/**
    * Copyright 2005-2014 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.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.rice.krad.uif.util;
  
  import org.apache.commons.collections.CollectionUtils;
  import org.kuali.rice.core.api.util.type.KualiDecimal;
  import org.kuali.rice.krad.comparator.NumericValueComparator;
  import org.kuali.rice.krad.comparator.TemporalValueComparator;
  import org.kuali.rice.krad.uif.UifConstants;
  import org.kuali.rice.krad.uif.container.CollectionGroup;
  import org.kuali.rice.krad.uif.container.CollectionGroupLineBuilder;
  import org.kuali.rice.krad.uif.container.collections.LineBuilderContext;
  import org.kuali.rice.krad.uif.field.DataField;
  import org.kuali.rice.krad.uif.field.Field;
  import org.kuali.rice.krad.uif.layout.TableLayoutManager;
  import org.kuali.rice.krad.uif.layout.collections.TableRow;
  import org.kuali.rice.krad.uif.layout.collections.TableRowBuilder;
  import org.kuali.rice.krad.uif.lifecycle.ViewLifecycle;
  import org.kuali.rice.krad.uif.lifecycle.ViewLifecyclePhase;
  import org.kuali.rice.krad.uif.view.ExpressionEvaluator;
  import org.kuali.rice.krad.uif.view.View;
  import org.kuali.rice.krad.uif.view.ViewModel;
  import org.kuali.rice.krad.util.KRADUtils;
  
  import java.util.Comparator;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.WeakHashMap;
  
  /**
   * Comparator used for server side sorting of CollectionGroup data.
   * 
   * <p>
   * This may include DataFields, as well as Fields that don't map directly to elements in the model
   * collection, such as {@link org.kuali.rice.krad.uif.field.LinkField}s that may contain
   * expressions.
   * </p>
   * 
   * <p>
   * NOTE: This class is not thread safe, and each instance is intended to be used only once.
   * </p>
   * 
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class MultiColumnComparator implements Comparator<Integer> {
  
      private final List<Object> modelCollection;
      private final CollectionGroup collectionGroup;
      private final List<ColumnSort> columnSorts;
      private final View view;
      private final ViewModel form;
  
      // we use the layout manager a lot, so for convenience we'll keep a handy reference to it
      private final TableLayoutManager tableLayoutManager;
  
      // we need the prototype row to be able to get Fields that can be used in extracting & calculating column values
      private final List<Field> prototypeRow;
  
      // if we have to evaluate expressions to sort a column, we want to cache the values so we don't have to
      // evaluate the same expressions repeatedly.  This cache could get too big, so we'll use a weak reference map
      private final WeakHashMap<String, String> calculatedValueCache;
  
      // Reflection is used to determine the class of certain column values.  Cache those classes
      private final HashMap<String, Class> propertyClassCache;
  
      /**
       * Constructs a MultiColumnComparator instance
       * 
       * @param modelCollection the model collection that the CollectionGroup is associated with
       * @param collectionGroup the CollectionGroup whose columns are being sorted
       * @param columnSorts A list from highest to lowest precedence of the column sorts to apply
       * @param form object containing the view's data
       * @param view The view
       */
      public MultiColumnComparator(List<Object> modelCollection, CollectionGroup collectionGroup,
              List<ColumnSort> columnSorts, ViewModel form, View view) {
          this.modelCollection = modelCollection;
          this.collectionGroup = collectionGroup;
          this.columnSorts = columnSorts;
          this.view = view;
          this.form = form;
  
          //
          // initialize convenience members and calculated members.  Caches first!
          //
 
         calculatedValueCache = new WeakHashMap<String, String>();
         propertyClassCache = new HashMap<String, Class>();
 
         tableLayoutManager = (TableLayoutManager) collectionGroup.getLayoutManager();
         prototypeRow = buildPrototypeRow();
     }
 
