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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * particular file as subject to the "Classpath" exception as provided
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package sun.security.ec;

import java.io.IOException;
import java.math.BigInteger;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.NamedParameterSpec;
import java.util.Collections;
import java.util.Map;
import java.util.HashMap;
import java.util.Optional;
import java.util.function.Function;
import java.util.function.Supplier;

import sun.security.util.ObjectIdentifier;
import sun.security.x509.AlgorithmId;

public class XECParameters {

    // Naming/identification parameters
    private final ObjectIdentifier oid;
    private final String name;

    // Curve/field parameters
    private final int bits;
    private final BigInteger p;
    private final int logCofactor;
    private final int a24;
    private final byte basePoint;

    
Construct an object holding the supplied parameters. No parameters are
checked, so this method always succeeds. This method supports
Montgomery curves of the form y^2 = x^3 + ax^2 + x.
Params:
bits – The number of relevant bits in a public/private key.
p – The prime that defines the finite field.
a24 – The value of (a - 2) / 4, where a is the second-degree curve
           coefficient.
basePoint – The point that generates the desired group
logCofactor – The base-2 logarithm of the cofactor of the curve
oid – 
name – /**
     *
     * Construct an object holding the supplied parameters. No parameters are
     * checked, so this method always succeeds. This method supports
     * Montgomery curves of the form y^2 = x^3 + ax^2 + x.
     *
     * @param bits The number of relevant bits in a public/private key.
     * @param p The prime that defines the finite field.
     * @param a24 The value of (a - 2) / 4, where a is the second-degree curve
     *            coefficient.
     * @param basePoint The point that generates the desired group
     * @param logCofactor The base-2 logarithm of the cofactor of the curve
     * @param oid
     * @param name
     */
    public XECParameters(int bits, BigInteger p, int a24,
                         byte basePoint, int logCofactor,
                         ObjectIdentifier oid, String name) {

        this.bits = bits;
        this.logCofactor = logCofactor;
        this.p = p;
        this.a24 = a24;
        this.basePoint = basePoint;
        this.oid = oid;
        this.name = name;

    }

    public int getBits() {
        return bits;
    }
    public int getBytes() {
        return (bits + 7) / 8;
    }
    public int getLogCofactor() {
        return logCofactor;
    }
    public BigInteger getP() {
        return p;
    }
    public int getA24() {
        return a24;
    }
    public byte getBasePoint() {
        return basePoint;
    }
    public ObjectIdentifier getOid() {
        return oid;
    }
    public String getName() {
        return name;
    }

    private static final Map<Integer, XECParameters> SIZE_MAP;
    private static final Map<ObjectIdentifier, XECParameters> OID_MAP;
    private static final Map<String, XECParameters> NAME_MAP;

    static {
        final BigInteger TWO = BigInteger.valueOf(2);

        Map<Integer, XECParameters> bySize = new HashMap<>();
        Map<ObjectIdentifier, XECParameters> byOid = new HashMap<>();
        Map<String, XECParameters> byName = new HashMap<>();

        // set up X25519
        try {
            BigInteger p = TWO.pow(255).subtract(BigInteger.valueOf(19));
            addParameters(255, p, 121665, (byte) 0x09, 3,
                new int[]{1, 3, 101, 110}, NamedParameterSpec.X25519.getName(),
                bySize, byOid, byName);

        } catch (IOException ex) {
            // Unable to set X25519 parameters---it will be disabled
        }

        // set up X448
        try {
            BigInteger p = TWO.pow(448).subtract(TWO.pow(224))
                .subtract(BigInteger.ONE);
            addParameters(448, p, 39081, (byte) 0x05, 2,
                new int[]{1, 3, 101, 111}, NamedParameterSpec.X448.getName(),
                bySize, byOid, byName);

        } catch (IOException ex) {
            // Unable to set X448 parameters---it will be disabled
        }

        SIZE_MAP = Collections.unmodifiableMap(bySize);
        OID_MAP = Collections.unmodifiableMap(byOid);
        NAME_MAP = Collections.unmodifiableMap(byName);
    }

    private static void addParameters(int bits, BigInteger p, int a24,
        byte basePoint, int logCofactor, int[] oidBytes, String name,
        Map<Integer, XECParameters> bySize,
        Map<ObjectIdentifier, XECParameters> byOid,
        Map<String, XECParameters> byName) throws IOException {

