package info.frostfs.sdk;

import info.frostfs.sdk.exceptions.ProcessFrostFSException;
import info.frostfs.sdk.exceptions.ValidationFrostFSException;
import org.bouncycastle.asn1.sec.SECNamedCurves;
import org.bouncycastle.asn1.sec.SECObjectIdentifiers;
import org.bouncycastle.asn1.x9.X9ECParameters;
import org.bouncycastle.crypto.params.ECDomainParameters;
import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.jce.spec.ECNamedCurveSpec;

import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.ECParameterSpec;
import java.security.spec.ECPrivateKeySpec;
import java.security.spec.ECPublicKeySpec;
import java.security.spec.InvalidKeySpecException;

import static info.frostfs.sdk.constants.ErrorConst.COMPRESSED_PUBLIC_KEY_WRONG_LENGTH_TEMPLATE;
import static info.frostfs.sdk.constants.ErrorConst.INPUT_PARAM_IS_MISSING;
import static java.util.Objects.isNull;
import static org.bouncycastle.util.BigIntegers.fromUnsignedByteArray;

public class KeyExtension {
    private static final String CURVE_NAME = "secp256r1";
    private static final String SECURITY_ALGORITHM = "EC";
    private static final int COMPRESSED_PUBLIC_KEY_LENGTH = 33;

    private KeyExtension() {
    }

    public static PrivateKey loadPrivateKey(byte[] privateKey) {
        checkInputValue(privateKey);

        X9ECParameters params = SECNamedCurves.getByOID(SECObjectIdentifiers.secp256r1);
        ECDomainParameters domain = new ECDomainParameters(
                params.getCurve(), params.getG(), params.getN(), params.getH()
        );
        ECPrivateKeyParameters ecParams = new ECPrivateKeyParameters(fromUnsignedByteArray(privateKey), domain);

        ECParameterSpec ecParameterSpec = new ECNamedCurveSpec(
                CURVE_NAME, params.getCurve(), params.getG(), params.getN(), params.getH()
        );
        ECPrivateKeySpec privateKeySpec = new ECPrivateKeySpec(ecParams.getD(), ecParameterSpec);
        try {
            KeyFactory kf = KeyFactory.getInstance(SECURITY_ALGORITHM);
            return kf.generatePrivate(privateKeySpec);
        } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
            throw new ProcessFrostFSException(e);
        }
    }

    public static PublicKey getPublicKeyFromBytes(byte[] publicKey) {
        checkInputValue(publicKey);

        if (publicKey.length != COMPRESSED_PUBLIC_KEY_LENGTH) {
            throw new ValidationFrostFSException(String.format(
                    COMPRESSED_PUBLIC_KEY_WRONG_LENGTH_TEMPLATE, COMPRESSED_PUBLIC_KEY_LENGTH, publicKey.length
            ));
        }

        X9ECParameters secp256R1 = SECNamedCurves.getByOID(SECObjectIdentifiers.secp256r1);
        ECDomainParameters domain = new ECDomainParameters(
                secp256R1.getCurve(), secp256R1.getG(), secp256R1.getN(), secp256R1.getH()
        );
        var ecPoint = secp256R1.getCurve().decodePoint(publicKey);
        var publicParams = new ECPublicKeyParameters(ecPoint, domain);
        java.security.spec.ECPoint point = new java.security.spec.ECPoint(
                publicParams.getQ().getRawXCoord().toBigInteger(), publicParams.getQ().getRawYCoord().toBigInteger()
        );
        ECParameterSpec ecParameterSpec = new ECNamedCurveSpec(
                CURVE_NAME, secp256R1.getCurve(), secp256R1.getG(), secp256R1.getN(), secp256R1.getH(),
                secp256R1.getSeed()
        );
        ECPublicKeySpec publicKeySpec = new ECPublicKeySpec(point, ecParameterSpec);

        try {
            KeyFactory kf = KeyFactory.getInstance(SECURITY_ALGORITHM);
            return kf.generatePublic(publicKeySpec);
        } catch (Exception e) {
            throw new ProcessFrostFSException(e);
        }
    }

    private static void checkInputValue(byte[] data) {
        if (isNull(data) || data.length == 0) {
            throw new ValidationFrostFSException(INPUT_PARAM_IS_MISSING);
        }
    }
}