/*
    * Copyright 2019 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.bremersee.security.authentication;
  
  import java.io.IOException;
  import java.util.Optional;
  import net.minidev.json.JSONObject;
  import net.minidev.json.JSONValue;
  import org.bremersee.exception.AccessTokenRetrieverAuthenticationException;
  import org.springframework.http.HttpEntity;
  import org.springframework.http.HttpHeaders;
  import org.springframework.http.HttpMethod;
  import org.springframework.http.HttpStatus;
  import org.springframework.http.MediaType;
  import org.springframework.http.client.ClientHttpResponse;
  import org.springframework.lang.NonNull;
  import org.springframework.util.StringUtils;
  import org.springframework.web.client.DefaultResponseErrorHandler;
  import org.springframework.web.client.RestTemplate;
  
  /**
   * The rest template access token retriever.
   *
   * @author Christian Bremer
   */
  public class RestTemplateAccessTokenRetriever implements AccessTokenRetriever<String> {
  
    private final RestTemplate restTemplate;
  
    private final AccessTokenCache accessTokenCache;
  
    /**
     * Instantiates a new rest template access token retriever.
     *
     * @param restTemplate the rest template
     */
    public RestTemplateAccessTokenRetriever(RestTemplate restTemplate) {
      this(restTemplate, null);
    }
  
    /**
     * Instantiates a new rest template access token retriever.
     *
     * @param restTemplate the rest template
     * @param accessTokenCache the access token cache
     */
    public RestTemplateAccessTokenRetriever(
        RestTemplate restTemplate,
        AccessTokenCache accessTokenCache) {
  
      this.restTemplate = restTemplate;
      this.restTemplate.setErrorHandler(new ErrorHandler());
      this.accessTokenCache = accessTokenCache;
    }
  
    @Override
    public String retrieveAccessToken(AccessTokenRetrieverProperties input) {
      final String cacheKey = input.createCacheKeyHashed();
      return Optional.ofNullable(accessTokenCache)
          .flatMap(cache -> cache.findAccessToken(cacheKey))
          .orElseGet(() -> {
            final HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
            input.getBasicAuthProperties()
                .ifPresent(basicAuthProperties -> headers.setBasicAuth(
                    basicAuthProperties.getUsername(),
                    basicAuthProperties.getPassword()));
            final HttpEntity<?> request = new HttpEntity<>(input.createBody(), headers);
            final String response = restTemplate.exchange(
                    input.getTokenEndpoint(),
                    HttpMethod.POST,
                    request,
                    String.class)
                .getBody();
            final JSONObject json = (JSONObject) JSONValue.parse(response);
            final String accessToken = json.getAsString("access_token");
            if (StringUtils.hasText(accessToken)) {
              if (accessTokenCache != null) {
                accessTokenCache.putAccessToken(cacheKey, accessToken);
              }
              return accessToken;
            }
            throw new AccessTokenRetrieverAuthenticationException(HttpStatus.UNAUTHORIZED,
                "There is no access token in the response: " + accessToken);
          });
   }
 
   private static class ErrorHandler extends DefaultResponseErrorHandler {
 
     @Override
     protected void handleError(final ClientHttpResponse response, @NonNull final HttpStatus statusCode)
         throws IOException {
       final String statusText = response.getStatusText();
       throw new AccessTokenRetrieverAuthenticationException(statusCode, statusText);
     }
   }
 
 }