content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.cassandra.cql3;
  
  import java.util.Collection;
  
  import javax.annotation.Nullable;
  
  import org.apache.cassandra.db.marshal.AbstractType;
  
  public interface AssignmentTestable
  {
      /**
       * @return whether this object can be assigned to the provided receiver. We distinguish
       * between 3 values: 
       *   - EXACT_MATCH if this object is exactly of the type expected by the receiver
       *   - WEAKLY_ASSIGNABLE if this object is not exactly the expected type but is assignable nonetheless
       *   - NOT_ASSIGNABLE if it's not assignable
       * Most caller should just call the isAssignable() method on the result, though functions have a use for
       * testing "strong" equality to decide the most precise overload to pick when multiple could match.
       */
      public TestResult testAssignment(String keyspace, ColumnSpecification receiver);
  
      /**
       * @return A data type that can represent this, or {@code null} if we can't determine that type. The returned type
       * won't necessarely be the exact type, but one that is compatible with it.
       */
      @Nullable
      public AbstractType<?> getCompatibleTypeIfKnown(String keyspace);
  
      /**
       * @return A data type that can represent all the specified types, or {@code null} if there isn't one.
       */
      @Nullable
      public static AbstractType<?> getCompatibleTypeIfKnown(Collection<AbstractType<?>> types)
      {
          return types.stream()
                      .filter(type -> types.stream().allMatch(t -> t.testAssignment(type).isAssignable()))
                      .findFirst()
                      .orElse(null);
      }
  
      public enum TestResult
      {
          EXACT_MATCH, WEAKLY_ASSIGNABLE, NOT_ASSIGNABLE;
  
          public boolean isAssignable()
          {
              return this != NOT_ASSIGNABLE;
          }
  
          public boolean isExactMatch()
          {
              return this == EXACT_MATCH;
          }
  
          // Test all elements of toTest for assignment. If all are exact match, return exact match. If any is not assignable,
          // return not assignable. Otherwise, return weakly assignable.
          public static TestResult testAll(String keyspace, ColumnSpecification receiver, Collection<? extends AssignmentTestable> toTest)
          {
              TestResult res = EXACT_MATCH;
              for (AssignmentTestable rt : toTest)
              {
                  if (rt == null)
                  {
                      res = WEAKLY_ASSIGNABLE;
                      continue;
                  }
  
                  TestResult t = rt.testAssignment(keyspace, receiver);
                  if (t == NOT_ASSIGNABLE)
                      return NOT_ASSIGNABLE;
  
                  if (t == WEAKLY_ASSIGNABLE)
                      res = WEAKLY_ASSIGNABLE;
              }
              return res;
          }
      }
  }
  