Suggest splitting `PackageURL.java` into multiple files

[dwalluck]

For me, PackageURL.java is getting pretty large. What do you think about splitting out the various utilities, like an ASCII utils and a URI utils class?

[ppkarwasz]

I think that helper methods should be moved out of PackageURL too, probably into an internal package that will not be exported by the JPMS module descriptor.

Since PURL supports many types with different validation and canonicalization rules, it might be useful to extract some TypeValidator interface to validate the different part of the PURL:

public interface TypeValidator {
    String validateNameSpace(String nameSpace);
    String validateName(String name);
    String validateVersion(String version);
    void validateQualifier(String key, String value);
    String validateSubpath(String subpath);
}

[dwalluck]

I think they need the full list of qualifiers since some types need to check for specific ones like qualifiers.get("channel").

It's possible that a single method might work. The types really need to get the full components in parsed and normalized form before they do anything with them (the default normalizer has to be applied first), so they really can't process them at separate times.

If it's a single method, it probably has to create a new PackageURL to store the components which maybe isn't ideal.

[ppkarwasz]

I think they need the full list of qualifiers since some types need to check for specific ones like qualifiers.get("channel").

That is sure, each type should have a list of allowed qualifiers and an action could be taken for each invalid one (either drop or throw). For that purpose an interface similar to the SAX ErrorHandler could be used, which could be used also in other places to implement both a strict (throw) and lenient (warn) parser behavior.

It's possible that a single method might work. The types really need to get the full components in parsed and normalized form before they do anything with them (the default normalizer has to be applied first), so they really can't process them at separate times.

If it's a single method, it probably has to create a new PackageURL to store the components which maybe isn't ideal.

Sure, validate(PackageURL) could work as well and it has the advantage of being a functional interface! 💯

[jeremylong]

I'm all for this. However, I'd like to continue to get the backlog of PRs cleaned up before continuing to add to the merge conflict race ;)

[dwalluck]

Done in #220.