/*
 *
 *  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.metron.stellar.common.shell.specials;

import org.apache.metron.stellar.common.shell.StellarShellExecutor;
import org.apache.metron.stellar.common.shell.StellarResult;

import java.util.function.Function;

/**
 * A special command that can be run within a Stellar execution
 * environment.
 *
 * Most functionality expected of running Stellar in a shell-like
 * environment, that is not directly implemented in the Stellar
 * language itself, is implemented as a SpecialCommand. This
 * includes magics, doc strings, comments and quit.
 *
 * This is typically an action performed on the execution
 * environment, not something that could be executed within Stellar.
 */
public interface SpecialCommand {

  /**
   * @return A function that when applied to the input buffer returns
   * true, if this special command should be applied.
   */
  Function<String, Boolean> getMatcher();

  /**
   * @return The name of the command, used for auto-completion.
   */
  String getCommand();

  /**
   * Execute the magic command.
   * @param expression The expression to execute.
   * @param executor A stellar execution environment.
   * @return The result of executing the magic command.
   */
  StellarResult execute(String expression, StellarShellExecutor executor);
}
