// What a thread is doing, from the watch's point of view. Ported from T3 Code's
// `packages/shared/src/agentAwareness.ts` (MIT), which drives T3's own mobile notifications.

import type { ThreadShell } from "./t3/types.ts";

export type Phase =
  | "starting"
  | "running"
  | "waiting_for_approval"
  | "waiting_for_input"
  | "completed"
  | "failed";

type AwarenessFields = Pick<
  ThreadShell,
  | "activityRunStatus"
  | "lineage"
  | "latestRunStopRequested"
  | "pendingBackgroundTasks"
  | "pendingRuntimeRequest"
  | "settledOverride"
  | "status"
>;

/**
 * The phase to show for a thread, or null when the watch should not show it: subagent children,
 * threads that never ran or were stopped, and finished work the user already settled.
 */
export function threadPhase(thread: AwarenessFields): Phase | null {
  if (thread.lineage.relationshipToParent === "subagent") return null;
  const phase = resolvePhase(thread);
  if (phase === null) return null;
  if (phase === "completed" && thread.latestRunStopRequested === true) return null;
  if (
    thread.settledOverride === "settled" &&
    (phase === "completed" || phase === "failed") &&
    !backgroundWorkHoldsCompletion(thread.pendingBackgroundTasks ?? [])
  ) {
    return null;
  }
  return phase;
}

function resolvePhase(thread: AwarenessFields): Phase | null {
  const runStatus = thread.activityRunStatus ?? thread.status;
  const request = thread.pendingRuntimeRequest;
  if (
    request?.kind === "user_input" &&
    (request.blocking !== false || !(runStatus === "preparing" || runStatus === "starting" || runStatus === "running"))
  ) {
    return "waiting_for_input";
  }
  if (request && request.kind !== "user_input" && request.kind !== "auth_refresh") {
    return "waiting_for_approval";
  }
  switch (runStatus) {
    case "preparing":
    case "starting":
      return "starting";
    case "running":
    case "waiting":
      return "running";
    case "completed":
      return backgroundWorkHoldsCompletion(thread.pendingBackgroundTasks ?? []) ? "running" : "completed";
    case "failed":
      return "failed";
    default:
      return null;
  }
}

// Commands and monitors are as often a dev server or its watchdog as a wait, so they hold
// completion only when the agent marks them awaited.
function backgroundWorkHoldsCompletion(tasks: NonNullable<ThreadShell["pendingBackgroundTasks"]>): boolean {
  return tasks.some((task) => task.awaited === true || task.kind === "subagent" || task.kind === "background_task");
}