-- This is a sample custom writer for pandoc. It produces output
-- that is very similar to that of pandoc's HTML writer.
-- There is one new feature: code blocks marked with class 'dot'
-- are piped through graphviz and images are included in the HTML
-- output using 'data:' URLs.
--
-- Invoke with: pandoc -t sample.lua
--
-- Note: you need not have lua installed on your system to use this
-- custom writer. However, if you do have lua installed, you can
-- use it to test changes to the script. 'lua sample.lua' will
-- produce informative error messages if your code contains
-- syntax errors.
-- Character escaping
local function escape(s, in_attribute)
return s:gsub("[<>&\"']",
function(x)
if x == '<' then
return '<'
elseif x == '>' then
return '>'
elseif x == '&' then
return '&'
elseif x == '"' then
return '"'
elseif x == "'" then
return '''
else
return x
end
end)
end
-- Helper function to convert an attributes table into
-- a string that can be put into HTML tags.
local function attributes(attr)
local attr_table = {}
for x,y in pairs(attr) do
if y and y ~= "" then
table.insert(attr_table, ' ' .. x .. '="' .. escape(y,true) .. '"')
end
end
return table.concat(attr_table)
end
-- Run cmd on a temporary file containing inp and return result.
local function pipe(cmd, inp)
local tmp = os.tmpname()
local tmph = io.open(tmp, "w")
tmph:write(inp)
tmph:close()
local outh = io.popen(cmd .. " " .. tmp,"r")
local result = outh:read("*all")
outh:close()
os.remove(tmp)
return result
end
-- Table to store footnotes, so they can be included at the end.
local notes = {}
-- Blocksep is used to separate block elements.
function Blocksep()
return "\n\n"
end
-- This function is called once for the whole document. Parameters:
-- body is a string, metadata is a table, variables is a table.
-- This gives you a fragment. You could use the metadata table to
-- fill variables in a custom lua template. Or, pass `--template=...`
-- to pandoc, and pandoc will add do the template processing as
-- usual.
function Doc(body, metadata, variables)
local buffer = {}
local function add(s)
table.insert(buffer, s)
end
add(body)
if #notes > 0 then
add('<ol class="footnotes">')
for _,note in pairs(notes) do
add(note)
end
add('</ol>')
end
return table.concat(buffer,'\n') .. '\n'
end
-- The functions that follow render corresponding pandoc elements.
-- s is always a string, attr is always a table of attributes, and
-- items is always an array of strings (the items in a list).
-- Comments indicate the types of other variables.
function Str(s)
return escape(s)
end
function Space()
return " "
end
function SoftBreak()
return "\n"
end
function LineBreak()
return "<br/>"
end
function Emph(s)
return "<em>" .. s .. "</em>"
end
function Strong(s)
return "<strong>" .. s .. "</strong>"
end
function Subscript(s)
return "<sub>" .. s .. "</sub>"
end
function Superscript(s)
return "<sup>" .. s .. "</sup>"
end
function SmallCaps(s)
return '<span style="font-variant: small-caps;">' .. s .. '</span>'
end
function Strikeout(s)
return '<del>' .. s .. '</del>'
end
function Link(s, src, tit, attr)
return "<a href='" .. escape(src,true) .. "' title='" ..
escape(tit,true) .. "'>" .. s .. "</a>"
end
function Image(s, src, tit, attr)
return "<img src='" .. escape(src,true) .. "' title='" ..
escape(tit,true) .. "'/>"
end
function Code(s, attr)
return "<code" .. attributes(attr) .. ">" .. escape(s) .. "</code>"
end
function InlineMath(s)
return "\\(" .. escape(s) .. "\\)"
end
function DisplayMath(s)
return "\\[" .. escape(s) .. "\\]"
end
function Note(s)
local num = #notes + 1
-- insert the back reference right before the final closing tag.
s = string.gsub(s,
'(.*)</', '%1 <a href="#fnref' .. num .. '">↩</a></')
-- add a list item with the note to the note table.
table.insert(notes, '<li id="fn' .. num .. '">' .. s .. '</li>')
-- return the footnote reference, linked to the note.
return '<a id="fnref' .. num .. '" href="#fn' .. num ..
'"><sup>' .. num .. '</sup></a>'
end
function Span(s, attr)
return "<span" .. attributes(attr) .. ">" .. s .. "</span>"
end
function RawInline(format, str)
if format == "html" then
return str
else
return ''
end
end
function Cite(s, cs)
local ids = {}
for _,cit in ipairs(cs) do
table.insert(ids, cit.citationId)
end
return "<span class=\"cite\" data-citation-ids=\"" .. table.concat(ids, ",") ..
