freeCodeCamp/common/app/routes/challenges/components/step/Step.jsx

import React, { PropTypes } from 'react';
import classnames from 'classnames';
import { connect } from 'react-redux';
import { createSelector } from 'reselect';
import { goToStep } from '../../redux/actions';
import PureComponent from 'react-pure-render/component';
import ReactTransitionReplace from 'react-css-transition-replace';

import { Button, Col, Image, Row } from 'react-bootstrap';

const transitionTimeout = 1000;
const mapStateToProps = createSelector(
  state => state.challengesApp.currentStep,
  state => state.challengesApp.previousStep,
  (currentStep, previousStep) => ({
    currentStep,
    previousStep,
    isGoingForward: currentStep > previousStep
  })
);

const dispatchActions = {
  goToStep
};

export class StepChallenge extends PureComponent {
  static displayName = 'StepChallenge';
  static defaultProps = {
    currentStep: 0,
    previousStep: -1
  };

  static propTypes = {
    challenge: PropTypes.object,
    currentStep: PropTypes.number,
    previousStep: PropTypes.number,
    isGoingForward: PropTypes.bool,
    goToStep: PropTypes.func
  };

  renderActionButton(action) {
    if (!action) {
      return null;
    }
    return (
      <div>
        <Button
          block={ true }
          bsSize='large'
          bsStyle='primary'
          href={ action }
          target='_blank'>
          Open link in new tab (this unlocks the next step)
        </Button>
        <div className='spacer' />
      </div>
    );
  }

  renderBackButton(index) {
    const { goToStep } = this.props;
    if (index === 0) {
      return (
        <Col
          className='hidden-xs'
          md={ 4 }>
          { ' ' }
        </Col>
      );
    }
    return (
      <Button
        bsSize='large'
        bsStyle='primary'
        className='col-sm-4 col-xs-12'
        onClick={ () => goToStep(index - 1) }>
        Go to my previous step
      </Button>
    );
  }

  renderNextButton(hasAction, index, numOfSteps, isCompleted) {
    const { goToStep } = this.props;
    const isLastStep = index + 1 >= numOfSteps;
    const btnClass = classnames({
      'col-sm-4 col-xs-12': true,
      disabled: hasAction && !isCompleted
    });
    return (
      <Button
        bsSize='large'
        bsStyle='primary'
        className={ btnClass }
        onClick={ () => !isLastStep ? goToStep(index + 1) : () => {} }>
        { isLastStep ? 'Finish challenge' : 'Go to my next step'}
      </Button>
    );
  }

  renderStep(step, currentStep, numOfSteps) {
    if (!Array.isArray(step)) {
      return null;
    }
    const [imgUrl, imgAlt, info, action] = step;
    return (
      <div
        className=''
        key={ imgUrl }>
        <a href={ imgUrl }>
          <Image
            alt={ imgAlt }
            responsive={ true }
            src={ imgUrl } />
        </a>
        <Row>
          <div className='spacer' />
          <Col
            md={ 8 }
            mdOffset={ 2 }
            sm={ 10 }
            smOffset={ 1 }
            xs={ 12 }>
            <p
              className='challenge-step-description'
              dangerouslySetInnerHTML={{ __html: info }} />
          </Col>
        </Row>
        <div className='spacer' />
        <div className='challenge-button-block'>
          { this.renderActionButton(action) }
          { this.renderBackButton(currentStep) }
          <Col
            className='challenge-step-counter large-p text-center'
            sm={ 4 }
            xs={ 12 }>
            ( { currentStep + 1 } / { numOfSteps })
          </Col>
          {
            this.renderNextButton(
              !!action,
              currentStep,
              numOfSteps,
              true
            )
          }
        </div>
        <div className='clearfix' />
      </div>
    );
  }

  renderImages(steps) {
    // will preload all the image
    if (!Array.isArray(steps)) {
      return null;
    }
    return steps.map(([imgUrl, imgAlt]) => (
      <div key={ imgUrl }>
        <Image
          alt={ imgAlt }
          responsive={ true }
          src={ imgUrl } />
      </div>
    ));
  }

  render() {
    const { challenge, currentStep, isGoingForward } = this.props;
    const numOfSteps = Array.isArray(challenge.description) ?
      challenge.description.length :
      0;
    const step = challenge.description[currentStep];
    const transitionName = 'challenge-step-' +
      (isGoingForward ? 'forward' : 'backward');

    return (
      <Col
        md={ 8 }
        mdOffset={ 2 }>
        <ReactTransitionReplace
          transitionEnterTimeout={ transitionTimeout }
          transitionLeaveTimeout={ transitionTimeout }
          transitionName={ transitionName }>
          { this.renderStep(step, currentStep, numOfSteps) }
        </ReactTransitionReplace>
        <div className='hidden'>
          { this.renderImages(challenge.description) }
        </div>
        <div className='spacer' />
      </Col>
    );
  }
}

export default connect(mapStateToProps, dispatchActions)(StepChallenge);