// Refreshes data/sp500.json with daily S&P 500 close prices from Yahoo Finance's
// public chart endpoint (no API key required). Run with: node scripts/fetch-sp500.mjs
import { writeFileSync } from "node:fs";
import { fileURLToPath } from "node:url";
import { dirname, join } from "node:path";

const __dirname = dirname(fileURLToPath(import.meta.url));
const OUT_PATH = join(__dirname, "..", "data", "sp500.json");
const URL =
  "https://query1.finance.yahoo.com/v8/finance/chart/%5EGSPC?range=10y&interval=1d";

const res = await fetch(URL, { headers: { "User-Agent": "Mozilla/5.0" } });
if (!res.ok) {
  throw new Error(`Yahoo Finance request failed: ${res.status} ${res.statusText}`);
}
const data = await res.json();
const result = data?.chart?.result?.[0];
if (!result) {
  throw new Error("Unexpected response shape from Yahoo Finance");
}

const { timestamp } = result;
const closes = result.indicators.quote[0].close;

const series = [];
for (let i = 0; i < timestamp.length; i++) {
  if (closes[i] == null) continue;
  const date = new Date(timestamp[i] * 1000).toISOString().slice(0, 10);
  series.push({ date, close: Number(closes[i].toFixed(2)) });
}

writeFileSync(OUT_PATH, JSON.stringify({ source: "yahoo-finance:^GSPC", updatedAt: new Date().toISOString(), series }, null, 2));
console.log(`Wrote ${series.length} points to ${OUT_PATH}`);