"\">" .. s .. "</span>"
end
function Plain(s)
return s
end
function Para(s)
return "<p>" .. s .. "</p>"
end
-- lev is an integer, the header level.
function Header(lev, s, attr)
return "<h" .. lev .. attributes(attr) .. ">" .. s .. "</h" .. lev .. ">"
end
function BlockQuote(s)
return "<blockquote>\n" .. s .. "\n</blockquote>"
end
function HorizontalRule()
return "<hr/>"
end
function LineBlock(ls)
return '<div style="white-space: pre-line;">' .. table.concat(ls, '\n') ..
'</div>'
end
function CodeBlock(s, attr)
-- If code block has class 'dot', pipe the contents through dot
-- and base64, and include the base64-encoded png as a data: URL.
if attr.class and string.match(' ' .. attr.class .. ' ',' dot ') then
local png = pipe("base64", pipe("dot -Tpng", s))
return '<img src="data:image/png;base64,' .. png .. '"/>'
-- otherwise treat as code (one could pipe through a highlighter)
else
return "<pre><code" .. attributes(attr) .. ">" .. escape(s) ..
"</code></pre>"
end
end
function BulletList(items)
local buffer = {}
for _, item in pairs(items) do
table.insert(buffer, "<li>" .. item .. "</li>")
end
return "<ul>\n" .. table.concat(buffer, "\n") .. "\n</ul>"
end
function OrderedList(items)
local buffer = {}
for _, item in pairs(items) do
table.insert(buffer, "<li>" .. item .. "</li>")
end
return "<ol>\n" .. table.concat(buffer, "\n") .. "\n</ol>"
end
function DefinitionList(items)
local buffer = {}
for _,item in pairs(items) do
local k, v = next(item)
table.insert(buffer, "<dt>" .. k .. "</dt>\n<dd>" ..
table.concat(v, "</dd>\n<dd>") .. "</dd>")
end
return "<dl>\n" .. table.concat(buffer, "\n") .. "\n</dl>"
end
-- Convert pandoc alignment to something HTML can use.
-- align is AlignLeft, AlignRight, AlignCenter, or AlignDefault.
function html_align(align)
if align == 'AlignLeft' then
return 'left'
elseif align == 'AlignRight' then
return 'right'
elseif align == 'AlignCenter' then
return 'center'
else
return 'left'
end
end
function CaptionedImage(src, tit, caption, attr)
return '<div class="figure">\n<img src="' .. escape(src,true) ..
'" title="' .. escape(tit,true) .. '"/>\n' ..
'<p class="caption">' .. caption .. '</p>\n</div>'
end
-- Caption is a string, aligns is an array of strings,
-- widths is an array of floats, headers is an array of
-- strings, rows is an array of arrays of strings.
function Table(caption, aligns, widths, headers, rows)
local buffer = {}
local function add(s)
table.insert(buffer, s)
end
add("<table>")
if caption ~= "" then
add("<caption>" .. caption .. "</caption>")
end
if widths and widths[1] ~= 0 then
for _, w in pairs(widths) do
add('<col width="' .. string.format("%.0f%%", w * 100) .. '" />')
end
end
local header_row = {}
local empty_header = true
for i, h in pairs(headers) do
local align = html_align(aligns[i])
table.insert(header_row,'<th align="' .. align .. '">' .. h .. '</th>')
empty_header = empty_header and h == ""
end
if empty_header then
head = ""
else
add('<tr class="header">')
for _,h in pairs(header_row) do
add(h)
end
add('</tr>')
end
local class = "even"
for _, row in pairs(rows) do
class = (class == "even" and "odd") or "even"
add('<tr class="' .. class .. '">')
for i,c in pairs(row) do
add('<td align="' .. html_align(aligns[i]) .. '">' .. c .. '</td>')
end
add('</tr>')
end
add('</table')
return table.concat(buffer,'\n')
end
function RawBlock(format, str)
if format == "html" then
return str
else
return ''
end
end
function Div(s, attr)
return "<div" .. attributes(attr) .. ">\n" .. s .. "</div>"
end
-- The following code will produce runtime warnings when you haven't defined
-- all of the functions you need for the custom writer, so it's useful
-- to include when you're working on a writer.
local meta = {}
meta.__index =
function(_, key)
io.stderr:write(string.format("WARNING: Undefined function '%s'\n",key))
return function() return "" end
end
setmetatable(_G, meta)