# Cash on Delivery (COD) Implementation Plan

**Branch:** `feature/cash-on-delivery`  
**Status:** In Development  
**Created:** March 29, 2026  

---

## 1. ARCHITECTURE DECISIONS

### Payment Method Type: Simple Transaction
- Uses Saleor's native `Transaction` objects
- No Payment App required (COD is manual payment)
- Creates transaction with status `NOT_CHARGED`
- Staff marks as paid via Dashboard when cash collected

### Why This Approach:
- ✅ Native Saleor data structures
- ✅ Appears in Dashboard automatically
- ✅ No metadata hacks
- ✅ Extensible to other simple payments (Bank Transfer)
- ✅ Compatible with Payment Apps later (Stripe, etc.)

---

## 2. FILE STRUCTURE

```
src/
├── lib/
│   ├── config/
│   │   └── paymentMethods.ts          # Payment methods configuration
│   └── saleor/
│       └── payments/
│           ├── types.ts                # Payment type definitions
│           ├── cod.ts                  # COD-specific logic
│           └── createTransaction.ts    # Generic transaction creator
│
├── components/
│   └── payment/
│       ├── PaymentMethodSelector.tsx   # Payment method selection UI
│       ├── PaymentMethodCard.tsx       # Individual payment card
│       └── CODInstructions.tsx         # COD-specific instructions
│
├── app/[locale]/checkout/
│   ├── page.tsx                        # Updated checkout page
│   └── components/
│       └── PaymentSection.tsx          # Checkout payment section wrapper
│
└── i18n/messages/
    ├── en.json                         # Payment translations
    ├── sr.json                         # Payment translations
    ├── de.json                         # Payment translations
    └── fr.json                         # Payment translations
```

---

## 3. DATA MODELS

### PaymentMethod Interface
```typescript
interface PaymentMethod {
  id: string;
  name: string;
  description: string;
  type: 'simple' | 'app';
  fee: number;
  available: boolean;
  availableInChannels: string[];
  icon?: string;
}
```

### COD Transaction Structure
```typescript
const codTransaction = {
  name: "Cash on Delivery",
  pspReference: `COD-${orderNumber}-${timestamp}`,
  availableActions: ["CHARGE"],
  amountAuthorized: { amount: 0, currency: "RSD" },
  amountCharged: { amount: 0, currency: "RSD" }
};
```

---

## 4. IMPLEMENTATION PHASES

### Phase 1: Configuration & Types (Files 1-3)
**Files:**
1. `lib/config/paymentMethods.ts` - Payment methods config
2. `lib/saleor/payments/types.ts` - Type definitions
3. `lib/saleor/payments/cod.ts` - COD transaction logic

**Deliverables:**
- [ ] Payment methods configuration
- [ ] TypeScript interfaces
- [ ] COD transaction creation function

### Phase 2: UI Components (Files 4-6)
**Files:**
4. `components/payment/PaymentMethodCard.tsx`
5. `components/payment/PaymentMethodSelector.tsx`
6. `components/payment/CODInstructions.tsx`

**Deliverables:**
- [ ] Payment method selection UI
- [ ] COD instructions component
- [ ] Responsive design

### Phase 3: Checkout Integration (Files 7-8)
**Files:**
7. `app/[locale]/checkout/components/PaymentSection.tsx`
8. `app/[locale]/checkout/page.tsx` (updated)

**Deliverables:**
- [ ] Payment section in checkout
- [ ] Integration with checkout flow
- [ ] Transaction creation on complete

### Phase 4: Translations (Files 9-12)
**Files:**
9-12. Update `i18n/messages/{en,sr,de,fr}.json`

**Deliverables:**
- [ ] All translation keys
- [ ] Serbian, English, German, French

### Phase 5: Testing
**Tasks:**
- [ ] Test COD flow end-to-end
- [ ] Verify transaction created in Saleor
- [ ] Test mobile responsiveness
- [ ] Test locale switching

