Send Arbitrary Commands Over Wifi

--[[ HELPER FUNCTIONS ]]
-- Removes leading and trailing spaces.
function trim( s )
	return (string.gsub(s, "^%s*(.-)%s*$", "%1"))
end

-- explode(string, seperator)
function explode(p, d)
  local t, ll
  t={}
  ll=0
  if(#p == 1) then return {p} end
	while true do
	  l=string.find(p,d,ll,true) -- find the next d in the string
	  if l~=nil then -- if "not not" found then..
		table.insert(t, string.sub(p,ll,l-1)) -- Save it in our array.
		ll=l+1 -- save just after where we found it for searching next time.
	  else
		table.insert(t, string.sub(p,ll)) -- Save what's left in our array.
		break -- Break at end, as it should be, according to the lua manual.
	  end
	end
  return t
end

--[[ CORE FUNCTIONS ]]

-- Retrieves arguments from a string within brackets and converts them according to these rules:
-- "house"  => becomes the string 'house'
-- true	 => becomes the boolean 'true'
-- false	=> becomes the boolean 'false'
-- 123	  => becomes the number '123'
-- Returns:
--	  true and a table with the arguments, if successful.
--	  false and nil, if not successful.
function getArgs( _sFuncCall )
	local nStart, nEnd = string.find( _sFuncCall, "%(.*%)" )	-- Find content between brackets.
	nStart = nStart + 1 -- Adjust starting position.
	nEnd = nEnd - 1 -- Adjust ending position.
	local content = string.sub( _sFuncCall, nStart, nEnd )	-- Get content between brackets.
	content = trim( content )
	if #content < 1 then return true, nil end  -- There are no arguments, so we can stop here already and return nil.
	
	content = content..""   -- Temporary fix for the string.find() problem.
	content = explode( content, "," )   -- Separate contents at the commas.
	
	-- Replace table string values with the types they actually represent, e.g. replace a string 'true' with a boolean 'true', etc.
	for i = 1, #content do
		if content[i] ~= nil then
			content[i] = trim( content[i] )
			
			if string.lower( content[i] ) == "true" then
				-- Boolean TRUE
				content[i] = true
			elseif string.lower( content[i] ) == "false" then
				-- Boolean FALSE
				content[i] = false
			elseif tonumber( content[i] ) ~= nil then
				-- NUMBER
				content[i] = tonumber( content[i] )
			else
				-- STRING
				-- Assume the string is encased within double quotes.
				local nStart, nEnd = string.find( content[i], "%\".*%\"" )	-- Find content between double quotes.
				if nStart == nil then
					return false, "Error at argument '"..content[i].."'\nOnly strings, booleans and numbers are supported (yet)."
				end
				nStart = nStart + 1 -- Adjust starting position.
				nEnd = nEnd - 1 -- Adjust ending position.
				content[i] = string.sub( content[i], nStart, nEnd )	 -- Get content between double quotes.
				content[i] = content[i]..""	-- Temporary fix for the string.find() problem.
			end
		end
	end
	return true, content
end

-- _sFuncCall - Command-Call in string form.
-- Returns:
--	  The function to the given comand, if successful.
--	  nil, if not successful.
function getFunc( _sFuncCall )
	local tSub = explode( _sFuncCall, "." )
	local func = tSub[1]
	
	if func == "shell" then
		func = shell	-- 'shell' isn't in the global table, it's actually a program within which THIS program has been executed from.
	else
		func = _G[ func ]
	end
	
	if type( func ) == "table" then
		local nStart, nEnd = string.find( tSub[2], "%(.*%)" )   -- Find content between brackets.
		if nStart == nil then return nil end	-- There are no brackets, so we don't treat this as a function call.
		
		tSub[2] = string.sub( tSub[2], 1, nStart - 1 )	-- Everything, excluding the brackets and its contents.
		if type( func[ tSub[2] ] ) == "function" then
			return func[ tSub[2] ]
		else
			return nil
		end
	end
end

--[[ EXAMPLE ON HOW TO MAKE USE OF IT ]]
local modemSide = "right"
term.setCursorPos( 1, 1 )
term.clear()
print("Listening...")
rednet.open( modemSide )

while true do
	local sEvent, p1, p2 = os.pullEvent()
	
	if sEvent == "rednet_message" then
		print( "Message from Computer #"..p1 )
		print( "Command:\n"..p2 )
		
		local func = getFunc( p2 )
		if type( func ) == "function" then
			local ok, tArgs = getArgs( p2 )
			
			if ok and tArgs ~= nil then
				print( "Result:\n"..tostring( func( unpack( tArgs ) ) ) )
			elseif ok and tArgs == nil then
				print( "Result:\n"..tostring( func() ) )
			else
				print( tArgs )
			end
			print()
		end
	end
	
	if sEvent == "char" and p1 == "q" then break end
	if sEvent == "char" and p1 == "c" then term.setCursorPos( 1, 1 ) term.clear() print("Listening...") end
end

rednet.close( modemSide )
print("Finished")