Editing Module:Sandbox/pppery/list markup

local p = {}
local yesno = require("Module:Yesno")
function p.main(frame)
	if frame.args.text == nil then
		if frame.args.page == nil then
			frame.args.text = mw.title.getCurrentTitle():getContent()
		else
			frame.args.text = mw.title.new(frame.args.page):getContent()
		end
	end
	return p._main(frame.args.text,yesno(frame.args.strict))
end
function p._main(text, strict)
	local out = ""
	local lastindent = ""
	local blanklines = ""
	for line in mw.text.gsplit(text, "\n") do
		local _, endindent = line:find("^[:*#]+")
		if endindent == nil then
			-- not an indented comment
			if #lastindent ~= 0 and #mw.text.trim(line) == 0 then
				-- buffer blank lines or lines containing whitespace until we see the next non-blank line
				blanklines = blanklines .. line .. "\n"
			else
				-- reset state, emitting any blank lines
				out = out .. blanklines .. line .. "\n"
				blanklines = ""
				lastindent = ""
			end
		else
			local thisindent = line:sub(1, endindent)
			if endindent > #lastindent then
				thisindent = lastindent .. line:sub(#lastindent + 1, endindent)
			elseif endindent == #lastindent then
				if strict then
					thisindent = lastindent
				else
					-- err on the side of keeping markup that causes visual changes, despite being incorrect
					if #thisindent == 1 and #lastindent == 1 and thisindent ~= lastindent then
						-- add back blank lines if there is going to be a breakpoint anyway
						out = out .. blanklines
					end
					thisindent = lastindent:sub(1, -2) .. thisindent:sub(-1)
				end
			elseif strict then
				thisindent = lastindent:sub(1, endindent - #lastindent - 1)
			else
				--  as before, erring on the side of keeping markup that causes a visual change
				if #thisindent == 1 and #lastindent == 1 and thisindent ~= lastindent then
					-- add back blank lines if there is going to be a breakpoint anyway
					out = out .. blanklines
				end
				thisindent = lastindent:sub(1, endindent - #lastindent - 2) .. thisindent:sub(-1)
			end
			blanklines = ""
			lastindent = thisindent
			out = out .. (thisindent .. line:sub(endindent + 1)) .. "\n"
		end
	end
	return out
end
return p