vscroll/dist/esm2015/processes/adapter/insert.js

Virtual scroll engine

import Update from './update';
import { BaseAdapterProcessFactory, AdapterProcess, ProcessStatus } from '../misc/index';
import { Item } from '../../classes/item';
import { Direction } from '../../inputs/index';
export default class Insert extends BaseAdapterProcessFactory(AdapterProcess.insert) {
  static run(scroller, options) {
    const { params } = Insert.parseInput(scroller, options);
    if (!params) {
      return;
    }
    const shouldInsert = Insert.doInsert(scroller, params);
    scroller.workflow.call({
      process: Insert.process,
      status: shouldInsert ? ProcessStatus.next : ProcessStatus.done
    });
  }
  static doInsert(scroller, params) {
    if (!Insert.insertEmpty(scroller, params)) {
      if (!Insert.insertInBuffer(scroller, params)) {
        if (!Insert.insertVirtually(scroller, params)) {
          return false;
        }
      }
    }
    return true;
  }
  static insertEmpty(scroller, params) {
    const { buffer, routines, state: { fetch } } = scroller;
    if (buffer.size) {
      return false;
    }
    const { beforeIndex, afterIndex, items, decrease } = params;
    if (!buffer.fillEmpty(items, beforeIndex, afterIndex, !!decrease, (index, data) => new Item(index, data, routines))) {
      return false;
    }
    fetch.fill(buffer.items, buffer.startIndex);
    return true;
  }
  static insertInBuffer(scroller, params) {
    const { before, after, beforeIndex, afterIndex, items, decrease } = params;
    const indexToInsert = scroller.buffer.getIndexToInsert(before || after, beforeIndex, afterIndex);
    if (params.virtualize || isNaN(indexToInsert)) {
      return false;
    }
    const isBackward = Number.isInteger(beforeIndex) || before;
    const updateOptions = {
      predicate: ({ $index, data }) => {
        if (indexToInsert === $index) {
          return isBackward ? [...items, data] : [data, ...items];
        }
        return true;
      },
      fixRight: decrease
    };
    return Update.doUpdate(scroller, updateOptions);
  }
  static insertVirtually(scroller, params) {
    const { beforeIndex, afterIndex, items, decrease } = params;
    const { buffer, state: { fetch }, viewport } = scroller;
    const direction = Number.isInteger(beforeIndex) ? Direction.backward : Direction.forward;
    const indexToInsert = (direction === Direction.backward ? beforeIndex : afterIndex);
    if (!buffer.insertVirtually(items, indexToInsert, direction, !!decrease)) {
      return false;
    }
    const { index, diff } = viewport.getEdgeVisibleItem(buffer.items, Direction.backward);
    fetch.firstVisible.index = index;
    if (!isNaN(index)) {
      fetch.simulate = true;
      fetch.firstVisible.delta = -buffer.getSizeByIndex(index) + diff;
    }
    return true;
  }
}
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