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/*
 * Copyright (c) 2010-2021 Allette Systems (Australia)
 *    http://www.allette.com.au
 *
 * Licensed 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.pageseeder.diffx.api;

import org.jetbrains.annotations.NotNull;

import java.io.UncheckedIOException;

/**
 * An interface for handling the output of diff processors and algorithms.
 *
 * Handlers may be used to filter or format the operations of diff processors.
 *
 * @param  The type of token the handler is designed for
 *
 * @author Christophe Lauret
 * @version 0.9.0
 */
@FunctionalInterface
public interface DiffHandler {

  /**
   * Receives notification of the start of the processing.
   *
   * @apiNote This method is called before any other method. Implementations can use this method to initialise
   * objects required by the handler. The default implementation does nothing.
   */
  default void start() {
  }

  /**
   * Handles the specified operation reported by the diff processor.
   *
   * @param operator The operator
   * @param token    The token to handle
   *
   * @throws UncheckedIOException  Should an I/O exception occur.
   * @throws IllegalStateException If the handler is not in a state to run this method.
   * @throws IllegalStateException If the handler is not in a state to run this method.
   */
  void handle(@NotNull Operator operator, @NotNull T token);

  /**
   * Receives notification of the end of the processing.
   *
   * @apiNote This method is called after any other method. Implementations can use this method to initialise
   * objects required by the handler. The default implementation does nothing.
   */
  default void end() {
  }

}