/**
* Lib draft
*/

const objectPicker = _.pickBy(_.isObject);

const mapper = (arg) => {
  const mapping = arg.mapping ? arg.mapping : arg;

  const transformFlatKeys = _.mapKeys(key => {
    const mappingVal = mapping[key];
    if (mappingVal) {
      if (_.isString(mappingVal)) return mappingVal;
      if (_.isObject(mappingVal) && mappingVal.key) return  mappingVal.key;
    }
    return key;
  });

  const mapValuesWithKey = _.mapValues.convert({ cap: false});

  const transformSubObjects = mapValuesWithKey((val, key) => {
    const mappingVal = mapping[key];
    if (_.isObject(val) && _.isObject(mappingVal)) {
      return mapper(mappingVal)(val);
    }
    return val;
  });


  const flow = [];

  if (arg.picker) {
    if (typeof arg.picker == 'function') flow.push(arg.picker);
    else flow.push(_.pick(arg.picker));
  }

  if (arg.defaults) {
    flow.push((obj) => {
      console.log('defaults => ', obj);
      const a = _.defaults(arg.defaults)(obj);
            console.log('defaults after => ', a);
      return a;
    });
  }

  if (arg.omiter) {
    if (typeof arg.omiter == 'function') flow.push(arg.omiter);
    else flow.push(_.omit(arg.omiter));
  }

  flow.push(transformSubObjects);
  flow.push(transformFlatKeys);

  const ff = _.flow(flow);

  return obj => ff(obj);
}


/**
*
* Sample code
*
*/


// mappings
const adressMapping = {
  cityPlace: 'city'
}

const contactMapping = {
  managerId: 'manager_id',
  test: '100',
  adress: {
    key: 'location',
    picker: ['cityPlace', 'postal'],
    mapping: adressMapping,
    defaults: {
      number: '100',
    }
  }
};

const userMapping = {
  n1Id: 'n1_id',
  contact: {
    omiter: ['fieldIdontWant'],
    defaults:{
      firstname: 'Cyndie',
      adress: {},
    },
    mapping: contactMapping,
  },
};


// data
const user = {
  n1Id: 10,
  firstname: 'Alex',
  contact: {
    managerId: 10,
    id: 10,
    fieldIdontWant: 'COUCOU',
    adress: {
      cityPlace: 'Orsay'
    }
  },
};


const transformer = mapper({
  mapping: userMapping,
  picker: ['n1Id', 'firstname', 'contact'],
  defaults: {
    lastname: '',
  }
});


const sU = transformer(user);

console.log(sU);