Using Regex to parse a chat transcript

Question

I need to classify each line as "announce, whisper or chat" once I have that sorted out I need to extract certain values to be processed.

Right now my regex is as follow:

var regex = new Regex(@"^\[(\d{2}:\d{2}:\d{2})\]\s*(?:(\[System Message\])?\s*<([^>]*)>|((.+) Whisper You :))\s*(.*)$");

• Group 0 is the entire message.
• Group 1 is the hour time of when the message was sent.
• Group 2 is wether it was an announce or chat.
• Group 3 is who sent the announce.
• Group 4 is if it was a whisper or not.
• Group 5 is who sent the whisper.
• Group 6 is the sent message by the user or system.

Classify each line:

if 4 matches
 means it is a whisper
   else if 2 matches
     means it is an announce
       else
         normal chat

Should I change anything to my regex to make it more precise/accurate on the matches ?

Sample data:

[02:33:03] John Whisper You :  Heya
[02:33:03] John Whisper You :  How is it going
[02:33:12] <John> [02:33:16] [System Message] bla bla
[02:33:39] <John> heya
[02:33:40] <John> hello :S
[02:33:57] <John> hi
[02:33:57] [System Message] <John> has left the room 
[02:33:57] [System Message] <John> has entered the room 

Answer 1

You can always break it down in multiple lines to make it more readable. You can also use named groups which take the "magic" out of the group numbers (4 == whisper, 3 == normal, etc).

        var regex = new Regex(@"^\[(?<TimeStamp>\d{2}:\d{2}:\d{2})\]\s*" +
            @"(?:" +
                @"(?<SysMessage>\[System Message\])?\s*" +
                @"<(?<NormalWho>[^>]*)>|" +
                @"(?<Whisper>(?<WhisperWho>.+) Whisper You :))\s*" +
            @"(?<Message>.*)$");

        string data = @"[02:33:03] John Whisper You :  Heya
[02:33:03] John Whisper You :  How is it going
[02:33:12] <John> [02:33:16] [System Message] bla bla
[02:33:39] <John> heya
[02:33:40] <John> hello :S
[02:33:57] <John> hi
[02:33:57] [System Message] <John> has left the room 
[02:33:57] [System Message] <John> has entered the room";

        foreach (var msg in data.Split(new char[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries))
        {
            Match match = regex.Match(msg);
            if (match.Success)
            {
                if (match.Groups["Whisper"].Success)
                {
                    Console.WriteLine("[whis from {0}]: {1}", match.Groups["WhisperWho"].Value, msg);
                }
                else if (match.Groups["SysMessage"].Success)
                {
                    Console.WriteLine("[sys msg]: {0}", msg);
                }
                else
                {
                    Console.WriteLine("[normal from {0}]: {1}", match.Groups["NormalWho"].Value, msg);
                }
            }
        }