'use strict';

/*
 * 1. Check if the browser supports `position: sticky` natively or is too old to run the polyfill.
 *    If either of these is the case set `seppuku` flag. It will be checked later to disable key features
 *    of the polyfill, but the API will remain functional to avoid breaking things.
 */
let seppuku = false;

const isWindowDefined = typeof window !== 'undefined';

// The polyfill can’t function properly without `window` or `window.getComputedStyle`.
if (!isWindowDefined || !window.getComputedStyle) seppuku = true;
else {
  // Dont’t get in a way if the browser supports `position: sticky` natively.
  const testNode = document.createElement('div');

  if (
    [ '', '-webkit-', '-moz-', '-ms-' ].some((prefix) => {
      try {
        testNode.style.position = prefix + 'sticky';
      } catch (e) {}

      return testNode.style.position != '';
    })
  )
    seppuku = true;
}

/*
 * 2. “Global” vars used across the polyfill
 */
let isInitialized = false;

// Check if Shadow Root constructor exists to make further checks simpler
const shadowRootExists = typeof ShadowRoot !== 'undefined';

// Last saved scroll position
const scroll = {
  top: null,
  left: null
};

// Array of created Sticky instances
const stickies = [];

/*
 * 3. Utility functions
 */
function extend (targetObj, sourceObject) {
  for (var key in sourceObject) {
    if (sourceObject.hasOwnProperty(key)) {
      targetObj[key] = sourceObject[key];
    }
  }
}

function parseNumeric (val) {
  return parseFloat(val) || 0;
}

function getDocOffsetTop (node) {
  let docOffsetTop = 0;

  while (node) {
    docOffsetTop += node.offsetTop;
    node = node.offsetParent;
  }

  return docOffsetTop;
}

/*
 * 4. Sticky class
 */
class Sticky {
  constructor (node) {
    if (!(node instanceof HTMLElement)) throw new Error('First argument must be HTMLElement');
    if (stickies.some((sticky) => sticky._node === node))
      throw new Error('Stickyfill is already applied to this node');

    this._node = node;
    this._stickyMode = null;
    this._active = false;

    stickies.push(this);

    this.refresh();
  }

  refresh () {
    if (seppuku || this._removed) return;
    if (this._active) this._deactivate();

    const node = this._node;

    /*
         * 1. Save node computed props
         */
    const nodeComputedStyle = getComputedStyle(node);
    const nodeComputedProps = {
      position: nodeComputedStyle.position,
      top: nodeComputedStyle.top,
      display: nodeComputedStyle.display,
      marginTop: nodeComputedStyle.marginTop,
      marginBottom: nodeComputedStyle.marginBottom,
      marginLeft: nodeComputedStyle.marginLeft,
      marginRight: nodeComputedStyle.marginRight,
      cssFloat: nodeComputedStyle.cssFloat
    };

    /*
         * 2. Check if the node can be activated
         */
    if (
      isNaN(parseFloat(nodeComputedProps.top)) ||
			nodeComputedProps.display == 'table-cell' ||
			nodeComputedProps.display == 'none'
    )
      return;

    this._active = true;

    /*
         * 3. Check if the current node position is `sticky`. If it is, it means that the browser supports sticky positioning,
         *    but the polyfill was force-enabled. We set the node’s position to `static` before continuing, so that the node
         *    is in it’s initial position when we gather its params.
         */
    const originalPosition = node.style.position;
    if (nodeComputedStyle.position == 'sticky' || nodeComputedStyle.position == '-webkit-sticky')
      node.style.position = 'static';

    /*
         * 4. Get necessary node parameters
         */
    const referenceNode = node.parentNode;
    const parentNode = shadowRootExists && referenceNode instanceof ShadowRoot ? referenceNode.host : referenceNode;
    const nodeWinOffset = node.getBoundingClientRect();
    const parentWinOffset = parentNode.getBoundingClientRect();
    const parentComputedStyle = getComputedStyle(parentNode);

    this._parent = {
      node: parentNode,
      styles: {
        position: parentNode.style.position
      },
      offsetHeight: parentNode.offsetHeight
    };
    this._offsetToWindow = {
      left: nodeWinOffset.left,
      right: document.documentElement.clientWidth - nodeWinOffset.right
    };
    this._offsetToParent = {
      top: nodeWinOffset.top - parentWinOffset.top - parseNumeric(parentComputedStyle.borderTopWidth),
      left: nodeWinOffset.left - parentWinOffset.left - parseNumeric(parentComputedStyle.borderLeftWidth),
      right: -nodeWinOffset.right + parentWinOffset.right - parseNumeric(parentComputedStyle.borderRightWidth)
    };
    this._styles = {
      position: originalPosition,
      top: node.style.top,
      bottom: node.style.bottom,
      left: node.style.left,
      right: node.style.right,
      width: node.style.width,
      marginTop: node.style.marginTop,
      marginLeft: node.style.marginLeft,
      marginRight: node.style.marginRight
    };

    const nodeTopValue = parseNumeric(nodeComputedProps.top);
    this._limits = {
      start: nodeWinOffset.top + window.pageYOffset - nodeTopValue,
      end:
				parentWinOffset.top +
				window.pageYOffset +
				parentNode.offsetHeight -
				parseNumeric(parentComputedStyle.borderBottomWidth) -
				node.offsetHeight -
				nodeTopValue -
				parseNumeric(nodeComputedProps.marginBottom)
    };

