A simple string variation builder (GZDoom / ZScript)

string-builder.cs

// Make a string from a variable template
static string BuildVariableString(string msg){
	// some input example strings:
	// "an empty {beer|soda|wine|champagne} bottle. {It is {cracked|broken|unlabeled}.}"
	// "a {small|large|||} plush {emoji|cacodemon|teddy bear|furbie} toy."

	// Collapse substrings, repeat until no more { }
	while(true){
		int LeftBrace = msg.RightIndexOf("{"); // find the rightmost left-brace {
		int RightBrace = msg.IndexOf("}",LeftBrace+1); // find the nearest matching right-brace }
		if (LeftBrace == -1 || RightBrace == -1) { break; } // stop looping if no more {}

		string substring = msg.Mid(LeftBrace+1, (RightBrace-LeftBrace)-1); // get inner text string, without {} braces
		msg.Remove(LeftBrace+1, (RightBrace-LeftBrace)-1); // remove the inner text string, leave the {} braces
		
		// build an array of substrings from the extracted string, separated by |
		array<string> substrings;
		substring.Split(substrings,"|");

		// pick a random sub-string from the {|||} set
		// replace the leftover {} with the picked substring
		// empty || pairs can be used for random null results
		msg.Replace("{}", substrings[random(0,substrings.Size()-1)]);
	}

	// Remove double-spaces, repeat until no more
	while (true) {
		if (msg.IndexOf("  ", 0) > -1) { msg.Replace("  ", " "); }
		else { break; }
	}

	return msg;
}