Function buildNestedToc

lib/get-mini-toc-items.js:80–124

(allItems, startIndex = 0)

// Recursively build a tree from the list of allItems
function buildNestedToc(allItems, startIndex = 0) {
  const startItem = allItems[startIndex]
  if (!startItem) {
    return []
  }
  let curLevelIndentation = startItem.indentationLevel
  const currentLevel = []

  for (let cursor = startIndex; cursor < allItems.length; cursor++) {
    const cursorItem = allItems[cursor]
    const nextItem = allItems[cursor + 1]
    const nextItemIsNested = nextItem && nextItem.indentationLevel > cursorItem.indentationLevel

    // if it's the current indentation level, push it on and keep going
    if (curLevelIndentation === cursorItem.indentationLevel) {
      currentLevel.push({
        ...cursorItem,
        items: nextItemIsNested ? buildNestedToc(allItems, cursor + 1) : [],
      })
      continue
    }

    // these items were already handled via recursion
    if (curLevelIndentation < cursorItem.indentationLevel) {
      continue
    }

    // current root indentation is _greater_ than our current cursor item,
    if (curLevelIndentation > cursorItem.indentationLevel) {
      // special scenario where the initial list started with "less important" headers
      // so we need to reset our expectations of what level to judge the indentation on
      if (startIndex === 0) {
        curLevelIndentation = cursorItem.indentationLevel
        currentLevel.push({
          ...cursorItem,
          items: nextItemIsNested ? buildNestedToc(allItems, cursor + 1) : [],
        })
        continue
      }
      break
    }
  }

  return currentLevel
}

// Strip the bits and pieces from each object in the array that are
// not needed in the React component rendering.