header-tools-demo.md

title
Demo

Background {#background}

History

Tips

Main

Syntax {#syntax}

BEFORE

\ChapterToc

AFTER

Expressions

Special expressions

Statements

Library

Appendix

Acknowledgements

header-tools.lua

--[[
  Features of this filter:
  – Not supported for HTML: --top-level-division=part. This filter numbers parts correctly.
  – Chapter TOCs via \ChapterToc
  
  Configure:
  --metadata=header_tools_add_numbers:true
  --metadata=header_tools_has_parts:true
]]

local headersToIgnore = {
  ["List of Figures"] = true,
  ["List of Listings"] = true,
  ["List of Tables"] = true,
}

local PART_LEVEL
local CHAPTER_LEVEL
local DO_NUMBER_HEADERS

local idToChapterToc = {}

-- ////////// Visit Headers \\\\\\\\\\
-- Constantly update the counters (careful w.r.t. parts!)
-- If configured, prefer Headers with section numbers (text derived from counters)
-- Per chapter, collect the Headers (needed by chapter TOCs, below)

local counters = {}
local currentChapterToc

function VisitHeader(hdr)
  local headerPlainText = pandoc.utils.stringify(hdr)
  if headersToIgnore[headerPlainText] then
    return nil
  end
  
  local counterStr = incCounters(hdr)
  updateChapterToc(hdr, counterStr)
  
  if DO_NUMBER_HEADERS then
    local content = append({pandoc.Str(counterStr .. " ")}, hdr.content)
    return pandoc.Header(hdr.level, content, hdr.attr)
  else
    return nil
  end
end

function updateChapterToc(hdr, counterStr)
  if hdr.level <= CHAPTER_LEVEL then
    -- Part or new chapter? Don’t log sections, anymore
    currentChapterToc = nil
  end
  if hdr.level == CHAPTER_LEVEL then
    currentChapterToc = {}
    idToChapterToc[hdr.identifier] = currentChapterToc
  end
  if hdr.level > CHAPTER_LEVEL and currentChapterToc ~= nil and (hdr.level - CHAPTER_LEVEL) <= 2 then
    table.insert(currentChapterToc,
      {
        indent  = hdr.level,
        content = pandoc.Plain({
          pandoc.Str(counterStr .. " "),
          pandoc.Link(hdr.content, "#" .. hdr.identifier)
        })
      })
  end
end

function incCounters(hdr)
  local firstCounterLevel
  if hdr.level == PART_LEVEL then
    -- Parts don’t affect subsequent levels
    addZerosUntilAtLevel(hdr.level)
    firstCounterLevel = PART_LEVEL
  else
    addZerosUntilAtLevel(hdr.level)
    pruneToLevel(hdr.level)
    firstCounterLevel = CHAPTER_LEVEL
  end
  counters[hdr.level] = counters[hdr.level] + 1
  return countersToString(firstCounterLevel, hdr.level)
end

function addZerosUntilAtLevel(level)
  while #counters < level do
    table.insert(counters, 0)
  end
end

function pruneToLevel(level)
  while #counters > level do
    table.remove(counters)
  end  
end

function countersToString(firstCounterLevel, lastCounterLevel)
  -- For parts, only the part number is used, subsequent levels are ignored
  -- For chapters and lower, the part number is ignored
  local result = ""
  for k,v in pairs(counters) do
    if k > lastCounterLevel then break end
    if k >= firstCounterLevel then
      if k == PART_LEVEL then
        result = result .. pandoc.utils.to_roman_numeral(v) .. "."
      else
        result = result .. v .. "."
      end
    end
  end
  return result
end

-- ////////// Create chapter TOCs \\\\\\\\\\

local currentChapterId

function TrackChapterId(hdr)
  if hdr.level == CHAPTER_LEVEL then
    currentChapterId = hdr.identifier
  end
end

function ChapterTocBlock(el)
  if (el.format == "tex") then
    if (el.text == "\\ChapterToc" and currentChapterId ~= nil) then
      local result = {}
      table.insert(result, pandoc.HorizontalRule())
      
      local tocEntries = idToChapterToc[currentChapterId]
      local bulletList = tocEntriesToBulletLists(tocEntries, 1, 0).bulletList
      if bulletList ~= nil then
        table.insert(result, pandoc.Div(bulletList, pandoc.Attr(nil, {"chapter-toc"})))
      end
      
      table.insert(result, pandoc.HorizontalRule())
      return result
    end
  end
  return nil
end

