Regex - Include space before only when one OR item is match

Is there a way to include a space before an item of Or structure only when match to one of it ? The items can repeat inside string.

REGEX:

^([A-ZÁÂÉÊÍÓÔÚ][a-záãâéêíóõôúç]+)([(e|da|das|de|do|dos)]*[\s][A-ZÁÂÉÊÍÓÔÚ][a-záãâéêíóõôúç]+)+$

Space before one of this items (mandatory): [(e|da|das|de|do|dos)]

Result I want:

Paulo César Oliveira (this is working)
Antonio Carlos da Silva (must have ONE space before "da")
João da Silva dos Santos e Souza (must have ONE space before "da", "dos" and "e")

Solution

You can use

^\p{Lu}\p{Ll}+(?:(?:\s(?:e|d(?:[ao]s|[aeo])))?\s\p{Lu}\p{Ll}+)+$
^[A-ZÁÂÉÊÍÓÔÚ][a-záãâéêíóõôúç]+(?:(?:\s(?:e|d(?:[ao]s|[aeo])))?\s[A-ZÁÂÉÊÍÓÔÚ][a-záãâéêíóõôúç]+)+$

See the regex demo. \p{Lu} and \p{Ll} may be unsupported by your regex engine, then keep on using your character classes.

Details:

^ - start of string
\p{Lu}\p{Ll}+ - an uppercase letter followed with one or more lowercase letters
(?:(?:\s(?:e|d(?:[ao]s|[aeo])))?\s\p{Lu}\p{Ll}+)+ - one or more occurrences of the following patterns:
- (?:\s(?:e|d(?:[ao]s|[aeo])))? - an optional occurrence of:
  - \s - a whitespaces
  - (?:e|d(?:[ao]s|[aeo])) - e or d followed with either os/as or a, e, o
- \s - a whitespaces
- \p{Lu}\p{Ll}+ - an uppercase letter followed with one or more lowercase letters
$ - end of string.