austrian-cpi/src/getters.js

Query and merge Austrian CPI time series data for economic modeling

import { extractSeriesValues } from "./cpiUtils.js";

/**
 * Get the latest available numeric value for a CPI series
 * @param {string} seriesKey
 * @param {'monthly'|'yearly'} [frequency='monthly']
 * @returns {{ date: string, value: number } | null}
 */
function getLatestValue(seriesKey, frequency = "monthly") {
  const values = extractSeriesValues(seriesKey, frequency);
  return values.length ? values[values.length - 1] : null;
}

/**
 * Get the %CH between the latest two CPI values
 * @param {string} seriesKey
 * @param {'monthly'|'yearly'} [frequency='monthly']
 * @returns {{ from: string, to: string, rateOfChange: number } | null}
 */
function getLatestRateOfChange(seriesKey, frequency = "monthly") {
  const values = extractSeriesValues(seriesKey, frequency);
  if (values.length < 2) return null;

  const prev = values[values.length - 2];
  const curr = values[values.length - 1];
  const rate = ((curr.value - prev.value) / prev.value) * 100;

  return {
    from: prev.date,
    to: curr.date,
    rateOfChange: parseFloat(rate.toFixed(2)),
  };
}

/**
 * Generic RoC for custom date ranges
 * @param {string} seriesKey
 * @param {object} options
 * @param {'monthly'|'yearly'} [options.frequency='monthly']
 * @param {string} [options.start]
 * @param {string} [options.end]
 * @returns {{ from: string, to: string, rateOfChange: number } | null}
 */
function getRateOfChange(
  seriesKey,
  { frequency = "monthly", start, end } = {},
) {
  const values = extractSeriesValues(seriesKey, frequency, start, end);
  if (values.length < 2) return null;

  const first = values[0];
  const last = values[values.length - 1];
  const rate = ((last.value - first.value) / first.value) * 100;

  return {
    from: first.date,
    to: last.date,
    rateOfChange: parseFloat(rate.toFixed(2)),
  };
}

export { getLatestValue, getRateOfChange, getLatestRateOfChange };