usefull code

local function ReadFile(path)
    local f = fs.open(path, "r")
    local data = f.readAll()
    f.close()
    return data
end

local function WriteFile(path, data)
    local f = fs.open(path, "w")
    f.write(data)
    f.close()
end

local function getpastebin(paste)
    local response = http.get(
        "http://pastebin.com/raw/"..textutils.urlEncode( paste )
    )

    if response then
        local sResponse = response.readAll()
        response.close()
        return true, sResponse
    else
        return false
    end
end

local function CheckAPI(name, pastebin, required, downloadfilename)
    local path = settings.get(name, nil)
    if path ~= nil then
        if fs.exists(path) then
            os.loadAPI(path)
            return true
        else
            if http then
                local suc, paste = getpastebin(pastebin)
                if suc then
                    WriteFile(path, paste)
                    os.loadAPI(path)
                    return true
                else
                    if required then error(name .. " API not found and was not able to download! specify path to " .. name .. " API in settings, do 'set " .. name .. " <path>' to set path")
                end
            else
                if required then error(name .. " API not found and was not able to download! specify path to " .. name .. " API in settings, do 'set " .. name .. " <path>' to set path")
            end
        end
    else
        if fs.exists(name) then
            os.loadAPI(name)
            return true
        else
            if http then
                local suc, paste = getpastebin(pastebin)
                if suc then
                    if downloadfilename then
                        WriteFile(downloadfilename, paste)
                        settings.set(name, downloadfilename)
                        os.loadAPI(downloadfilename)
                    else
                        WriteFile(name, paste)
                        os.loadAPI(name)
                    end
                    return true
                else
                    if required then error(name .. " API not found and was not able to download! specify path to " .. name .. " API in settings, do 'set " .. name .. " <path>' to set path")
                end
            else
                if required then error(name .. " API not found and was not able to download! specify path to " .. name .. " API in settings, do 'set " .. name .. " <path>' to set path")
            end
        end
    end
    return false
end