Handling Responses

// Response from /v1/prices/latest?by_code=WTI_USD
{
  "status": "success",
  "data": {
    "price": 74.52,
    "formatted": "$74.52",
    "currency": "USD",
    "code": "WTI_USD",
    "created_at": "2025-12-29T15:30:00.000Z",
    "type": "spot_price",
    "source": "market_reporting",
    "metadata": {
      "source": "market_reporting",
      "source_description": "Business Insider - Most accurate source matching ICE exchange prices"
    }
  }
}

// Parsing in JavaScript
const response = await fetch(url, options);
const result = await response.json();

if (result.status === 'success') {
  const { price, formatted, code, created_at } = result.data;
  console.log(`${code}: ${formatted}`);  // "WTI_USD: $74.52"
  console.log(`Updated: ${new Date(created_at).toLocaleString()}`);
}

// JavaScript - Calculate average price
function calculateAverage(historicalData) {
  const prices = historicalData.data.prices; // data.prices is an array
  const sum = prices.reduce((acc, item) => acc + item.price, 0);
  return sum / prices.length;
}

// Find price trends
function analyzeTrend(historicalData) {
  const prices = historicalData.data.prices;
  const firstPrice = prices[prices.length - 1].price; // oldest
  const lastPrice = prices[0].price; // most recent
  const change = lastPrice - firstPrice;
  const changePercent = (change / firstPrice) * 100;

  return {
    trend: change > 0 ? "upward" : "downward",
    changeAmount: change.toFixed(2),
    changePercent: changePercent.toFixed(2),
  };
}

async function makeAPICall(url, options) {
  try {
    const response = await fetch(url, options);

    if (response.status === 401) {
      // { "error": { "code": "UNAUTHORIZED", "message": ..., "request_id": ... } }
      const body = await response.json();
      console.error(`Auth failed (${body.error.code}):`, body.error.message);
      console.error("Include header: Authorization: Token YOUR_API_KEY");
      return null;
    }

    if (response.status === 400) {
      // { "status": "fail", "data": { "error": "invalid_code", "invalid_codes": [...] } }
      const body = await response.json();
      console.error("Bad request:", body.data.error, body.data.message);
      // For a bad commodity code, fetch the valid list from GET /v1/commodities
      return null;
    }

    if (response.status === 429) {
      const retryAfter = response.headers.get("Retry-After") || 60;
      console.warn(`Rate limited. Retry after ${retryAfter}s.`);
      return null;
    }

    if (response.status === 404) {
      // 404 returns an empty body — do not parse JSON
      console.error("Not found:", url);
      return null;
    }

    return await response.json();
  } catch (err) {
    console.error("Network error:", err);
    return null;
  }
}

class UsageMonitor {
  constructor() {
    this.usage = {
      limit: null,
      remaining: null,
      resetAt: null,
    };
  }

  updateFromHeaders(headers) {
    this.usage.limit = parseInt(headers.get("x-ratelimit-limit"));
    this.usage.remaining = parseInt(headers.get("x-ratelimit-remaining"));
    this.usage.resetAt = new Date(
      parseInt(headers.get("x-ratelimit-reset")) * 1000,
    );

    this.checkUsage();
  }

  checkUsage() {
    const percentUsed =
      ((this.usage.limit - this.usage.remaining) / this.usage.limit) * 100;

    if (percentUsed > 90) {
      console.warn(`API usage at ${percentUsed.toFixed(1)}%`);
      this.sendUsageAlert();
    }
  }

  getDaysUntilReset() {
    const now = new Date();
    const msUntilReset = this.usage.resetAt - now;
    return Math.ceil(msUntilReset / (1000 * 60 * 60 * 24));
  }
}

function formatPriceDisplay(priceData) {
  const formatter = new Intl.NumberFormat("en-US", {
    style: "currency",
    currency: priceData.currency,
    minimumFractionDigits: 2,
    maximumFractionDigits: 2,
  });

  const pct = priceData.changes?.["24h"]?.percent ?? 0;
  return {
    formatted: priceData.formatted, // API returns a pre-formatted string, e.g. "$68.58"
    unit: priceData.unit,
    change: pct > 0 ? "↑" : "↓",
    changeColor: pct > 0 ? "green" : "red",
    changeText: `${pct > 0 ? "+" : ""}${pct}%`,
  };
}

// Usage — find the commodity in the prices array
const wti = result.data.prices.find((p) => p.code === "WTI_USD");
const display = formatPriceDisplay(wti);
console.log(`${display.formatted}/${display.unit} ${display.changeText}`);
// Output: $68.58/barrel +1.06%

ws.onmessage = (event) => {
  const message = JSON.parse(event.data);

  if (message.type === "price_update") {
    updatePriceDisplay(message.data); // { code, price, currency, created_at, ... }
  }
};