Discountify Laravel Package

Getting Started

Minimal Setup

1. Installation:

   composer require safemood/discountify
   php artisan vendor:publish --tag="discountify-config"
   

2. First Use Case: Define a simple discount condition in AppServiceProvider:

   use Safemood\Discountify\Facades\Condition;
   
   public function boot()
   {
       Condition::define('test_discount', fn($items) => true, 10);
   }
   

3. Apply Discounts:

   use Safemood\Discountify\Facades\Discountify;
   
   $items = [['price' => 100, 'quantity' => 1]];
   $total = Discountify::setItems($items)->total();
   

Key Starting Points

• Facade: Discountify for core calculations (total(), totalDetailed()).
• Facade: Condition for defining rules.
• Facade: Coupon for coupon-based discounts.
• Artisan Command: discountify:condition for scaffolding class-based conditions.

Implementation Patterns

Core Workflow

1. Define Discount Rules:

   // Inline conditions (ServiceProvider)
   Condition::define('bulk_discount', fn($items) => count($items) > 5, 15);
   
   // Class-based (auto-discovered)
   // App/Conditions/SeasonalDiscount.php
   class SeasonalDiscount implements ConditionInterface {
       public function __invoke($items) { return now()->month === 12; }
   }
   

2. Set Cart Items:

   Discountify::setItems([
       ['price' => 50, 'quantity' => 2],
       ['price' => 100, 'quantity' => 1, 'type' => 'premium']
   ]);
   

3. Calculate Totals:

   $total = Discountify::total(); // Basic total
   $detailed = Discountify::totalDetailed(); // Array with subtotal, tax, savings
   

Integration Tips

• Dynamic Fields: Override default price/quantity keys via config or runtime:

  Discountify::setFields(['price' => 'amount', 'quantity' => 'qty']);
  

• Global Adjustments:

  Discountify::setGlobalDiscount(10)->setGlobalTaxRate(20);
  

• Coupon Flow:

  Discountify::applyCoupon('SUMMER20')->total();
  

Event-Driven Extensions

Listen for discount application events in EventServiceProvider:

Event::listen(DiscountAppliedEvent::class, function ($event) {
    // Log discounts or trigger notifications
    logger()->info('Discount applied', $event->discounts);
});

Gotchas and Tips

Common Pitfalls

1. Slug Requirement:

   • Since v1.0.0, Condition::define() requires a slug parameter. Older code may break:

     // Old (deprecated)
     Condition::define('test', fn($items) => true, 10);
     
     // New
     Condition::define('test_slug', fn($items) => true, 10);
     

   • Fix: Update all condition definitions to include slugs.

2. Coupon Scoping:

   • User-restricted coupons (userIds) must pass the user ID explicitly:

     Discountify::applyCoupon('EXCLUSIVE', auth()->id());
     

   • Debug: Check storage/app/discountify/coupons.json for coupon state.

3. Field Mismatches:

   • If price/quantity keys don’t match config, calculations fail silently.
   • Tip: Use setFields() dynamically or verify config:

     $discountify->setFields(config('discountify.fields'));
     

Debugging Tips

• Inspect Conditions:

  dd(Discountify::getConditions()); // List all registered conditions
  

• Coupon Validation:

  if (!Discountify::validateCoupon('INVALID')) {
      // Handle invalid coupon
  }
  

• Event Payloads: Dump DiscountAppliedEvent or CouponAppliedEvent to verify applied discounts:

  Event::listen(DiscountAppliedEvent::class, fn($e) => dd($e->discounts));
  

Performance Quirks

• Class-Based Conditions: Auto-discovered but loaded on first use. For critical paths, eager-load:

  app()->make('Safemood\Discountify\Contracts\ConditionInterface');
  

• Coupon Storage: Coupon state is stored in storage/app/discountify/coupons.json. Clear it for testing:

  php artisan discountify:clear-coupons
  

Extension Points

1. Custom Condition Logic: Extend ConditionInterface for reusable logic:

   class MinCartValueDiscount implements ConditionInterface {
       public function __invoke($items) {
           return array_sum(array_column($items, 'price')) > 100;
       }
   }
   

2. Tax Calculation Overrides: Bind a custom tax calculator:

   app()->bind('discountify.tax', fn() => new CustomTaxCalculator());
   

3. Event Modifiers: Subscribe to DiscountAppliedEvent to adjust discounts dynamically:

   Event::listen(DiscountAppliedEvent::class, function ($event) {
       $event->discounts[] = ['slug' => 'admin_override', 'value' => 5];
   });