pgpainless/pgpainless-core/src/main/kotlin/org/pgpainless/bouncycastle/extensions/PGPPublicKeyExtensions.kt

// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
//
// SPDX-License-Identifier: Apache-2.0

package org.pgpainless.bouncycastle.extensions

import org.bouncycastle.asn1.gnu.GNUObjectIdentifiers
import org.bouncycastle.bcpg.ECDHPublicBCPGKey
import org.bouncycastle.bcpg.ECDSAPublicBCPGKey
import org.bouncycastle.bcpg.EdDSAPublicBCPGKey
import org.bouncycastle.jcajce.provider.asymmetric.util.ECUtil
import org.bouncycastle.openpgp.PGPPublicKey
import org.pgpainless.algorithm.PublicKeyAlgorithm
import org.pgpainless.key.OpenPgpFingerprint
import org.pgpainless.key.generation.type.eddsa.EdDSACurve

/**
 * For secret keys of types [PublicKeyAlgorithm.ECDSA], [PublicKeyAlgorithm.ECDH] and
 * [PublicKeyAlgorithm.EDDSA], this method returns the name of the underlying elliptic curve.
 *
 * For other key types or unknown curves, this method throws an [IllegalArgumentException].
 *
 * @return curve name
 */
fun PGPPublicKey.getCurveName(): String {
    PublicKeyAlgorithm.requireFromId(algorithm)
        .let {
            when (it) {
                PublicKeyAlgorithm.ECDSA -> publicKeyPacket.key as ECDSAPublicBCPGKey
                PublicKeyAlgorithm.ECDH -> publicKeyPacket.key as ECDHPublicBCPGKey
                PublicKeyAlgorithm.EDDSA -> publicKeyPacket.key as EdDSAPublicBCPGKey
                else -> throw IllegalArgumentException("No an elliptic curve public key ($it).")
            }
        }
        .let {
            if (it.curveOID == GNUObjectIdentifiers.Ed25519) return EdDSACurve._Ed25519.curveName
            else it.curveOID
        }
        .let { it to ECUtil.getCurveName(it) }
        .let {
            if (it.second != null) return it.second
            else throw IllegalArgumentException("Unknown curve: ${it.first}")
        }
}

/** Return the [PublicKeyAlgorithm] of this key. */
val PGPPublicKey.publicKeyAlgorithm: PublicKeyAlgorithm
    get() = PublicKeyAlgorithm.requireFromId(algorithm)

/** Return the [OpenPgpFingerprint] of this key. */
val PGPPublicKey.openPgpFingerprint: OpenPgpFingerprint
    get() = OpenPgpFingerprint.of(this)