Extract and manipulate the string with Regex in apex

Question

I need help a with building a regex for extracting a particular string and manipulating it. Here's the example

Actual Input:

( 12s ) Agent K: Hello Guest, How are you doing today?<br> <br>How Can I help<br>
( 18s ) Guest:   Hello there! Need access to XYZ<br>
( 53s ) Agent K: Granted the access<br>
( 1m 9s ) Guest: Ok thanks, Agent K<br>

I want to identify the appearances of "Agent K:", "Guest:" and all timings coming within brackets and manipulate it to

<b>Agent K:</b>.12s Hello Guest, How are you doing today?<br> <br>How Can I help<br>
<b>Guest:</b>.18s   Hello there! Need access to XYZ<br>
<b>Agent K:</b>.53s Granted the access<br>
<b>Guest:</b>.1m 9s Ok thanks, Agent K<br>

I started writing regex function to identify the appearances of ) Agent K: and ) Guest: so that I'm uniquely identifying their places. For that, I'm using below which returns true

string htmlValue = '<br>( 15s ) Agent K: Test Message from user';

string s1 = ') Agent K:';

Boolean found = Pattern.compile('(?i)' + Pattern.quote(s1)).matcher(htmlValue).find();

But I'm not sure how I can move next to start manipulating it. Any help is greatly appreciated!

Answer 1

You can use String.replaceAll to do this in one tidy step:

String output = input.replaceAll(
  '(?m)^\\s*\\(\\s*(.+?)\\s*\\)\\s*(.+?:)\\s*\\s*(.+)\\s*$',
  '<strong>$2</strong>.$1 $3'
);

Here's an example output:

String input = '( 12s ) Agent K: Hello Guest, How are you doing today?<br> <br>How Can I help<br>\n( 18s ) Guest:   Hello there! Need access to XYZ<br>\n( 53s ) Agent K: Granted the access<br>\n( 1m 9s ) Guest: Ok thanks, Agent K<br>';
String output = input.replaceAll(
  '(?m)^\\s*\\(\\s*(.+?)\\s*\\)\\s*(.+?:)\\s*\\s*(.+)\\s*$',
  '<strong>$2</strong>.$1 $3'
);
System.debug(output);

Result:

<strong>Agent K:</strong>.12s Hello Guest, How are you doing today?<br> <br>How Can I help<br>
<strong>Guest:</strong>.18s Hello there! Need access to XYZ<br>
<strong>Agent K:</strong>.53s Granted the access<br>
<strong>Guest:</strong>.1m 9s Ok thanks, Agent K<br>

---

There's a ton of regex here, but it's simple. I'll break it down:

• ( and ) create "numbered capture groups"
• (?m) multiline mode, matches newlines with ^ and $
• ^ Start of a line (in beginning position)
• $ End of a line (in end position)
• \\s* Zero or more spaces (we use this a lot to skip whitespace)
• \\( and \\), literal parentheses
• (.+?) Match any character sequence, but non-greedy (so, up to the next )).
• (.+?:) match any sequence ending in :.
• (.+) match to end of line

And for the replacement string, $1 refers to the first capture group, $2 to the second group, etc.

P.S. <b> and <i> are strongly discouraged in modern HTML. You should use <strong> for bold emphasis (a keyword or heavy emphasis, a concept that must be understood), and <i> should now be <em> for emphasis.