/*
    * 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.web.reactive.function.client;
  
  import org.bremersee.security.authentication.AccessTokenProvider;
  import org.bremersee.security.authentication.AccessTokenRetriever;
  import org.bremersee.security.authentication.AccessTokenRetrieverProperties;
  import org.bremersee.security.authentication.ReactiveAccessTokenProviders;
  import org.springframework.http.HttpHeaders;
  import org.springframework.lang.NonNull;
  import org.springframework.util.Assert;
  import org.springframework.util.StringUtils;
  import org.springframework.web.reactive.function.client.ClientRequest;
  import org.springframework.web.reactive.function.client.ClientResponse;
  import org.springframework.web.reactive.function.client.ExchangeFilterFunction;
  import org.springframework.web.reactive.function.client.ExchangeFunction;
  import reactor.core.publisher.Mono;
  
  /**
   * The access token appender.
   *
   * @author Christian Bremer
   */
  public class AccessTokenAppender implements ExchangeFilterFunction {
  
    private final AccessTokenProvider<Mono<String>> accessTokenProvider;
  
    /**
     * Instantiates a new access token appender.
     *
     * @param accessTokenProvider the access token provider
     */
    public AccessTokenAppender(AccessTokenProvider<Mono<String>> accessTokenProvider) {
      Assert.notNull(accessTokenProvider, "Access token provider must be present.");
      this.accessTokenProvider = accessTokenProvider;
    }
  
    @NonNull
    @Override
    public Mono<ClientResponse> filter(@NonNull ClientRequest request, @NonNull ExchangeFunction next) {
      return accessTokenProvider.getAccessToken()
          .switchIfEmpty(Mono.just(""))
          .flatMap(tokenValue -> exchangeWithToken(request, tokenValue, next));
    }
  
    private Mono<ClientResponse> exchangeWithToken(
        ClientRequest request,
        String tokenValue,
        ExchangeFunction next) {
  
      if (StringUtils.hasText(tokenValue)) {
        return next.exchange(ClientRequest
            .from(request)
            .headers(headers -> headers.set(HttpHeaders.AUTHORIZATION, "Bearer " + tokenValue))
            .build());
      } else {
        return next.exchange(request);
      }
    }
  
    /**
     * From authentication access token appender.
     *
     * @return the access token appender
     */
    public static AccessTokenAppender fromAuthentication() {
      return new AccessTokenAppender(ReactiveAccessTokenProviders.fromAuthentication());
    }
  
    /**
     * With access token retriever access token appender.
     *
     * @param properties the properties
     * @return the access token appender
     */
    @SuppressWarnings("unused")
    public static AccessTokenAppender withAccessTokenRetriever(
        final AccessTokenRetrieverProperties properties) {
      return new AccessTokenAppender(
          ReactiveAccessTokenProviders.withAccessTokenRetriever(properties));
    }
  
    /**
     * With access token retriever access token appender.
     *
    * @param retriever the retriever
    * @param properties the properties
    * @return the access token appender
    */
   public static AccessTokenAppender withAccessTokenRetriever(
       final AccessTokenRetriever<Mono<String>> retriever,
       final AccessTokenRetrieverProperties properties) {
     return new AccessTokenAppender(
         ReactiveAccessTokenProviders.withAccessTokenRetriever(retriever, properties));
   }
 
 }