algorithm-visualizer/src/components/ResizableContainer/index.js

import React from 'react';
import { classes } from 'common/util';
import { Divider } from 'components';
import styles from './ResizableContainer.module.scss';

class ResizableContainer extends React.Component {
  handleResize(prevIndex, index, targetElement, clientX, clientY) {
    const { horizontal, visibles, onChangeWeights } = this.props;
    const weights = [...this.props.weights];

    const { left, top } = targetElement.getBoundingClientRect();
    const { offsetWidth, offsetHeight } = targetElement.parentElement;
    const position = horizontal ? clientX - left : clientY - top;
    const containerSize = horizontal ? offsetWidth : offsetHeight;

    let totalWeight = 0;
    let subtotalWeight = 0;
    weights.forEach((weight, i) => {
      if (visibles && !visibles[i]) return;
      totalWeight += weight;
      if (i < index) subtotalWeight += weight;
    });
    const newWeight = position / containerSize * totalWeight;
    let deltaWeight = newWeight - subtotalWeight;
    deltaWeight = Math.max(deltaWeight, -weights[prevIndex]);
    deltaWeight = Math.min(deltaWeight, weights[index]);
    weights[prevIndex] += deltaWeight;
    weights[index] -= deltaWeight;
    onChangeWeights(weights);
  }

  render() {
    const { className, children, horizontal, weights, visibles } = this.props;

    const elements = [];
    let lastIndex = -1;
    const totalWeight = weights.filter((weight, i) => !visibles || visibles[i])
      .reduce((sumWeight, weight) => sumWeight + weight, 0);
    children.forEach((child, i) => {
      if (!visibles || visibles[i]) {
        if (~lastIndex) {
          const prevIndex = lastIndex;
          elements.push(
            <Divider key={`divider-${i}`} horizontal={horizontal}
                     onResize={((target, dx, dy) => this.handleResize(prevIndex, i, target, dx, dy))} />,
          );
        }
        elements.push(
          <div key={i} className={classes(styles.wrapper)} style={{
            flexGrow: weights[i] / totalWeight,
          }}>
            {child}
          </div>,
        );
        lastIndex = i;
      }
    });

    return (
      <div className={classes(styles.resizable_container, horizontal && styles.horizontal, className)}>
        {elements}
      </div>
    );
  }
}

export default ResizableContainer;