script.lua

-- This is a challenge, the goal is to read arbitary files on the machine running this script

local dangerous_functions = { 'io.open', 'io.popen', 'io.input', 'io.lines', 'io.write', 'io.output', 'dofile', 'loadfile', 'loadstring', 'load', 'require', 'module', 'os.execute'};

-- remove every dangerous function from the global environment :D
for k,v in pairs(dangerous_functions) do
    _G[v] = nil;
end

account = { };

function account.greet()
    print"Greetings";
end

local function print_menu()
    print'\n\nAccount Management Service';
    print'You are free to do whatever you want with your object';
    print'[0] display current account\n[1] add a key-value pair to the account\n[2] display attribute / call method on the current account';
end

local function inspect_account()
    print'Account properties:'
    for k,v in pairs(account) do
        print('\t' .. k .. ' : ' .. type(v));
    end
end

local function parse_value(value)
    if value:find'^%d+$' then
        return tonumber(value); -- its a number
    elseif value:find"^'[^']+'$" or value:find'^"[^"]+"$' then
        return value:sub(2, -2); -- its a string, what is between the quotes
    else
        return _G[value]; -- return the value of the global variable that has the name value
    end
end

local function add_entry_to_account()
    print'Enter the name of the key you want to add to your account';
    key_name = io.read'l';
    print'Enter the value you want to associate with that key';
    print'It can be an integer, a string, or the name of a global variable';
    value = parse_value(io.read'l');
    account[key_name] = value;
end

local function access_entry_from_account()
    inspect_account();
    print'Enter the name of the attribute that you want to read, or the method that you want to call';
    local key_name = io.read'l';
    if type(account[key_name]) == 'function' then
        local arguments = { };
        -- read the arguments from the user, they can be strings, numbers, or references to global variables!
        while true do
            print'Please specify the arguments, enter an empty line to stop entering arguments';
            local argum = io.read'l';
            if argum == '' then break;
            end
            arguments[#arguments+1] = parse_value(argum);
        end
        account[key_name](table.unpack(arguments)); -- call the function and pass it the given arguments, no dangerous functions can be called Haha!
    else
        if type(account[key_name]) == 'string' or type(account[key_name]) == 'number' then
            print('The value associated with the key ' .. key_name .. ' is ' .. account[key_name]);
        else
            -- the value is not string and not number, just print its type
            print('The value associated with the key ' .. key_name .. ' is a ' .. type(account[key_name]) .. ' object');
        end
    end
end

while true do
    print_menu();
    local choice = tonumber(io.read'l');
    if choice == 0 then
        inspect_account();
    elseif choice == 1 then
        add_entry_to_account();
    elseif choice == 2 then
        access_entry_from_account();
    else
        print'Unexpected input, enter a number between 0 and 2';
    end
end