/**
 * Example written by Bruno Lowagie in answer to:
 * http://stackoverflow.com/questions/29378407/how-can-you-eliminate-white-space-in-multiple-columns-using-itextsharp
 */
package sandbox.objects;

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.ColumnText;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfWriter;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import sandbox.WrapToTest;

@WrapToTest
public class ColumnTextParagraphs2 {

    public static final String DEST = "results/objects/column_paragraphs2.pdf";

    public static final String TEXT = "This is some long paragraph that will be added over and over again to prove a point.";
    public static final float COLUMN_WIDTH = 254;
    public static final float ERROR_MARGIN = 16;
    public static final Rectangle[] COLUMNS = {
        new Rectangle(36, 36, 36 + COLUMN_WIDTH, 806),
        new Rectangle(305, 36, 305 + COLUMN_WIDTH, 806)
    };
    
    public static void main(String[] args) throws IOException, DocumentException {
        File file = new File(DEST);
        file.getParentFile().mkdirs();
        new ColumnTextParagraphs2().createPdf(DEST);
    }

    public void createPdf(String dest) throws IOException, DocumentException {
        // step 1
        Document document = new Document();
        // step 2
        PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(dest));
        // step 3
        document.open();
        // step 4
        PdfContentByte canvas = writer.getDirectContent();
        ColumnText ct = new ColumnText(canvas);
        addContent(ct);
        float height = getNecessaryHeight(ct);
        addContent(ct);
        Rectangle left;
        float top = COLUMNS[0].getTop();
        float middle = (COLUMNS[0].getLeft() + COLUMNS[1].getRight()) / 2;
        float columnheight;
        int status = ColumnText.START_COLUMN;
        while (ColumnText.hasMoreText(status)) {
            if (checkHeight(height)) {
                columnheight = COLUMNS[0].getHeight();
                left = COLUMNS[0];
            }
            else {
                columnheight = (height / 2) + ERROR_MARGIN;
                left = new Rectangle(
                    COLUMNS[0].getLeft(),
                    COLUMNS[0].getTop() - columnheight,
                    COLUMNS[0].getRight(),
                    COLUMNS[0].getTop()
                );
           }
            // left half
            ct.setSimpleColumn(left);
            ct.go();
            height -= COLUMNS[0].getTop() - ct.getYLine();
            // separator
            canvas.moveTo(middle, top - columnheight);
            canvas.lineTo(middle, top);
            canvas.stroke();
            // right half
            ct.setSimpleColumn(COLUMNS[1]);
            status = ct.go();
            height -= COLUMNS[1].getTop() - ct.getYLine();
            // new page
            document.newPage();
        }
        // step 5
        document.close();
    }
    
    public void addContent(ColumnText ct) {
        for (int i = 0; i < 35; i++) {
            ct.addElement(new Paragraph(String.format("Paragraph %s: %s", i, TEXT)));
        }
    }
    
    public float getNecessaryHeight(ColumnText ct) throws DocumentException {
        ct.setSimpleColumn(new Rectangle(0, 0, COLUMN_WIDTH, -500000));
        ct.go(true);
        return -ct.getYLine();
    }
    
    public boolean checkHeight(float height) {
        height -= COLUMNS[0].getHeight() + COLUMNS[1].getHeight() + ERROR_MARGIN;
        return height > 0;
    }
}