/*
 * This class is part of the book "iText in Action - 2nd Edition"
 * written by Bruno Lowagie (ISBN: 9781935182610)
 * For more info, go to: http://itextpdf.com/examples/
 * This example only works with the AGPL version of iText.
 */

package part3.chapter12;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.GeneralSecurityException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.PrivateKey;
import java.security.Security;
import java.security.cert.Certificate;
import java.util.Properties;

import org.bouncycastle.jce.provider.BouncyCastleProvider;

import com.itextpdf.text.BaseColor;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Image;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.PdfAnnotation;
import com.itextpdf.text.pdf.PdfAppearance;
import com.itextpdf.text.pdf.PdfFormField;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfSignatureAppearance;
import com.itextpdf.text.pdf.PdfStamper;
import com.itextpdf.text.pdf.PdfWriter;
import com.itextpdf.text.pdf.security.ExternalSignature;
import com.itextpdf.text.pdf.security.MakeSignature.CryptoStandard;
import com.itextpdf.text.pdf.security.BouncyCastleDigest;
import com.itextpdf.text.pdf.security.ExternalDigest;
import com.itextpdf.text.pdf.security.PrivateKeySignature;
import com.itextpdf.text.pdf.security.MakeSignature;

public class SignatureField {

    /** The resulting PDF */
    public static String ORIGINAL = "results/part3/chapter12/unsigned.pdf";
    /** The resulting PDF */
    public static String SIGNED1 = "results/part3/chapter12/signed_1.pdf";
    /** The resulting PDF */
    public static String SIGNED2 = "results/part3/chapter12/signed_2.pdf";

    /** One of the resources. */
    public static final String RESOURCE
        = "resources/img/1t3xt.gif";

    /**
     * A properties file that is PRIVATE.
     * You should make your own properties file and adapt this line.
     */
    public static String PATH = "c:/home/blowagie/key.properties";
    /** Some properties used when signing. */
    public static Properties properties = new Properties();
    
    /**
     * Creates a PDF document.
     * @param filename the path to the new PDF document
     * @throws DocumentException 
     * @throws IOException 
     */
    public void createPdf(String filename) throws IOException, DocumentException {
    	// step 1
        Document document = new Document();
        // step 2
        PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(filename));
        // step 3
        document.open();
        // step 4
        document.add(new Paragraph("Hello World!"));
        PdfFormField field = PdfFormField.createSignature(writer);
        field.setWidget(new Rectangle(72, 732, 144, 780), PdfAnnotation.HIGHLIGHT_INVERT);
        field.setFieldName("mySig");
        field.setFlags(PdfAnnotation.FLAGS_PRINT);
        field.setPage();
        field.setMKBorderColor(BaseColor.BLACK);
        field.setMKBackgroundColor(BaseColor.WHITE);
        PdfAppearance tp = PdfAppearance.createAppearance(writer, 72, 48);
        tp.rectangle(0.5f, 0.5f, 71.5f, 47.5f);
        tp.stroke();
        field.setAppearance(PdfAnnotation.APPEARANCE_NORMAL, tp);
        writer.addAnnotation(field);
        // step 5
        document.close();
    }

    /**
     * Manipulates a PDF file src with the file dest as result
     * @param src the original PDF
     * @param dest the resulting PDF
     * @throws GeneralSecurityException 
     * @throws IOException 
     * @throws DocumentException 
     * @throws FileNotFoundException 
     * @throws KeyStoreException 
     * @throws Exception 
     */
    public void signPdf(String src, String dest, boolean certified, boolean graphic) throws GeneralSecurityException, IOException, DocumentException {
        // private key and certificate
    	String path = properties.getProperty("PRIVATE");
        String keystore_password = properties.getProperty("PASSWORD");
        String key_password = properties.getProperty("PASSWORD");
        KeyStore ks = KeyStore.getInstance("pkcs12", "BC");
        ks.load(new FileInputStream(path), keystore_password.toCharArray());
        String alias = (String)ks.aliases().nextElement();
        PrivateKey pk = (PrivateKey)ks.getKey(alias, key_password.toCharArray());
        Certificate[] chain = ks.getCertificateChain(alias);
        // reader and stamper
        PdfReader reader = new PdfReader(ORIGINAL);
        PdfStamper stamper = PdfStamper.createSignature(reader, new FileOutputStream(dest), '\0');
        // appearance
        PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
        appearance.setVisibleSignature("mySig");
        appearance.setReason("It's personal.");
        appearance.setLocation("Foobar");
        if (certified)
            appearance.setCertificationLevel(PdfSignatureAppearance.CERTIFIED_NO_CHANGES_ALLOWED);
        if (graphic) {
            appearance.setSignatureGraphic(Image.getInstance(RESOURCE));
            appearance.setRenderingMode(PdfSignatureAppearance.RenderingMode.GRAPHIC);
        }
        // signature
        ExternalSignature es = new PrivateKeySignature(pk, "SHA-256", "BC");
        ExternalDigest digest = new BouncyCastleDigest();
        MakeSignature.signDetached(appearance, digest, es, chain, null, null, null, 0, CryptoStandard.CMS);
    }
    
    /**
     * Main method.
     *
     * @param    args    no arguments needed
     */
    public static void main(String[] args)
        throws Exception {
        Security.addProvider(new BouncyCastleProvider());
        properties.load(new FileInputStream(PATH));
        SignatureField signatures = new SignatureField();
        signatures.createPdf(ORIGINAL);
        signatures.signPdf(ORIGINAL, SIGNED1, false, false);
        signatures.signPdf(ORIGINAL, SIGNED2, true, true);
    }
}