/**
 * The count beside the Diagnostics nav item.
 *
 * Three things have to be visible and only one of them is a number. Open
 * episodes are the count. A `degraded` rollup with no open episode still has to
 * show something, or a degraded box looks exactly like a healthy one. And a
 * health poll that failed is not evidence of health: it shows the same neutral
 * mark, because the alternative is an unbadged item claiming all is well on no
 * evidence at all.
 *
 * "Fresh" here means the latest poll succeeded, never TanStack's `isStale`:
 * healthQuery's `staleTime` is 0, so staleness is true in every gap between
 * polls and would badge the item permanently.
 */

import type { Health } from "@/lib/types";
import { formatCount } from "@/lib/format";

export interface NavBadge {
	/** What the badge shows. Shape and text, never colour alone. */
	text: string;
	/** What a screen reader hears in its place. */
	label: string;
}

export function diagnosticsBadge(health: Health | undefined, pollFailed: boolean): NavBadge | null {
	// The one hidden unknown, and only because it is momentary: the first poll has
	// not answered yet, and there is nothing to be right or wrong about.
	if (health === undefined && !pollFailed) return null;
	if (pollFailed) return { text: "!", label: "Health unavailable" };
	if (health === undefined) return null;
	const open = health.diagnostics.active_warnings + health.diagnostics.active_errors;
	if (open > 0) {
		return {
			text: formatCount(open),
			label: `${formatCount(open)} active diagnostic ${open === 1 ? "event" : "events"}`,
		};
	}
	if (health.status === "degraded") return { text: "!", label: "Health degraded" };
	return null;
}