import { createVNode } from 'vue';
import classnames from 'classnames';
import { cloneElement } from '../../_util/vnode';
import { flattenChildren } from '../../_util/props-util';
import { lazyStartIndex, lazyEndIndex, getPreClones } from './utils/innerSliderUtils';

// given specifications/props for a slide, fetch all the classes that need to be applied to the slide
const getSlideClasses = spec => {
  let slickActive, slickCenter;
  let centerOffset, index;

  if (spec.rtl) {
    index = spec.slideCount - 1 - spec.index;
  } else {
    index = spec.index;
  }
  const slickCloned = index < 0 || index >= spec.slideCount;
  if (spec.centerMode) {
    centerOffset = Math.floor(spec.slidesToShow / 2);
    slickCenter = (index - spec.currentSlide) % spec.slideCount === 0;
    if (index > spec.currentSlide - centerOffset - 1 && index <= spec.currentSlide + centerOffset) {
      slickActive = true;
    }
  } else {
    slickActive = spec.currentSlide <= index && index < spec.currentSlide + spec.slidesToShow;
  }
  const slickCurrent = index === spec.currentSlide;
  return {
    'slick-slide': true,
    'slick-active': slickActive,
    'slick-center': slickCenter,
    'slick-cloned': slickCloned,
    'slick-current': slickCurrent, // dubious in case of RTL
  };
};

const getSlideStyle = function(spec) {
  const style = {};

  if (spec.variableWidth === undefined || spec.variableWidth === false) {
    style.width = spec.slideWidth + (typeof spec.slideWidth === 'number' ? 'px' : '');
  }

  if (spec.fade) {
    style.position = 'relative';
    if (spec.vertical) {
      style.top = -spec.index * parseInt(spec.slideHeight) + 'px';
    } else {
      style.left = -spec.index * parseInt(spec.slideWidth) + 'px';
    }
    style.opacity = spec.currentSlide === spec.index ? 1 : 0;
    style.transition =
      'opacity ' +
      spec.speed +
      'ms ' +
      spec.cssEase +
      ', ' +
      'visibility ' +
      spec.speed +
      'ms ' +
      spec.cssEase;
    style.WebkitTransition =
      'opacity ' +
      spec.speed +
      'ms ' +
      spec.cssEase +
      ', ' +
      'visibility ' +
      spec.speed +
      'ms ' +
      spec.cssEase;
  }

  return style;
};

const getKey = (child, fallbackKey) => child.key || (child.key === 0 && '0') || fallbackKey;

const renderSlides = function(spec, children) {
  let key;
  const slides = [];
  const preCloneSlides = [];
  const postCloneSlides = [];
  const childrenCount = children.length;
  const startIndex = lazyStartIndex(spec);
  const endIndex = lazyEndIndex(spec);

  children.forEach((elem, index) => {
    let child;
    const childOnClickOptions = {
      message: 'children',
      index,
      slidesToScroll: spec.slidesToScroll,
      currentSlide: spec.currentSlide,
    };

    // in case of lazyLoad, whether or not we want to fetch the slide
    if (!spec.lazyLoad || (spec.lazyLoad && spec.lazyLoadedList.indexOf(index) >= 0)) {
      child = elem;
    } else {
      child = createVNode('div');
    }
    const childStyle = getSlideStyle({ ...spec, index });
    const slideClass = child.props.class || '';
    let slideClasses = getSlideClasses({ ...spec, index });
    // push a cloned element of the desired slide
    slides.push(
      cloneElement(child, {
        key: 'original' + getKey(child, index),
        tabindex: '-1',
        'data-index': index,
        'aria-hidden': !slideClasses['slick-active'],
        class: classnames(slideClasses, slideClass),
        style: { outline: 'none', ...(child.props.style || {}), ...childStyle },
        onClick: () => {
          // child.props && child.props.onClick && child.props.onClick(e)
          if (spec.focusOnSelect) {
            spec.focusOnSelect(childOnClickOptions);
          }
        },
      }),
    );

    // if slide needs to be precloned or postcloned
    if (spec.infinite && spec.fade === false) {
      const preCloneNo = childrenCount - index;
      if (preCloneNo <= getPreClones(spec) && childrenCount !== spec.slidesToShow) {
        key = -preCloneNo;
        if (key >= startIndex) {
          child = elem;
        }
        slideClasses = getSlideClasses({ ...spec, index: key });
        preCloneSlides.push(
          cloneElement(child, {
            key: 'precloned' + getKey(child, key),
            class: classnames(slideClasses, slideClass),
            tabindex: '-1',
            'data-index': key,
            'aria-hidden': !slideClasses['slick-active'],
            style: { ...(child.props.style || {}), ...childStyle },
            onClick: () => {
              // child.props && child.props.onClick && child.props.onClick(e)
              if (spec.focusOnSelect) {
                spec.focusOnSelect(childOnClickOptions);
              }
            },
          }),
        );
      }

      if (childrenCount !== spec.slidesToShow) {
        key = childrenCount + index;
        if (key < endIndex) {
          child = elem;
        }
        slideClasses = getSlideClasses({ ...spec, index: key });
        postCloneSlides.push(
          cloneElement(child, {
            key: 'postcloned' + getKey(child, key),
            tabindex: '-1',
            'data-index': key,
            'aria-hidden': !slideClasses['slick-active'],
            class: classnames(slideClasses, slideClass),
            style: { ...(child.props.style || {}), ...childStyle },
            onClick: () => {
              // child.props && child.props.onClick && child.props.onClick(e)
              if (spec.focusOnSelect) {
                spec.focusOnSelect(childOnClickOptions);
              }
            },
          }),
        );
      }
    }
  });
  if (spec.rtl) {
    return preCloneSlides.concat(slides, postCloneSlides).reverse();
  } else {
    return preCloneSlides.concat(slides, postCloneSlides);
  }
};

const Track = (_, { attrs, slots }) => {
  const slides = renderSlides(attrs, flattenChildren(slots?.default()));
  const { onMouseenter, onMouseover, onMouseleave } = attrs;
  const mouseEvents = { onMouseenter, onMouseover, onMouseleave };
  const trackProps = {
    class: 'slick-track',
    style: attrs.trackStyle,
    ...mouseEvents,
  };
  return <div {...trackProps}>{slides}</div>;
};

Track.inheritAttrs = false;

export default Track;
