import-from.mjs

import fs from 'fs';
import path from 'path';
import * as postcss from 'postcss';
import { parse } from 'postcss-values-parser';

async function getCustomPropertiesFromCSSFile(from) {
  const css = await readFile(from); // eslint-disable-next-line no-unused-vars

  postcss.parse(css, {
    from,
  });
  throw new Error('Importing from CSS files not supported yet'); //return getCustomPropertiesFromRoot(root, { preserve: true });
}
/* Get Custom Properties from Object
/* ========================================================================== */

function getCustomPropertiesFromObject(object) {
  const customProperties = Object.assign(
    {},
    Object(object).customProperties,
    Object(object)['custom-properties'],
  );

  for (const key in customProperties) {
    customProperties[key] = parse(String(customProperties[key])).nodes;
  }

  return customProperties;
}
/* Get Custom Properties from JSON file
/* ========================================================================== */

async function getCustomPropertiesFromJSONFile(from) {
  const object = await readJSON(from);
  return getCustomPropertiesFromObject(object);
}
/* Get Custom Properties from JS file
/* ========================================================================== */

async function getCustomPropertiesFromJSFile(from) {
  const object = await import(from);

  return getCustomPropertiesFromObject(object);
}

export default function getCustomPropertiesFromImports(sources) {
  return sources
    .map(source => {
      if (source instanceof Promise) {
        return source;
      } else if (source instanceof Function) {
        return source();
      } // read the source as an object

      const opts =
        source === Object(source)
          ? source
          : {
              from: String(source),
            }; // skip objects with Custom Properties

      if (opts.customProperties || opts['custom-properties']) {
        return opts;
      } // source pathname

      const from = path.resolve(String(opts.from || '')); // type of file being read from

      const type = (opts.type || path.extname(from).slice(1)).toLowerCase();
      return {
        type,
        from,
      };
    })
    .reduce(async (customProperties, source) => {
      const { type, from } = await source;

      if (type === 'css') {
        return Object.assign(
          await customProperties,
          await getCustomPropertiesFromCSSFile(from),
        );
      }

      if (type === 'js') {
        return Object.assign(
          await customProperties,
          await getCustomPropertiesFromJSFile(from),
        );
      }

      if (type === 'json') {
        return Object.assign(
          await customProperties,
          await getCustomPropertiesFromJSONFile(from),
        );
      }

      return Object.assign(
        await customProperties,
        await getCustomPropertiesFromObject(await source),
      );
    }, {});
}

const readFile = from =>
  new Promise((resolve, reject) => {
    fs.readFile(from, 'utf8', (error, result) => {
      if (error) {
        reject(error);
      } else {
        resolve(result);
      }
    });
  });

const readJSON = async from => JSON.parse(await readFile(from));
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