import * as moment from 'moment';

/*
 * groups an array of object into an object of arrays,
 * with as a key an identifier that is shared between
 * the array's objects that should be grouped
 */
export function groupBy(array: Object[], identifier: string | ((item: Object) => any)) {
  return array.reduce((groupedValues, currentValue) => {
    const id = typeof identifier === 'string' ? currentValue[identifier] : identifier(currentValue);

    if (!groupedValues[id]) {
      groupedValues[id] = [currentValue];
    } else {
      groupedValues[id].push(currentValue);
    }

    return groupedValues;
  }, {});
}

/*
 * returns the last n items of the given array,
 * or all of them if the desired count is greater than the items in the array
 */
export function lastItems(array: any[], count: number) {
  return array.length > count ? array.slice(array.length - count) : array;
}


/*
/* turns Date into string of format 'HH:mm:ss'
*/
export function dateToDaytime(date: Date) {
  return `${date.getHours()}:${date.getMinutes()}:${date.getSeconds()}`;
}

/**
 * TODO: FIND A (non-optimal) solution for correct dateparsing in safari
 * @param string datetime string
 */
export function parseDate(string: string): Date {
  return moment(string).toDate();
}

/**
 * turns a UTC datestring into a Date
 * @param string string representing UTC date
 */
export function stringToUTCDate(string: string): Date {
  const date = new Date(string);
  return new Date(
    Date.UTC(
      date.getFullYear(),
      date.getMonth(),
      date.getDate(),
      date.getHours(),
      date.getMinutes(),
      date.getSeconds(),
    )
  );
}