/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2011 by Rapid-I and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapid-i.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package com.rapidminer.operator.ports.metadata;

import com.rapidminer.operator.ports.InputPort;

/** A simple precondition of an {@link InputPort}. In an early design phase, preconditions 
 *  used to be special {@link MDTransformationRule}s rules, but having them separately 
 *  attached to the input ports has advantages for GUI design and auto-wiring processes.   
 *   
 *   @author Simon Fischer
 *   */
public interface Precondition {

	/** Checks whether the precondition is satisfied, registering a {@link MetaDataError} with the input port if not. 
	 * 
	 *  @param metaData the delivered meta data. Note that this may differ from the meta data currently assigned to the 
	 *     input port for which this Precondition was created, e.g. for a ClooectionPrecondition. 
	 * */
	public void check(MetaData metaData);

	/** Returns a human readable description. */
	public String getDescription();

	/** Returns true if the given object is compatible with this precondition. */
	public boolean isCompatible(MetaData input, CompatibilityLevel level);
	
	/** Assume that the precondition is satisfied, i.e., artificially generate
	 *  compatible meta data at the input port. This method is used to check what
	 *  output would be generated if the input was correctly delivered. */
	public void assumeSatisfied();
	
	/** Returns the meta data required by this precondition. */
	public MetaData getExpectedMetaData();
}
