Feat: configurable postcode resolver

[wychoong]

postcode format varies for each countries. it will be hard to only have 1 lunar resolver to cater for all

this PR enables dev to replace with own resolver that suit the countries the store is running

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
lunar-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 20, 2024 3:03am

[glennjacobs]

Sounds like a good idea. I'll review with @alecritson when he's back from annual leave.

[alecritson]

I had a little look at this, my 15 minutes of thought is, instead of making this config specific, why not make it country specific? This way we just need to register new postcode resolvers for countries and let the core handle it...

We already have a Lunar\Shipping\DataTransferObjects\PostcodeLookup DTO which has the postcode string and also a Country model property. So have both of what we need already. We could then add a method to the DTO getParts which resolves to the correct postcode resolver based on the country (or fallsback to the default)

So instead of this:

$postcodeParts = (new PostcodeResolver)->getParts(
    $this->postcodeLookup->postcode
);
$query->whereIn('postcode', $postcodeParts);

We have this:

$query->whereIn('postcode', $this->postcodeLookup->getParts());

The getParts method could look something like this:

public function getParts(): array
{
   // New facade? Could resolve to a postcode manager class
   return Postcode::country($this->country)->getParts($this->postcode);
}

On this new manager class we could have

class PostcodeManager
{
    protected array $resolvers = [];
    
    public function addResolver(string $class)
    {
        $this->resolvers[] = $class;
    }
    
    public function country(Country $country)
    {
        foreach ($this->resolvers as $resolver) {
            // Check the resolver works for this country and return it...
        }
    }
}

Need to think about if multiple resolvers are registered, however we could have some sort of key signature on the array or make it so the last in the array is the "first" so the default will always come last in the matching 🤷

A postcode resolver could look like:

class PostcodeResolver implements PostcodeResolveInterface
{
    protected array $countries = ['GB'];

    public function supportsCountry(Country $country): bool
    {
        // The default one will just return true
        return in_array($country->iso2, $this->countries);
    }
    
    // ...
}

Then maybe to register a new resolve you just do:

// Again, new facade?
Postcode::addResolver(MyCustomResolver::class);

Idk this was my "thinking out loud" 🤔

[wychoong]

I like the idea postcode resolvers. The only thing I would add on is to allow adding the supported countries to a resolver