// @ts-check

/**
 * Creates an asymmetric matcher for approximate numeric equality.
 *
 * This helper is intended for use in test frameworks (e.g., Jest) where
 * values need to be compared within a configurable decimal precision
 * instead of strict equality.
 *
 * The comparison succeeds when:
 *
 *   |actual - expected| < 10^(-precision)
 *
 * For example, with `precision = 3`, values must be within `0.001`.
 *
 * @param {number} expected The expected numeric value to compare against.
 *
 * @param {number} [precision=10]
 *   The number of decimal places of tolerance. Higher values mean stricter
 *   comparison. Internally converted to epsilon = 10^-precision.
 *
 * @returns {{
 *   asymmetricMatch(actual: unknown): boolean,
 *   toAsymmetricMatcher(): string
 * }} An object implementing Jest-style asymmetric matcher methods.
 *
 */
export function approxNumber(expected, precision = 10) {
  return {
    asymmetricMatch(actual) {
      if (typeof actual !== "number" || typeof expected !== "number") {
        return false;
      }
      const epsilon = Math.pow(10, -precision);
      return Math.abs(actual - expected) < epsilon;
    },
    toAsymmetricMatcher() {
      return `≈ ${expected} (precision ${precision})`;
    },
  };
}