/*
    * Metis: Java Data Framework
    * Copyright 2012-2026. Tony Washer
    *
    * 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 io.github.tonywasher.joceanus.metis.field;
  
  import io.github.tonywasher.joceanus.oceanus.format.OceanusDataFormatter;
  import io.github.tonywasher.joceanus.metis.data.MetisDataDifference;
  import io.github.tonywasher.joceanus.metis.data.MetisDataResource;
  
  import java.util.ArrayDeque;
  import java.util.Deque;
  import java.util.Iterator;
  
  /**
   * Data Version History.
   */
  public class MetisFieldVersionHistory
          implements MetisFieldItem {
      /*
       * FieldSet definitions.
       */
      static {
          MetisFieldSet.newFieldSet(MetisFieldVersionHistory.class);
      }
  
      /**
       * The stack of valueSet changes.
       */
      private final Deque<MetisFieldVersionValues> theStack;
  
      /**
       * The stack of valueSetDelta fields.
       */
      private final Deque<MetisFieldVersionDelta> theDeltas;
  
      /**
       * The current set of values for this object.
       */
      private MetisFieldVersionValues theCurr;
  
      /**
       * The original set of values if any changes have been made.
       */
      private MetisFieldVersionValues theOriginal;
  
      /**
       * Constructor.
       *
       * @param pCurr the current values
       */
      protected MetisFieldVersionHistory(final MetisFieldVersionValues pCurr) {
          /* Allocate the values */
          theCurr = pCurr;
          theOriginal = theCurr;
  
          /* Allocate the stack */
          theStack = new ArrayDeque<>();
          theDeltas = new ArrayDeque<>();
      }
  
      @Override
      public MetisFieldSetDef getDataFieldSet() {
          /* Allocate new local fields */
          final MetisFieldSet<MetisFieldVersionHistory> myLocal = MetisFieldSet.newFieldSet(this);
          final String myVersion = MetisDataResource.DATA_VERSION.getValue();
  
          /* Loop through the fields */
          final Iterator<MetisFieldVersionDelta> myIterator = theDeltas.descendingIterator();
          while (myIterator.hasNext()) {
              /* Access the Delta */
              final MetisFieldVersionDelta myDelta = myIterator.next();
  
              /* Declare the field */
              myLocal.declareLocalField(myVersion + "(" + myDelta.getVersion() + ")", f -> myDelta);
          }
  
          /* Return the fieldSet */
          return myLocal;
      }
  
      @Override
      public String formatObject(final OceanusDataFormatter pFormatter) {
          return MetisFieldVersionHistory.class.getSimpleName() + "(" + theStack.size() + ")";
      }
  
      /**
      * Initialise the current values.
      *
      * @param pValues the current values
      */
     protected void setValues(final MetisFieldVersionValues pValues) {
         /* Store details and clear the stack */
         theCurr = pValues;
         theOriginal = theCurr;
         theStack.clear();
         theDeltas.clear();
     }
 
     /**
      * Get the changeable values object for this item.
      *
      * @return the object
      */
     protected MetisFieldVersionValues getValueSet() {
         return theCurr;
     }
 
     /**
      * Get original values.
      *
      * @return original values
      */
     protected MetisFieldVersionValues getOriginalValues() {
         return theOriginal;
     }
 
     /**
      * Push Item to the history.
      *
      * @param pVersion the new version
      */
     public void pushHistory(final int pVersion) {
         /* Create a new ValueSet */
         final MetisFieldVersionValues mySet = theCurr.cloneIt();
         mySet.setVersion(pVersion);
 
         /* Add the delta to the stack */
         theDeltas.push(new MetisFieldVersionDelta(mySet, theCurr));
 
         /* Add old values to the stack and record new values */
         theStack.push(theCurr);
         theCurr = mySet;
     }
 
     /**
      * popItem from the history and remove from history.
      */
     public void popTheHistory() {
         /* If we have an item on the stack */
         if (hasHistory()) {
             /* Remove it from the list */
             theCurr = theStack.pop();
             theDeltas.pop();
         }
     }
 
     /**
      * popItem from the history if equal to current.
      *
      * @return was a change made
      */
     public boolean maybePopHistory() {
         /* If there is no change */
         if (!theStack.isEmpty()
                 && theCurr.differs(theStack.peek()).isIdentical()) {
             /* Just pop the history */
             popTheHistory();
             return false;
         }
 
         /* Return that we have made a change */
         return true;
     }
 
     /**
      * Is there any history?
      *
      * @return whether there are entries in the history list
      */
     public boolean hasHistory() {
         return !theStack.isEmpty();
     }
 
     /**
      * Obtain the last values.
      *
      * @return the last values (or null)
      */
     public MetisFieldVersionValues getLastValues() {
         return theStack.peek();
     }
 
     /**
      * Clear history.
      */
     protected void clearHistory() {
         /* Remove all history */
         theStack.clear();
         theDeltas.clear();
         theOriginal = theCurr;
         theOriginal.setVersion(0);
     }
 
     /**
      * Reset history.
      */
     protected void resetHistory() {
         /* Remove all history */
         theStack.clear();
         theDeltas.clear();
         theCurr = theOriginal;
     }
 
     /**
      * Set history explicitly.
      *
      * @param pBase the base item
      */
     public void setHistory(final MetisFieldVersionValues pBase) {
         theStack.clear();
         theDeltas.clear();
         theOriginal = theCurr.cloneIt();
         theOriginal.copyFrom(pBase);
         theStack.push(theOriginal);
         theCurr.setVersion(1);
 
         /* Add the delta to the stack */
         theDeltas.push(new MetisFieldVersionDelta(theCurr, theOriginal));
     }
 
     /**
      * Condense history.
      *
      * @param pNewVersion the new maximum version
      */
     protected void condenseHistory(final int pNewVersion) {
         /* If we need to condense history */
         if (theCurr.getVersion() > pNewVersion) {
             /* While we have unnecessary stack entries */
             boolean bNewDelta = false;
             while (!theStack.isEmpty()
                     && theStack.peek().getVersion() >= pNewVersion) {
                 /* Clear them */
                 theStack.pop();
                 theDeltas.pop();
                 bNewDelta = true;
             }
 
             /* Set the desired version */
             theCurr.setVersion(pNewVersion);
 
             /* If we need to adjust the delta */
             if (bNewDelta && !theStack.isEmpty()) {
                 /* remove old delta */
                 theDeltas.pop();
 
                 /* Add the new delta to the stack */
                 theDeltas.push(new MetisFieldVersionDelta(theCurr, theStack.peek()));
             }
         }
     }
 
     /**
      * Determines whether a particular field has changed.
      *
      * @param pField the field
      * @return the difference
      */
     public MetisDataDifference fieldChanged(final MetisFieldDef pField) {
         /* Handle irrelevant cases */
         if (!(pField instanceof MetisFieldVersionedDef)) {
             return MetisDataDifference.IDENTICAL;
         }
         if (!((MetisFieldVersionedDef) pField).isEquality()) {
             return MetisDataDifference.IDENTICAL;
         }
 
         /* Call the function from the interface */
         return theCurr.fieldChanged(pField, theOriginal);
     }
 }