/*
    * SPDX-FileCopyrightText: none
    * SPDX-License-Identifier: CC0-1.0
    */
   
   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 final 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());
     }
   }
 }