     /**
      * Compares the modelCollecton element at index1 to the element at index2 based on the provided
      * {@link org.kuali.rice.krad.uif.util.ColumnSort}s.
      * 
      * @param index1 the index of the first modelCollection element used for comparison
      * @param index2 the index of the second modelCollection element used for comparison
      * @return 0 if the two elements are considered equal, a positive integer if the element at
      *         index1 is considered greater, else a negative integer
      */
     @Override
     public int compare(Integer index1, Integer index2) {
         int sortResult = 0;
 
         for (ColumnSort columnSort : columnSorts) {
             Field protoField = prototypeRow.get(columnSort.getColumnIndex());
 
             Object modelElement1 = modelCollection.get(index1);
             Object modelElement2 = modelCollection.get(index2);
 
             if (isOneNull(modelElement1, modelElement2)) { // is one of the modelCollection elements null?
                 sortResult = compareOneIsNull(modelElement1, modelElement2);
             } else if (protoField instanceof DataField) {
                 sortResult = compareDataFieldValues(columnSort, (DataField) protoField, index1, index2);
             } else {
                 sortResult = compareFieldStringValues(columnSort, protoField, index1, index2);
             }
 
             if (sortResult != 0) { // stop looking at additional columns, we've made our determination
                 // Handle sort direction here
                 if (columnSort.getDirection() == ColumnSort.Direction.DESC) {
                     sortResult *= -1;
                 }
 
                 break;
             }
         }
 
         return sortResult;
     }
 
     /**
      * Compare the DataField values for the two modelCollection element indexes.
      * 
      * @param columnSort the comparison metadata (which column number, which direction, what type of
      *        sort)
      * @param protoField the prototype DataField for the column being sorted
      * @param index1 the index of the first modelCollection element for comparison
      * @param index2 the index of the second modelCollection element for comparison
      * @return 0 if the two elements are considered equal, a positive integer if the element at
      *         index1 is considered greater, else a negative integer
      */
     private int compareDataFieldValues(ColumnSort columnSort, DataField protoField, Integer index1, Integer index2) {
         final int sortResult;// for DataFields, try to get the property value and use it directly
 
         final Object modelElement1 = modelCollection.get(index1);
         final Object modelElement2 = modelCollection.get(index2);
 
         // get the rest of the property path after the collection
         final String propertyPath = protoField.getBindingInfo().getBindingName();
         final Class<?> columnDataClass = getColumnDataClass(propertyPath);
 
         // we can do smart comparisons for Comparables
         if (Comparable.class.isAssignableFrom(columnDataClass)) {
             Comparable datum1 = (Comparable) ObjectPropertyUtils.getPropertyValue(modelElement1, propertyPath);
             Comparable datum2 = (Comparable) ObjectPropertyUtils.getPropertyValue(modelElement2, propertyPath);
 
             if (isOneNull(datum1, datum2)) {
                 sortResult = compareOneIsNull(datum1, datum2);
             } else if (String.class.equals(columnDataClass)) {
                 sortResult = columnTypeCompare((String) datum1, (String) datum2, columnSort.getSortType());
             } else {
                 sortResult = datum1.compareTo(datum2);
             }
         } else { // resort to basic column string value comparison if the column data class isn't Comparable
             sortResult = compareFieldStringValues(columnSort, protoField, index1, index2);
         }
 
         return sortResult;
     }
 
     /**
      * Attempt to determine the class of the column data value using the given modelCollection.
      * 
      * <p>
      * If the class can not be determined, Object will be returned.
      * </p>
      * 
      * @param propertyPath the path to the datum (which applies to modelCollection elements) whose
      *        class we are attempting to determine
      * @return the class of the given property from the modelElements, or Object if the class cannot
      *         be determined.
      */
     private Class<?> getColumnDataClass(String propertyPath) {
         Class<?> dataClass = propertyClassCache.get(propertyPath);
 
         if (dataClass == null) {
 
             // for the elements in the modelCollection while dataClass is null
             for (int i = 0; i < modelCollection.size() && dataClass == null; i++) {
                 // try getting the class from the modelCollection element
                 dataClass = ObjectPropertyUtils.getPropertyType(modelCollection.get(i), propertyPath);
             }
 
