Common tags

[mikkokar]

Description

Introduces a CommonTag class to simplify and harmonise Styx object tags API. Now each Tag will be represented as a CommonTag instance, with provided name, encode and decode functions.

This imposes a common format: name = tag-value.

Each tag is associated with value type T. The encode and decode functions convert between values of T and encoded tag value strings.

All common tag operations, like creating, searching, matching, and removing tags are now implemented as higher order functions in the common base class.

Alternative API

Some of the common functions could be implemented as Kotlin extension methods. Which method do you prefer? Let me know and we can shape the code accordingly.

An alternative to CommonTags find method would be:

fun <T> Set<String>.valueOf(tag: CommonValueTag<T>): T? = this.firstOrNull { tag.match(it) }
        ?.let { tag.valuePart(it) }
        ?.let { tag.decode(it) }

Similarly, an alternative to match would be:

fun String.isA(tag: CommonValueTag<*>) = tag.match(this)

An alternative to valueOf method would be:

fun <T> String.match(tag: CommonValueTag<T>) = tag.valuePart(this)
         ?.let { tag.decode(it) }

[chrisgresty]

A few small observations, nothing particularly significant.

[chrisgresty]

Is it worth providing defaults for encode and decode as { it } ?

[mikkokar]

Is this possible without knowing the type T?