package stirling.software.SPDF.controller.api.security;

import java.awt.*;
import java.io.*;
import java.nio.file.Files;
import java.security.*;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.Calendar;
import java.util.List;

import org.apache.commons.io.FileUtils;
import org.apache.pdfbox.examples.signature.CreateSignatureBase;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.PDResources;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.common.PDStream;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.apache.pdfbox.pdmodel.font.PDType1Font;
import org.apache.pdfbox.pdmodel.font.Standard14Fonts.FontName;
import org.apache.pdfbox.pdmodel.graphics.blend.BlendMode;
import org.apache.pdfbox.pdmodel.graphics.form.PDFormXObject;
import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;
import org.apache.pdfbox.pdmodel.graphics.state.PDExtendedGraphicsState;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotationWidget;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAppearanceDictionary;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAppearanceStream;
import org.apache.pdfbox.pdmodel.interactive.digitalsignature.PDSignature;
import org.apache.pdfbox.pdmodel.interactive.digitalsignature.SignatureOptions;
import org.apache.pdfbox.pdmodel.interactive.form.PDAcroForm;
import org.apache.pdfbox.pdmodel.interactive.form.PDField;
import org.apache.pdfbox.pdmodel.interactive.form.PDSignatureField;
import org.apache.pdfbox.util.Matrix;
import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
import org.bouncycastle.asn1.x500.RDN;
import org.bouncycastle.asn1.x500.X500Name;
import org.bouncycastle.asn1.x500.style.BCStyle;
import org.bouncycastle.asn1.x500.style.IETFUtils;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openssl.PEMDecryptorProvider;
import org.bouncycastle.openssl.PEMEncryptedKeyPair;
import org.bouncycastle.openssl.PEMKeyPair;
import org.bouncycastle.openssl.PEMParser;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
import org.bouncycastle.openssl.jcajce.JceOpenSSLPKCS8DecryptorProviderBuilder;
import org.bouncycastle.openssl.jcajce.JcePEMDecryptorProviderBuilder;
import org.bouncycastle.operator.InputDecryptorProvider;
import org.bouncycastle.operator.OperatorCreationException;
import org.bouncycastle.pkcs.PKCS8EncryptedPrivateKeyInfo;
import org.bouncycastle.pkcs.PKCSException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.ClassPathResource;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

import io.github.pixee.security.Filenames;
import io.swagger.v3.oas.annotations.Operation;
import io.swagger.v3.oas.annotations.tags.Tag;

import lombok.extern.slf4j.Slf4j;

import stirling.software.SPDF.model.api.security.SignPDFWithCertRequest;
import stirling.software.SPDF.service.CustomPDDocumentFactory;
import stirling.software.SPDF.utils.WebResponseUtils;

@RestController
@RequestMapping("/api/v1/security")
@Slf4j
@Tag(name = "Security", description = "Security APIs")
public class CertSignController {

    static {
        Security.addProvider(new BouncyCastleProvider());
    }

    private final CustomPDDocumentFactory pdfDocumentFactory;

    @Autowired
    public CertSignController(CustomPDDocumentFactory pdfDocumentFactory) {
        this.pdfDocumentFactory = pdfDocumentFactory;
    }

    private static void sign(
            CustomPDDocumentFactory pdfDocumentFactory,
            byte[] input,
            OutputStream output,
            CreateSignature instance,
            Boolean showSignature,
            Integer pageNumber,
            String name,
            String location,
            String reason,
            Boolean showLogo) {
        try (PDDocument doc = pdfDocumentFactory.load(input)) {
            PDSignature signature = new PDSignature();
            signature.setFilter(PDSignature.FILTER_ADOBE_PPKLITE);
            signature.setSubFilter(PDSignature.SUBFILTER_ADBE_PKCS7_DETACHED);
            signature.setName(name);
            signature.setLocation(location);
            signature.setReason(reason);
            signature.setSignDate(Calendar.getInstance());

            if (showSignature) {
                SignatureOptions signatureOptions = new SignatureOptions();
                signatureOptions.setVisualSignature(
                        instance.createVisibleSignature(doc, signature, pageNumber, showLogo));
                signatureOptions.setPage(pageNumber);

                doc.addSignature(signature, instance, signatureOptions);

            } else {
                doc.addSignature(signature, instance);
            }
            doc.saveIncremental(output);
        } catch (Exception e) {
            log.error("exception", e);
        }
    }

