import { reach } from './reach.js';

/**
 * Transform an object or collection to a different form.
 *
 * @param  {Object} source    The object to transform.
 * @param  {Object} map       Object that describes how to transform the source: { [path.in.transformed.object]: [path.in.source] }.
 * @return {Object}           A new object with the new structure.
 */
export const transform = (source, map) => {
  const sep = '.';

  if (Array.isArray(source)) {
    const results = [];
    for (let i = 0; i < source.length; ++i) {
      results.push(transform(source[i], map));
    }
    return results;
  }

  const result = {};
  const keys = Object.keys(map);

  for (let i = 0, li = keys.length; i < li; ++i) {
    const key = keys[i];
    const path = key.split(sep);
    const srcPath = map[key];

    if (typeof srcPath !== 'string') {
      console.warn('Transformation path invalid. Skipping.');
      continue;
    }

    let segment;
    let res = result;

    while (path.length > 1) {
      segment = path.shift();
      if (!res[segment]) {
        res[segment] = {};
      }
      res = res[segment];
    }
    segment = path.shift();
    res[segment] = reach(srcPath, source);
  }

  return result;
}