Add GET and LIST APIs for retrieving registered patterns

[embano1]

Currently in quamina when using the default matcher, i.e. quamina.New() there is no way to retrieve the registered patterns, e.g. for debugging, inspection, pattern handling (review/replace during runtime, etc.).

The following APIs would be useful (just a proposal, need to figure return types):

• func (q *Quamina) GetPattern(x X) (string, error) (note: assumes pattern is of type string)
• func (q *Quamina) ListPatterns() ([]string, error) (note: assumes pattern is of type string)

[timbray]

Good idea, but remember that you can say

q.AddPattern(`{"a": [1]}` )
q.AddPattern(`{"a":{"b": ["33"]}}`

I.e. multiple patterns for the same X. So the first API needs to be something like:

func (q *Quamina) GetPatternsFor(x X) ([]string, error)

I'm trying to think of a use-case for the second proposal and coming up empty so far. Nothing wrong with the proposal though.

Finally, my experience suggests anything that returns a plural result will probably eventually need pagination tokens.

[embano1]

Good idea, but remember that you can say

q.AddPattern(`{"a": [1]}` )

q.AddPattern(`{"a":{"b": ["33"]}}`

I.e. multiple patterns for the same X. So the first API needs to be something like:

func (q *Quamina) GetPatternsFor(x X) ([]string, error)

Good point (multiple patterns). IMHO GetPatterns(x X) (or even just Patterns(x X)) still works as name bc it's pretty clear even without For, just needs []string as you suggest.

I'm trying to think of a use-case for the second proposal and coming up empty so far. Nothing wrong with the proposal though.

Finally, my experience suggests anything that returns a plural result will probably eventually need pagination tokens.

All fair points, let's defer List for now then.

[timbray]

Hey @jsmorph is there anything about this that would be hard?

[jsmorph]

The Pruner has LivePatternState, which offers something close. The standard implementation is memState, which really is just a map[X]stringSet. GetPattern(X) ([]string, error) would be fine to add, I think.

Re ListPatterns: I personally prefer a function like func(func(x X, pattern string) error) error in order to reduce allocation and/or avoid pagination. LivePatternState has Iterate(func(x X, pattern string) error) error).