package eu.siacs.utils;

import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.asn1.DERIA5String;
import org.bouncycastle.asn1.DERTaggedObject;
import org.bouncycastle.asn1.DERUTF8String;
import org.bouncycastle.asn1.DLSequence;
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.cert.jcajce.JcaX509CertificateHolder;

import java.io.IOException;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.SSLSession;

public class XmppDomainVerifier implements HostnameVerifier {

    private static XmppDomainVerifier instance = new XmppDomainVerifier();

    private final static String SRVName = "1.3.6.1.5.5.7.8.7";
    private final static  String xmppAddr = "1.3.6.1.5.5.7.8.5";

    @Override
    public boolean verify(String domain, SSLSession sslSession) {
        try {
            Certificate[] chain = sslSession.getPeerCertificates();
            if (chain.length == 0 || !(chain[0] instanceof X509Certificate)) {
                return false;
            }
            X509Certificate certificate = (X509Certificate) chain[0];
            Collection<List<?>> alternativeNames = certificate.getSubjectAlternativeNames();
            List<String> xmppAddrs = new ArrayList<>();
            List<String> srvNames = new ArrayList<>();
            List<String> domains = new ArrayList<>();
            if (alternativeNames != null) {
                for (List<?> san : alternativeNames) {
                    Integer type = (Integer) san.get(0);
                    if (type == 0) {
                        OtherName otherName = parseOtherName((byte[]) san.get(1));
                        if (otherName != null) {
                            switch (otherName.oid) {
                                case SRVName:
                                    srvNames.add(otherName.value);
                                    break;
                                case xmppAddr:
                                    xmppAddrs.add(otherName.value);
                                    break;
                            }
                        }
                    } else if (type == 2) {
                        Object value = san.get(1);
                        if (value instanceof String) {
                            domains.add((String) value);
                        }
                    }
                }
            }
            if (srvNames.size() == 0 && xmppAddrs.size() == 0 && domains.size() == 0) {
                X500Name x500name = new JcaX509CertificateHolder(certificate).getSubject();
                RDN[] rdns = x500name.getRDNs(BCStyle.CN);
                for (int i = 0; i < rdns.length; ++i) {
                    domains.add(IETFUtils.valueToString(x500name.getRDNs(BCStyle.CN)[i].getFirst().getValue()));
                }
            }
            return xmppAddrs.contains(domain) || srvNames.contains("_xmpp-client." + domain) || matchDomain(domain, domains);
        } catch (Exception e) {
            return false;
        }
    }

    private static OtherName parseOtherName(byte[] otherName) {
        try {
            ASN1Primitive asn1Primitive = ASN1Primitive.fromByteArray(otherName);
            if (asn1Primitive instanceof DERTaggedObject) {
                ASN1Primitive inner = ((DERTaggedObject) asn1Primitive).getObject();
                if (inner instanceof DLSequence) {
                    DLSequence sequence = (DLSequence) inner;
                    if (sequence.size() >= 2 && sequence.getObjectAt(1) instanceof DERTaggedObject) {
                        String oid = sequence.getObjectAt(0).toString();
                        ASN1Primitive value = ((DERTaggedObject) sequence.getObjectAt(1)).getObject();
                        if (value instanceof DERUTF8String) {
                            return new OtherName(oid, ((DERUTF8String) value).getString());
                        } else if (value instanceof DERIA5String) {
                            return new OtherName(oid, ((DERIA5String) value).getString());
                        }
                    }
                }
            }
            return null;
        } catch (IOException e) {
            return null;
        }
    }

    private static boolean matchDomain(String needle, List<String> haystack) {
        for (String entry : haystack) {
            if (entry.startsWith("*.")) {
                int i = needle.indexOf('.');
                if (i != -1 && needle.substring(i).equals(entry.substring(1))) {
                    return true;
                }
            } else {
                if (entry.equals(needle)) {
                    return true;
                }
            }
        }
        return false;
    }

    public static XmppDomainVerifier getInstance() {
        return instance;
    }

    private static class OtherName {
        private final String oid;
        private final String value;
        private OtherName(String oid, String value) {
            this.oid = oid;
            this.value = value;
        }
    }
}