#app

@import url('https://fonts.googleapis.com/css?family=Playfair+Display:700|IBM+Plex+Sans:500&display=swap');

:root {
  --color-primary: #6B7A8F;
  --color-secondary: #101118;
  --color-accent: #1D1F2F;
  --color-focus: #6D64F7;
  --base-duration: 600ms;
  --base-ease: cubic-bezier(0.25, 0.46, 0.45, 0.84);
}

// =========================
// Global
// =========================

*, *:before, *:after {
  box-sizing: border-box;
}

html, body {
  height: 100%;
}

body {
  font-family: 'IBM Plex Sans', sans-serif;
  background-color: var(--color-secondary);
}

#app {
  align-items: center;
  display: flex;
  height: 100%;
  justify-content: center;
  overflow-x: hidden;
  width: 100%;
}

h1, h2, h3 {
  font-family: 'Playfair Display', serif;
}

.visuallyhidden { 
  clip: rect(1px, 1px, 1px, 1px);  
  height: 1px; 
  overflow: hidden;
  position: absolute !important;
  white-space: nowrap;
  width: 1px;
}


// =========================
// Icons
// =========================

.icon {
  fill: var(--color-primary);
  width: 100%;
}


// =========================
// Buttons
// =========================

.btn {
  background-color: var(--color-primary);
  border: none;
  border-radius: 0.125rem;
  color: white;
  cursor: pointer;
  font-family: inherit;
  font-size: inherit;
  padding: 1rem 2.5rem 1.125rem;
  
  &:focus {
    outline-color: var(--color-focus);
    outline-offset: 2px;
    outline-style: solid;
    outline-width: 3px;
  }
  
  &:active {
    transform: translateY(1px);
  }
}


// =========================
// Slider controls
// =========================

.slider__controls {
  display: flex;
  justify-content: center;
  position: absolute;
  top: calc(100% + 1rem);
  width: 100%;
  
  .btn {
    --size: 3rem;
    
    align-items: center;
    background-color: transparent;
    border: 3px solid transparent;
    border-radius: 100%;
    display: flex;
    height: var(--size);
    padding: 0;
    width: var(--size);
    
    &:focus {
      border-color: var(--color-focus);
      outline: none;
    }
        
    &--previous > * {
      transform: rotate(180deg);
    }
  }
}


// =========================
// Slider
// =========================

.slider {
  --slide-size: 70vmin;
  --slide-margin: 4vmin;
  
  height: var(--slide-size);
  margin: 0 auto;
  position: relative;
  width: var(--slide-size);
}

.slider__wrapper {
  display: flex;
  margin: 0 calc(var(--slide-margin) * -1);
  position: absolute;
  transition: transform var(--base-duration) cubic-bezier(0.25, 1, 0.35, 1);
}


// =========================
// Slide
// =========================

.slide {
  align-items: center;
  color: white;
  display: flex;
  flex: 1;
  flex-direction: column;
  height: var(--slide-size);
  justify-content: center;
  margin: 0 var(--slide-margin);
  opacity: 0.25;
  position: relative;
  text-align: center;
  transition: 
    opacity calc(var(--base-duration) / 2) var(--base-ease),
    transform calc(var(--base-duration) / 2) var(--base-ease);
  width: var(--slide-size);
  z-index: 1;
  
  &--previous,
  &--next {    
    &:hover {
      opacity: 0.5;
    }
  }
  
  &--previous {
    cursor: w-resize;
    
    &:hover {
      transform: translateX(2%);
    }
  }
  
  &--next {
    cursor: e-resize;
    
    &:hover {
      transform: translateX(-2%);
    }
  }
}

.slide--current {
  --x: 0;
  --y: 0;
  --d: 50;

  opacity: 1;
  pointer-events: auto;
  user-select: auto;
  
  @media (hover: hover) {
    &:hover .slide__image-wrapper {
      transform: 
        scale(1.025)
        translate(
          calc(var(--x) / var(--d) * 1px),
          calc(var(--y) / var(--d) * 1px)
        );
    }    
  }
}

.slide__image-wrapper {
  background-color: var(--color-accent);
  border-radius: 1%;
  height: 100%;
  left: 0%;
  overflow: hidden;
  position: absolute;
  top: 0%;  
  transition: transform calc(var(--base-duration) / 4) var(--base-ease);
  width: 100%;
}

.slide__image {
  --d: 20;
  
  height: 110%;
  left: -5%;
  object-fit: cover;
  opacity: 0;
  pointer-events: none;
  position: absolute;
  top: -5%;
  transition:
    opacity var(--base-duration) var(--base-ease),
    transform var(--base-duration) var(--base-ease);
  user-select: none;
  width: 110%;
  
  @media (hover: hover) {
    .slide--current & {      
      transform: 
        translate(
          calc(var(--x) / var(--d) * 1px),
          calc(var(--y) / var(--d) * 1px)
        ); 
    }
  }
}

.slide__headline {
  font-size: 8vmin;
  font-weight: 600;
  position: relative;
}

.slide__content {
  --d: 60;
  
  opacity: 0;
  padding: 4vmin;
  position: relative;
  transition: transform var(--base-duration) var(--base-ease);
  visibility: hidden;
  
  .slide--current & {
    animation: fade-in calc(var(--base-duration) / 2) var(--base-ease) forwards;
    visibility: visible;
    
    @media (hover: hover) {
      transform: 
        translate(
          calc(var(--x) / var(--d) * -1px),
          calc(var(--y) / var(--d) * -1px)
        );
    }
  }
  
