import { findUpVirtual } from '../../commons/dom';

function normalizeFontWeight(weight) {
  switch (weight) {
    case 'lighter':
      return 100;
    case 'normal':
      return 400;
    case 'bold':
      return 700;
    case 'bolder':
      return 900;
  }
  weight = parseInt(weight);
  return !isNaN(weight) ? weight : 400;
}

function getTextContainer(elm) {
  let nextNode = elm;
  const outerText = elm.textContent.trim();
  let innerText = outerText;

  while (innerText === outerText && nextNode !== undefined) {
    let i = -1;
    elm = nextNode;
    if (elm.children.length === 0) {
      return elm;
    }

    do {
      // find the first non-empty child
      i++;
      innerText = elm.children[i].textContent.trim();
    } while (innerText === '' && i + 1 < elm.children.length);
    nextNode = elm.children[i];
  }

  return elm;
}

function getStyleValues(node) {
  const style = window.getComputedStyle(getTextContainer(node));
  return {
    fontWeight: normalizeFontWeight(style.getPropertyValue('font-weight')),
    fontSize: parseInt(style.getPropertyValue('font-size')),
    isItalic: style.getPropertyValue('font-style') === 'italic'
  };
}

function isHeaderStyle(styleA, styleB, margins) {
  return margins.reduce((out, margin) => {
    return (
      out ||
      ((!margin.size || styleA.fontSize / margin.size > styleB.fontSize) &&
        (!margin.weight ||
          styleA.fontWeight - margin.weight > styleB.fontWeight) &&
        (!margin.italic || (styleA.isItalic && !styleB.isItalic)))
    );
  }, false);
}

function pAsHeadingEvaluate(node, options, virtualNode) {
  const siblings = Array.from(node.parentNode.children);
  const currentIndex = siblings.indexOf(node);

  options = options || {};
  const margins = options.margins || [];

  const nextSibling = siblings
    .slice(currentIndex + 1)
    .find(elm => elm.nodeName.toUpperCase() === 'P');

  const prevSibling = siblings
    .slice(0, currentIndex)
    .reverse()
    .find(elm => elm.nodeName.toUpperCase() === 'P');

  const currStyle = getStyleValues(node);
  const nextStyle = nextSibling ? getStyleValues(nextSibling) : null;
  const prevStyle = prevSibling ? getStyleValues(prevSibling) : null;

  if (!nextStyle || !isHeaderStyle(currStyle, nextStyle, margins)) {
    return true;
  }

  const blockquote = findUpVirtual(virtualNode, 'blockquote');
  if (blockquote && blockquote.nodeName.toUpperCase() === 'BLOCKQUOTE') {
    return undefined;
  }

  if (prevStyle && !isHeaderStyle(currStyle, prevStyle, margins)) {
    return undefined;
  }

  return false;
}

export default pAsHeadingEvaluate;