package org.checkerframework.framework.type;

import java.util.Objects;
import org.checkerframework.framework.type.visitor.SimpleAnnotatedTypeScanner;

/**
 * Computes the hashcode of an AnnotatedTypeMirror using the underlying type and primary annotations
 * and the hash code of component types of AnnotatedTypeMirror.
 *
 * <p>This class should be synchronized with EqualityAtmComparer.
 *
 * @see org.checkerframework.framework.type.EqualityAtmComparer for more details.
 *     <p>This is used by AnnotatedTypeMirror.hashcode.
 */
public class HashcodeAtmVisitor extends SimpleAnnotatedTypeScanner<Integer, Void> {

  /** Creates a {@link HashcodeAtmVisitor}. */
  public HashcodeAtmVisitor() {
    super(Integer::sum, 0);
  }

  /**
   * Generates hashcode for type using the underlying type and the primary annotation. This method
   * does not descend into component types (this occurs in the scan method)
   *
   * @param type the type
   */
  @Override
  protected Integer defaultAction(AnnotatedTypeMirror type, Void v) {
    // To differentiate between partially initialized type's (which may have null components)
    // and fully initialized types, null values are allowed
    if (type == null) {
      return 0;
    }
    return Objects.hash(type.getUnderlyingTypeHashCode(), type.getAnnotations().toString());
  }
}