/*
    * 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.metapath;
  
  import gov.nist.secauto.metaschema.core.util.ObjectUtils;
  
  import java.util.List;
  import java.util.stream.Collectors;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  final class ExpressionUtils {
    private ExpressionUtils() {
      // disable
    }
  
    @NonNull
    public static <RESULT_TYPE> Class<? extends RESULT_TYPE> analyzeStaticResultType(
        @NonNull Class<RESULT_TYPE> baseType,
        @NonNull List<IExpression> expressions) {
  
      Class<? extends RESULT_TYPE> retval;
      if (expressions.isEmpty()) {
        // no expressions, so use the base type
        retval = baseType;
      } else {
        List<Class<?>> expressionClasses = ObjectUtils.notNull(expressions.stream()
            .map(expr -> expr.getStaticResultType()).collect(Collectors.toList()));
  
        // check if the expression classes, are derived from the base type
        if (checkDerivedFrom(baseType, expressionClasses)) {
          retval = findCommonBase(baseType, expressionClasses);
        } else {
          retval = baseType;
        }
      }
      return retval;
    }
  
    @NonNull
    private static <RESULT_TYPE> Class<? extends RESULT_TYPE> findCommonBase(
        @NonNull Class<RESULT_TYPE> baseType,
        @NonNull List<Class<?>> expressionClasses) {
      Class<? extends RESULT_TYPE> retval;
      if (expressionClasses.size() == 1) {
        @SuppressWarnings("unchecked") Class<? extends RESULT_TYPE> result
            = (Class<? extends RESULT_TYPE>) expressionClasses.iterator().next();
        assert result != null;
        retval = result;
      } else {
        @SuppressWarnings("unchecked") Class<? extends RESULT_TYPE> first
            = (Class<? extends RESULT_TYPE>) expressionClasses.iterator().next();
        assert first != null;
        if (baseType.equals(first)) {
          // the first type is the same as the base, which is the least common type
          retval = baseType;
        } else {
          // search for the least common type
          Class<?> leastCommon = getCommonBaseClass(
              baseType,
              first,
              ObjectUtils.notNull(expressionClasses.subList(1, expressionClasses.size())));
          @SuppressWarnings("unchecked") Class<? extends RESULT_TYPE> newBase
              = (Class<? extends RESULT_TYPE>) leastCommon;
          if (newBase != null) {
            retval = newBase;
          } else {
            retval = baseType;
          }
        }
      }
      return retval;
    }
  
   @Nullable
   private static Class<?> getCommonBaseClass(@NonNull Class<?> baseType,
       @NonNull Class<?> first, @NonNull List<Class<?>> expressionClasses) {
     boolean match = true;
     for (Class<?> clazz : expressionClasses) {
       if (!first.isAssignableFrom(clazz)) {
         match = false;
         break;
       }
     }
 
     Class<?> retval = null;
     if (match) {
       retval = first;
     } else {
       for (Class<?> clazz : first.getInterfaces()) {
         assert clazz != null;
         // ensure the new interface is a sublass of the baseType
         if (baseType.isAssignableFrom(clazz)) {
           Class<?> newBase = getCommonBaseClass(baseType, clazz, expressionClasses);
           if (newBase != null) {
             retval = newBase;
             break;
           }
         }
       }
     }
     return retval;
   }
 
   private static boolean checkDerivedFrom(@NonNull Class<?> baseType,
       @NonNull List<Class<?>> expressionClasses) {
     boolean retval = true;
     for (Class<?> clazz : expressionClasses) {
       if (!baseType.isAssignableFrom(clazz)) {
         retval = false;
         break;
       }
     }
     return retval;
   }
 
 }