// Copyright 2026 @quantus/crypto authors & contributors
// SPDX-License-Identifier: Apache-2.0

/**
 * Which ML-DSA parameter set a call refers to.
 *
 * These are the chain's own `DilithiumSignatureScheme` variant indices, not a
 * private numbering — the value here is the byte a signed extrinsic carries on
 * the wire. Keeping them identical means the keyring's `TYPE_PREFIX` is the
 * identity function on a scheme, with no table to get backwards.
 */
export enum Scheme {
  /** ML-DSA-87. Legacy: accounts created before the scheme was recorded, and the dev-genesis accounts. */
  MlDsa87 = 0,
  /** ML-DSA-65. What new accounts use. */
  MlDsa65 = 1
}

/**
 * The name each scheme is stored under, matching `quantus-cli` and the mobile
 * wallet so a wallet exported from one tool imports into another.
 */
export const SCHEME_NAME: Record<Scheme, string> = {
  [Scheme.MlDsa87]: 'ml-dsa-87',
  [Scheme.MlDsa65]: 'ml-dsa-65'
};

/**
 * FIPS 204 context for on-chain extrinsic signatures.
 *
 * Only from spec 148 onward — earlier runtimes verify under the empty context,
 * and a signature made under the wrong one is valid, rejected by the chain, and
 * indistinguishable locally. Callers pass the spec version and get the right
 * answer from {@link contextForSpec}; nothing here guesses.
 */
export const EXTRINSIC_CONTEXT = new TextEncoder().encode('QUANTUS_EXTRINSIC');

/** First spec version that verifies extrinsics under {@link EXTRINSIC_CONTEXT}. */
export const EXTRINSIC_MIN_SPEC = 148;

/** The signing context a runtime at `specVersion` expects. */
export function contextForSpec (specVersion: number): Uint8Array {
  return specVersion >= EXTRINSIC_MIN_SPEC
    ? EXTRINSIC_CONTEXT
    : new Uint8Array();
}