/*
 * **A twin made by one producer is not rebuilt by another.** Pure.
 *
 * ── What went wrong (2026-09-24) ─────────────────────────────────────────────
 * An import's instance id is the adapter's site id (`master.source`). Importing the warehouse connection
 * `wms-miratek` with site id `miratek` — the same as the plant connection's — landed on the running plant
 * mirror `miratek`, and `ingestMaster` gave it the warehouse structure as a new revision: 16 places,
 * 23 equipment, 17 people and 14 assets gone. The row already said who made it (`origin.source` was
 * `mes-miratek`); nothing asked.
 *
 * ── The rule (chief architect ruling, 2026-09-24) ────────────────────────────
 * Compare producers by identity, not by the whole origin: a reference is kind + source, a template is
 * kind + templateId. The same import carries more or fewer fields at different call sites (siteId,
 * spaceId), and a template re-run has new params — those are the same producer re-reading its own twin.
 *
 *   both declared, same producer     allowed (resync, re-import, re-run)
 *   both declared, different         refused, naming the producer that owns it
 *   prior undeclared, incoming not   refused — nobody can say who made it; delete it first to replace it
 *   prior declared, incoming not     refused — same reason, the other way
 *   neither declared                 allowed — the demo seed re-ingesting its own twin at boot. Closes when
 *                                    the seed declares a template origin.
 */

export const INSTANCE_TAKEN = 'instance-taken-by-another-source'

export interface ProducerRefusal {
  code: typeof INSTANCE_TAKEN
  params: { instance: string; producer: string }
  message: string
}

/** Who produced a twin, as one comparable string — or undefined when the origin says nothing usable. */
export function producerOf(origin: unknown): string | undefined {
  if (!origin || typeof origin !== 'object') return undefined
  const o = origin as { kind?: unknown; source?: unknown; templateId?: unknown }
  if (o.kind === 'reference' && typeof o.source === 'string' && o.source) return `reference:${o.source}`
  if (o.kind === 'template' && typeof o.templateId === 'string' && o.templateId) return `template:${o.templateId}`
  /* A kind this guard does not know is still somebody — keep it distinct rather than reading it as none. */
  if (typeof o.kind === 'string' && o.kind) return `${o.kind}:${String(o.source ?? o.templateId ?? '')}`
  return undefined
}

function nameOf(origin: unknown): string {
  const o = (origin ?? {}) as { source?: unknown; templateId?: unknown }
  return String(o.source ?? o.templateId ?? '') || 'undeclared'
}

/** null when `incoming` may rebuild the twin `prior` was made by; otherwise the refusal. */
export function refuseOverwriteByAnotherProducer(
  instance: string,
  priorOrigin: unknown,
  incomingOrigin: unknown
): ProducerRefusal | null {
  const had = producerOf(priorOrigin)
  const comes = producerOf(incomingOrigin)
  if (!had && !comes) return null
  if (had && comes && had === comes) return null
  const producer = had ? nameOf(priorOrigin) : 'undeclared'
  return {
    code: INSTANCE_TAKEN,
    params: { instance, producer },
    message: `twin "${instance}" was made by ${producer} — delete it first, or import this site under another id`
  }
}