TemplateRegexMatcher.getStartRegex sometimes returns a regex that matches with an index before the license start

[sdheh]

Version 1.1.11
Example 1 greedy regex after optional:

String licenseText = "ab cd text";
String licenseTemplate = "<<beginOptional>>cd<<endOptional>> <<var;name=\"copyright\";original=\"Copyright (c) <year> <copyright holders>  \";match=\".{0,5000}\">> text";
TemplateRegexMatcher templateRegexMatcher = new TemplateRegexMatcher(licenseTemplate);
String startRegex = templateRegexMatcher.getStartRegex(25);
System.out.println("start regex: " + startRegex);
Matcher matcher = Pattern.compile(startRegex).matcher(licenseText);
if (matcher.find()) {
    System.out.println("start index found: " + matcher.start());
}

Returns

start regex: (?im)(\Qcd\E\s*)?(.{0,5000})\Qtext\E\s*
start index found: 0

but the start index should be 3.

Example 2 greedy regex at start:

String licenseText = "abtext";
String licenseTemplate = "<<var;name=\"copyright\";original=\"Copyright (c) <year> <copyright holders>  \";match=\".{0,5000}\">> text";
TemplateRegexMatcher templateRegexMatcher = new TemplateRegexMatcher(licenseTemplate);
String startRegex = templateRegexMatcher.getStartRegex(25);
System.out.println("start regex: " + startRegex);
Matcher matcher = Pattern.compile(startRegex).matcher(licenseText);
if (matcher.find()) {
    System.out.println("start index found: " + matcher.start());
}

Returns

start regex: (?im)(.?{0,5000})\Qtext\E\s*
start index found: 1

but the start index should be 2.
.?{0,5000} doesn't seem to work as expected. It is an unusual regex that some online regex websites say is invalid: https://regex101.com/r/l3810b/1, regexr.com/81kfo.
https://www.freeformatter.com/java-regex-tester.html says the regular expression is valid.

I think maybe to fix this you could just offer a method for a regex to find the beginning of the non-optional part. Otherwise a changing the regular expressions in these two cases to something like the following could work

(?im)((\Qcd\E\s*)(.{0,5000})\Qtext\E\s*)|(\Qtext\E\s*)
(?im)\Qtext\E\s*

In the first case if there were multiple optional parts it would get even more complicated to do it correctly.

[goneall]

Now that I review this issue, I do tend to agree that this is an issue if the method is being used without following on with the template matcher.

@sdheh - It looks like you have a pretty good handle on approaches to fix this. Can you create a pull request?