/*
    * Portions of this software was developed by employees of the National Institute
    * of Standards and Technology (NIST), an agency of the Federal Government and is
    * being made available as a public service. Pursuant to title 17 United States
    * Code Section 105, works of NIST employees are not subject to copyright
    * protection in the United States. This software may be subject to foreign
    * copyright. Permission in the United States and in foreign countries, to the
    * extent that NIST may hold copyright, to use, copy, modify, create derivative
    * works, and distribute this software and its documentation without fee is hereby
   * granted on a non-exclusive basis, provided that this notice and disclaimer
   * of warranty appears in all copies.
   *
   * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
   * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
   * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
   * INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
   * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE.  IN NO EVENT
   * SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
   * INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
   * OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
   * CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
   * PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
   * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
   */
  
  package gov.nist.secauto.metaschema.databind.io;
  
  import com.fasterxml.jackson.core.JsonFactory;
  import com.fasterxml.jackson.core.format.DataFormatDetector;
  import com.fasterxml.jackson.core.format.DataFormatMatcher;
  import com.fasterxml.jackson.core.format.MatchStrength;
  import com.fasterxml.jackson.dataformat.xml.XmlFactory;
  import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
  
  import gov.nist.secauto.metaschema.core.configuration.DefaultConfiguration;
  import gov.nist.secauto.metaschema.core.configuration.IConfiguration;
  import gov.nist.secauto.metaschema.core.util.ObjectUtils;
  import gov.nist.secauto.metaschema.databind.io.json.JsonFactoryFactory;
  import gov.nist.secauto.metaschema.databind.io.yaml.impl.YamlFactoryFactory;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  
  /**
   * Provides a means to analyze content to determine what {@link Format} the data
   * is represented as.
   */
  public class FormatDetector {
  
    private final DataFormatDetector detector;
  
    /**
     * Construct a new format detector using the default configuration.
     */
    public FormatDetector() {
      this(new DefaultConfiguration<>());
    }
  
    /**
     * Construct a new format detector using the provided {@code configuration}.
     *
     * @param configuration
     *          the deserialization configuration to use for detection
     */
    public FormatDetector(
        @NonNull IConfiguration<DeserializationFeature<?>> configuration) {
      this(configuration, newDetectorFactory(configuration));
    }
  
    /**
     * Construct a new format detector using the provided {@code configuration}.
     *
     * @param configuration
     *          the deserialization configuration to use for detection
     * @param detectors
     *          the JSON parser instances to use for format detection
     */
    protected FormatDetector(
        @NonNull IConfiguration<DeserializationFeature<?>> configuration,
        @NonNull JsonFactory... detectors) {
      int lookaheadBytes = configuration.get(DeserializationFeature.FORMAT_DETECTION_LOOKAHEAD_LIMIT);
      this.detector = new DataFormatDetector(detectors)
          .withMinimalMatch(MatchStrength.INCONCLUSIVE)
          .withOptimalMatch(MatchStrength.SOLID_MATCH)
          .withMaxInputLookahead(lookaheadBytes - 1);
  
    }
  
    @NonNull
    private static JsonFactory[] newDetectorFactory(@NonNull IConfiguration<DeserializationFeature<?>> config) {
      JsonFactory[] detectorFactory = new JsonFactory[3];
      detectorFactory[0] = YamlFactoryFactory.newParserFactoryInstance(config);
      detectorFactory[1] = JsonFactoryFactory.instance();
      detectorFactory[2] = new XmlFactory();
      return detectorFactory;
   }
 
   /**
    * Analyzes the provided {@code resource} to determine it's format.
    *
    * @param resource
    *          the resource to analyze
    * @return the analysis result
    * @throws IOException
    *           if an error occurred while reading the resource
    */
   @NonNull
   public Result detect(@NonNull URL resource) throws IOException {
     try (InputStream is = ObjectUtils.notNull(resource.openStream())) {
       return detect(is);
     }
   }
 
   /**
    * Analyzes the data from the provided {@code inputStream} to determine it's
    * format.
    *
    * @param inputStream
    *          the resource stream to analyze
    * @return the analysis result
    * @throws IOException
    *           if an error occurred while reading the resource
    */
   @NonNull
   public Result detect(@NonNull InputStream inputStream) throws IOException {
     DataFormatMatcher matcher = detector.findFormat(inputStream);
     switch (matcher.getMatchStrength()) {
     case FULL_MATCH:
     case SOLID_MATCH:
     case WEAK_MATCH:
     case INCONCLUSIVE:
       return new Result(matcher);
     case NO_MATCH:
     default:
       throw new IOException("Unable to identify format");
     }
   }
 
   public static class Result {
     @NonNull
     private final DataFormatMatcher matcher;
 
     private Result(@NonNull DataFormatMatcher matcher) {
       this.matcher = matcher;
     }
 
     /**
      * Get the detected format.
      *
      * @return the format
      */
     @NonNull
     public Format getFormat() {
       Format retval;
       String formatName = matcher.getMatchedFormatName();
       if (YAMLFactory.FORMAT_NAME_YAML.equals(formatName)) {
         retval = Format.YAML;
       } else if (JsonFactory.FORMAT_NAME_JSON.equals(formatName)) {
         retval = Format.JSON;
       } else if (XmlFactory.FORMAT_NAME_XML.equals(formatName)) {
         retval = Format.XML;
       } else {
         throw new UnsupportedOperationException(String.format("The detected format '%s' is not supported", formatName));
       }
       return retval;
     }
 
     /**
      * Get an {@link InputStream} that can be used to read the analyzed data from
      * the start.
      *
      * @return the stream
      */
     @SuppressWarnings("resource")
     @NonNull
     public InputStream getDataStream() {
       return ObjectUtils.notNull(matcher.getDataStream());
     }
 
     // @SuppressWarnings("resource")
     // @NonNull
     // public JsonParser getParser() throws IOException {
     // return ObjectUtils.notNull(matcher.createParserWithMatch());
     // }
 
     /**
      * Get the strength of the match.
      *
      * @return the strength
      */
     @NonNull
     public MatchStrength getMatchStrength() {
       return ObjectUtils.notNull(matcher.getMatchStrength());
     }
   }
 }