import { formatUsd } from "./status-widget.js";
import { isTerminal } from "../controller/state-machine.js";
import type { UltraController } from "../controller/controller.js";
import type { ControllerState } from "../controller/state-machine.js";

export const HUD_KEY = "ultrapi";

/** The minimum a person needs to know a fleet is alive: what stage, how many, on what, at what cost. */
export function hudLine(controller: UltraController): string | undefined {
  const status = controller.status();
  const live = status.activeRuns.filter((run) => !isTerminal(run.state as ControllerState));
  const run = live.at(-1);
  if (!run) return undefined;
  const queued = live.length > 1 ? ` +${live.length - 1}` : "";
  const working = run.nodes.filter((node) => node.state !== "done").length;
  const health = status.health.state === "healthy" ? "" : ` · ${status.health.state}`;
  const agents = working ? ` · ${working} agent${working === 1 ? "" : "s"}` : "";
  return `UltraPi ${run.topology}/${run.state}${queued} · [${run.progress.done}/${run.progress.total}]${agents} · ${run.model ?? "model unselected"}${health} · est. ${formatUsd(status.spentUsd)}`;
}

export interface HudSurface { setStatus?: (key: string, text: string | undefined) => void }

/**
 * A painter that writes the line into Pi's footer whenever it changes, and clears it when the
 * last run settles. It holds the last painted text so an idle session never touches the status
 * bar and a busy one repaints only on real movement.
 *
 * Painting can never throw. A HUD exists to tell you a run is alive; a HUD that can end the run
 * it reports on is worse than no HUD, so every failure here — a host without `setStatus`, a
 * controller that is not ready, a renderer that rejects the string — is swallowed. Losing a
 * frame costs the user a moment of not knowing; propagating would cost them the run.
 */
export function createHudPainter(controller: UltraController): (ui: HudSurface | undefined) => void {
  let painted: string | undefined;
  return (ui) => {
    try {
      if (typeof ui?.setStatus !== "function") return;
      const line = hudLine(controller);
      if (line === painted) return;
      painted = line;
      ui.setStatus(HUD_KEY, line);
    } catch {}
  };
}

export function clearHud(ui: HudSurface | undefined): void {
  try { ui?.setStatus?.(HUD_KEY, undefined); } catch {}
}