All files PaginationStream.ts

94.11% Statements 32/34
90.9% Branches 10/11
100% Functions 3/3
94.11% Lines 32/34

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import { Readable } from 'stream'
import { PaginationList, PaginationListWithCount } from './apiTypes.js'
 
// eslint-disable-next-line no-unused-vars
type FetchPage<T> = (
  pageno: number
) =>
  | PaginationList<T>
  | PromiseLike<PaginationList<T>>
  | PaginationListWithCount<T>
  | PromiseLike<PaginationListWithCount<T>>
 
export default class PaginationStream<T> extends Readable {
  private _fetchPage: FetchPage<T>
 
  private _nitems?: number
 
  private _pageno = 0
 
  private _items: T[] = []
 
  private _itemsRead = 0
 
  constructor(fetchPage: FetchPage<T>) {
    super({ objectMode: true })
    this._fetchPage = fetchPage
  }
 
  override async _read() {
    if (this._items.length > 0) {
      this._itemsRead++
      process.nextTick(() => this.push(this._items.pop()))
      return
    }
 
    if (this._nitems != null && this._itemsRead >= this._nitems) {
      process.nextTick(() => this.push(null))
      return
    }
 
    try {
      const { items, ...rest } = await this._fetchPage(++this._pageno)
      if ('count' in rest) {
        this._nitems = rest.count
      }
 
      this._items = Array.from(items)
      this._items.reverse()
 
      this._read()
    } catch (err) {
      this.emit('error', err)
    }
  }
}