/**
    * Copyright 2012 The Kuali Foundation Licensed under the
    * Educational Community 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.osedu.org/licenses/ECL-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.
   *
   * Created by Charles on 10/1/12
   */
  package org.kuali.student.r2.common.permutation;
  
  import org.aspectj.weaver.Lint;
  import org.kuali.student.enrollment.courseoffering.dto.ActivityOfferingClusterInfo;
  import org.kuali.student.enrollment.courseoffering.dto.ActivityOfferingSetInfo;
  import org.kuali.student.enrollment.courseoffering.dto.RegistrationGroupInfo;
  import org.kuali.student.r2.common.exceptions.DataValidationErrorException;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * Used to generate permutations
   *
   * @author Kuali Student Team
   */
  public class PermutationCounter {
      private int [] counter;
      private int [] maxSizes;
      private int totalIterations;
  
      public PermutationCounter(int numDigits) {
          counter = new int[numDigits];
          maxSizes = new int[numDigits];
          for (int i = 0; i < counter.length; i++) {
              counter[i] = 0;
              maxSizes[i] = -1;
          }
          totalIterations = 0;
      }
  
      public boolean isValid() {
          for (int i = 0; i < counter.length; i++) {
              if (maxSizes[i] == -1) {
                  return false;
              }
          }
          return true;
      }
      /**
       *
       * @param maxSize The max value for this "digit" is maxSize - 1
       * @param index The digit position with 0 as the most significant digit
       */
      public void setMaxSizeAtIndex(int maxSize, int index) {
          maxSizes[index] = maxSize;
          totalIterations = _computerNumIterations();
      }
  
      public int size() {
          return counter.length;
      }
  
      public void clear() {
          for (int i = 0; i < counter.length; i++) {
              counter[i] = 0;
              maxSizes[i] = -1;
          }
      }
  
      public int getMaxSizeAtIndex(int index) {
          return maxSizes[index];
      }
  
      public int get(int index) {
          return counter[index];
      }
  
      public void increment() {
          // Although it doesn't matter much, index 0 is being treated as the most significant "digit"
          for (int i = counter.length - 1; i >= 0; i--) {
              counter[i] += 1;
              if (counter[i] >= maxSizes[i]) {
                  counter[i] = 0;
              } else {
                  break;
              }
          }
      }
 
     /**
      * Number of iterations to go through the entire counter.
      * @return number of iterations to go through entire counter once
      */
     public int numIterations() {
         return totalIterations;
     }
 
     private int _computerNumIterations() {
         int prod = 1;
         for (int i = 0; i < maxSizes.length; i++) {
             int max = maxSizes[i];
             if (max == -1){
                 max = 0; // Force product to be zero
             }
             prod *= max;
         }
         return prod;
     }
 
     // ============================== Static method ===============================
     public static Set<List<String>> computeMissingRegGroupAoIdsInCluster(ActivityOfferingClusterInfo cluster,
                                                                         List<RegistrationGroupInfo> currentRGs)
             throws DataValidationErrorException {
 
         // Initialize counter
         PermutationCounter counter = new PermutationCounter(cluster.getActivityOfferingSets().size());
         List<ActivityOfferingSetInfo> aoSets = cluster.getActivityOfferingSets();
 
         for (int i = 0; i < aoSets.size(); i++) {
             ActivityOfferingSetInfo setInfo = aoSets.get(i);
             int aoSetSize = setInfo.getActivityOfferingIds().size();
             counter.setMaxSizeAtIndex(aoSetSize, i);
         }
         // Make sure it's valid before going on
         if (!counter.isValid()) {
             throw new DataValidationErrorException("Counter is invalid: can't generate permutations");
         }
         // Find reg group AO sets for existing reg groups
         Set<Set<String>> actualRegGroupAoSets = new HashSet<Set<String>>();
         for (RegistrationGroupInfo rgInfo: currentRGs) {
             Set<String> regGroupAoIds = new HashSet<String>();
             regGroupAoIds.addAll(rgInfo.getActivityOfferingIds()); // Set of AO IDs in the reg group
             actualRegGroupAoSets.add(regGroupAoIds);
         }
 
         // Compute every permutation
         Set<List<String>> missingRegGroupAoSets = new HashSet<List<String>>();
         for (int i = 0; i < counter.numIterations(); i++, counter.increment()) {
             // Put each permutation of a reg group AOs into a set called regGroupAoIdSetPermutation
             List<String> regGroupAoIdListPermutation = _computeRegGroupAoPermutation(cluster, counter);
             Set<String> aoIdsSet = new HashSet<String>(regGroupAoIdListPermutation); // make into a set
             // If this set of AO Ids does not exist in one of the RGs, then add it to those that are missing
             if (!actualRegGroupAoSets.contains(aoIdsSet)) {
                 missingRegGroupAoSets.add(regGroupAoIdListPermutation);
             }
         }
 
         return missingRegGroupAoSets;
     }
 
     private static List<String> _computeRegGroupAoPermutation(ActivityOfferingClusterInfo cluster, PermutationCounter counter) {
         List<String> regGroupAoIdSetPermutation = new ArrayList<String>();
         for (int aoSetIndex = 0; aoSetIndex < counter.size(); aoSetIndex++) {
             // Picks an AO ID from each AO type
             int aoIdIndex = counter.get(aoSetIndex);
             String aoId = cluster.getActivityOfferingSets().get(aoSetIndex).getActivityOfferingIds().get(aoIdIndex);
             regGroupAoIdSetPermutation.add(aoId);
         }
         return regGroupAoIdSetPermutation;
     }
 }