    @PostMapping(consumes = "multipart/form-data", value = "/cert-sign")
    @Operation(
            summary = "Sign PDF with a Digital Certificate",
            description =
                    "This endpoint accepts a PDF file, a digital certificate and related"
                        + " information to sign the PDF. It then returns the digitally signed PDF"
                        + " file. Input:PDF Output:PDF Type:SISO")
    public ResponseEntity<byte[]> signPDFWithCert(@ModelAttribute SignPDFWithCertRequest request)
            throws Exception {
        MultipartFile pdf = request.getFileInput();
        String certType = request.getCertType();
        MultipartFile privateKeyFile = request.getPrivateKeyFile();
        MultipartFile certFile = request.getCertFile();
        MultipartFile p12File = request.getP12File();
        MultipartFile jksfile = request.getJksFile();
        String password = request.getPassword();
        Boolean showSignature = request.isShowSignature();
        String reason = request.getReason();
        String location = request.getLocation();
        String name = request.getName();
        Integer pageNumber = request.getPageNumber() - 1;
        Boolean showLogo = request.isShowLogo();

        if (certType == null) {
            throw new IllegalArgumentException("Cert type must be provided");
        }

        KeyStore ks = null;

        switch (certType) {
            case "PEM":
                ks = KeyStore.getInstance("JKS");
                ks.load(null);
                PrivateKey privateKey = getPrivateKeyFromPEM(privateKeyFile.getBytes(), password);
                Certificate cert = (Certificate) getCertificateFromPEM(certFile.getBytes());
                ks.setKeyEntry(
                        "alias", privateKey, password.toCharArray(), new Certificate[] {cert});
                break;
            case "PKCS12":
                ks = KeyStore.getInstance("PKCS12");
                ks.load(p12File.getInputStream(), password.toCharArray());
                break;
            case "JKS":
                ks = KeyStore.getInstance("JKS");
                ks.load(jksfile.getInputStream(), password.toCharArray());
                break;
            default:
                throw new IllegalArgumentException("Invalid cert type: " + certType);
        }

        CreateSignature createSignature = new CreateSignature(ks, password.toCharArray());
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        sign(
                pdfDocumentFactory,
                pdf.getBytes(),
                baos,
                createSignature,
                showSignature,
                pageNumber,
                name,
                location,
                reason,
                showLogo);
        return WebResponseUtils.boasToWebResponse(
                baos,
                Filenames.toSimpleFileName(pdf.getOriginalFilename()).replaceFirst("[.][^.]+$", "")
                        + "_signed.pdf");
    }

    private PrivateKey getPrivateKeyFromPEM(byte[] pemBytes, String password)
            throws IOException, OperatorCreationException, PKCSException {
        try (PEMParser pemParser =
                new PEMParser(new InputStreamReader(new ByteArrayInputStream(pemBytes)))) {
            Object pemObject = pemParser.readObject();
            JcaPEMKeyConverter converter = new JcaPEMKeyConverter().setProvider("BC");
            PrivateKeyInfo pkInfo;
            if (pemObject instanceof PKCS8EncryptedPrivateKeyInfo pkcs8EncryptedPrivateKeyInfo) {
                InputDecryptorProvider decProv =
                        new JceOpenSSLPKCS8DecryptorProviderBuilder().build(password.toCharArray());
                pkInfo = pkcs8EncryptedPrivateKeyInfo.decryptPrivateKeyInfo(decProv);
            } else if (pemObject instanceof PEMEncryptedKeyPair pemEncryptedKeyPair) {
                PEMDecryptorProvider decProv =
                        new JcePEMDecryptorProviderBuilder().build(password.toCharArray());
                pkInfo = pemEncryptedKeyPair.decryptKeyPair(decProv).getPrivateKeyInfo();
            } else {
                pkInfo = ((PEMKeyPair) pemObject).getPrivateKeyInfo();
            }
            return converter.getPrivateKey(pkInfo);
        }
    }

    private Certificate getCertificateFromPEM(byte[] pemBytes)
            throws IOException, CertificateException {
        try (ByteArrayInputStream bis = new ByteArrayInputStream(pemBytes)) {
            return CertificateFactory.getInstance("X.509").generateCertificate(bis);
        }
    }

    class CreateSignature extends CreateSignatureBase {
        File logoFile;

