more fun with pandoc lua

[John MacFarlane <fiddlosopher-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

-- This Lua script, when run using `pandoc lua`, will create an HTML
-- file rosetta.html that compares how the same content is represented
-- in all the text markup languages pandoc supports:

local inp = [[
# Heading

## level 2

### level 3

#### level 4 with attributes {.blue #foobar}

- Unordered
- list

1. ordered
2. list

a) Lettered list

   with continuation paragraph

> Block quote

``` {.lua}
local formats = pandoc.writers
for format,_ in formats do
  print(format)
end
```

*emphasized text **with strong emphasis***

`verbatim text` and a [link with `verbatim`](http://example.com)
]]
local doc = pandoc.read(inp, "markdown")

local formats = pandoc.writers
-- remove binary formats:
formats.docx = nil
formats.pptx = nil
formats.odt = nil
formats.epub2 = nil
formats.epub3 = nil
formats.epub = nil
formats.chunkedhtml = nil
formats.biblatex = nil
formats.bibtex = nil
formats.csljson = nil

local blocks = {}

-- Table of code languages to use for highlighting, when it differs
-- from the format name:
local langs = {
  icml = "xml",
  jira = "xml",
  fb2 = "xml",
  docbook = "xml",
  docbook4 = "xml",
  docbook5 = "xml",
  commonmark = "markdown",
  commonmark_x = "markdown",
  context = "latex",
  dzslides = "html5",
  slideous = "html",
  slidy = "html",
  man = "troff",
  ms = "troff",
  gfm = "markdown",
  markdown_mmd = "multimarkdown",
  markdown_github = "markdown",
  revealjs = "html",
  beamer = "latex",
  ipynb = "json",
  opendocument = "xml",
  native = "haskell",
  html5 = "html",
  html4 = "html",
}

local sorted_formats = {}
for format,_ in pairs(formats) do
  table.insert(sorted_formats, format)
end
table.sort(sorted_formats)

-- construct document part for each format
for _,format in ipairs(sorted_formats) do
  table.insert(blocks, pandoc.Header(2, format))
  local lang = langs[format] or format
  table.insert(blocks,
      pandoc.CodeBlock(pandoc.write(doc, format), {class = lang}))
end

local template = pandoc.template.compile(pandoc.template.default("html5"))
local html = pandoc.write(pandoc.Pandoc(blocks,
                            {title = "Markup Rosetta Stone"}),
                "html5",
                { template = template })

io.open("rosetta.html", "w"):write(html)
print("Created rosetta.html")