meyfa/ka-mensa-api

import { formatDate, parseDate } from './util/date-format.js'
import type { Adapter } from 'fs-adapters'
import type { CanteenPlan, DateSpec } from 'ka-mensa-fetch'
 
/**
 * ENOENT error code.
 */
const ENOENT = 'ENOENT'
 
/**
 * Build the file name from the given date object.
 *
 * @param date The date object.
 * @returns The file name.
 */
function buildFileName (date: DateSpec): string {
  return `${formatDate(date)}.json`
}
 
/**
 * A cache directory manager, providing retrieval and insertion of canteen plans.
 */
export class Cache {
  private readonly fsAdapter: Adapter
 
  /**
   * Construct a new Cache with the specified file system adapter.
   *
   * @param fsAdapter The I/O interface.
   */
  constructor (fsAdapter: Adapter) {
    this.fsAdapter = fsAdapter
  }
 
  /**
   * Get the cache contents for the given date.
   *
   * If the cache does not contain data for the given date, returns undefined.
   *
   * @param date The date object.
   * @returns Resolves to the cache contents, or undefined if not cached.
   */
  async get (date: DateSpec): Promise<CanteenPlan[] | undefined> {
    const file = buildFileName(date)
 
    try {
      const contents = await this.fsAdapter.read(file, { encoding: 'utf8' }) as string
      return JSON.parse(contents)
    } catch (e: any) {
      if (e?.code === ENOENT) {
        // missing file - item not found
        return undefined
      }
      // some more critical error
      throw e
    }
  }
 
  /**
   * Insert the contents into the cache for the given date.
   *
   * @param date The date object.
   * @param contents The cache contents (array of plans for the date).
   * @returns Resolves when done.
   */
  async put (date: DateSpec, contents: CanteenPlan[]): Promise<void> {
    const file = buildFileName(date)
    await this.fsAdapter.write(file, JSON.stringify(contents))
  }
 
  /**
   * Obtain a list of all cached plans, in unspecified order.
   *
   * @returns Resolves to an array of date objects.
   */
  async list (): Promise<DateSpec[]> {
    return (await this.fsAdapter.listFiles())
      .map((file) => file.endsWith('.json') ? parseDate(file.slice(0, file.lastIndexOf('.'))) : undefined)
      .filter((date: DateSpec | undefined): date is DateSpec => date != null)
  }
}