             if (dataClass == null) {
                 dataClass = Object.class; // default
             }
 
             propertyClassCache.put(propertyPath, dataClass);
         }
 
         return dataClass;
     }
 
     /**
      * Compare the field values by computing the two string values and comparing them based on the
      * sort type.
      * 
      * @param columnSort the comparison metadata (which column number, which direction, what type of
      *        sort)
      * @param protoField the prototype Field for the column being sorted
      * @param index1 the index of the first modelCollection element for comparison
      * @param index2 the index of the second modelCollection element for comparison
      * @return 0 if the two elements are considered equal, a positive integer if the element at
      *         index1 is considered greater, else a negative integer
      */
     private int compareFieldStringValues(ColumnSort columnSort, Field protoField, Integer index1, Integer index2) {
         final int sortResult;
         final String fieldValue1;
         final String fieldValue2;
 
         if (!CollectionUtils.sizeIsEmpty(protoField.getPropertyExpressions())) {
             // We have to evaluate expressions
             fieldValue1 = calculateFieldValue(protoField, index1, columnSort.getColumnIndex());
             fieldValue2 = calculateFieldValue(protoField, index2, columnSort.getColumnIndex());
         } else {
             fieldValue1 = KRADUtils.getSimpleFieldValue(modelCollection.get(index1), protoField);
             fieldValue2 = KRADUtils.getSimpleFieldValue(modelCollection.get(index2), protoField);
         }
 
         sortResult = columnTypeCompare(fieldValue1, fieldValue2, columnSort.getSortType());
         return sortResult;
     }
 
     /**
      * Calculates the value for a field that may contain expressions.
      * 
      * <p>
      * Checks for a cached value for this calculated value, and if there isn't one, expressions are
      * evaluated before getting the value, which is then cached and returned.
      * </p>
      * 
      * @param protoField the Field whose expressions need evaluation
      * @param collectionIndex the index of the model collection element being used in the
      *        calculation
      * @param columnIndex the index of the column whose value is being calculated
      * @return the calculated value for the field for this collection line
      */
     private String calculateFieldValue(Field protoField, Integer collectionIndex, int columnIndex) {
         final String fieldValue1;
 
         // cache key format is "<elementIndex>,<columnIndex>"
         final String cacheKey = String.format("%d,%d", collectionIndex, columnIndex);
         String cachedValue = calculatedValueCache.get(cacheKey);
 
         if (cachedValue == null) {
             View view = ViewLifecycle.getView();
             
             Object collectionElement = modelCollection.get(collectionIndex);
             ExpressionEvaluator expressionEvaluator = ViewLifecycle.getExpressionEvaluator();
 
             // set up expression context
             Map<String, Object> viewContext = view.getContext();
             Map<String, Object> expressionContext = new HashMap<String, Object>();
             
             if (viewContext != null) {
                 expressionContext.putAll(viewContext);
             }
 
             ViewLifecyclePhase phase = ViewLifecycle.getPhase();
             if (phase.getParent() instanceof CollectionGroup) {
                 CollectionGroup collectionGroup = (CollectionGroup) phase.getParent();
                 expressionContext.put(UifConstants.ContextVariableNames.COLLECTION_GROUP, collectionGroup);
                 expressionContext.put(UifConstants.ContextVariableNames.MANAGER, collectionGroup.getLayoutManager());
                 expressionContext.put(UifConstants.ContextVariableNames.PARENT, collectionGroup);
             }
             
             expressionContext.put(UifConstants.ContextVariableNames.LINE, collectionElement);
             expressionContext.put(UifConstants.ContextVariableNames.INDEX, collectionIndex);
             expressionContext.put(UifConstants.ContextVariableNames.COMPONENT, protoField);
 
             expressionEvaluator.evaluateExpressionsOnConfigurable(view, protoField, expressionContext);
 