function tocEntriesToBulletLists(tocEntries, index, parentIndent)
  if index > #tocEntries then
    return { nextIndex = index, bulletList = nil }
  end
  local listIndent = tocEntries[index].indent
  if listIndent <= parentIndent then
    return { nextIndex = index, bulletList = nil }
  end
  local bulletListItems = {}
  while true do
    if index > #tocEntries then
      break
    end
    local tocEntry = tocEntries[index]
    if tocEntry.indent < listIndent then
      break
    end
    if tocEntry.indent > listIndent then
      -- Should have been collected as a child
      error()
    end
    local children = tocEntriesToBulletLists(tocEntries, index+1, listIndent)
    if children.bulletList ~= nil then
      table.insert(bulletListItems, {tocEntry.content, children.bulletList})
    else
      table.insert(bulletListItems, {tocEntry.content})
    end
    index = children.nextIndex
  end
  return { nextIndex = index, bulletList = pandoc.BulletList(bulletListItems) }
end

function ChapterTocBlockLatex(el)
  if (el.format == "tex") then
    if (el.text == "\\ChapterToc") then
      return pandoc.RawBlock("latex", "\\minitoc")
    end
  end
  return nil
end

-- ////////// Set up everything \\\\\\\\\\

function setup(meta)
  -- Command line: --metadata=header_tools_add_numbers:true
  if meta.header_tools_add_numbers == true or meta.header_tools_add_numbers == false then
    DO_NUMBER_HEADERS = meta.header_tools_add_numbers
  else
    error("Illegal value for 'header_tools_add_numbers': " .. meta.header_tools_add_numbers)
  end
  
  -- Command line: --metadata=header_tools_has_parts:true
  if meta.header_tools_has_parts == true then
    PART_LEVEL = 1
    CHAPTER_LEVEL = 2
  elseif meta.header_tools_has_parts == false then
    PART_LEVEL = -1
    CHAPTER_LEVEL = 1
  else
    error("Illegal value for 'header_tools_has_parts': " .. meta.header_tools_has_parts)
  end
end

-- ////////// Tool functions \\\\\\\\\\

function insertInto(source, target)
  for _,v in pairs(source) do
    table.insert(target, v)
  end
  return target
end

function append(t1, t2)
  local result = {};
  insertInto(t1, result)
  insertInto(t2, result)
  return result
end

function printTable(tbl)
  for k,v in pairs(tbl) do
    print('KEY', k, 'VALUE', v)
  end 
end

-- ////////// Specify passes \\\\\\\\\\

if FORMAT == "latex" then
  return {{RawBlock = ChapterTocBlockLatex}}
else
  return {
    {Meta = setup}, {Header = VisitHeader}, -- setup, number Headers
    {Header = TrackChapterId, RawBlock = ChapterTocBlock} -- create chapter TOCs
  }
end

output.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang="" xml:lang="">
<head>
  <meta charset="utf-8" />
  <meta name="generator" content="pandoc" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes" />
  <title>Demo</title>
  <style type="text/css">
      code{white-space: pre-wrap;}
      span.smallcaps{font-variant: small-caps;}
      span.underline{text-decoration: underline;}
      div.column{display: inline-block; vertical-align: top; width: 50%;}
  </style>
  <!--[if lt IE 9]>
    <script src="//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.3/html5shiv-printshiv.min.js"></script>
  <![endif]-->
</head>
<body>
<header id="title-block-header">
<h1 class="title">Demo</h1>
</header>
<nav id="TOC">
<ul>
<li><a href="#background">I. Background</a><ul>
<li><a href="#history">1. History</a></li>
<li><a href="#tips">2. Tips</a></li>
</ul></li>
<li><a href="#main">II. Main</a><ul>
<li><a href="#syntax">3. Syntax</a><ul>
<li><a href="#expressions">3.1. Expressions</a></li>
<li><a href="#statements">3.2. Statements</a></li>
</ul></li>
<li><a href="#library">4. Library</a></li>
</ul></li>
<li><a href="#appendix">III. Appendix</a><ul>
<li><a href="#acknowledgements">5. Acknowledgements</a></li>
</ul></li>
</ul>
</nav>
<h1 id="background">I. Background</h1>
<h2 id="history">1. History</h2>
<h2 id="tips">2. Tips</h2>
<h1 id="main">II. Main</h1>
<h2 id="syntax">3. Syntax</h2>
<p>BEFORE</p>
<hr />
<div class="chapter-toc">
<ul>
<li>3.1. <a href="#expressions">Expressions</a>
<ul>
<li>3.1.1. <a href="#special-expressions">Special expressions</a></li>
</ul></li>
<li>3.2. <a href="#statements">Statements</a></li>
</ul>
</div>
<hr />
<p>AFTER</p>
<h3 id="expressions">3.1. Expressions</h3>
<h4 id="special-expressions">3.1.1. Special expressions</h4>
<h3 id="statements">3.2. Statements</h3>
<h2 id="library">4. Library</h2>
<h1 id="appendix">III. Appendix</h1>
<h2 id="acknowledgements">5. Acknowledgements</h2>
<!--
pandoc -t html --standalone --toc --lua-filter=header-tools.lua --metadata=header_tools_has_parts:true --metadata=header_tools_add_numbers:true header-tools-demo.md
-->
</body>
</html>