trace in the log.
        log.error("handleProxyMethodException: request {}, exception {}", request.getDescription(false),
            ex.getMessage());
        if (ex instanceof HttpStatusCodeException) {
            HttpStatusCodeException hsce = (HttpStatusCodeException) ex;
            return new ResponseEntity<>(new ErrorTransport(hsce.getRawStatusCode(), hsce.getResponseBodyAsString(),
                ex.toString(), request.getDescription(false)), HttpStatus.BAD_GATEWAY);
        } else {
            return new ResponseEntity<>(new ErrorTransport(500, ex), HttpStatus.BAD_GATEWAY);
        }
    }

}