Module:Chessboard
local p = {}
 
 local cfg, nrows, ncols
 
 local function innerboard(args, size, rev)
 	pattern = cfg.pattern or '%w%w'
 	local root = mw.html.create('div')
 	root:addClass('chess-board')
 		:css('position', 'relative')
 		:wikitext(cfg.image_board(size))
 	
 	for trow = 1,nrows do
 		local row = rev and trow or ( 1 + nrows - trow )
 		for tcol = 1,ncols do
 			local col = rev and ( 1 + ncols - tcol ) or tcol
 			local piece = args[ncols * ( nrows - row ) + col + 2] or ''
 			if piece:match( pattern ) then
 				local img = cfg.image_square(piece:match(pattern), row, col, size )
 				root:tag('div')
 					:css('position', 'absolute')
 					:css('z-index', '3')
 					:css('top', tostring(( trow - 1 ) * size) .. 'px')
 					:css('left', tostring(( tcol - 1 ) * size) .. 'px')
 					:css('width', size .. 'px')
 					:css('height', size .. 'px')
 					:wikitext(img)
 			end
 		end
 	end
 
 	return tostring(root)
 end
 
 function chessboard(args, size, rev, letters, numbers, header, footer, align, clear)
 	function letters_row( rev, num_lt, num_rt )
 		local letters = cfg.letters()
 		local root = mw.html.create('')
 		if num_lt then
 			root:tag('td')
 				:css('vertical-align', 'inherit')
 				:css('padding', '0')
 		end
 		for k = 1,ncols do
 			root:tag('td')
 				:css('padding', '0')
 				:css('vertical-align', 'inherit')
 				:css('text-align', 'center')
 				:css('height', '18px')
 				:css('width', size .. 'px')
 				:wikitext(rev and letters[1+ncols-k] or letters[k])
 		end
 		if num_rt then
 			root:tag('td')
 				:css('vertical-align', 'inherit')
 				:css('padding', '0')
 		end
 		return tostring(root)
 	end
 	
 	local letters_tp = letters:match( 'both' ) or letters:match( 'top' )
 	local letters_bt = letters:match( 'both' ) or letters:match( 'bottom' )
 	local numbers_lt = numbers:match( 'both' ) or numbers:match( 'left' )
 	local numbers_rt = numbers:match( 'both' ) or numbers:match( 'right' )
 	local width = ncols * size + 2
 	if ( numbers_lt ) then width = width + 18 end
 	if ( numbers_rt ) then width = width + 18 end
 
 	local root = mw.html.create('div')
 		:addClass('thumb')
 		:addClass('noviewer')
 		:addClass(align)
 	if( header and header ~= '' ) then
 		root:tag('div'):addClass('center'):css('line-height', '130%'):css('margin', '0 auto'):css('max-width', (width + ncols) .. 'px'):wikitext(header)
 	end
 	local div = root:tag('div')
 		:addClass('thumbinner')
 		:css('width', width .. 'px')
 	local b = div:tag('table')
 		:attr('cellpadding', '0')
 		:attr('cellspacing', '0')
 		:css('background', 'white')
 		:css('font-size', '88%')
 		:css('border' , '1px #c8ccd1 solid')
 		:css('padding', '0')
 		:css('margin', 'auto')
 
 	if ( letters_tp ) then
 		b:tag('tr')
 			:css('vertical-align', 'middle')
 			:wikitext(letters_row( rev, numbers_lt, numbers_rt ))
 	end
 	local tablerow = b:tag('tr'):css('vertical-align','middle')
 	if ( numbers_lt ) then 
 		tablerow:tag('td')
 			:css('padding', '0')
 			:css('vertical-align', 'inherit')
 			:css('text-align', 'center')
 			:css('width', '18px')
 			:css('height', size .. 'px')
 			:wikitext(rev and 1 or nrows) 
 	end
 	local td = tablerow:tag('td')
 		:attr('colspan', ncols)
 		:attr('rowspan', nrows)
 		:css('padding', '0')
 		:css('vertical-align', 'inherit')
 		:wikitext(innerboard(args, size, rev))
 	
 	if ( numbers_rt ) then 
 		tablerow:tag('td')
 			:css('padding', '0')
 			:css('vertical-align', 'inherit')
 			:css('text-align', 'center')
 			:css('width', '18px')
 			:css('height', size .. 'px')
 			:wikitext(rev and 1 or nrows) 
 	end
 	if ( numbers_lt or numbers_rt ) then
 		for trow = 2, nrows do
 			local idx = rev and trow or ( 1 + nrows - trow )
 			tablerow = b:tag('tr')
 				:css('vertical-align', 'middle')
 			if ( numbers_lt ) then 
 				tablerow:tag('td')
 					:css('padding', '0')
 					:css('vertical-align', 'inherit')
 					:css('text-align', 'center')
 					:css('height', size .. 'px')
 					:wikitext(idx)
 			end
 			if ( numbers_rt ) then 
 				tablerow:tag('td')
 					:css('padding', '0')
 					:css('vertical-align', 'inherit')
 					:css('text-align', 'center')
 					:css('height', size .. 'px')
 					:wikitext(idx)
 			end
 		end
 	end
 	if ( letters_bt ) then
 		b:tag('tr')
 			:css('vertical-align', 'middle')
 			:wikitext(letters_row( rev, numbers_lt, numbers_rt ))
 	end
 
