vscroll/dist/esm2015/processes/postFetch.js

Virtual scroll engine

import { BaseProcessFactory, CommonProcess, ProcessStatus } from './misc/index';
import { Item } from '../classes/item';
export default class PostFetch extends BaseProcessFactory(CommonProcess.postFetch) {
  static run(scroller) {
    const { workflow } = scroller;
    if (PostFetch.setItems(scroller)) {
      PostFetch.setBufferLimits(scroller);
      workflow.call({
        process: PostFetch.process,
        status: scroller.state.fetch.hasNewItems
          ? ProcessStatus.next
          : ProcessStatus.done
      });
    }
    else {
      workflow.call({
        process: PostFetch.process,
        status: ProcessStatus.error,
        payload: { error: 'Can\'t set buffer items' }
      });
    }
  }
  static setBufferLimits(scroller) {
    const { buffer, state: { fetch, cycle: { innerLoop } } } = scroller;
    const { items, first: { index: first }, last: { index: last } } = fetch;
    if (!items.length) {
      if (last < buffer.minIndex || innerLoop.isInitial) {
        buffer.absMinIndex = buffer.minIndex;
      }
      if (first > buffer.maxIndex || innerLoop.isInitial) {
        buffer.absMaxIndex = buffer.maxIndex;
      }
    }
    else {
      const lastIndex = items.length - 1;
      if (first < items[0].$index) {
        buffer.absMinIndex = items[0].$index;
      }
      if (last > items[lastIndex].$index) {
        buffer.absMaxIndex = items[lastIndex].$index;
      }
    }
  }
  static setItems(scroller) {
    const { buffer, state: { fetch, cycle } } = scroller;
    const items = fetch.newItemsData;
    if (!items || !items.length) { // empty result
      return true;
    }
    // eof/bof case, need to shift fetch index if bof
    let fetchIndex = fetch.index;
    if (items.length < fetch.count) {
      if (cycle.innerLoop.isInitial) {
        // let's treat initial poor fetch as startIndex-bof
        fetchIndex = buffer.startIndex;
      }
      else if (fetch.first.index < buffer.minIndex) {
        // normal bof
        fetchIndex = buffer.firstIndex - items.length;
      }
    }
    fetch.items = items.map((item, index) => new Item(fetchIndex + index, item, scroller.routines));
    return buffer.setItems(fetch.items);
  }
}
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