/* @flow */
"use strict";

const _ = require("lodash");
const blurInterpolation = require("./blurInterpolation");
const isStandardSyntaxValue = require("./isStandardSyntaxValue");
const valueParser = require("postcss-value-parser");

/**
 * Get unit from value node
 *
 * Returns `null` if the unit is not found.
 */
module.exports = function(node /*: Object*/) /*: ?string*/ {
  if (!node || (node && !node.value)) {
    return null;
  }

  const value = blurInterpolation(node.value, "")
    // ignore hack unit
    .replace("\\0", "")
    .replace("\\9", "")
    // ignore decimal place
    .replace(".", "");

  if (
    node.type !== "word" ||
    !isStandardSyntaxValue(value) ||
    !_.isFinite(parseInt(value)) ||
    node.value[0] === "#"
  ) {
    return null;
  }

  const parsedUnit = valueParser.unit(value);

  if (!parsedUnit) {
    return null;
  }

  return parsedUnit.unit;
};