Regex for parsing Kirby tags

Question

I am developing a plugin for Kirby CMS. It has a data type called kirby tags. I want to parse it.

I have the following input:

(link: http://google.com/ nospace:yes text: hello world foo: tesat: baz)

From which I extract:

link: http://google.com/ nospace:yes text: hello world foo: tesat: baz

Then, I need to parse this input and get the following output:

array (
  'link' => 'http://google.com/',
  'nospace' => 'yes',
  'text' => 'hello world',
  'foo' => '',
  'tesat' => 'baz',
)

I almost have the desired result, but I have trouble with handling empty pairs and values with whitespace. Check my regex here:

([a-z0-9_-]+):(?:\s?(\S+))?

Basically, I need to match the start of the string or some whitespace, then some characters (the key), a colon, and all the rest, until I reach another whitespace + characters combination.

Is there a way to make it work?