/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.conscrypt;

import java.math.BigInteger;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidParameterException;
import java.security.spec.ECField;
import java.security.spec.ECFieldF2m;
import java.security.spec.ECFieldFp;
import java.security.spec.ECParameterSpec;
import java.security.spec.ECPoint;
import java.security.spec.EllipticCurve;

public final class OpenSSLECGroupContext {
    private final NativeRef.EC_GROUP groupCtx;

    public OpenSSLECGroupContext(NativeRef.EC_GROUP groupCtx) {
        this.groupCtx = groupCtx;
    }

    public static OpenSSLECGroupContext getCurveByName(String curveName) {
        // Workaround for OpenSSL not supporting SECG names for NIST P-192 and P-256
        // (aka ANSI X9.62 prime192v1 and prime256v1) curve names.
        if ("secp256r1".equals(curveName)) {
            curveName = "prime256v1";
        } else if ("secp192r1".equals(curveName)) {
            curveName = "prime192v1";
        }

        final long ctx = NativeCrypto.EC_GROUP_new_by_curve_name(curveName);
        if (ctx == 0) {
            return null;
        }
        NativeRef.EC_GROUP groupRef = new NativeRef.EC_GROUP(ctx);

        NativeCrypto.EC_GROUP_set_point_conversion_form(groupRef,
                NativeConstants.POINT_CONVERSION_UNCOMPRESSED);
        NativeCrypto.EC_GROUP_set_asn1_flag(groupRef, NativeConstants.OPENSSL_EC_NAMED_CURVE);

        return new OpenSSLECGroupContext(groupRef);
    }

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof OpenSSLECGroupContext)) {
            return false;
        }

        final OpenSSLECGroupContext other = (OpenSSLECGroupContext) o;
        return NativeCrypto.EC_GROUP_cmp(groupCtx, other.groupCtx);
    }

    @Override
    public int hashCode() {
        // TODO Auto-generated method stub
        return super.hashCode();
    }

    public NativeRef.EC_GROUP getNativeRef() {
        return groupCtx;
    }

    public static OpenSSLECGroupContext getInstance(ECParameterSpec params)
            throws InvalidAlgorithmParameterException {
        String curveName = Platform.getCurveName(params);
        if (curveName != null) {
            return OpenSSLECGroupContext.getCurveByName(curveName);
        }

        // Try to find recognise the underlying curve from the parameters.
        final EllipticCurve curve = params.getCurve();
        final ECField field = curve.getField();

        final BigInteger p;
        if (field instanceof ECFieldFp) {
            p = ((ECFieldFp) field).getP();
        } else {
            throw new InvalidParameterException("unhandled field class "
                    + field.getClass().getName());
        }

        final ECPoint generator = params.getGenerator();
        final BigInteger b = curve.getB();
        final BigInteger x = generator.getAffineX();
        final BigInteger y = generator.getAffineY();

