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package zeroecho.core.spec;

import java.util.Objects;

/**
 * Immutable composition of a signature scheme and a compatible public-key
 * identity.
 *
 * <p>
 * The suite keeps signature and key semantics separate. In particular, an
 * ECDSA signature identity contains its digest while the public-key identity
 * contains the named curve. Compatibility is evaluated by capability and
 * policy, not inferred from an X.509 signature OID.
 * </p>
 *
 * @param signature exact signature-scheme identity
 * @param publicKey exact public-key identity
 */
public record AlgorithmSuite(AlgorithmIdentity signature, AlgorithmIdentity publicKey) {

    /**
     * Creates a validated signature suite.
     *
     * @throws NullPointerException     if an identity is {@code null}
     * @throws IllegalArgumentException if an identity has the wrong semantic kind
     */
    public AlgorithmSuite {
        Objects.requireNonNull(signature, "signature");
        Objects.requireNonNull(publicKey, "publicKey");
        if (signature.kind() != AlgorithmIdentity.Kind.SIGNATURE) {
            throw new IllegalArgumentException("signature must have SIGNATURE kind");
        }
        if (publicKey.kind() != AlgorithmIdentity.Kind.PUBLIC_KEY) {
            throw new IllegalArgumentException("publicKey must have PUBLIC_KEY kind");
        }
    }

    /**
     * Returns the deterministic suite representation.
     *
     * @return signature and key canonical identities in a length-independent form
     */
    public String canonicalForm() {
        return "zesuite:1:" + signature.canonicalForm() + "|" + publicKey.canonicalForm();
    }
}