---

## 5. CHECKOUT FLOW

```
1. User adds items to cart
   ↓
2. User proceeds to checkout
   ↓
3. Checkout page loads with:
   - Contact form (email, phone)
   - Shipping address form
   - Billing address form (same as shipping default)
   - Shipping method selector
   - PAYMENT METHOD SELECTOR (NEW)
     └─ COD selected by default
   - Order summary
   - Complete Order button
   ↓
4. User fills all required fields
   ↓
5. User clicks "Complete Order"
   ↓
6. System:
   a. Validates all fields
   b. Creates order via checkoutComplete
   c. Creates COD Transaction on order
   d. Redirects to order confirmation
   ↓
7. Order Confirmation page shows:
   - Order number
   - Total amount
   - Payment method: "Cash on Delivery"
   - Instructions: "Please prepare cash for delivery"
   ↓
8. Staff sees order in Dashboard:
   - Status: UNFULFILLED
   - Payment Status: NOT_CHARGED
   - Transaction: "Cash on Delivery (COD-123)"
   ↓
9. On delivery:
   - Delivery person collects cash
   - Staff marks order as FULFILLED in Dashboard
   - (Optional: Create CHARGE_SUCCESS transaction event)
```

---

## 6. SALESOR DASHBOARD VIEW

### Order Details:
```
Order #1234
├─ Status: UNFULFILLED
├─ Payment Status: NOT_CHARGED
├─ Transactions:
│  └─ Cash on Delivery (COD-1234-1743214567890)
│     ├─ Status: NOT_CHARGED
│     ├─ Amount: 3,200 RSD
│     └─ Available Actions: [CHARGE]
└─ Actions: [Fulfill] [Cancel]
```

### When Cash Collected:
```
Staff clicks [Fulfill]
  ↓
Order Status: FULFILLED
Payment Status: (still NOT_CHARGED, but order is complete)
```

---

## 7. TRANSLATION KEYS

### English (en.json):
```json
{
  "Payment": {
    "title": "Payment Method",
    "cod": {
      "name": "Cash on Delivery",
      "description": "Pay when you receive your order",
      "instructions": {
        "title": "Payment Instructions",
        "prepareCash": "Please prepare the exact amount in cash",
        "inspectOrder": "You can inspect your order before paying",
        "noFee": "No additional fee for cash on delivery"
      }
    },
    "card": {
      "name": "Credit Card",
      "description": "Secure online payment",
      "comingSoon": "Coming soon"
    },
    "selectMethod": "Select payment method",
    "securePayment": "Secure payment processing"
  }
}
```

### Serbian (sr.json):
```json
{
  "Payment": {
    "title": "Način Plaćanja",
    "cod": {
      "name": "Plaćanje Pouzećem",
      "description": "Platite kada primite porudžbinu",
      "instructions": {
        "title": "Uputstva za Plaćanje",
        "prepareCash": "Pripremite tačan iznos u gotovini",
        "inspectOrder": "Možete pregledati porudžbinu pre plaćanja",
        "noFee": "Bez dodatne naknade za plaćanje pouzećem"
      }
    }
  }
}
```

---

## 8. TESTING CHECKLIST

### Functional Tests:
- [ ] COD radio button selected by default
- [ ] Payment section visible in checkout
- [ ] Order completes with COD selected
- [ ] Transaction created with correct details
- [ ] Transaction visible in Saleor Dashboard
- [ ] Order confirmation shows COD
- [ ] Translations work in all locales

### Edge Cases:
- [ ] Checkout validation fails - payment method preserved
- [ ] Network error during transaction creation
- [ ] User switches payment methods (when multiple available)
- [ ] Mobile viewport - payment section responsive

### Integration Tests:
- [ ] End-to-end COD flow
- [ ] Order appears in Dashboard
- [ ] Staff can fulfill COD order
- [ ] Multiple payment methods display correctly

---

## 9. FUTURE ENHANCEMENTS

### Phase 2 (Post-MVP):
- [ ] Add Bank Transfer payment method
- [ ] Payment method icons
- [ ] Save payment preference for logged-in users

### Phase 3 (Advanced):
- [ ] Bitcoin (manual) payment method
- [ ] Bitcoin (automated) via custom handler
- [ ] Payment Apps integration (Stripe, etc.)

---

## 10. NOTES

### Why No Metadata:
- Saleor has native Transaction objects
- Transactions are typed and validated
- Appear in Dashboard automatically
- Support proper lifecycle (NOT_CHARGED → CHARGED)

### Why Simple Type (Not App):
- COD doesn't need async processing
- No external API to integrate
- No PCI compliance requirements
- Manual verification by staff

### Compatibility:
- Current architecture supports Payment Apps later
- Can add Stripe/PayPal as `type: 'app'` without breaking COD
- Bitcoin can be added as `type: 'async'` when ready

---

**Last Updated:** March 29, 2026  
**Next Review:** After Phase 1 completion