cli.ts

import axios, { AxiosInstance } from 'axios';
import moment from 'moment';
import * as readline from 'readline';

const FIELDS = ['applicant', 'location', 'DayOrder', 'start24', 'end24'];

const serializeFields = (fields: string[]) =>
  fields.map(field => `\`${field}\``).join(',');

const range = (start: number, end: number) =>
  Array.from({ length: end - start }, (_, i) => i + start);

const getDateFilter = () => {
  const now = moment();
  const mapHourToString = (hour: number) => moment()
    .startOf('day')
    .set('hour', hour)
    .format('HH:mm')
  const startHours = range(0, now.hour()).map(mapHourToString);
  const endHours = range(now.add(1, 'hour').hour(), 24).map(mapHourToString);
  const startHourQuery = startHours.map(hour => `start24='${hour}'`).join(' OR ');
  const endHourQuery = endHours.map(hour => `end24='${hour}'`).join(' OR ');
  return `(${startHourQuery}) AND (${endHourQuery})`;
};

/**
 * Resource for food trucks.
 */
class FoodTrucks {
  private instance: AxiosInstance;

  constructor(resource: string) {
    // Create an individual scoped axios instance for this food truck instance.
    this.instance = axios.create({
      baseURL: resource,
    });
  }

  getPage(page: number, increment: number = 10) {
    return this.instance.get('/', {
      params: {
        DayOrder: moment().day(),
        $where: getDateFilter(),
        $limit: increment,
        $offset: page * increment,
        $select: serializeFields(FIELDS),
        $order: 'applicant',
      },
    });
  }

  async *[Symbol.asyncIterator]() {
    let page = 0;
    while (true) {
      const { status, data } = await this.getPage(page);
      if (data.length && status === 200) {
        yield { data, page };
      }
      page += 1;
    }
  }
}

/**
 * Starts the CLI and prompts for input.
 */
async function start() {
  const trucks = new FoodTrucks('https://data.sfgov.org/resource/bbb8-hzi6.json');

  const cli = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  });

  // Promisify
  const prompt = () =>
    new Promise((resolve, reject) => {
      cli.question('Load more? ("next" to load more)\t', answer => {
        if (answer === 'next') {
          resolve();
          // If not "yes" specifically, will exit.
        } else {
          reject(new Error('Unrecognized command'));
        }
      });
    });

  try {
    for await (const { data, page } of trucks) {
      console.log('Page', page);
      console.table(data);
      await prompt();
    }
    console.log('No more results');
    // Not sure of the intended behavior here. Assume close and exit.
    cli.close();
    process.exit();
  } catch (e) {
    console.log(e.message);
    cli.close();
  }
}

start();