function selectors(parent, node) {
  const result = []
  parent.selectors.forEach(function(i) {
    node.selectors.forEach(function(j) {
      if (j.indexOf('&') === -1) {
        result.push(i + ' ' + j)
      } else {
        result.push(j.replace(/&/g, i))
      }
    })
  })
  return result
}

function pickComment(comment, after) {
  if (comment && comment.type === 'comment') {
    return comment.moveAfter(after)
  } else {
    return after
  }
}

function atruleChilds(rule, atrule) {
  const children = []
  atrule.each(function(child) {
    if (child.type === 'comment') {
      children.push(child)
    }
    if (child.type === 'decl') {
      children.push(child)
    } else if (child.type === 'rule') {
      child.selectors = selectors(rule, child)
    } else if (child.type === 'atrule') {
      atruleChilds(rule, child)
    }
  })
  if (children.length) {
    const clone = rule.clone({ nodes: [] })
    for (const i = 0; i < children.length; i++) children[i].moveTo(clone)
    atrule.prepend(clone)
  }
}

function processRule(rule, bubble) {
  let unwrapped = false
  let after = rule
  rule.each(function(child) {
    if (child.type === 'rule') {
      unwrapped = true
      child.selectors = selectors(rule, child)
      after = pickComment(child.prev(), after)
      after = child.moveAfter(after)
    } else if (child.type === 'atrule') {
      if (bubble.indexOf(child.name) !== -1) {
        unwrapped = true
        atruleChilds(rule, child)
        after = pickComment(child.prev(), after)
        after = child.moveAfter(after)
      }
    }
  })
  if (unwrapped) {
    rule.raws.semicolon = true
    if (rule.nodes.length === 0) rule.remove()
  }
}

const bubble = ['media', 'supports', 'document']

const process = node => {
  node.each(function(child) {
    if (child.type === 'rule') {
      processRule(child, bubble)
    } else if (child.type === 'atrule') {
      process(child)
    }
  })
}

export default process