[1.3+] O'Reillys Persistent Variables (Tables, Encryption, Namespaces...)

--assuming the API is saved under a folder called "oreilly"
os.loadAPI("/oreilly/persistent")

-- you don't need to 'create' variables in advance - it's all automatic
persistent.update("Namespace","Variable","Value")
persistent.read("Namespace","Variable")

-- complex tables 'just work' thanks to Immibis
example={a=10,b=20,c="Hello world!",d={another="table"}}
example.e=example
persistent.update("testing","table",example)
result.e.a
-- prints 10
result.e.a + result.b
-- prints 30
result.d.another
-- prints "table"

-- last, easy existence checking and removal
persistent.exists("testing","table")
-- prints "true"
persistent.delete("testing","table")
-- will remove the file, and therefore the variable

--Copyright (C) Paul O'Reilly, paul.oreilly@digime.co.nz
--[[
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
The software is provided "as is", without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. in no event shall the author be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with the software or the use or other dealings in the software.
]]

os.loadAPI("/strutils/StrUtils")
os.loadAPI("/immibis/serialize")

persistent_path = "/var"
if fs.exists( persistent_path ) == false then fs.makeDir( persistent_path ) end

function _doNothing( value ) return value end
persistent_encryption = _doNothing
persistent_decryption = _doNothing


function _getpersistentVariablePath( path, name )
	-- will create path if required
	local complete_path = persistent_path..'/'..path
	local path_fragments = StrUtils.seperate(complete_path, "/")
	local current_path = ""
	for k,v in pairs( path_fragments ) do
		current_path = current_path.."/"..v
		if not fs.exists( current_path ) then fs.makeDir( current_path ) end
	end  
	return complete_path.."/"..name..".var"
end


function exists( path, name )
	local path = _getpersistentVariablePath( path, name )
	return fs.exists( path )
end


function delete( path, name )
	local variable_path = _getpersistentVariablePath( path, name )
	if exists( path, name ) then fs.delete( variable_path )
	else return "Variable doesn't exist"
	end
end


function update( path, name, value )
	local variable_path = _getpersistentVariablePath( path, name )
	local as_string = serialize.serialize( value )
	if not ( persistent_encryption == nil ) then
		as_string = persistent_encryption( as_string )
	end
	local persistent_file = io.open( variable_path, "w" )
	if persistent_file then
		persistent_file:write( as_string )
		persistent_file:close()
	else return "Error opening file" end
end


function read( path, name )
	local variable_path = _getpersistentVariablePath( path, name )
	if fs.exists( variable_path ) then
		local persistent_file = io.open( variable_path, "r" )
		if persistent_file then
			content = persistent_file:read("*a")
			persistent_file:close()
			if not ( persistent_decryption == nil ) then
				content = persistent_decryption( content )
			end
			return serialize.deserialize( content )
		else return "Error opening file" end
	else return "Variable doesn't exist"
	end
end