/**
 * Optional host-provided agent inventory: lets the market refuse plugin
 * mutations while a live agent is mid-turn. Mutating `node_modules` under a
 * running agent replaces files the running plugin modules may still read or
 * lazily import — the update "succeeds" while old code and new files mix.
 */

export interface RunningAgentLike {
  id?: unknown
  status?: unknown
}

export interface AgentsServiceLike {
  list(): RunningAgentLike[]
}

export type AgentsLookup = () => AgentsServiceLike | undefined

/**
 * Ids of the host's currently running agents, or [] when the host has no
 * agents service. Only a positive `status === 'running'` blocks an update —
 * unknown statuses are treated as not running, so a future agent
 * implementation with different wording fails open (the market stays
 * usable) instead of wedging the plugin page.
 */
export function runningAgentIds(agents: AgentsServiceLike | undefined): string[] {
  if (agents === undefined) return []
  let listed: RunningAgentLike[]
  try {
    listed = agents.list()
  } catch {
    // A half-disposed registry must never take the market's routes down.
    return []
  }
  if (!Array.isArray(listed)) return []
  const ids: string[] = []
  for (const agent of listed) {
    if (agent === null || typeof agent !== 'object' || agent.status !== 'running') continue
    const id = typeof agent.id === 'string' && agent.id !== '' ? agent.id : 'agent'
    if (!ids.includes(id)) ids.push(id)
  }
  return ids
}