/* ====================================================================
   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.poi.ss.formula.eval.forked;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import org.apache.poi.ss.formula.EvaluationCell;
import org.apache.poi.ss.formula.EvaluationSheet;
import org.apache.poi.ss.formula.EvaluationWorkbook;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.util.CellReference;

/**
 * Represents a sheet being used for forked evaluation.  Initially, objects of this class contain
 * only the cells from the master workbook. By calling {@link #getOrCreateUpdatableCell(int, int)},
 * the master cell object is logically replaced with a {@link ForkedEvaluationCell} instance, which
 * will be used in all subsequent evaluations.
 *
 * @author Josh Micich
 */
final class ForkedEvaluationSheet implements EvaluationSheet {

	private final EvaluationSheet _masterSheet;
	/**
	 * Only cells which have been split are put in this map.  (This has been done to conserve memory).
	 */
	private final Map<RowColKey, ForkedEvaluationCell> _sharedCellsByRowCol;

	public ForkedEvaluationSheet(EvaluationSheet masterSheet) {
		_masterSheet = masterSheet;
		_sharedCellsByRowCol = new HashMap<RowColKey, ForkedEvaluationCell>();
	}

	public EvaluationCell getCell(int rowIndex, int columnIndex) {
		RowColKey key = new RowColKey(rowIndex, columnIndex);

		ForkedEvaluationCell result = _sharedCellsByRowCol.get(key);
		if (result == null) {
			return _masterSheet.getCell(rowIndex, columnIndex);
		}
		return result;
	}

	public ForkedEvaluationCell getOrCreateUpdatableCell(int rowIndex, int columnIndex) {
		RowColKey key = new RowColKey(rowIndex, columnIndex);

		ForkedEvaluationCell result = _sharedCellsByRowCol.get(key);
		if (result == null) {
			EvaluationCell mcell = _masterSheet.getCell(rowIndex, columnIndex);
			if (mcell == null) {
				CellReference cr = new CellReference(rowIndex, columnIndex);
				throw new UnsupportedOperationException("Underlying cell '"
						+ cr.formatAsString() + "' is missing in master sheet.");
			}
			result = new ForkedEvaluationCell(this, mcell);
			_sharedCellsByRowCol.put(key, result);
		}
		return result;
	}

	public void copyUpdatedCells(Sheet sheet) {
		RowColKey[] keys = new RowColKey[_sharedCellsByRowCol.size()];
		_sharedCellsByRowCol.keySet().toArray(keys);
		Arrays.sort(keys);
		for (int i = 0; i < keys.length; i++) {
			RowColKey key = keys[i];
			Row row = sheet.getRow(key.getRowIndex());
			if (row == null) {
				row = sheet.createRow(key.getRowIndex());
			}
			Cell destCell = row.getCell(key.getColumnIndex());
			if (destCell == null) {
				destCell = row.createCell(key.getColumnIndex());
			}

			ForkedEvaluationCell srcCell = _sharedCellsByRowCol.get(key);
			srcCell.copyValue(destCell);
		}
	}

	public int getSheetIndex(EvaluationWorkbook mewb) {
		return mewb.getSheetIndex(_masterSheet);
	}

	private static final class RowColKey implements Comparable<RowColKey>{
		private final int _rowIndex;
		private final int _columnIndex;

		public RowColKey(int rowIndex, int columnIndex) {
			_rowIndex = rowIndex;
			_columnIndex = columnIndex;
		}
		@Override
		public boolean equals(Object obj) {
			assert obj instanceof RowColKey : "these private cache key instances are only compared to themselves";
			RowColKey other = (RowColKey) obj;
			return _rowIndex == other._rowIndex && _columnIndex == other._columnIndex;
		}
		@Override
		public int hashCode() {
			return _rowIndex ^ _columnIndex;
		}
		public int compareTo(RowColKey o) {
			int cmp = _rowIndex - o._rowIndex;
			if (cmp != 0) {
				return cmp;
			}
			return _columnIndex - o._columnIndex;
		}
		public int getRowIndex() {
			return _rowIndex;
		}
		public int getColumnIndex() {
			return _columnIndex;
		}
	}
}
