import { createElement, elementChildren, setCSSProperty } from '../../shared/utils.js';
export default function Virtual({
  swiper,
  extendParams,
  on,
  emit
}) {
  extendParams({
    virtual: {
      enabled: false,
      slides: [],
      cache: true,
      renderSlide: null,
      renderExternal: null,
      renderExternalUpdate: true,
      addSlidesBefore: 0,
      addSlidesAfter: 0
    }
  });
  let cssModeTimeout;
  swiper.virtual = {
    cache: {},
    from: undefined,
    to: undefined,
    slides: [],
    offset: 0,
    slidesGrid: []
  };
  const tempDOM = document.createElement('div');

  function renderSlide(slide, index) {
    const params = swiper.params.virtual;

    if (params.cache && swiper.virtual.cache[index]) {
      return swiper.virtual.cache[index];
    } // eslint-disable-next-line


    let slideEl;

    if (params.renderSlide) {
      slideEl = params.renderSlide.call(swiper, slide, index);

      if (typeof slideEl === 'string') {
        tempDOM.innerHTML = slideEl;
        slideEl = tempDOM.children[0];
      }
    } else if (swiper.isElement) {
      slideEl = createElement('swiper-slide');
    } else {
      slideEl = createElement('div', swiper.params.slideClass);
    }

    slideEl.setAttribute('data-swiper-slide-index', index);

    if (!params.renderSlide) {
      slideEl.textContent = slide;
    }

    if (params.cache) swiper.virtual.cache[index] = slideEl;
    return slideEl;
  }

  function update(force) {
    const {
      slidesPerView,
      slidesPerGroup,
      centeredSlides,
      loop: isLoop
    } = swiper.params;
    const {
      addSlidesBefore,
      addSlidesAfter
    } = swiper.params.virtual;
    const {
      from: previousFrom,
      to: previousTo,
      slides,
      slidesGrid: previousSlidesGrid,
      offset: previousOffset
    } = swiper.virtual;

    if (!swiper.params.cssMode) {
      swiper.updateActiveIndex();
    }

    const activeIndex = swiper.activeIndex || 0;
    let offsetProp;
    if (swiper.rtlTranslate) offsetProp = 'right';else offsetProp = swiper.isHorizontal() ? 'left' : 'top';
    let slidesAfter;
    let slidesBefore;

    if (centeredSlides) {
      slidesAfter = Math.floor(slidesPerView / 2) + slidesPerGroup + addSlidesAfter;
      slidesBefore = Math.floor(slidesPerView / 2) + slidesPerGroup + addSlidesBefore;
    } else {
      slidesAfter = slidesPerView + (slidesPerGroup - 1) + addSlidesAfter;
      slidesBefore = (isLoop ? slidesPerView : slidesPerGroup) + addSlidesBefore;
    }

    let from = activeIndex - slidesBefore;
    let to = activeIndex + slidesAfter;

    if (!isLoop) {
      from = Math.max(from, 0);
      to = Math.min(to, slides.length - 1);
    }

    let offset = (swiper.slidesGrid[from] || 0) - (swiper.slidesGrid[0] || 0);

    if (isLoop && activeIndex >= slidesBefore) {
      from -= slidesBefore;
      if (!centeredSlides) offset += swiper.slidesGrid[0];
    } else if (isLoop && activeIndex < slidesBefore) {
      from = -slidesBefore;
      if (centeredSlides) offset += swiper.slidesGrid[0];
    }

    Object.assign(swiper.virtual, {
      from,
      to,
      offset,
      slidesGrid: swiper.slidesGrid,
      slidesBefore,
      slidesAfter
    });

    function onRendered() {
      swiper.updateSlides();
      swiper.updateProgress();
      swiper.updateSlidesClasses();
      emit('virtualUpdate');
    }

    if (previousFrom === from && previousTo === to && !force) {
      if (swiper.slidesGrid !== previousSlidesGrid && offset !== previousOffset) {
        swiper.slides.forEach(slideEl => {
          slideEl.style[offsetProp] = `${offset}px`;
        });
      }

      swiper.updateProgress();
      emit('virtualUpdate');
      return;
    }

    if (swiper.params.virtual.renderExternal) {
      swiper.params.virtual.renderExternal.call(swiper, {
        offset,
        from,
        to,
        slides: function getSlides() {
          const slidesToRender = [];

          for (let i = from; i <= to; i += 1) {
            slidesToRender.push(slides[i]);
          }

          return slidesToRender;
        }()
      });

      if (swiper.params.virtual.renderExternalUpdate) {
        onRendered();
      } else {
        emit('virtualUpdate');
      }

      return;
    }

    const prependIndexes = [];
    const appendIndexes = [];

    const getSlideIndex = index => {
      let slideIndex = index;

      if (index < 0) {
        slideIndex = slides.length + index;
      } else if (slideIndex >= slides.length) {
        // eslint-disable-next-line
        slideIndex = slideIndex - slides.length;
      }

      return slideIndex;
    };

    if (force) {
      swiper.slidesEl.querySelectorAll(`.${swiper.params.slideClass}, swiper-slide`).forEach(slideEl => {
        slideEl.remove();
      });
    } else {
      for (let i = previousFrom; i <= previousTo; i += 1) {
        if (i < from || i > to) {
          const slideIndex = getSlideIndex(i);
          swiper.slidesEl.querySelectorAll(`.${swiper.params.slideClass}[data-swiper-slide-index="${slideIndex}"], swiper-slide[data-swiper-slide-index="${slideIndex}"]`).forEach(slideEl => {
            slideEl.remove();
          });
        }
      }
    }

    const loopFrom = isLoop ? -slides.length : 0;
    const loopTo = isLoop ? slides.length * 2 : slides.length;

