/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.apache.syncope.sra.filters;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.charset.Charset;
  import java.nio.charset.StandardCharsets;
  import org.apache.commons.lang3.BooleanUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.jsoup.Jsoup;
  import org.jsoup.nodes.Document;
  import org.springframework.http.server.reactive.ServerHttpResponseDecorator;
  import org.springframework.web.server.ServerWebExchange;
  
  public class LinkRewriteGatewayFilterFactory extends ModifyResponseGatewayFilterFactory {
  
      @Override
      protected boolean skipCond(final ServerHttpResponseDecorator decorator) {
          return decorator.getHeaders().getContentType() == null
                  || !StringUtils.containsIgnoreCase(decorator.getHeaders().getContentType().toString(), "html");
      }
  
      private Charset getCharset(final ServerHttpResponseDecorator decorator) {
          return decorator.getHeaders().getContentType() != null
                  && decorator.getHeaders().getContentType().getCharset() != null
                  ? decorator.getHeaders().getContentType().getCharset()
                  : StandardCharsets.UTF_8;
      }
  
      private void replace(final Document doc, final String element, final String attr, final String prefix) {
          doc.select(element).forEach(link -> {
              String attrValue = link.attributes().get(attr);
              if (attrValue.startsWith("/") && !attrValue.startsWith("//")) {
                  link.attr(attr, attrValue.replace(attrValue, prefix + attrValue));
              }
          });
      }
  
      @Override
      protected byte[] modifyResponse(
              final InputStream responseBody,
              final Config config,
              final ServerHttpResponseDecorator decorator,
              final ServerWebExchange exchange)
              throws IOException {
  
          String[] keyValue = config.getData().split(",");
  
          String oldBase = StringUtils.appendIfMissing(keyValue[0], "/");
          String newBase = StringUtils.appendIfMissing(keyValue[1], "/");
          String newBaseAsPrefix = StringUtils.removeEnd(keyValue[1], "/");
  
          boolean rewriterRootAttrs = true;
          if (keyValue.length == 3) {
              rewriterRootAttrs = BooleanUtils.toBoolean(keyValue[2]);
          }
  
          Document doc = Jsoup.parse(
                  responseBody, getCharset(decorator).name(), exchange.getRequest().getURI().toASCIIString());
  
          if (rewriterRootAttrs) {
              replace(doc, "a", "href", newBaseAsPrefix);
              replace(doc, "link", "href", newBaseAsPrefix);
              replace(doc, "img", "src", newBaseAsPrefix);
              replace(doc, "script", "src", newBaseAsPrefix);
              replace(doc, "object", "data", newBaseAsPrefix);
          }
  
          return doc.toString().replace(oldBase, newBase).getBytes();
      }
  }