Function resolveBenchmark

packages/dataflows/src/returns.ts:18–29

(
  ticker: string,
  benchmarkMap: Record<string, string>,
  defaultBenchmark = "SPY",
)

/** Pick the benchmark for a ticker by suffix (default SPY). */
export function resolveBenchmark(
  ticker: string,
  benchmarkMap: Record<string, string>,
  defaultBenchmark = "SPY",
): string {
  const t = ticker.toUpperCase();
  // Longest matching suffix wins (e.g. ".NS" before "").
  const suffixes = Object.keys(benchmarkMap)
    .filter((s) => s === "" || t.endsWith(s.toUpperCase()))
    .sort((a, b) => b.length - a.length);
  return suffixes.length ? benchmarkMap[suffixes[0]!] ?? defaultBenchmark : defaultBenchmark;
}

interface Series {
  date: string; // YYYY-MM-DD