/*
    * 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.core.model.validation;
  
  import gov.nist.secauto.metaschema.core.model.constraint.IConstraint.Level;
  import gov.nist.secauto.metaschema.core.util.ObjectUtils;
  
  import org.xml.sax.ErrorHandler;
  import org.xml.sax.SAXException;
  import org.xml.sax.SAXParseException;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URI;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.List;
  
  import javax.xml.XMLConstants;
  import javax.xml.transform.Source;
  import javax.xml.transform.stream.StreamSource;
  import javax.xml.validation.Schema;
  import javax.xml.validation.SchemaFactory;
  import javax.xml.validation.Validator;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  
  public class XmlSchemaContentValidator
      extends AbstractContentValidator {
    private final Schema schema;
  
    @SuppressWarnings("null")
    @NonNull
    private static Schema toSchema(@NonNull List<? extends Source> schemaSources) throws SAXException {
      SchemaFactory schemafactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
      // schemafactory.setResourceResolver(new ClasspathResourceResolver());
      Schema retval;
      if (schemaSources.isEmpty()) {
        retval = schemafactory.newSchema();
      } else {
        retval = schemafactory.newSchema(schemaSources.toArray(new Source[0]));
      }
  
      // TODO verify source input streams are closed
      return retval;
    }
  
    public XmlSchemaContentValidator(@NonNull List<? extends Source> schemaSources) throws SAXException {
      this(toSchema(ObjectUtils.requireNonNull(schemaSources, "schemaSources")));
    }
  
    protected XmlSchemaContentValidator(@NonNull Schema schema) {
      this.schema = ObjectUtils.requireNonNull(schema, "schema");
    }
  
    public Schema getSchema() {
      return schema;
    }
  
    @Override
    public IValidationResult validate(InputStream is, URI documentUri) throws IOException {
      Source xmlSource = new StreamSource(is, documentUri.toASCIIString());
  
      Validator validator = schema.newValidator();
      XmlValidationErrorHandler errorHandler = new XmlValidationErrorHandler(documentUri);
      validator.setErrorHandler(errorHandler);
      try {
        validator.validate(xmlSource);
      } catch (SAXException ex) {
        throw new IOException(String.format("Unexpected failure during validation of '%s'", documentUri), ex);
      }
      return errorHandler;
    }
  
    public static class XmlValidationFinding implements IValidationFinding {
     @NonNull
     private final URI documentUri;
     @NonNull
     private final SAXParseException exception;
     @NonNull
     private final Level severity;
 
     public XmlValidationFinding(@NonNull Level severity, @NonNull SAXParseException exception,
         @NonNull URI documentUri) {
       this.documentUri = ObjectUtils.requireNonNull(documentUri, "documentUri");
       this.exception = ObjectUtils.requireNonNull(exception, "exception");
       this.severity = ObjectUtils.requireNonNull(severity, "severity");
     }
 
     @Override
     public Level getSeverity() {
       return severity;
     }
 
     @SuppressWarnings("null")
     @Override
     public URI getDocumentUri() {
       String systemId = getCause().getSystemId();
       return systemId == null ? documentUri : URI.create(systemId);
     }
 
     @SuppressWarnings("null")
     @Override
     public String getMessage() {
       return getCause().getLocalizedMessage();
     }
 
     @NonNull
     @Override
     public SAXParseException getCause() {
       return exception;
     }
   }
 
   private static class XmlValidationErrorHandler implements ErrorHandler, IValidationResult {
     @NonNull
     private final URI documentUri;
     @NonNull
     private final List<XmlValidationFinding> findings = new LinkedList<>();
     @NonNull
     private Level highestSeverity = Level.INFORMATIONAL;
 
     public XmlValidationErrorHandler(@NonNull URI documentUri) {
       this.documentUri = ObjectUtils.requireNonNull(documentUri, "documentUri");
     }
 
     @NonNull
     public URI getDocumentUri() {
       return documentUri;
     }
 
     private void adjustHighestSeverity(@NonNull Level severity) {
       if (highestSeverity.ordinal() < severity.ordinal()) {
         highestSeverity = severity;
       }
     }
 
     @SuppressWarnings("null")
     @Override
     public void warning(SAXParseException ex) throws SAXException {
       findings.add(new XmlValidationFinding(Level.WARNING, ex, getDocumentUri()));
       adjustHighestSeverity(Level.WARNING);
     }
 
     @SuppressWarnings("null")
     @Override
     public void error(SAXParseException ex) throws SAXException {
       findings.add(new XmlValidationFinding(Level.ERROR, ex, getDocumentUri()));
       adjustHighestSeverity(Level.ERROR);
     }
 
     @SuppressWarnings("null")
     @Override
     public void fatalError(SAXParseException ex) throws SAXException {
       findings.add(new XmlValidationFinding(Level.CRITICAL, ex, getDocumentUri()));
       adjustHighestSeverity(Level.CRITICAL);
     }
 
     @SuppressWarnings("null")
     @Override
     @NonNull
     public List<XmlValidationFinding> getFindings() {
       return Collections.unmodifiableList(findings);
     }
 
     @Override
     public Level getHighestSeverity() {
       return highestSeverity;
     }
   }
 }