import type { PlannerDecisionItem } from "./types";

export type PlannerHistoryState =
  | { kind: "populated"; decisions: PlannerDecisionItem[] }
  | { kind: "empty_cloud_transport" }
  | { kind: "direct_transport_hidden" }
  | { kind: "unknown_host_transport" };

/**
 * Decide which empty-state or populated-state message to show for a task's
 * planner decision history, based on whether any decisions were returned and
 * the assigned host's configured planner transport.
 *
 * - **populated**: decisions exist — render them.
 * - **direct_transport_hidden**: host uses the `direct` transport, which never
 *   sends prompts to Cloud. Show an explicit "not reported" message instead of
 *   an empty list.
 * - **empty_cloud_transport**: host IS cloud-transport but no decisions have
 *   been persisted yet (task just started or no steps executed).
 * - **unknown_host_transport**: host not found or transport field not reported.
 */
export function computePlannerHistoryState(
  decisions: PlannerDecisionItem[],
  hostTransport: "direct" | "cloud" | null,
): PlannerHistoryState {
  if (decisions.length > 0) {
    return { kind: "populated", decisions };
  }
  if (hostTransport === "direct") {
    return { kind: "direct_transport_hidden" };
  }
  if (hostTransport === "cloud") {
    return { kind: "empty_cloud_transport" };
  }
  return { kind: "unknown_host_transport" };
}