        public CreateSignature(KeyStore keystore, char[] pin)
                throws KeyStoreException,
                        UnrecoverableKeyException,
                        NoSuchAlgorithmException,
                        IOException,
                        CertificateException {
            super(keystore, pin);
            ClassPathResource resource = new ClassPathResource("static/images/signature.png");
            try (InputStream is = resource.getInputStream()) {
                logoFile = Files.createTempFile("signature", ".png").toFile();
                FileUtils.copyInputStreamToFile(is, logoFile);
            } catch (IOException e) {
                log.error("Failed to load image signature file");
                throw e;
            }
        }

        public InputStream createVisibleSignature(
                PDDocument srcDoc, PDSignature signature, Integer pageNumber, Boolean showLogo)
                throws IOException {
            // modified from org.apache.pdfbox.examples.signature.CreateVisibleSignature2
            try (PDDocument doc = new PDDocument()) {
                PDPage page = new PDPage(srcDoc.getPage(pageNumber).getMediaBox());
                doc.addPage(page);
                PDAcroForm acroForm = new PDAcroForm(doc);
                doc.getDocumentCatalog().setAcroForm(acroForm);
                PDSignatureField signatureField = new PDSignatureField(acroForm);
                PDAnnotationWidget widget = signatureField.getWidgets().get(0);
                List<PDField> acroFormFields = acroForm.getFields();
                acroForm.setSignaturesExist(true);
                acroForm.setAppendOnly(true);
                acroForm.getCOSObject().setDirect(true);
                acroFormFields.add(signatureField);

                PDRectangle rect = new PDRectangle(0, 0, 200, 50);

                widget.setRectangle(rect);

                // from PDVisualSigBuilder.createHolderForm()
                PDStream stream = new PDStream(doc);
                PDFormXObject form = new PDFormXObject(stream);
                PDResources res = new PDResources();
                form.setResources(res);
                form.setFormType(1);
                PDRectangle bbox = new PDRectangle(rect.getWidth(), rect.getHeight());
                float height = bbox.getHeight();
                form.setBBox(bbox);
                PDFont font = new PDType1Font(FontName.TIMES_BOLD);

                // from PDVisualSigBuilder.createAppearanceDictionary()
                PDAppearanceDictionary appearance = new PDAppearanceDictionary();
                appearance.getCOSObject().setDirect(true);
                PDAppearanceStream appearanceStream = new PDAppearanceStream(form.getCOSObject());
                appearance.setNormalAppearance(appearanceStream);
                widget.setAppearance(appearance);

                try (PDPageContentStream cs = new PDPageContentStream(doc, appearanceStream)) {
                    if (showLogo) {
                        cs.saveGraphicsState();
                        PDExtendedGraphicsState extState = new PDExtendedGraphicsState();
                        extState.setBlendMode(BlendMode.MULTIPLY);
                        extState.setNonStrokingAlphaConstant(0.5f);
                        cs.setGraphicsStateParameters(extState);
                        cs.transform(Matrix.getScaleInstance(0.08f, 0.08f));
                        PDImageXObject img =
                                PDImageXObject.createFromFileByExtension(logoFile, doc);
                        cs.drawImage(img, 100, 0);
                        cs.restoreGraphicsState();
                    }

                    // show text
                    float fontSize = 10;
                    float leading = fontSize * 1.5f;
                    cs.beginText();
                    cs.setFont(font, fontSize);
                    cs.setNonStrokingColor(Color.black);
                    cs.newLineAtOffset(fontSize, height - leading);
                    cs.setLeading(leading);

                    X509Certificate cert = (X509Certificate) getCertificateChain()[0];

                    // https://stackoverflow.com/questions/2914521/
                    X500Name x500Name = new X500Name(cert.getSubjectX500Principal().getName());
                    RDN cn = x500Name.getRDNs(BCStyle.CN)[0];
                    String name = IETFUtils.valueToString(cn.getFirst().getValue());

                    String date = signature.getSignDate().getTime().toString();
                    String reason = signature.getReason();

                    cs.showText("Signed by " + name);
                    cs.newLine();
                    cs.showText(date);
                    cs.newLine();
                    cs.showText(reason);

                    cs.endText();
                }

                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                doc.save(baos);
                return new ByteArrayInputStream(baos.toByteArray());
            }
        }
    }
}
