package eu.siacs.conversations.utils;

import android.os.Bundle;
import android.util.Pair;

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.security.MessageDigest;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateParsingException;
import java.security.cert.X509Certificate;
import java.security.SecureRandom;
import java.text.Normalizer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Locale;

import eu.siacs.conversations.Config;
import eu.siacs.conversations.R;
import eu.siacs.conversations.entities.Message;
import eu.siacs.conversations.xmpp.jid.InvalidJidException;
import eu.siacs.conversations.xmpp.jid.Jid;

public final class CryptoHelper {
	public static final String FILETRANSFER = "?FILETRANSFERv1:";
	private final static char[] hexArray = "0123456789abcdef".toCharArray();
	final public static byte[] ONE = new byte[] { 0, 0, 0, 1 };

	public static String bytesToHex(byte[] bytes) {
		char[] hexChars = new char[bytes.length * 2];
		for (int j = 0; j < bytes.length; j++) {
			int v = bytes[j] & 0xFF;
			hexChars[j * 2] = hexArray[v >>> 4];
			hexChars[j * 2 + 1] = hexArray[v & 0x0F];
		}
		return new String(hexChars);
	}

	public static byte[] hexToBytes(String hexString) {
		int len = hexString.length();
		byte[] array = new byte[len / 2];
		for (int i = 0; i < len; i += 2) {
			array[i / 2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character
					.digit(hexString.charAt(i + 1), 16));
		}
		return array;
	}

	public static String hexToString(final String hexString) {
		return new String(hexToBytes(hexString));
	}

	public static byte[] concatenateByteArrays(byte[] a, byte[] b) {
		byte[] result = new byte[a.length + b.length];
		System.arraycopy(a, 0, result, 0, a.length);
		System.arraycopy(b, 0, result, a.length, b.length);
		return result;
	}

	/**
	 * Escapes usernames or passwords for SASL.
	 */
	public static String saslEscape(final String s) {
		final StringBuilder sb = new StringBuilder((int) (s.length() * 1.1));
		for (int i = 0; i < s.length(); i++) {
			char c = s.charAt(i);
			switch (c) {
				case ',':
					sb.append("=2C");
					break;
				case '=':
					sb.append("=3D");
					break;
				default:
					sb.append(c);
					break;
			}
		}
		return sb.toString();
	}

	public static String saslPrep(final String s) {
		return Normalizer.normalize(s, Normalizer.Form.NFKC);
	}

	public static String prettifyFingerprint(String fingerprint) {
		if (fingerprint==null) {
			return "";
		} else if (fingerprint.length() < 40) {
			return fingerprint;
		}
		StringBuilder builder = new StringBuilder(fingerprint.toLowerCase(Locale.US).replaceAll("\\s", ""));
		for(int i=8;i<builder.length();i+=9) {
			builder.insert(i, ' ');
		}
		return builder.toString();
	}

	public static String prettifyFingerprintCert(String fingerprint) {
		StringBuilder builder = new StringBuilder(fingerprint);
		for(int i=2;i < builder.length(); i+=3) {
			builder.insert(i,':');
		}
		return builder.toString();
	}

	public static String[] getOrderedCipherSuites(final String[] platformSupportedCipherSuites) {
		final Collection<String> cipherSuites = new LinkedHashSet<>(Arrays.asList(Config.ENABLED_CIPHERS));
		final List<String> platformCiphers = Arrays.asList(platformSupportedCipherSuites);
		cipherSuites.retainAll(platformCiphers);
		cipherSuites.addAll(platformCiphers);
		filterWeakCipherSuites(cipherSuites);
		return cipherSuites.toArray(new String[cipherSuites.size()]);
	}

	private static void filterWeakCipherSuites(final Collection<String> cipherSuites) {
		final Iterator<String> it = cipherSuites.iterator();
		while (it.hasNext()) {
			String cipherName = it.next();
			// remove all ciphers with no or very weak encryption or no authentication
			for (String weakCipherPattern : Config.WEAK_CIPHER_PATTERNS) {
				if (cipherName.contains(weakCipherPattern)) {
					it.remove();
					break;
				}
			}
		}
	}

	public static Pair<Jid,String> extractJidAndName(X509Certificate certificate) throws CertificateEncodingException, InvalidJidException, CertificateParsingException {
		Collection<List<?>> alternativeNames = certificate.getSubjectAlternativeNames();
		List<String> emails = new ArrayList<>();
		if (alternativeNames != null) {
			for(List<?> san : alternativeNames) {
				Integer type = (Integer) san.get(0);
				if (type == 1) {
					emails.add((String) san.get(1));
				}
			}
		}
		X500Name x500name = new JcaX509CertificateHolder(certificate).getSubject();
		if (emails.size() == 0) {
			emails.add(IETFUtils.valueToString(x500name.getRDNs(BCStyle.EmailAddress)[0].getFirst().getValue()));
		}
		String name = IETFUtils.valueToString(x500name.getRDNs(BCStyle.CN)[0].getFirst().getValue());
		if (emails.size() >= 1) {
			return new Pair<>(Jid.fromString(emails.get(0)), name);
		} else {
			return null;
		}
	}

	public static Bundle extractCertificateInformation(X509Certificate certificate) {
		Bundle information = new Bundle();
		try {
			JcaX509CertificateHolder holder = new JcaX509CertificateHolder(certificate);
			X500Name subject = holder.getSubject();
			try {
				information.putString("subject_cn", subject.getRDNs(BCStyle.CN)[0].getFirst().getValue().toString());
			} catch (Exception e) {
				//ignored
			}
			try {
				information.putString("subject_o",subject.getRDNs(BCStyle.O)[0].getFirst().getValue().toString());
			} catch (Exception e) {
				//ignored
			}

			X500Name issuer = holder.getIssuer();
			try {
				information.putString("issuer_cn", issuer.getRDNs(BCStyle.CN)[0].getFirst().getValue().toString());
			} catch (Exception e) {
				//ignored
			}
			try {
				information.putString("issuer_o", issuer.getRDNs(BCStyle.O)[0].getFirst().getValue().toString());
			} catch (Exception e) {
				//ignored
			}
			try {
				MessageDigest md = MessageDigest.getInstance("SHA-1");
				byte[] fingerprint = md.digest(certificate.getEncoded());
				information.putString("sha1", prettifyFingerprintCert(bytesToHex(fingerprint)));
			} catch (Exception e) {

			}
			return information;
		} catch (CertificateEncodingException e) {
			return information;
		}
	}

	public static int encryptionTypeToText(int encryption) {
		switch (encryption) {
			case Message.ENCRYPTION_OTR:
				return R.string.encryption_choice_otr;
			case Message.ENCRYPTION_AXOLOTL:
				return R.string.encryption_choice_omemo;
			case Message.ENCRYPTION_NONE:
				return R.string.encryption_choice_unencrypted;
			default:
				return R.string.encryption_choice_pgp;
		}
	}
}