Discountify Laravel Package

Getting Started

1. Install the package via Composer:

   composer require safemood/discountify
   

2. Publish the config file to customize field mappings and behavior:

   php artisan vendor:publish --tag="discountify-config"
   

3. First use case: Define and apply a simple conditional discount in AppServiceProvider::boot():

   use Safemood\Discountify\Facades\Condition;
   use Safemood\Discountify\Facades\Discountify;
   
   Condition::define(
       'large_order_10_percent',
       fn (array $items) => collect($items)->sum('quantity') > 5,
       10
   );
   
   $total = Discountify::setItems($items)
       ->total(); // Automatically applies the condition if met
   

4. Explore documentation: Start with the Usage section of the README — especially Define Conditions, Calculate Total Amounts, and Class-Based Discounts.

Implementation Patterns

• Hybrid condition definitions: Combine callable-based and class-based conditions depending on complexity:

  • Use Condition::define() for simple, inline logic.
  • Use discountify:condition Artisan command + classes (php artisan discountify:condition ShippingThreshold) for reusable, testable logic.

• Field abstraction: When working with legacy or third-party item structures, use dynamic field mapping:

  Discountify::setFields(['price' => 'unit_price', 'quantity' => 'qty'])
      ->setItems($items)
      ->total();
  

• Layered discount application:

  • Apply global discounts first via setGlobalDiscount()
  • Add conditional discounts via Condition::define()
  • Finally, apply coupon-based discounts with applyCoupon($code) Example workflow:

  $total = Discountify::setItems($items)
      ->setGlobalDiscount(5) // e.g., seasonal site-wide sale
      ->applyCoupon('WELCOME10') // user coupon
      ->total();
  

• Extensibility via events: Register listeners to tie discount actions to business logic:

  • DiscountAppliedEvent: Update analytics or trigger loyalty points
  • CouponAppliedEvent: Log redemption attempts or enforce usage limits via Redis

• State management: Configure state_file_path for persistent coupon tracking (e.g., single-use or usage-limited coupons), especially useful in CLI or headless environments where sessions don’t exist.

Gotchas and Tips

• Breaking change in v1.0+: define() and defineIf() now require a slug. Existing code without slugs will break — always provide it:

  // ❌ Invalid after v1.0
  Condition::define('condition_name', $callback, 10);
  
  // ✅ Valid
  Condition::define('slug-unique', $callback, 10);
  

• skip field behavior: Set $skip = true on class-based conditions or pass 'skip' => true in Condition::add() — otherwise conditions are always evaluated, even if the callback returns false.

• Field name mismatches: Default field names are 'price' and 'quantity'. If your items use 'amount' or 'qty', either update config/discountify.php or call setFields() per request — mixing defaults and custom fields causes silent calculation errors.

• Discount precedence: The package applies all non-skipped conditions but does not prioritize or chain discounts additively — it uses the highest single discount among matching conditions. Double-check with totalDetailed() to verify which condition(s) applied.

• Tax calculations: calculateTaxAmount(19, true) applies tax after discounts — ensure tax logic aligns with your legal/financial requirements. The default tax() method applies tax on the pre-discount subtotal.

• Coupon persistence: By default, coupons are stored in a JSON file. For production, override the state_file_path to a database-backed driver (e.g., Redis or DB table) — especially for high-traffic apps or multi-server deployments where storage/app/discountify/coupons.json won’t be shared.

• Debugging tip: Always use totalDetailed() during development to verify discount logic, applied rates, savings, and tax breakdown in one go.