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
   *
   *     https://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.avro.compiler.schema;
  
  import org.apache.avro.Schema;
  
  public interface SchemaVisitor<T> {
  
    /**
     * Invoked for schemas that do not have "child" schemas (like string, int ...)
     * or for a previously encountered schema with children, which will be treated
     * as a terminal. (to avoid circular recursion)
     *
     * @param terminal
     */
    SchemaVisitorAction visitTerminal(Schema terminal);
  
    /**
     * Invoked for schema with children before proceeding to visit the children.
     *
     * @param nonTerminal
     */
    SchemaVisitorAction visitNonTerminal(Schema nonTerminal);
  
    /**
     * Invoked for schemas with children after its children have been visited.
     *
     * @param nonTerminal
     */
    SchemaVisitorAction afterVisitNonTerminal(Schema nonTerminal);
  
    /**
     * Invoked when visiting is complete.
     *
     * @return a value which will be returned by the visit method.
     */
    T get();
  
  }
  