accounts-frontend/packages/app/components/ui/motion/SlideMotion.tsx

import React from 'react';
import { Motion, spring } from 'react-motion';

import MeasureHeight from 'app/components/MeasureHeight';

import styles from './slide-motion.scss';

interface Props {
  activeStep: number;
  children: React.ReactNode;
}

interface State {
  version: string;
  prevChildren: React.ReactNode | undefined;
  stepsHeights: Record<Props['activeStep'], number>;
}

class SlideMotion extends React.PureComponent<Props, State> {
  state: State = {
    prevChildren: undefined, // to track version updates
    version: `${this.props.activeStep}.0`,
    stepsHeights: [],
  };

  private isHeightMeasured: boolean;

  static getDerivedStateFromProps(props: Props, state: State) {
    let [, version] = state.version.split('.').map(Number);

    if (props.children !== state.prevChildren) {
      version++;
    }

    // mark this view as dirty to re-measure height
    return {
      prevChildren: props.children,
      version: `${props.activeStep}.${version}`,
    };
  }

  render() {
    const { activeStep, children } = this.props;

    const { version } = this.state;

    const activeStepHeight = this.state.stepsHeights[activeStep] || 0;

    // a hack to disable height animation on first render
    const { isHeightMeasured } = this;
    this.isHeightMeasured = isHeightMeasured || activeStepHeight > 0;

    const motionStyle = {
      transform: spring(activeStep * 100, {
        stiffness: 500,
        damping: 50,
        precision: 0.5,
      }),
      height: isHeightMeasured
        ? spring(activeStepHeight, {
            stiffness: 500,
            damping: 20,
            precision: 0.5,
          })
        : activeStepHeight,
    };

    return (
      <Motion style={motionStyle}>
        {(interpolatingStyle) => (
          <div
            style={{
              overflow: 'hidden',
              height: `${interpolatingStyle.height}px`,
            }}
          >
            <div
              className={styles.container}
              style={{
                WebkitTransform: `translateX(-${interpolatingStyle.transform}%)`,
                transform: `translateX(-${interpolatingStyle.transform}%)`,
              }}
            >
              {React.Children.map(children, (child, index) => (
                <MeasureHeight
                  className={styles.item}
                  onMeasure={this.onStepMeasure(index)}
                  state={version}
                  key={index}
                >
                  {child}
                </MeasureHeight>
              ))}
            </div>
          </div>
        )}
      </Motion>
    );
  }

  onStepMeasure = (step: number) => (height: number) => {
    this.setState({
      stepsHeights: {
        ...this.state.stepsHeights,
        [step]: height,
      },
    });
  };
}

export default SlideMotion;