        // The 'a' value isn't checked in the following because it's unclear
        // whether users would set it to -3 or p-3.
        switch (p.bitLength()) {
            case 224:
                if (p.toString(16).equals("ffffffffffffffffffffffffffffffff000000000000000000000001") &&
                    b.toString(16).equals("b4050a850c04b3abf54132565044b0b7d7bfd8ba270b39432355ffb4") &&
                    x.toString(16).equals("b70e0cbd6bb4bf7f321390b94a03c1d356c21122343280d6115c1d21") &&
                    y.toString(16).equals("bd376388b5f723fb4c22dfe6cd4375a05a07476444d5819985007e34")) {
                    curveName = "secp224r1";
                }
                break;
            case 256:
                if (p.toString(16).equals("ffffffff00000001000000000000000000000000ffffffffffffffffffffffff") &&
                    b.toString(16).equals("5ac635d8aa3a93e7b3ebbd55769886bc651d06b0cc53b0f63bce3c3e27d2604b") &&
                    x.toString(16).equals("6b17d1f2e12c4247f8bce6e563a440f277037d812deb33a0f4a13945d898c296") &&
                    y.toString(16).equals("4fe342e2fe1a7f9b8ee7eb4a7c0f9e162bce33576b315ececbb6406837bf51f5")) {
                    curveName = "prime256v1";
                }
                break;
            case 384:
                if (p.toString(16).equals("fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffeffffffff0000000000000000ffffffff") &&
                    b.toString(16).equals("b3312fa7e23ee7e4988e056be3f82d19181d9c6efe8141120314088f5013875ac656398d8a2ed19d2a85c8edd3ec2aef") &&
                    x.toString(16).equals("aa87ca22be8b05378eb1c71ef320ad746e1d3b628ba79b9859f741e082542a385502f25dbf55296c3a545e3872760ab7") &&
                    y.toString(16).equals("3617de4a96262c6f5d9e98bf9292dc29f8f41dbd289a147ce9da3113b5f0b8c00a60b1ce1d7e819d7a431d7c90ea0e5f")) {
                    curveName = "secp384r1";
                }
                break;
            case 521:
                if (p.toString(16).equals("1ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff") &&
                    b.toString(16).equals("051953eb9618e1c9a1f929a21a0b68540eea2da725b99b315f3b8b489918ef109e156193951ec7e937b1652c0bd3bb1bf073573df883d2c34f1ef451fd46b503f00") &&
                    x.toString(16).equals("c6858e06b70404e9cd9e3ecb662395b4429c648139053fb521f828af606b4d3dbaa14b5e77efe75928fe1dc127a2ffa8de3348b3c1856a429bf97e7e31c2e5bd66") &&
                    y.toString(16).equals("11839296a789a3bc0045c8a5fb42c7d1bd998f54449579b446817afbd17273e662c97ee72995ef42640c550b9013fad0761353c7086a272c24088be94769fd16650")) {
                    curveName = "secp521r1";
                }
                break;
        }

        if (curveName != null) {
            return OpenSSLECGroupContext.getCurveByName(curveName);
        }

        final BigInteger a = curve.getA();
        final BigInteger order = params.getOrder();
        final int cofactor = params.getCofactor();

        long group;
        try {
            group = NativeCrypto.EC_GROUP_new_arbitrary(
                        p.toByteArray(), a.toByteArray(), b.toByteArray(), x.toByteArray(),
                        y.toByteArray(), order.toByteArray(), cofactor);
        } catch (Throwable exception) {
            throw new InvalidAlgorithmParameterException("EC_GROUP_new_arbitrary failed",
                                                         exception);
        }

        if (group == 0) {
            throw new InvalidAlgorithmParameterException("EC_GROUP_new_arbitrary returned NULL");
        }

        NativeRef.EC_GROUP groupRef = new NativeRef.EC_GROUP(group);
        NativeCrypto.EC_GROUP_set_point_conversion_form(groupRef,
                NativeConstants.POINT_CONVERSION_UNCOMPRESSED);

        return new OpenSSLECGroupContext(groupRef);
    }

    public ECParameterSpec getECParameterSpec() {
        final String curveName = NativeCrypto.EC_GROUP_get_curve_name(groupCtx);

        final byte[][] curveParams = NativeCrypto.EC_GROUP_get_curve(groupCtx);
        final BigInteger p = new BigInteger(curveParams[0]);
        final BigInteger a = new BigInteger(curveParams[1]);
        final BigInteger b = new BigInteger(curveParams[2]);

        final ECField field;
        final int type = NativeCrypto.get_EC_GROUP_type(groupCtx);
        if (type == NativeCrypto.EC_CURVE_GFP) {
            field = new ECFieldFp(p);
        } else if (type == NativeCrypto.EC_CURVE_GF2M) {
            field = new ECFieldF2m(p.bitLength() - 1, p);
        } else {
            throw new RuntimeException("unknown curve type " + type);
        }

        final EllipticCurve curve = new EllipticCurve(field, a, b);

        final OpenSSLECPointContext generatorCtx = new OpenSSLECPointContext(this,
                new NativeRef.EC_POINT(NativeCrypto.EC_GROUP_get_generator(groupCtx)));
        final ECPoint generator = generatorCtx.getECPoint();

        final BigInteger order = new BigInteger(NativeCrypto.EC_GROUP_get_order(groupCtx));
        final BigInteger cofactor = new BigInteger(NativeCrypto.EC_GROUP_get_cofactor(groupCtx));

        ECParameterSpec spec = new ECParameterSpec(curve, generator, order, cofactor.intValue());
        Platform.setCurveName(spec, curveName);
        return spec;
    }
}