xxphantom/backend-project-lvl2

import _ from 'lodash';

const flags = {
  deleted: 'removed',
  added: 'added with value:',
};
const formatNestedProp = (body) => {
  if (typeof body === 'string') {
    return ` '${body}'`;
  }
  return _.isObject(body) ? ' [complex value]' : ` ${body}`;
};

const formatPlain = (ast) => {
  const iter = (tree, parentKey = '') => tree.flatMap((node) => {
    const {
      key, nodeType, value1, value2, children,
    } = node;
    const chainNodeNames = [parentKey, key].filter((n) => n !== '').join('.');

    switch (nodeType) {
      case 'unchanged':
        return [];
      case 'nested':
        return iter(children, `${chainNodeNames}`);
      case 'changed':
        return `Property '${chainNodeNames}' was updated. From${formatNestedProp(value1)} to${formatNestedProp(value2)}`;
      case 'deleted':
        return `Property '${chainNodeNames}' was ${flags[nodeType]}`;
      case 'added':
        return `Property '${chainNodeNames}' was ${flags[nodeType]}${formatNestedProp(value2)}`;
      default:
        throw new Error(`Unexpected nodeType: ${nodeType}`);
    }
  });
  return iter(ast).join('\n').trim();
};
export default formatPlain;