export type WeeklyQuota = {
	usedPercent: number;
	remainingPercent: number;
	resetsAt?: number;
};

type QuotaWindow = {
	usedPercent: number;
	windowMinutes?: number;
	resetsAt?: number;
};

function asRecord(value: unknown): Record<string, unknown> | undefined {
	return typeof value === "object" && value !== null && !Array.isArray(value) ? (value as Record<string, unknown>) : undefined;
}

function numberValue(record: Record<string, unknown>, keys: readonly string[]): number | undefined {
	for (const key of keys) {
		const value = record[key];
		if (typeof value === "number" && Number.isFinite(value)) return value;
	}
	return undefined;
}

function readWindow(value: unknown): QuotaWindow | undefined {
	const record = asRecord(value);
	if (!record) return undefined;
	const usedPercent = numberValue(record, ["used_percent", "usedPercent"]);
	if (usedPercent === undefined) return undefined;

	const windowSeconds = numberValue(record, ["limit_window_seconds", "window_seconds"]);
	return {
		usedPercent,
		windowMinutes: numberValue(record, ["window_minutes", "windowMinutes"]) ??
			(windowSeconds === undefined ? undefined : windowSeconds / 60),
		resetsAt: numberValue(record, ["resets_at", "reset_at", "resetsAt", "resetAt"]),
	};
}

function collectWindows(value: unknown, windows: QuotaWindow[] = []): QuotaWindow[] {
	const record = asRecord(value);
	if (!record) return windows;

	const window = readWindow(record);
	if (window) windows.push(window);
	for (const nested of Object.values(record)) collectWindows(nested, windows);
	return windows;
}

/**
 * Extract the rolling seven-day Codex quota from the undocumented ChatGPT
 * usage payload. OpenAI has used both `rate_limit` and `rate_limits` shapes.
 */
export function extractWeeklyQuota(payload: unknown): WeeklyQuota | undefined {
	const windows = collectWindows(payload);
	const weekly = windows
		.filter((window) => window.windowMinutes !== undefined && window.windowMinutes >= 6 * 24 * 60)
		.sort((a, b) => (b.windowMinutes ?? 0) - (a.windowMinutes ?? 0))[0];
	if (!weekly) return undefined;

	const usedPercent = Math.max(0, Math.min(100, weekly.usedPercent));
	return {
		usedPercent,
		remainingPercent: Math.max(0, 100 - usedPercent),
		resetsAt: weekly.resetsAt,
	};
}