-- 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('') add('') add('') add('' .. (metadata['title'] or '') .. '') add('') add('') if metadata['title'] and metadata['title'] ~= "" then add('

' .. metadata['title'] .. '

') end for _, author in pairs(metadata['author'] or {}) do add('

' .. author .. '

') end if metadata['date'] and metadata['date'] ~= "" then add('

' .. metadata.date .. '

') end add(body) if #notes > 0 then add('
    ') for _,note in pairs(notes) do add(note) end add('
') end add('') add('') 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 "
" end function Emph(s) return "" .. s .. "" end function Strong(s) return "" .. s .. "" end function Subscript(s) return "" .. s .. "" end function Superscript(s) return "" .. s .. "" end function SmallCaps(s) return '' .. s .. '' end function Strikeout(s) return '' .. s .. '' end function Link(s, src, tit) return "" .. s .. "" end function Image(s, src, tit) return "" end function Code(s, attr) return "" .. escape(s) .. "" 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, '(.*)↩' .. s .. '') -- return the footnote reference, linked to the note. return '' .. num .. '' end function Span(s, attr) return "" .. s .. "" end function Plain(s) return s end function Para(s) return "

" .. s .. "

" end -- lev is an integer, the header level. function Header(lev, s, attr) return "" .. s .. "" end function BlockQuote(s) return "
\n" .. s .. "\n
" end function HorizontalRule() return "
" 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 '' -- otherwise treat as code (one could pipe through a highlighter) else return "
" .. escape(s) ..
           "
" end end function BulletList(items) local buffer = {} for _, item in pairs(items) do table.insert(buffer, "
  • " .. item .. "
    • ") end return "" end function OrderedList(items) local buffer = {} for _, item in pairs(items) do table.insert(buffer, "
  • " .. item .. "
    • ") end return "
      \n" .. table.concat(buffer, "\n") .. "\n
    " 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,"
    " .. k .. "
    \n
    " .. table.concat(v,"
    \n
    ") .. "
    ") end end return "
    \n" .. table.concat(buffer, "\n") .. "\n
    " 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("") if caption ~= "" then add("") end if widths and widths[1] ~= 0 then for _, w in pairs(widths) do add('') 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,'') empty_header = empty_header and h == "" end if empty_header then head = "" else add('') for _,h in pairs(header_row) do add(h) end add('') end local class = "even" for _, row in pairs(rows) do class = (class == "even" and "odd") or "even" add('') for i,c in pairs(row) do add('') end add('') end add('\n" .. s .. "" 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)
    " .. caption .. "
    ' .. h .. '
    ' .. c .. '