  > * + * {
    margin-top: 2rem;
  }
}


// =========================
// Animations
// =========================

@keyframes fade-in {
  from { opacity: 0 }
  to   { opacity: 1 }
}

const slideData = [
  {
    index: 0,
    headline: 'New Fashion Apparel',
    button: 'Shop now',
    src: 'https://s3-us-west-2.amazonaws.com/s.cdpn.io/225363/fashion.jpg'
  },
  {
    index: 1,
    headline: 'In The Wilderness',
    button: 'Book travel',
    src: 'https://s3-us-west-2.amazonaws.com/s.cdpn.io/225363/forest.jpg'
  },
  {
    index: 2,
    headline: 'For Your Current Mood',
    button: 'Listen',
    src: 'https://s3-us-west-2.amazonaws.com/s.cdpn.io/225363/guitar.jpg'
  },
  {
    index: 3,
    headline: 'Focus On The Writing',
    button: 'Get Focused',
    src: 'https://s3-us-west-2.amazonaws.com/s.cdpn.io/225363/typewriter.jpg'
  }
]


// =========================
// Slide
// =========================

class Slide extends React.Component {
  constructor(props) {
    super(props)

    this.handleMouseMove = this.handleMouseMove.bind(this)
    this.handleMouseLeave = this.handleMouseLeave.bind(this)
    this.handleSlideClick = this.handleSlideClick.bind(this)
    this.imageLoaded = this.imageLoaded.bind(this)
    this.slide = React.createRef()
  }
  
  handleMouseMove(event) {
    const el = this.slide.current
    const r = el.getBoundingClientRect()

    el.style.setProperty('--x', event.clientX - (r.left + Math.floor(r.width / 2)))
    el.style.setProperty('--y', event.clientY - (r.top + Math.floor(r.height / 2)))
  }
  
  handleMouseLeave(event) {    
    this.slide.current.style.setProperty('--x', 0)
    this.slide.current.style.setProperty('--y', 0)
  }
  
  handleSlideClick(event) {
    this.props.handleSlideClick(this.props.slide.index)
  }
  
  imageLoaded(event) {
    event.target.style.opacity = 1
  }
  
  render() {
    const { src, button, headline, index } = this.props.slide
    const current = this.props.current
    let classNames = 'slide'
    
    if (current === index) classNames += ' slide--current'
    else if (current - 1 === index) classNames += ' slide--previous'
    else if (current + 1 === index) classNames += ' slide--next'
        
    return (
      <li 
        ref={this.slide}
        className={classNames} 
        onClick={this.handleSlideClick}
        onMouseMove={this.handleMouseMove}
        onMouseLeave={this.handleMouseLeave}
      >
        <div className="slide__image-wrapper">
          <img 
            className="slide__image"
            alt={headline}
            src={src}
            onLoad={this.imageLoaded}
          />
        </div>
        
        <article className="slide__content">
          <h2 className="slide__headline">{headline}</h2>
          <button className="slide__action btn">{button}</button>
        </article>
      </li>
    )
  }
}


// =========================
// Slider control
// =========================

const SliderControl = ({ type, title, handleClick }) => {
  return (
    <button className={`btn btn--${type}`} title={title} onClick={handleClick}>
      <svg className="icon" viewBox="0 0 24 24">
        <path d="M8.59,16.58L13.17,12L8.59,7.41L10,6L16,12L10,18L8.59,16.58Z" />
      </svg>
    </button>
  )
}


// =========================
// Slider
// =========================

class Slider extends React.Component {
  constructor(props) {
    super(props)
    
    this.state = { current: 0 }
    this.handlePreviousClick = this.handlePreviousClick.bind(this)
    this.handleNextClick = this.handleNextClick.bind(this)
    this.handleSlideClick = this.handleSlideClick.bind(this)
  }
  
  handlePreviousClick() {
    const previous = this.state.current - 1
        
    this.setState({ 
      current: (previous < 0) 
        ? this.props.slides.length - 1
        : previous
    })
  }
  
  handleNextClick() {
    const next = this.state.current + 1;
    
    this.setState({ 
      current: (next === this.props.slides.length) 
        ? 0
        : next
    })
  }
  
  handleSlideClick(index) {
    if (this.state.current !== index) {
      this.setState({
        current: index
      })
    }
  }

  render() {
    const { current, direction } = this.state
    const { slides, heading } = this.props 
    const headingId = `slider-heading__${heading.replace(/\s+/g, '-').toLowerCase()}`
    const wrapperTransform = {
      'transform': `translateX(-${current * (100 / slides.length)}%)`
    }
    
    return (
      <div className='slider' aria-labelledby={headingId}>
        <ul className="slider__wrapper" style={wrapperTransform}>
          <h3 id={headingId} class="visuallyhidden">{heading}</h3>
          
          {slides.map(slide => {
            return (
              <Slide
                key={slide.index}
                slide={slide}
                current={current}
                handleSlideClick={this.handleSlideClick}
              />
            )
          })}
        </ul>
        
        <div className="slider__controls">
          <SliderControl 
            type="previous"
            title="Go to previous slide"
            handleClick={this.handlePreviousClick}
          />
          
          <SliderControl 
            type="next"
            title="Go to next slide"
            handleClick={this.handleNextClick}
          />
        </div>
      </div>
    )
  }
}


ReactDOM.render(<Slider heading="Example Slider" slides={slideData} />, document.getElementById('app'));