    /*
         * 5. Ensure that the node will be positioned relatively to the parent node
         */
    const parentPosition = parentComputedStyle.position;

    if (parentPosition != 'absolute' && parentPosition != 'relative') {
      parentNode.style.position = 'relative';
    }

    /*
         * 6. Recalc node position.
         *    It’s important to do this before clone injection to avoid scrolling bug in Chrome.
         */
    this._recalcPosition();

    /*
         * 7. Create a clone
         */
    const clone = (this._clone = {});
    clone.node = document.createElement('div');

    // Apply styles to the clone
    extend(clone.node.style, {
      width: nodeWinOffset.right - nodeWinOffset.left + 'px',
      height: nodeWinOffset.bottom - nodeWinOffset.top + 'px',
      marginTop: nodeComputedProps.marginTop,
      marginBottom: nodeComputedProps.marginBottom,
      marginLeft: nodeComputedProps.marginLeft,
      marginRight: nodeComputedProps.marginRight,
      cssFloat: nodeComputedProps.cssFloat,
      padding: 0,
      border: 0,
      borderSpacing: 0,
      fontSize: '1em',
      position: 'static'
    });

    referenceNode.insertBefore(clone.node, node);
    clone.docOffsetTop = getDocOffsetTop(clone.node);
  }

  _recalcPosition () {
    if (!this._active || this._removed) return;

    const stickyMode =
			scroll.top <= this._limits.start ? 'start' : scroll.top >= this._limits.end ? 'end' : 'middle';

    if (this._stickyMode == stickyMode) return;

    switch (stickyMode) {
      case 'start':
        extend(this._node.style, {
          position: 'absolute',
          left: this._offsetToParent.left + 'px',
          right: this._offsetToParent.right + 'px',
          top: this._offsetToParent.top + 'px',
          bottom: 'auto',
          width: 'auto',
          marginLeft: 0,
          marginRight: 0,
          marginTop: 0
        });
        break;

      case 'middle':
        extend(this._node.style, {
          position: 'fixed',
          left: this._offsetToWindow.left + 'px',
          right: this._offsetToWindow.right + 'px',
          top: this._styles.top,
          bottom: 'auto',
          width: 'auto',
          marginLeft: 0,
          marginRight: 0,
          marginTop: 0
        });
        break;

      case 'end':
        extend(this._node.style, {
          position: 'absolute',
          left: this._offsetToParent.left + 'px',
          right: this._offsetToParent.right + 'px',
          top: 'auto',
          bottom: 0,
          width: 'auto',
          marginLeft: 0,
          marginRight: 0
        });
        break;
    }

    this._stickyMode = stickyMode;
  }

  _fastCheck () {
    if (!this._active || this._removed) return;

    if (
      Math.abs(getDocOffsetTop(this._clone.node) - this._clone.docOffsetTop) > 1 ||
			Math.abs(this._parent.node.offsetHeight - this._parent.offsetHeight) > 1
    )
      this.refresh();
  }

  _deactivate () {
    if (!this._active || this._removed) return;

    this._clone.node.parentNode.removeChild(this._clone.node);
    delete this._clone;

    extend(this._node.style, this._styles);
    delete this._styles;

    // Check whether element’s parent node is used by other stickies.
    // If not, restore parent node’s styles.
    if (
      !stickies.some((sticky) => sticky !== this && sticky._parent && sticky._parent.node === this._parent.node)
    ) {
      extend(this._parent.node.style, this._parent.styles);
    }
    delete this._parent;

    this._stickyMode = null;
    this._active = false;

    delete this._offsetToWindow;
    delete this._offsetToParent;
    delete this._limits;
  }

  remove () {
    this._deactivate();

    stickies.some((sticky, index) => {
      if (sticky._node === this._node) {
        stickies.splice(index, 1);
        return true;
      }
    });

    this._removed = true;
  }
}

/*
 * 5. Stickyfill API
 */
const Stickyfill = {
  stickies,
  Sticky,

  forceSticky () {
    seppuku = false;
    init();

    this.refreshAll();
  },

  addOne (node) {
    // Check whether it’s a node
    if (!(node instanceof HTMLElement)) {
      // Maybe it’s a node list of some sort?
      // Take first node from the list then
      if (node.length && node[0]) node = node[0];
      else return;
    }