 	if (footer and footer ~= '') then
 		div:tag('div')
 			:addClass('thumbcaption')
 			:wikitext(footer)
 	end
 
 	return tostring(root)
 end
 
 function convertFenToArgs( fen )
 	-- converts FEN notation to 64 entry array of positions, offset by 2
 	local res = { ' ', ' ' }
 	-- Loop over rows, which are delimited by /
 	for srow in string.gmatch( &quot;/&quot; .. fen, &quot;/%w+&quot; ) do
 		-- Loop over all letters and numbers in the row
 		for piece in srow:gmatch( &quot;%w&quot; ) do
 			if piece:match( &quot;%d&quot; ) then -- if a digit
 				for k=1,piece do
 					table.insert(res,' ')
 				end
 			else -- not a digit
 				local color = piece:match( '%u' ) and 'l' or 'd'
 				piece = piece:lower()
 				table.insert( res, piece .. color )
 			end
 		end
 	end
 
 	return res
 end
 
 function convertArgsToFen( args, offset )
 	function nullOrWhitespace( s ) return not s or s:match( '^%s*(.-)%s*$' ) == '' end
 	function piece( s ) 
 		return nullOrWhitespace( s ) and 1
 		or s:gsub( '%s*(%a)(%a)%s*', function( a, b ) return b == 'l' and a:upper() or a end )
 	end
 	
 	local res = ''
 	offset = offset or 0
 	for row = 1, 8 do
 		for file = 1, 8 do
 			res = res .. piece( args[8*(row - 1) + file + offset] )
 		end
 		if row &lt; 8 then res = res .. '/' end
 	end
 	return mw.ustring.gsub(res, '1+', function( s ) return #s end )
 end
 
 function p.board(frame)
 	local args = frame.args
 	local pargs = frame:getParent().args
 	local style = args.style or pargs.style or 'Chess'
 	cfg = require('Module:Chessboard/' .. style)
 	nrows, ncols = cfg.dims()
 	
 	local size = args.size or pargs.size or '26'
 	local reverse = ( args.reverse or pargs.reverse or '' ):lower() == &quot;true&quot;
 	local letters = ( args.letters or pargs.letters or 'both' ):lower() 
 	local numbers = ( args.numbers or pargs.numbers or 'both' ):lower() 
 	local header = args[2] or pargs[2] or ''
 	local footer = args[nrows*ncols + 3] or pargs[nrows*ncols + 3] or ''
 	local align = ( args[1] or pargs[1] or 'tright' ):lower()
 	local clear = args.clear or pargs.clear or ( align:match('tright') and 'right' ) or 'none'
 	local fen = args.fen or pargs.fen
 		
 	size = mw.ustring.match( size, '[%d]+' ) or '26' -- remove px from size
 	if (fen) then
 		align = args.align or pargs.align or 'tright'
 		clear = args.clear or pargs.clear or ( align:match('tright') and 'right' ) or 'none'
 		header = args.header or pargs.header or ''
 		footer = args.footer or pargs.footer or ''
 		return chessboard( convertFenToArgs( fen ), size, reverse, letters, numbers, header, footer, align, clear )
 	end
 	if args[3] then
 		return chessboard(args, size, reverse, letters, numbers, header, footer, align, clear)
 	else
 		return chessboard(pargs, size, reverse, letters, numbers, header, footer, align, clear)
 	end
 end
 
 function p.fen2ascii(frame)
 	-- {{#invoke:Chessboard|fen2ascii|fen=...}}
 	local b = convertFenToArgs( frame.args.fen )
 	local res = '|=\n'
 	local offset = 2
 	for row = 1,8 do
 		local n = (9 - row)
 		res = res .. n .. ' |' .. 
 			table.concat(b, '|', 8*(row-1) + 1 + offset, 8*(row-1) + 8 + offset) .. '|=\n'
 	end
 	res = mw.ustring.gsub( res,'\| \|', '|  |' )
 	res = mw.ustring.gsub( res,'\| \|', '|  |' )
 	return res .. '   a  b  c  d  e  f  g  h'
 end
 
 function p.ascii2fen( frame )
 	-- {{#invoke:Chessboard|ascii2fen|kl| | |....}}
 	return convertArgsToFen( frame.args, frame.args.offset or 1 )
 end