description = [[
Lists files and directories at the root of a gopher service.
]]

---
-- @usage
-- nmap -p 70 --script gopher-ls --script-args gopher-ls.maxfiles=100 <target>
--
-- @output
-- 70/tcp open  gopher
-- | gopher-ls:
-- | [txt] /gresearch.txt "Gopher, the next big thing?"
-- | [dir] /taxf "Tax Forms"
-- |_Only 2 shown. Use --script-args gopher-ls.maxfiles=-1 to see all.
--
-- @args gopher-ls.maxfiles If set, limits the amount of files returned by
--       the script. If set to 0 or less, all files are shown. The default
--       value is 10.


author = "Toni Ruottu"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"default", "discovery", "safe"}

require("nmap")
require("stdnse")
require("shortport")

portrule = shortport.port_or_service (70, "gopher", {"tcp"})

local function typelabel(gtype)
	if gtype == "0" then
		return "[txt]"
	end
	if gtype == "1" then
		return "[dir]"
	end
	return string.format("[%s]", gtype)

end

action = function( host, port )

	local INFO = "i"
	local maxfiles = nmap.registry.args[SCRIPT_NAME .. ".maxfiles"]
	if not maxfiles then
		maxfiles = 10
	else
                maxfiles = tonumber(maxfiles)
	end
	if maxfiles < 1 then
		maxfiles = nil
	end

	local socket = nmap.new_socket()
	local status, err = socket:connect(host.ip, port.number)
	if not status then
		return
	end
	
	socket:send("\r\n")

	local buffer, _ = stdnse.make_buffer(socket, "\r\n")
	local line = buffer()
	local files = {}

	while line ~= nil do
		if #line > 1 then
			local gtype = string.sub(line, 1, 1)
			local fields = stdnse.strsplit("\t", string.sub(line, 2))
			if #fields > 1 then
				local label = fields[1]
				local filename = fields[2]
				if gtype ~= INFO then
					if maxfiles and #files >= maxfiles then
						table.insert(files, string.format('Only %d shown. Use --script-args %s.maxfiles=-1 to see all.', maxfiles, SCRIPT_NAME))
						break
					else
						table.insert(files, string.format('%s %s "%s"', typelabel(gtype), filename, label))
					end
				end
			end
		end
		line = buffer()
	end
	return "\n" .. stdnse.strjoin("\n", files)
end