Add IPv6 string validation

[NeQuissimus]

Looks like IPv6 validation using a regex is what makes the most sense.

• I looked at sun.net.util.IPAddressUtil but that's an internal JDK API, not supposed to be used, not available for Scala.JS (it is the underlying implementation for java.net.InetAddress)
• java.net.InetAddress itself always tries to make DNS calls unless you convert the String into the address bytes. That would, however, require a lot of logic to undo compacting etc.
• Guava and Apache Commons Validator are JVM-only and fairly large

[codecov]

Codecov Report

Merging #357 into master will increase coverage by 0.19%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #357      +/-   ##
==========================================
+ Coverage   95.54%   95.73%   +0.19%     
==========================================
  Files          46       46              
  Lines         561      586      +25     
  Branches       12       12              
==========================================
+ Hits          536      561      +25     
  Misses         25       25

Impacted Files	Coverage Δ
...red/src/main/scala/eu/timepit/refined/string.scala	100% <100%> (ø)	⬆️

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[fthomas]

This looks very good but due to #356 there are now conflicts that need to be resolved. I also think there is an opportunity to make the regex more readable. Let me know what you think.

[fthomas]

Can we factor out common subexpressions to reduce the length of that regex? [0-9A-Fa-f]{1,4} seems to be a good candidate on a first glance. I'd imagine doing it like this:

val regex = {
  val group = "[0-9A-Fa-f]{1,4}"
  s"^(^(($group(((:$group){5}::$group) ..."
}

[derekmorr]

java.net.InetAddress only makes DNS calls if the input isn't an IP address literal. IPv6 address parsing is pretty complicated. It doesn't look like this parser handles embedded IPv4-literals:

scala>     val regex =
     |       "^(^(([0-9A-Fa-f]{1,4}(((:[0-9A-Fa-f]{1,4}){5}::[0-9A-Fa-f]{1,4})|((:[0-9A-Fa-f]{1,4}){4}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,1})|((:[0-9A-Fa-f]{1,4}){3}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,2})|((:[0-9A-Fa-f]{1,4}){2}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,3})|(:[0-9A-Fa-f]{1,4}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,4})|(::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,5})|(:[0-9A-Fa-f]{1,4}){7}))$|^(::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,6})$)|^::$)|^((([0-9A-Fa-f]{1,4}(((:[0-9A-Fa-f]{1,4}){3}::([0-9A-Fa-f]{1,4}){1})|((:[0-9A-Fa-f]{1,4}){2}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,1})|((:[0-9A-Fa-f]{1,4}){1}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,2})|(::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,3})|((:[0-9A-Fa-f]{1,4}){0,5})))|([:]{2}[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,4})):|::)((25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{0,2})\\.){3}(25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{0,2})$$".r.pattern
regex: java.util.regex.Pattern = ^(^(([0-9A-Fa-f]{1,4}(((:[0-9A-Fa-f]{1,4}){5}::[0-9A-Fa-f]{1,4})|((:[0-9A-Fa-f]{1,4}){4}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,1})|((:[0-9A-Fa-f]{1,4}){3}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,2})|((:[0-9A-Fa-f]{1,4}){2}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,3})|(:[0-9A-Fa-f]{1,4}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,4})|(::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,5})|(:[0-9A-Fa-f]{1,4}){7}))$|^(::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,6})$)|^::$)|^((([0-9A-Fa-f]{1,4}(((:[0-9A-Fa-f]{1,4}){3}::([0-9A-Fa-f]{1,4}){1})|((:[0-9A-Fa-f]{1,4}){2}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,1})|((:[0-9A-Fa-f]{1,4}){1}::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,2})|(::[0-9A-Fa-f]{1,4}(:[0-9A-Fa-f]{1,4}){0,3})|((:[0-9A-Fa-f]{1,4}){0,5})))|([:]{2}[0-9A-Fa-f]{1,4}(:[0-9A-Fa-...

scala> regex.matcher("2001:db8:122:344::192.0.2.33").matches // example from https://tools.ietf.org/html/rfc6052#section-2.4
res1: Boolean = false

scala> import java.net.InetAddress // But the JDK's parser works fine
import java.net.InetAddress

scala> InetAddress.getByName("2001:db8:122:344::192.0.2.33")
res2: java.net.InetAddress = /2001:db8:122:344:0:0:c000:221

[fthomas]

Thanks @derekmorr for this test case. https://stackoverflow.com/a/17871737/460387 shows that a regex can handle embedded IPv4 literals. @NeQuissimus what do you think about updating the regex to also support embedded IPv4 literals?

[NeQuissimus]

Sorry, I completely missed the feedback here. I will take a look.
I was aware of this, my regex only validates against RFC-8200.
I'll see if I can't make some improvements or maybe find a better regex online.

[kusamakura]

It might also be a nice touch to have an Inference for IPv4 ==> IPv6, if that's possible. (Or also the other way around for valid values.)

[NeQuissimus]

I fixed up the regex to account for embedded IPv4 addresses and I also extracted common elements.
I added tests for the new address formats.

@fthomas Can you kick off the Travis build again? No matter how often I run the tests locally, they pass...

[fthomas]

The Scala.js tests failed with

[info] ! StringValidate.IPv6.isValid.compact: Falsified after 0 passed tests.

This should be reproducible with coreJS/test.

[NeQuissimus]

wow, this took me a while! JavaScript's Regex engine has different eagerness rules than the one in the JVM...
I fixed it now and hopefully Travis will agree...

[fthomas]

LGTM, many thanks @NeQuissimus!