/**
 * T9 — relay-node ↔ control-plane trust boundary (the node analog of INV3). `nodeId` is derived
 * from the VERIFIED relay-node mTLS client-cert subject — NEVER from a body/query/header field.
 * A request that carries a `nodeId` payload has it IGNORED for identity. Non-mutually-authenticated
 * connections throw 401.
 *
 * OQ5 (open): who ISSUES/ROTATES the node service certs + the SVID format the CP pins
 * (`nodeMtlsTrustBundlePath`) is a P5/P1 boundary. Here we consume an already-verified peer cert.
 */
export interface NodeIdentity {
  readonly nodeId: string
}

export class NodeAuthError extends Error {
  readonly status = 401
  constructor(message: string) {
    super(message)
  }
}

/** The shape we need from a verified TLS peer certificate (subset of Node's PeerCertificate). */
export interface VerifiedPeerCert {
  readonly authorized: boolean // TLS stack verified the client cert against the trust bundle
  readonly subjectCommonName: string | null // SPIFFE-style node id in the cert subject CN / SAN URI
}

/** Pure derivation — the request wrapper below feeds it the extracted peer cert. */
export function deriveNodeIdentity(cert: VerifiedPeerCert | null): NodeIdentity {
  if (cert === null || !cert.authorized) {
    throw new NodeAuthError('relay-node connection is not mutually authenticated')
  }
  const cn = cert.subjectCommonName
  if (cn === null || cn.trim() === '') {
    throw new NodeAuthError('relay-node client cert has no subject identity')
  }
  return { nodeId: cn }
}

/** Minimal request shape carrying a TLS socket (Fastify/Node). */
export interface RequestWithTls {
  readonly socket: {
    authorized?: boolean
    getPeerCertificate?: () => { subject?: { CN?: string } } | undefined
  }
}

/**
 * Extract the verified node identity from a live request's TLS session. INTEGRATION SEAM: the
 * exact SAN/URI SVID parsing is finalized with OQ5; here we read authorized + subject CN.
 */
export function nodeIdentityFromRequest(req: RequestWithTls): NodeIdentity {
  const authorized = req.socket.authorized === true
  const peer = req.socket.getPeerCertificate?.()
  const cn = peer?.subject?.CN ?? null
  return deriveNodeIdentity({ authorized, subjectCommonName: cn })
}