startup

-- This script auto-updates the AE-Autocrafting-Request-System.lua file 
-- whenever a new version becomes available.

-- URL for the script.
local scriptURL = "https://raw.githubusercontent.com/ReallySecureShell/AE-Autocrafting-Request-System/master/program/AE-Autocrafting-Request-System.lua"

-- Find the absolute path of the script on the computer.
local scriptPath = unpack(fs.find("AE-Autocrafting-Request-System.lua"))

-- If the path does not exist, replace the scriptPath variable
-- with the string "null". Otherwise scriptPath will equal a
-- nil value, which will cause fs.exists to crash the script,
-- as it wants a string not a nil value.
if scriptPath == nil then scriptPath = "null" end

-- Check if the URL is accessible. By submitting an HTTP GET request
-- we can get the webservers response. However, if no internet
-- connection is present this just returns null. Which is why xpcall()
-- is being used, since it lets you run another function to handle
-- errors. In this instance if an error occurs we say that the HTTP
-- response is a 404.
local _,response = xpcall(function() 
						return http.get(scriptURL).getResponseCode()
						end, function(err)
						return 404
						end)

-- If the URL is not accessible, run the script if it exists.
if response ~= 200 then
	print('[WARN] Server responded with an HTTP: '..response..'. Cannot check for updates. Will execute the script if already present.')
	
	-- Check if the script is present on the computer before we
	-- try to run it.
	if fs.exists(scriptPath) then
		print('[INFO] Script present on system. Executing.')
		shell.run(scriptPath)
	else
		print('[ERROR] AE-Autocrafting-Request-System.lua does not exist on the system.')
		error()
	end
	
-- Else check if the remote and local versions are the same. 
-- If so, download the remote version then execute it.
else
	if fs.exists(scriptPath)then
		-- Get all content for the local copy into one variable.
		compareLocal = fs.open(scriptPath,"r")
			readAllLocal = compareLocal.readAll()
		compareLocal.close()
		
		-- If both the local and remote versions are the same,
		-- execute the local copy.
		if readAllLocal == http.get(scriptURL).readAll() then
			print('[INFO] '..scriptPath..' is up-to-date.')
			readAllLocal = nil
			shell.run(scriptPath)
			
		-- If both local and remote versions differ, replace
		-- the local copy with the remote one.
		else
			print('[WARN] '..scriptPath..' is out-of-date. Retrieving updated version from remote repository.')
			file = io.open(scriptPath,"w")
			io.output(file)
				readAllRemote = http.get(scriptURL).readAll()
				io.write(readAllRemote)
				readAllRemote = nil
			io.close()
			shell.run(scriptPath)
		end
		
	-- If the script doesn't exist on the system. Download it.
	else
		print('[INFO] AE-Autocrafting-Request-System.lua does not exist. Downloading it from remote repository.')
		file = io.open("AE-Autocrafting-Request-System.lua","w")
		io.output(file)
			readAllRemote = http.get(scriptURL).readAll()
			io.write(readAllRemote)
			readAllRemote = nil
		io.close()
		shell.run("AE-Autocrafting-Request-System.lua")
	end
end