implement filtering

[plastikfan]

The filters defined here will supercede the legacy ones defined in extendio by allowing muliple filters to be defined as a single overall mother filter. The mother filter will use its constituents by combining them into a mathematical expression. This will allow a filters to be composed together into an expression, for example:

(filter1 && filter2) || filter3

each of these constituent filters are in themselves reg-exes.

Need to consider using a 3rd party mathematical expression parser for example DOC: math parser for Go, ARTICLE. Actually this is a paid one, so you'll have to find another.

Perhaps we roll our own version. Ginkgo allows for expressions to be used in conditionally selecting tests by labels to be run.

And here's a stackoverflow question

We can just use the parser in the go standard library (go/parser, go/ast); in particluar, see ParseExpr For now, we just need to implement vanilla filters but make sure we can add an expression based filter later on.

So we have the following types of vanilla filters:

• regex
• glob
• poly

... and then we have an expression filter which can combine any vanilla filters into a boolean expression

Define an internal version of hooks that we'll call interceptors. This will enable us to keep filtering code out of the navigator and remain in the filter plugin as required. We cant use a life-cycle ebent because the filtering iis an internal affair that shouldnt be exposed to the client. We also can't use a bus event because we need the plugin to provide an internal operation; filter the children, but bus events are an output only mechanism. Hence we need internal hooks/interceptors.