// Test

const test = require('ava');
const reduce = require('./reduce');

test('Can groupBy', (t) => {
  const input = [
    {
      "type": "hotel",
      "name": "Intercontinental"
    },
    {
      "type": "airport",
      "name": "Heathrow"
    },
    {
      "type": "hotel",
      "name": "Hilton"
    },
    {
      "type": "station",
      "name": "King's Cross"
    },
    {
      "type": "airport",
      "name": "Stansted"
    }
  ];

  const expected = {
    airport: ['Heathrow', 'Stansted'],
    station: "King's Cross",
    hotel: ['Intercontinental', 'Hilton']
  }

  const reduced = reduce(input);

  t.deepEqual(expected, reduced);
});


// Solution

const reduce = (input) => {
  const result = input.reduce((collection, element) => {
    const current = collection[element.type]
    if(current && Array.isArray(current)) {
      collection[element.type].push(element.name);
    } else if(current) {
      collection[element.type] = [current, element.name]
    } else {
      collection[element.type] = element.name
    }
    return collection;
  }, {})
  return result;
};

module.exports = reduce;