import type { ProviderStatus, RateWindow, UsageSnapshot } from "@marckrenn/pi-sub-shared";

function clampPercent(value: number): number {
	return Math.max(0, Math.min(100, Math.round(value)));
}

function formatWindow(window: RateWindow): string {
	const percent = `${clampPercent(window.usedPercent)}%`;
	const label = window.resetDescription?.trim() || window.label.trim();
	return label ? `${label} ${percent}` : percent;
}

function mapIncident(status?: ProviderStatus): string | undefined {
	if (!status || status.indicator === "none") return undefined;
	switch (status.indicator) {
		case "minor":
			return "degraded";
		case "major":
		case "critical":
			return "outage";
		case "maintenance":
			return "maintenance";
		case "unknown":
		default:
			return "unknown";
	}
}

function isStale(usage: UsageSnapshot): boolean {
	return Boolean(usage.error && usage.lastSuccessAt);
}

function isSyntheticStaleStatus(usage: UsageSnapshot): boolean {
	// sub-core currently uses a minor status with an elapsed description for stale fallback data.
	return isStale(usage) && usage.status?.indicator === "minor";
}

/**
 * Format the current usage snapshot into a compact status-line string.
 */
export function formatCompactStatus(usage: UsageSnapshot | undefined): string | undefined {
	if (!usage || usage.windows.length === 0) {
		return undefined;
	}

	const parts = usage.windows.slice(0, 2).map(formatWindow);
	if (parts.length === 0) {
		return undefined;
	}

	if (isStale(usage)) {
		parts.push("stale");
	}

	if (!isSyntheticStaleStatus(usage)) {
		const incident = mapIncident(usage.status);
		if (incident) {
			parts.push(incident);
		}
	}

	return parts.join(" · ");
}