             fieldValue1 = KRADUtils.getSimpleFieldValue(collectionElement, protoField);
 
             calculatedValueCache.put(cacheKey, fieldValue1);
         } else {
             fieldValue1 = cachedValue;
         }
 
         return fieldValue1;
     }
 
     /**
      * Compare the string values based on the given sortType, which must match one of the constants
      * in {@link org.kuali.rice.krad.uif.UifConstants.TableToolsValues}.
      * 
      * @param val1 The first string value for comparison
      * @param val2 The second string value for comparison
      * @param sortType the sort type
      * @return 0 if the two elements are considered equal, a positive integer if the element at
      *         index1 is considered greater, else a negative integer
      */
     private int columnTypeCompare(String val1, String val2, String sortType) {
         final int result;
 
         if (isOneNull(val1, val2)) {
             result = compareOneIsNull(val1, val2);
         } else if (UifConstants.TableToolsValues.STRING.equals(sortType)) {
             result = val1.compareTo(val2);
         } else if (UifConstants.TableToolsValues.NUMERIC.equals(sortType)) {
             result = NumericValueComparator.getInstance().compare(val1, val2);
         } else if (UifConstants.TableToolsValues.PERCENT.equals(sortType)) {
             result = NumericValueComparator.getInstance().compare(val1, val2);
         } else if (UifConstants.TableToolsValues.DATE.equals(sortType)) {
             result = TemporalValueComparator.getInstance().compare(val1, val2);
         } else if (UifConstants.TableToolsValues.CURRENCY.equals(sortType)) {
             // strip off non-numeric symbols, convert to KualiDecimals, and compare
             KualiDecimal decimal1 = new KualiDecimal(val1.replaceAll("[^0-9.]", ""));
             KualiDecimal decimal2 = new KualiDecimal(val2.replaceAll("[^0-9.]", ""));
 
             result = decimal1.compareTo(decimal2);
         } else {
             throw new RuntimeException("unknown sort type: " + sortType);
         }
 
         return result;
     }
 
     /**
      * Is one of the given objects null?
      * 
      * @param o1 the first object
      * @param o2 the second object
      * @return true if one of the given references is null, false otherwise
      */
     private boolean isOneNull(Object o1, Object o2) {
         return (o1 == null || o2 == null);
     }
 
     /**
      * Compare two referenced objects (assuming at least one of them is null).
      * 
      * <p>
      * The arbitrary determination here is that a non-null reference is greater than a null
      * reference, and two null references are equal.
      * </p>
      * 
      * @param o1 the first object
      * @param o2 the second object
      * @return 0 if both are null, 1 if the first is non-null, and -1 if the second is non-null.
      */
     private int compareOneIsNull(Object o1, Object o2) {
         if (o1 == null) {
             if (o2 == null) {
                 return 0;
             }
 
             return -1;
         }
 
         if (o2 != null) {
             throw new IllegalStateException("at least one parameter must be null");
         }
 
         return 1;
     }
 
     /**
      * Build a List of prototype Fields representing a row of the table.
      * 
      * <p>Any DataFields will have their binding paths shortened to access the model collection
      * elements directly, instead of via the data object</p>
      * 
      * @return a List of prototype Fields representing a row in the table
      */
     protected List<Field> buildPrototypeRow() {
         LineBuilderContext lineBuilderContext = new LineBuilderContext(0, modelCollection.get(0), null, false, form,
                 collectionGroup, collectionGroup.getLineActions());
 
         CollectionGroupLineBuilder collectionGroupLineBuilder =
                 collectionGroup.getCollectionGroupBuilder().getCollectionGroupLineBuilder(lineBuilderContext);
         collectionGroupLineBuilder.preprocessLine();
 
         TableRowBuilder tableRowBuilder = new TableRowBuilder(collectionGroup, lineBuilderContext);
         TableRow tableRow = tableRowBuilder.buildRow();
 
         return tableRow.getColumns();
     }
 }