/**
 * (C) Copyright IBM Corp. 2010, 2015
 *
 * 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 com.ibm.bi.dml.hops.globalopt;

import java.util.HashMap;
import java.util.Map.Entry;

import com.ibm.bi.dml.hops.globalopt.gdfgraph.GDFNode;

/**
 * This MemoStructure is the central location for storing enumerated plans (configurations) and serves
 * two purposes:
 * 
 * 1) Plan Memoization: Due to the DAG structure (where a single node is reachable over alternative 
 * paths), our top-down, recursive optimization procedure might visit an operator multiple times. 
 * The memo structure memoizes and reuses already generated plans.
 * 
 * 2) config set cache
 * 
 * The internal structure is as follows:
 * Memo Structure := | LONG GDFNodeID | MemoEntry | *
 * Memo Entry := | InterestingPropertySet | DOUBLE COST | * 
 * 
 */
public class MemoStructure 
{
	
	private HashMap<Long, PlanSet> _entries = null; //NODEID | PLANSET
	private HashMap<Long, Long>    _nodeIDs = null; //NODEID | HOPID
	
	public MemoStructure()
	{
		_entries = new HashMap<Long, PlanSet>();
		_nodeIDs = new HashMap<Long, Long>();
	}
	
	///////////////////////////////////////////////////
	// basic access to memo structure entries
	
	public boolean constainsEntry( GDFNode node )
	{
		return _entries.containsKey( node.getID() );
	}
	
	public void putEntry( GDFNode node, PlanSet entry )
	{
		_entries.put( node.getID(), entry );
		if( node.getHop()!=null )
			_nodeIDs.put( node.getID(), node.getHop().getHopID() );
		else
			_nodeIDs.put( node.getID(), -1L );	
	}
	
	public PlanSet getEntry( GDFNode node )
	{
		return _entries.get( node.getID()) ;
	}
	
	@Override
	public String toString()
	{
		StringBuilder sb = new StringBuilder();
		sb.append("------------------------------------\n");
		sb.append("MEMO STRUCTURE (gdfnodeid, plans):  \n");
		sb.append("------------------------------------\n");
		
		for( Entry<Long, PlanSet> e : _entries.entrySet() )
		{
			sb.append("------------------------------------\n");
			sb.append("Node "+e.getKey()+" (hop "+_nodeIDs.get(e.getKey())+"):\n");
			for( Plan p : e.getValue().getPlans() ) {
				sb.append(p.toString());
				sb.append("\n");
			}
		}
		
		return sb.toString();
	}
}