resolveVariableDependencies.js

// @flow
/*
CAUTION!

This file could be included even after running the babel plugin.

Make sure you don't import large libraries.
*/
/* eslint-disable no-param-reassign */
const { DepGraph } = require("dependency-graph");
const { varRegExp, varRegExpNonGlobal } = require("../../util/cssRegExp");

module.exports = (
  definedVariables /*: { [key:string]: string } */,
  variablesFromScope /*: { [key:string]: string } */
) /*: { [key:string]: string } */ => {
  const graph = new DepGraph();

  const variableNames = Object.keys(definedVariables);

  variableNames.forEach(variableName => {
    graph.addNode(variableName);
  });

  variableNames.forEach(variableName => {
    const referencedVariableMatches = definedVariables[variableName].match(
      varRegExp
    );
    if (referencedVariableMatches == null) return;

    const referencedVariables = referencedVariableMatches
      .map(match => {
        const matchedVariable = match.match(varRegExpNonGlobal);
        return matchedVariable ? matchedVariable[1] : null;
      })
      .filter(Boolean);

    referencedVariables.forEach(referencedVariableName => {
      if (referencedVariableName in definedVariables) {
        graph.addDependency(variableName, referencedVariableName);
      }
    });
  });

  const appliedVariables = graph
    .overallOrder(false)
    .reduce((accum, variableName) => {
      const value = definedVariables[variableName].replace(
        varRegExp,
        (m, reference, fallback) =>
          accum[reference] || variablesFromScope[reference] || fallback
      );
      accum[variableName] = value;
      return accum;
    }, {});

  return appliedVariables;
};