Regular Expression: Ensure that if a string contains specified symbols, then they must be enclosed by

My regular expression needs to ensure that:

1. It consists of letters, so this can be done with:

^[a-zA-Z]+$"

2. [Question] The string also can contain dot(s) and/or comma(s) and/or hyphen(s) and they all must be enclosed by letters(e.g. a.a):

• Right: a.bc-d.e (All the symbols are enclosed by letters)
• Not Right: a..b (The first dot is not enclosed and so is the second)
• Not Right: .a (The dot in on enclosed)

In case you are interested the regular expression will be in a JSON schema and will be validated by some enterprise machine:

{
   "type": "string",
   "pattern": "my-regular-expression"
}

I have tried lookahead and lookbehind etc. but I am noob in regular expressions and I have not reached needed results by myself.

>Solution :

You can use an optional repetition of one of the allowed characters using a character class followed by A-Za-z

^[a-zA-Z]+(?:[.,-][a-zA-Z]+)*$

Regex demo