    // Check if Stickyfill is already applied to the node
    // and return existing sticky
    for (var i = 0; i < stickies.length; i++) {
      if (stickies[i]._node === node) return stickies[i];
    }

    // Create and return new sticky
    return new Sticky(node);
  },

  add (nodeList) {
    // If it’s a node make an array of one node
    if (nodeList instanceof HTMLElement) nodeList = [ nodeList ];
    // Check if the argument is an iterable of some sort
    if (!nodeList.length) return;

    // Add every element as a sticky and return an array of created Sticky instances
    const addedStickies = [];

    for (let i = 0; i < nodeList.length; i++) {
      const node = nodeList[i];

      // If it’s not an HTMLElement – create an empty element to preserve 1-to-1
      // correlation with input list
      if (!(node instanceof HTMLElement)) {
        addedStickies.push(void 0);
        continue;
      }

      // If Stickyfill is already applied to the node
      // add existing sticky
      if (
        stickies.some((sticky) => {
          if (sticky._node === node) {
            addedStickies.push(sticky);
            return true;
          }
        })
      )
        continue;

      // Create and add new sticky
      addedStickies.push(new Sticky(node));
    }

    return addedStickies;
  },

  refreshAll () {
    stickies.forEach((sticky) => sticky.refresh());
  },

  removeOne (node) {
    // Check whether it’s a node
    if (!(node instanceof HTMLElement)) {
      // Maybe it’s a node list of some sort?
      // Take first node from the list then
      if (node.length && node[0]) node = node[0];
      else return;
    }

    // Remove the stickies bound to the nodes in the list
    stickies.some((sticky) => {
      if (sticky._node === node) {
        sticky.remove();
        return true;
      }
    });
  },

  remove (nodeList) {
    // If it’s a node make an array of one node
    if (nodeList instanceof HTMLElement) nodeList = [ nodeList ];
    // Check if the argument is an iterable of some sort
    if (!nodeList.length) return;

    // Remove the stickies bound to the nodes in the list
    for (let i = 0; i < nodeList.length; i++) {
      const node = nodeList[i];

      stickies.some((sticky) => {
        if (sticky._node === node) {
          sticky.remove();
          return true;
        }
      });
    }
  },

  removeAll () {
    while (stickies.length) stickies[0].remove();
  }
};

/*
 * 6. Setup events (unless the polyfill was disabled)
 */
function init () {
  if (isInitialized) {
    return;
  }

  isInitialized = true;

  // Watch for scroll position changes and trigger recalc/refresh if needed
  function checkScroll () {
    if (window.pageXOffset != scroll.left) {
      scroll.top = window.pageYOffset;
      scroll.left = window.pageXOffset;

      Stickyfill.refreshAll();
    } else if (window.pageYOffset != scroll.top) {
      scroll.top = window.pageYOffset;
      scroll.left = window.pageXOffset;

      // recalc position for all stickies
      stickies.forEach((sticky) => sticky._recalcPosition());
    }
  }

  checkScroll();
  window.addEventListener('scroll', checkScroll);

  // Watch for window resizes and device orientation changes and trigger refresh
  window.addEventListener('resize', Stickyfill.refreshAll);
  window.addEventListener('orientationchange', Stickyfill.refreshAll);

  // Fast dirty check for layout changes every 500ms
  let fastCheckTimer;

  function startFastCheckTimer () {
    fastCheckTimer = setInterval(function () {
      stickies.forEach((sticky) => sticky._fastCheck());
    }, 500);
  }

  function stopFastCheckTimer () {
    clearInterval(fastCheckTimer);
  }

  let docHiddenKey;
  let visibilityChangeEventName;

  if ('hidden' in document) {
    docHiddenKey = 'hidden';
    visibilityChangeEventName = 'visibilitychange';
  } else if ('webkitHidden' in document) {
    docHiddenKey = 'webkitHidden';
    visibilityChangeEventName = 'webkitvisibilitychange';
  }

  if (visibilityChangeEventName) {
    if (!document[docHiddenKey]) startFastCheckTimer();

    document.addEventListener(visibilityChangeEventName, () => {
      if (document[docHiddenKey]) {
        stopFastCheckTimer();
      } else {
        startFastCheckTimer();
      }
    });
  } else startFastCheckTimer();
}

if (!seppuku) init();

/*
 * 7. Expose Stickyfill
 */
if (typeof module !== 'undefined' && module.exports) {
  module.exports = Stickyfill;
} else if (isWindowDefined) {
  window.Stickyfill = Stickyfill;
}