WeatherTool/web/src/cities/helpers.ts

import moment from "moment";

export function formatDateString(str: string): string {
    const date = moment(new Date(str));
    switch (str.length) {
      // year: 2023
      case 4: return date.format("yyyy");
      // year-month: 2023-06
      case 7: return date.format("yyyy-MM");
      // year-month-day: 2023-06-23
      case 10: return date.format("yyyy-MM-DD");
      // year-month-day hour:minute 2023-06-23T23:59
      default: return date.format("HH:mm");
    }
}

export interface QueryResult {
    query: DataQuery;
    result: {[key: string]: any};
}

export interface DataQuery {
    cities: string[];
    field: string;
    granularity: string;
    key: string;
}

export function isQueryResult(variable: any): variable is QueryResult {
    return variable
        && variable.query
        && isDataQuery(variable.query)
        && variable.result
        && (
            typeof variable.result === "object"
            && !Array.isArray(variable.result)
            && variable.result !== null
        );
}

export function isDataQuery(variable: any): variable is DataQuery {
  return variable && 
      Array.isArray(variable.cities) && 
      typeof variable.field === 'string' && 
      typeof variable.granularity === 'string' &&
      typeof variable.key === 'string';
}