Regex optional capture groups in any order

Question

I would like to capture groups based on a consecutive occurrence of matched groups in any order. And when one set type is repeated without the alternative set type, the alternative set is returned as nil.

I am trying to extract names and emails based on the following regex:

For names, two consecutive capitalized words:

[A-Z][\w]+\s+[A-Z][\w]+

For emails:

\b[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}\b

Example text:

John Doe john@doe.com random text
Jane Doe random text jane@doe.com
jim@doe.com  more random text tim@doe.com Tim Doe

So far I have used non-capture groups and positive look aheads to tackle the "in-no-particular-order-or-even-present" problem but only managed to do so by segmenting by newlines. So my regex looks like this:

^(?=(?:.*([A-Z][\w]+\s+[A-Z][\w]+))?)(?=(?:.*(\b[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}\b))?).*

And the results miss items where there are multiple contacts on the same line:

[
  ["John Doe", "john@doe.com"],
  ["Jane Doe", "jane@doe.com"],
  ["Tim Doe", "tim@doe.com"],
]

When what I'm looking for is:

[
  ["John Doe", "john@doe.com"],
  ["Jane Doe", "jane@doe.com"],
  [nil, "jim@doe.com"],
  ["Tim Doe", "tim@doe.com"],
]

My skills in regex are limited and I started using regex because it seemed like the best tool for matching names and emails.

Is regex the best tool to use for this kind of problem or are there more efficient alternatives using loops if we're extracting hundreds of contacts in this manner?

Answer 1

Your text is already almost too random to make this work. Even more names and emails are very difficult to capture at times. A more advanced email pattern would only help a little.There are not only unusual email addresses there are also all sorts of wild name patterns.
What about D'arcy Bly, Markus-Anthony Reid, Lee Z, and those are probably the simplest examples.

So, you have to make a lot of assumptions and won't be fully satisfied unless you are using more advanced techniques like Natural language processing.

If you insist on your approach, I came up with this (toothless) monstrosity:

([A-Z]\w+ [A-Z]\w+)(?:\w* )*([a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4})|
([a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4})(?:\w* )*([A-Z]\w+ [A-Z]\w+)|
([a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4})

The order of the alternation groups is important to be able to capture the stray email.

Demo

PS: The demo I uses a branch reset to capture only in group 1 and 2. However, it looks like Ruby 2.x does not support branch reset groups. So, you need to check all 5 groups for values.

Answer 2

Here's a rewrite of @wp78de's idea into Ruby regexp syntax:

regexp = /
    (?<name>
      [A-Z][\w]+\s+[A-Z][\w]+
    ){0}
    (?<email>
      \b[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}\b
    ){0}

    (?:
      \g<name> (?:\w*\s)* \g<email>
    | \g<email> (?:\w*\s)* \g<name>
    | \g<email>
    )
/x

text = <<-TEXT
John Doe john@doe.com random text
Jane Doe random text jane@doe.com
jim@doe.com  more random text tim@doe.com Tim Doe
TEXT

p text.scan(regexp)
# => [["John Doe", "john@doe.com"],
# =>  ["Jane Doe", "jane@doe.com"],
# =>  [nil, "jim@doe.com"],
# =>  ["Tim Doe", "tim@doe.com"]]