        ObjectIdentifier oid = new ObjectIdentifier(oidBytes);
        XECParameters params =
            new XECParameters(bits, p, a24, basePoint, logCofactor, oid, name);
        bySize.put(bits, params);
        byOid.put(oid, params);
        byName.put(name, params);
    }

    public static Optional<XECParameters> getByOid(ObjectIdentifier id) {
        return Optional.ofNullable(OID_MAP.get(id));
    }
    public static Optional<XECParameters> getBySize(int size) {
        return Optional.ofNullable(SIZE_MAP.get(size));
    }
    public static Optional<XECParameters> getByName(String name) {
        return Optional.ofNullable(NAME_MAP.get(name));
    }

    boolean oidEquals(XECParameters other) {
        return oid.equals(other.getOid());
    }

    // Utility method that is used by the methods below to handle exception
    // suppliers
    private static
    <A, B> Supplier<B> apply(final Function<A, B> func, final A a) {
        return new Supplier<B>() {
            @Override
            public B get() {
                return func.apply(a);
            }
        };
    }

    
Get parameters by key size, or throw an exception if no parameters are
defined for the specified key size. This method is used in several
contexts that should throw different exceptions when the parameters
are not found. The first argument is a function that produces the
desired exception.
Params:
exception – a function that produces an exception from a string
size – the desired key size
Type parameters:
<T> – the type of exception that is thrown
Throws:
T – when suitable parameters do not exist
Returns:
the parameters for the specified key size/**
     * Get parameters by key size, or throw an exception if no parameters are
     * defined for the specified key size. This method is used in several
     * contexts that should throw different exceptions when the parameters
     * are not found. The first argument is a function that produces the
     * desired exception.
     *
     * @param exception a function that produces an exception from a string
     * @param size the desired key size
     * @param <T> the type of exception that is thrown
     * @return the parameters for the specified key size
     * @throws T when suitable parameters do not exist
     */
    public static
    <T extends Throwable>
    XECParameters getBySize(Function<String, T> exception,
                            int size) throws T {

        Optional<XECParameters> xecParams = getBySize(size);
        return xecParams.orElseThrow(
            apply(exception, "Unsupported size: " + size));
    }

    
Get parameters by algorithm ID, or throw an exception if no
parameters are defined for the specified ID. This method is used in
several contexts that should throw different exceptions when the
parameters are not found. The first argument is a function that produces
the desired exception.
Params:
exception – a function that produces an exception from a string
algId – the algorithm ID
Type parameters:
<T> – the type of exception that is thrown
Throws:
T – when suitable parameters do not exist
Returns:
the parameters for the specified algorithm ID/**
     * Get parameters by algorithm ID, or throw an exception if no
     * parameters are defined for the specified ID. This method is used in
     * several contexts that should throw different exceptions when the
     * parameters are not found. The first argument is a function that produces
     * the desired exception.
     *
     * @param exception a function that produces an exception from a string
     * @param algId the algorithm ID
     * @param <T> the type of exception that is thrown
     * @return the parameters for the specified algorithm ID
     * @throws T when suitable parameters do not exist
     */
    public static
    <T extends Throwable>
    XECParameters get(Function<String, T> exception,
                      AlgorithmId algId) throws T {

        Optional<XECParameters> xecParams = getByOid(algId.getOID());
        return xecParams.orElseThrow(
            apply(exception, "Unsupported OID: " + algId.getOID()));
    }

    
Get parameters by algorithm parameter spec, or throw an exception if no
parameters are defined for the spec. This method is used in
several contexts that should throw different exceptions when the
parameters are not found. The first argument is a function that produces
the desired exception.
Params:
exception – a function that produces an exception from a string
params – the algorithm parameters spec
Type parameters:
<T> – the type of exception that is thrown
Throws:
T – when suitable parameters do not exist
Returns:
the parameters for the spec/**
     * Get parameters by algorithm parameter spec, or throw an exception if no
     * parameters are defined for the spec. This method is used in
     * several contexts that should throw different exceptions when the
     * parameters are not found. The first argument is a function that produces
     * the desired exception.
     *
     * @param exception a function that produces an exception from a string
     * @param params the algorithm parameters spec
     * @param <T> the type of exception that is thrown
     * @return the parameters for the spec
     * @throws T when suitable parameters do not exist
     */
    public static
    <T extends Throwable>
    XECParameters get(Function<String, T> exception,
                      AlgorithmParameterSpec params) throws T {

        if (params instanceof NamedParameterSpec) {
            NamedParameterSpec namedParams = (NamedParameterSpec) params;
            Optional<XECParameters> xecParams =
                getByName(namedParams.getName());
            return xecParams.orElseThrow(
                apply(exception, "Unsupported name: " + namedParams.getName()));
        } else {
            throw exception.apply("Only NamedParameterSpec is supported.");
        }
    }
}