Produce results in response of rule evaluations

[jubianchi]

See #94 for detailed information.

Todo:

• Implement the Rules collection with an SplPriorityQueue
• Use the hoa/heap library for the Rules collection
• Implement the Then rule class (it returns a result when the rule validates the input)
• Implement the ThenElse rule class (it returns a result when the rule validates the input and another when the rule does not validate the input)
• Implement an algorithm to resolve rules dependencies (indeed, a rule can depend on another one). hoa/graph could be a good candidate for this kind of work.
• Implement a rule() function to reference the result of one rule from another rule

Some notes about the technical choices:

• I used some clones in the code: this is to guarantee immutability of the passed objects. For example the Hoa\Ruler\Rules::initializeRuler() may alter the ruler's asserter. Before doing this, we clone the ruler and then alter its content. Finally we return it to be used where needed.
• I introduced a Hoa\Ruler\Result class (with a magic method: this will change). It also does a clone of the result in some cases: this is to avoid mutating the value returned by the rules.
• This class (Hoa\Ruler\Result) is also here to return a structured result letting developers keep track of the returned value, the rule that produced it and its name in the collection

[Hywan]

@jubianchi Tell me when you need a review.

[jubianchi]

@Hywan you can start reviewing when you want: any comment is good.

There are still some things to do but I'd be glad to fix any issue you already saw ;)

[Hywan]

ping?

[Pittiplatsch]

@jubianchi I am interested in this feature as well. Is there anything I can help you with?

[jubianchi]

I can finish this issue if someone can give me:

• clear feedbacks,
• code review,
• clear TODOs

With that I would be able to ship new code and fix everything you spotted in a single iteration. TBH I won't have time to come back here after every push so I'd rather do everything in a single iteration.

[mathroc]

Hi,

I took a look at the code because it seems similar to something I'm looking for. afaict, this PR provides classes to associate a result with a rule (Then & ThenElse) and a class to get the first valid result of a set of rules.
While that's useful it's not exactly what I'm after. I was hoping to have rules themselves return a result instead of a boolean, eg:

$rule = 'apply_discount(price, if(premium, 0.9, 1))';
$ruler = new Hoa\Ruler\Ruler();
$context         = new Hoa\Ruler\Context();
$context['user'] = true;
$context['product'] = '100';
// add apply_discount
assert($ruler->execute($rule, $context) === '90');

is this out of the scope of this PR ?

[coveralls]

Coverage remained the same at 97.383% when pulling 2e8f513 on jubianchi:rule-results into 28174ca on hoaproject:master.

[coveralls]

Coverage remained the same at 97.383% when pulling 2e8f513 on jubianchi:rule-results into 28174ca on hoaproject:master.

[Hywan]

@jubianchi Should we do another round review?

[jubianchi]

@Hywan yes you can if you think this feature really makes sense in Ruler.

I was asking myself if it should stay here or go somewhere else...

BTW I updated the PR to use hoa/heap instead of SplHeap as requested in previous discussions.