/*
    * Copyright (c) 2011-2022, jcabi.com
    * All rights reserved.
    *
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    * are met: 1) Redistributions of source code must retain the above
    * copyright notice, this list of conditions and the following
    * disclaimer. 2) Redistributions in binary form must reproduce the above
   * copyright notice, this list of conditions and the following
   * disclaimer in the documentation and/or other materials provided
   * with the distribution. 3) Neither the name of the jcabi.com nor
   * the names of its contributors may be used to endorse or promote
   * products derived from this software without specific prior written
   * permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
   * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
   * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package com.jcabi.w3c;
  
  import com.jcabi.aspects.Immutable;
  import com.jcabi.http.Request;
  import com.jcabi.http.Response;
  import com.jcabi.http.request.JdkRequest;
  import com.jcabi.http.response.XmlResponse;
  import com.jcabi.log.Logger;
  import com.jcabi.xml.XML;
  import java.io.IOException;
  import java.net.HttpURLConnection;
  import java.net.URI;
  import java.nio.charset.StandardCharsets;
  import java.util.List;
  import javax.ws.rs.core.HttpHeaders;
  import javax.ws.rs.core.MediaType;
  import lombok.EqualsAndHashCode;
  import lombok.ToString;
  
  /**
   * Implementation of (X)HTML validator.
   *
   * @see <a href="http://validator.w3.org/docs/api.html">W3C API</a>
   * @since 0.1
   */
  @Immutable
  @ToString
  @EqualsAndHashCode(callSuper = false, of = "uri")
  final class DefaultHtmlValidator
      extends AbstractBaseValidator implements Validator {
  
      /**
       * The URI to use in W3C.
       */
      private final transient String uri;
  
      /**
       * Public ctor.
       * @param entry Entry point to use
       */
      DefaultHtmlValidator(final URI entry) {
          super();
          this.uri = entry.toString();
      }
  
      @Override
      public ValidationResponse validate(final String html)
          throws IOException {
          final Request req = this.request(html);
          final Response response = req.fetch();
          if (response.status() != HttpURLConnection.HTTP_OK) {
              throw new IOException(
                  response.reason()
              );
          }
          return this.build(
              response.as(XmlResponse.class)
                  .registerNs("nu", "http://n.validator.nu/messages/")
                  .assertXPath("//nu:messages")
                  .assertXPath("//nu:source")
                  .xml()
          );
      }
  
      /**
       * Send request and return response.
       * @param entity The entity to POST
       * @return The response
       */
      private Request request(final String entity) {
         return new JdkRequest(this.uri)
             .method(Request.POST)
             .body().set(entity).back()
             .header(HttpHeaders.USER_AGENT, AbstractBaseValidator.USER_AGENT)
             .header(HttpHeaders.ACCEPT, MediaType.TEXT_HTML)
             .header(
                 HttpHeaders.CONTENT_TYPE,
                 Logger.format(
                     "%s; charset=%s",
                     MediaType.TEXT_HTML,
                     StandardCharsets.UTF_8
                 )
             );
     }
 
     /**
      * Build response from XML.
      * @param xml The response
      * @return The validation response just built
      */
     private ValidationResponse build(final XML xml) {
         final List<XML> errors = xml.nodes("//nu:error");
         final List<XML> warnings = xml.nodes("//nu:info");
         final DefaultValidationResponse resp = new DefaultValidationResponse(
             errors.isEmpty() && warnings.isEmpty(),
             URI.create(this.uri),
             AbstractBaseValidator.textOf(xml.xpath("//nu:source/@type")),
             AbstractBaseValidator.charset(
                 AbstractBaseValidator.textOf(xml.xpath("//nu:source/@encoding"))
             )
         );
         for (final XML node : errors) {
             resp.addError(DefaultHtmlValidator.defect(node));
         }
         for (final XML node : warnings) {
             resp.addWarning(DefaultHtmlValidator.defect(node));
         }
         return resp;
     }
 
     /**
      * Convert XML node to defect.
      * @param node The node
      * @return The defect
      */
     private static Defect defect(final XML node) {
         return new Defect(
             AbstractBaseValidator.intOf(node.xpath("nu:error/@last-line")),
             AbstractBaseValidator.intOf(node.xpath("nu:error/@last-column")),
             AbstractBaseValidator.textOf(node.xpath("nu:extract/text()")),
             AbstractBaseValidator.textOf(node.xpath("nu:elaboration/text()")),
             "",
             AbstractBaseValidator.textOf(node.xpath("nu:message/text()"))
         );
     }
 }