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
   * 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.bigtop.datagenerators.bigpetstore.generators.transaction;
  
  import java.util.List;
  import java.util.Map;
  
  import org.apache.bigtop.datagenerators.bigpetstore.Constants;
  import org.apache.bigtop.datagenerators.bigpetstore.datamodels.Product;
  import org.apache.bigtop.datagenerators.samplers.SeedFactory;
  import org.apache.bigtop.datagenerators.samplers.samplers.ConditionalSampler;
  import org.apache.bigtop.datagenerators.samplers.samplers.RouletteWheelSampler;
  import org.apache.bigtop.datagenerators.samplers.samplers.Sampler;
  import org.apache.bigtop.datagenerators.samplers.wfs.ConditionalWeightFunction;
  
  import com.google.common.collect.ImmutableMap;
  import com.google.common.collect.Lists;
  import com.google.common.collect.Maps;
  
  public class TransactionPurchasesHiddenMarkovModel implements ConditionalSampler<List<Product>, Double>
  {
  
  	protected final static String STOP_STATE = "STOP";
  
  	final ConditionalSampler<Product, String> purchasingProcesses;
  	final ConditionalWeightFunction<Double, Double> categoryWF;
  	final CustomerInventory inventory;
  
  	final SeedFactory seedFactory;
  
  	public TransactionPurchasesHiddenMarkovModel(ConditionalSampler<Product, String> purchasingProcesses,
  			ConditionalWeightFunction<Double, Double> categoryWF, CustomerInventory inventory,
  				SeedFactory seedFactory)
  	{
  		this.purchasingProcesses = purchasingProcesses;
  		this.inventory = inventory;
  		this.categoryWF = categoryWF;
  
  		this.seedFactory = seedFactory;
  	}
  
  	protected String chooseCategory(double transactionTime, int numPurchases) throws Exception
  	{
  		ImmutableMap<String, Double> exhaustionTimes = this.inventory.getExhaustionTimes();
  		Map<String, Double> weights = Maps.newHashMap();
  
  		for(Map.Entry<String, Double> entry : exhaustionTimes.entrySet())
  		{
  			String category = entry.getKey();
  			double weight = this.categoryWF.weight(entry.getValue(), transactionTime);
  			weights.put(category, weight);
  		}
  
  		if(numPurchases > 0)
  		{
  			weights.put(STOP_STATE, Constants.STOP_CATEGORY_WEIGHT);
  		}
  
  		Sampler<String> sampler = RouletteWheelSampler.create(weights, seedFactory);
  
  		return sampler.sample();
  	}
  
  	protected Product chooseProduct(String category) throws Exception
  	{
  		return this.purchasingProcesses.sample(category);
  	}
  
  	public List<Product> sample(Double transactionTime) throws Exception
  	{
  		int numPurchases = 0;
  
  		List<Product> purchasedProducts = Lists.newArrayList();
  
  		String category;
  		while(true)
  		{
  			category = this.chooseCategory(transactionTime, numPurchases);
  
  			if(category.equals(STOP_STATE))
  			{
  				break;
  			}
  
  			Product product = this.chooseProduct(category);
  
  			purchasedProducts.add(product);
  
  			this.inventory.simulatePurchase(transactionTime, product);
  			numPurchases += 1;
  		}
  
  		return purchasedProducts;
  	}
  }
  