import java.awt.Color;
import java.awt.Rectangle;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.poi.sl.usermodel.TableCell.BorderEdge;
import org.apache.poi.xslf.usermodel.XMLSlideShow;
import org.apache.poi.xslf.usermodel.XSLFSlide;
import org.apache.poi.xslf.usermodel.XSLFTable;
import org.apache.poi.xslf.usermodel.XSLFTableCell;
import org.apache.poi.xslf.usermodel.XSLFTableRow;

/**
 * Demonstrate problem with mergeCell rowspan in single column table
 * (POI writes out the rowspan=... to XML, but MS PowerPoint ignores it)
 */
public final class TestMergeCells {
  private TestMergeCells() {}

  // Populate a table
  private static void fillTable(XSLFTable tbl, int numRows, int numColumns, Color clr) {
    for (int r = 0; r < numRows; r++) {
      XSLFTableRow tr = tbl.addRow();
      tr.setHeight(50);
      for (int c = 0; c < numColumns; c++) {
        XSLFTableCell cell = tr.addCell();
        cell.setText("Row" + r + " Col" + c);

        cell.setBorderColor(BorderEdge.bottom, clr);
        cell.setBorderColor(BorderEdge.left, clr);
        cell.setBorderColor(BorderEdge.top, clr);
        cell.setBorderColor(BorderEdge.right, clr);
      }
    }
  }
  
  // Workaround function - should POI be doing this internally?
  private static void mergeCellsMod(XSLFTable tbl, int fromRow, int toRow, int fromCol, int toCol) {
    if (tbl.getNumberOfColumns() == 1) {
      double h = tbl.getRowHeight(fromRow);
      // accumulate spanned-over row heights as we remove them
      for (int r = toRow; r > fromRow; --r) {
        h += tbl.getRowHeight(r);
        tbl.removeRow(r);
      }
      tbl.setRowHeight(fromRow, h);
    }
    else {
      tbl.mergeCells(fromRow, toRow, fromCol, toCol);
    }
  }

  public static void main(String[] args) throws IOException{
    try (XMLSlideShow ppt = new XMLSlideShow()) {
      XSLFSlide slide = ppt.createSlide();

      // Red table has 2 columns, shows that merging rows works (and in 2nd column we demonstrate workaround function)
      XSLFTable ta = slide.createTable();
      ta.setAnchor(new Rectangle(50, 50, 300, 200));
      fillTable(ta, 4, 2, Color.red); // 4 rows, 2 cols

      // Blue Table has 1 column, shows that mergeCells is ineffective here when viewed in MS PowerPoint v2108
      XSLFTable tb = slide.createTable();
      tb.setAnchor(new Rectangle(400, 50, 150, 200));
      fillTable(tb, 4, 1, Color.blue); // 4 rows, 1 col

      // Green table, demonstrate basic workaround technique for row spans in single column tables
      XSLFTable tc = slide.createTable();
      tc.setAnchor(new Rectangle(200, 300, 150, 200));
      fillTable(tc, 4, 1, Color.green); // 4 rows, 1 col
	  tc.removeRow(2);
	  tc.setRowHeight(1, 100); // set height to 2x50

      // Magenta table demonstrates use a function to apply the workaround
	  XSLFTable td = slide.createTable();
      td.setAnchor(new Rectangle(500, 300, 150, 200));
      fillTable(td, 4, 1, Color.magenta); // 4 rows, 1 col
	  
      // Merge middle cells in first columns
      ta.mergeCells(1,2,0,0); // has the desired effect in 2-col table
      mergeCellsMod(ta, 0,1,1,1); // test workaround function on 2-col table
      mergeCellsMod(ta, 2,3,1,1); // ...and again
	  
      tb.mergeCells(1,2,0,0); // MS PowerPoint ignores rowspan request in single column table!

      mergeCellsMod(td, 1, 2, 0, 0);
	  
      try (FileOutputStream out = new FileOutputStream("TestMergeCells.pptx")) {
        ppt.write(out);
      }
    }
  }
}