    for (let i = loopFrom; i < loopTo; i += 1) {
      if (i >= from && i <= to) {
        const slideIndex = getSlideIndex(i);

        if (typeof previousTo === 'undefined' || force) {
          appendIndexes.push(slideIndex);
        } else {
          if (i > previousTo) appendIndexes.push(slideIndex);
          if (i < previousFrom) prependIndexes.push(slideIndex);
        }
      }
    }

    appendIndexes.forEach(index => {
      swiper.slidesEl.append(renderSlide(slides[index], index));
    });

    if (isLoop) {
      for (let i = prependIndexes.length - 1; i >= 0; i -= 1) {
        const index = prependIndexes[i];
        swiper.slidesEl.prepend(renderSlide(slides[index], index));
      }
    } else {
      prependIndexes.sort((a, b) => b - a);
      prependIndexes.forEach(index => {
        swiper.slidesEl.prepend(renderSlide(slides[index], index));
      });
    }

    elementChildren(swiper.slidesEl, '.swiper-slide, swiper-slide').forEach(slideEl => {
      slideEl.style[offsetProp] = `${offset}px`;
    });
    onRendered();
  }

  function appendSlide(slides) {
    if (typeof slides === 'object' && 'length' in slides) {
      for (let i = 0; i < slides.length; i += 1) {
        if (slides[i]) swiper.virtual.slides.push(slides[i]);
      }
    } else {
      swiper.virtual.slides.push(slides);
    }

    update(true);
  }

  function prependSlide(slides) {
    const activeIndex = swiper.activeIndex;
    let newActiveIndex = activeIndex + 1;
    let numberOfNewSlides = 1;

    if (Array.isArray(slides)) {
      for (let i = 0; i < slides.length; i += 1) {
        if (slides[i]) swiper.virtual.slides.unshift(slides[i]);
      }

      newActiveIndex = activeIndex + slides.length;
      numberOfNewSlides = slides.length;
    } else {
      swiper.virtual.slides.unshift(slides);
    }

    if (swiper.params.virtual.cache) {
      const cache = swiper.virtual.cache;
      const newCache = {};
      Object.keys(cache).forEach(cachedIndex => {
        const cachedEl = cache[cachedIndex];
        const cachedElIndex = cachedEl.getAttribute('data-swiper-slide-index');

        if (cachedElIndex) {
          cachedEl.setAttribute('data-swiper-slide-index', parseInt(cachedElIndex, 10) + numberOfNewSlides);
        }

        newCache[parseInt(cachedIndex, 10) + numberOfNewSlides] = cachedEl;
      });
      swiper.virtual.cache = newCache;
    }

    update(true);
    swiper.slideTo(newActiveIndex, 0);
  }

  function removeSlide(slidesIndexes) {
    if (typeof slidesIndexes === 'undefined' || slidesIndexes === null) return;
    let activeIndex = swiper.activeIndex;

    if (Array.isArray(slidesIndexes)) {
      for (let i = slidesIndexes.length - 1; i >= 0; i -= 1) {
        swiper.virtual.slides.splice(slidesIndexes[i], 1);

        if (swiper.params.virtual.cache) {
          delete swiper.virtual.cache[slidesIndexes[i]];
        }

        if (slidesIndexes[i] < activeIndex) activeIndex -= 1;
        activeIndex = Math.max(activeIndex, 0);
      }
    } else {
      swiper.virtual.slides.splice(slidesIndexes, 1);

      if (swiper.params.virtual.cache) {
        delete swiper.virtual.cache[slidesIndexes];
      }

      if (slidesIndexes < activeIndex) activeIndex -= 1;
      activeIndex = Math.max(activeIndex, 0);
    }

    update(true);
    swiper.slideTo(activeIndex, 0);
  }

  function removeAllSlides() {
    swiper.virtual.slides = [];

    if (swiper.params.virtual.cache) {
      swiper.virtual.cache = {};
    }

    update(true);
    swiper.slideTo(0, 0);
  }

  on('beforeInit', () => {
    if (!swiper.params.virtual.enabled) return;
    let domSlidesAssigned;

    if (typeof swiper.passedParams.virtual.slides === 'undefined') {
      const slides = swiper.slidesEl.querySelectorAll(`.${swiper.params.slideClass}, swiper-slide`);

      if (slides && slides.length) {
        swiper.virtual.slides = [...slides];
        domSlidesAssigned = true;
        slides.forEach((slideEl, slideIndex) => {
          slideEl.setAttribute('data-swiper-slide-index', slideIndex);
          swiper.virtual.cache[slideIndex] = slideEl;
          slideEl.remove();
        });
      }
    }

    if (!domSlidesAssigned) {
      swiper.virtual.slides = swiper.params.virtual.slides;
    }

    swiper.classNames.push(`${swiper.params.containerModifierClass}virtual`);
    swiper.params.watchSlidesProgress = true;
    swiper.originalParams.watchSlidesProgress = true;

    if (!swiper.params.initialSlide) {
      update();
    }
  });
  on('setTranslate', () => {
    if (!swiper.params.virtual.enabled) return;

    if (swiper.params.cssMode && !swiper._immediateVirtual) {
      clearTimeout(cssModeTimeout);
      cssModeTimeout = setTimeout(() => {
        update();
      }, 100);
    } else {
      update();
    }
  });
  on('init update resize', () => {
    if (!swiper.params.virtual.enabled) return;

    if (swiper.params.cssMode) {
      setCSSProperty(swiper.wrapperEl, '--swiper-virtual-size', `${swiper.virtualSize}px`);
    }
  });
  Object.assign(swiper.virtual, {
    appendSlide,
    prependSlide,
    removeSlide,
    removeAllSlides,
    update
  });
}