-- 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. -- One could use some kind of templating -- system here; this just gives you a simple standalone HTML file. function Doc(body, metadata, variables) local buffer = {} local function add(s) table.insert(buffer, s) end add('<!DOCTYPE html>') add('<html>') add('<head>') add('<title>' .. (metadata['title'] or '') .. '</title>') add('</head>') add('<body>') if metadata['title'] and metadata['title'] ~= "" then add('<h1 class="title">' .. metadata['title'] .. '</h1>') end for _, author in pairs(metadata['author'] or {}) do add('<h2 class="author">' .. author .. '</h2>') end if metadata['date'] and metadata['date'] ~= "" then add('<h3 class="date">' .. metadata.date .. '</h3>') end add(body) if #notes > 0 then add('<ol class="footnotes">') for _,note in pairs(notes) do add(note) end add('</ol>') end add('</body>') add('</html>') return table.concat(buffer,'\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 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) return "<a href='" .. escape(src,true) .. "' title='" .. escape(tit,true) .. "'>" .. s .. "</a>" end function Image(s, src, tit) 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 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 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 -- Revisit association list STackValue instance. function DefinitionList(items) local buffer = {} for _,item in pairs(items) do for k, v in pairs(item) do table.insert(buffer,"<dt>" .. k .. "</dt>\n<dd>" .. table.concat(v,"</dd>\n<dd>") .. "</dd>") end 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 -- 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("%d%%", 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 -- 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)