import type { TaskListItem, TaskStatus } from "./types";

/**
 * Statuses that represent an actively executing assignment, where live
 * in-progress step information is meaningful to surface.
 */
const ACTIVE_STATUSES: ReadonlySet<TaskStatus> = new Set<TaskStatus>([
  "assigned",
  "dispatched",
]);

/**
 * Format a task's latest in-progress step snapshot for inline display.
 *
 * Returns `null` when:
 * - the task is not actively executing (queued, done, failed) — terminal/queued
 *   status always wins over a stale progress snapshot; or
 * - no progress has been reported yet (`progress_step_index` is null/undefined
 *   or `progress_step_status` is missing).
 *
 * Otherwise returns a compact string like `"step 2 — running: tapping button"`.
 * The summary is truncated to a display-friendly length with a Unicode ellipsis
 * when it exceeds the limit.
 */
export function formatTaskProgress(
  task: Pick<
    TaskListItem,
    | "status"
    | "progress_step_index"
    | "progress_step_status"
    | "progress_summary"
  >,
  maxSummaryLength = 120,
): string | null {
  if (!ACTIVE_STATUSES.has(task.status)) return null;
  if (
    task.progress_step_index === null ||
    task.progress_step_index === undefined ||
    !task.progress_step_status
  ) {
    return null;
  }
  const summary = task.progress_summary ?? "";
  const trimmed = summary.trim();
  const display =
    trimmed.length > maxSummaryLength
      ? `${trimmed.slice(0, maxSummaryLength - 1).trimEnd()}\u2026`
      : trimmed;
  return `step ${task.progress_step_index} \u2014 ${task.progress_step_status}${
    display ? `: ${display}` : ""
  }`;
}