I wanna create a regex for a string can be with multi dash within a string optionally,

1. dash cannot place in first / last position

2. dash cannot be placed continously

Acceptable string: happy1231, asfa12312-asdf, asdf-asdfs-f-d-d-d-d-d, asd7976-asdf-asdfsa-d

Hope someone would give me a hand here. Thank you.