# Supplier Product/Price Association Implementation Plan

## Critical Feature for Automatic PO Creation

### Problem
Suppliers currently have no product/price associations. Without this data:
- ❌ Automatic Purchase Order (PO) creation cannot function
- ❌ System cannot determine which supplier to order from
- ❌ System cannot calculate PO amounts
- ❌ Procurement optimization is impossible

### Backend Support (Already Exists)
`SupplierPriceList` model in `/services/suppliers/app/models/suppliers.py`:
```python
class SupplierPriceList(Base):
    supplier_id: UUID
    inventory_product_id: UUID  # Reference to product
    unit_price: Decimal         # Price per unit
    unit_of_measure: String     # kg, g, L, ml, units
    minimum_order_quantity: Integer
    tier_pricing: JSONB         # Volume discounts
    effective_date: DateTime
    expiry_date: DateTime
    is_active: Boolean
```

### Frontend Implementation

#### Phase 1: Supplier Step Enhancement
**File**: `/frontend/src/components/domain/setup-wizard/steps/SuppliersSetupStep.tsx`

**New Features**:
1. **Product Association Section** (after supplier is created)
   - Expandable "Manage Products" for each supplier
   - Multi-select product picker from inventory
   - Price entry form for each selected product

2. **UI Flow**:
```
[Supplier Card]
├─ Name, Contact, Type
├─ [Manage Products ▼] button
└─ When expanded:
    ├─ [+ Add Product] button → Opens modal
    ├─ Product List (if any exist):
    │   └─ [Product Name] - [Price] [Unit] [Edit] [Delete]
    └─ [Save Products] button
```

3. **Product Selector Modal**:
```
Modal: "Add Products for [Supplier Name]"
├─ Multi-select dropdown (from inventory)
├─ For each selected product:
│   ├─ Product Name (read-only)
│   ├─ Unit Price (€) input *required
│   ├─ Unit of Measure select *required
│   └─ Min Order Qty input (optional)
└─ [Cancel] [Save Prices]
```

#### Phase 2: Backend Integration
**API Endpoints** (already exist):
- `POST /suppliers/{supplier_id}/price-lists` - Create price list item
- `GET /suppliers/{supplier_id}/price-lists` - Get supplier's price list
- `PUT /suppliers/{supplier_id}/price-lists/{price_list_id}` - Update price
- `DELETE /suppliers/{supplier_id}/price-lists/{price_list_id}` - Delete price

**Frontend Services** needed:
- `useSupplierPriceLists(supplierId)` - Fetch price lists
- `useCreateSupplierPriceList()` - Create price list items
- `useUpdateSupplierPriceList()` - Update prices
- `useDeleteSupplierPriceList()` - Delete price list items

#### Phase 3: Data Flow
```
User creates supplier
    ↓
Supplier card shows "Manage Products" button
    ↓
Click → Expand section showing current products (if any)
    ↓
Click "Add Product" → Modal opens
    ↓
Select products from inventory + Enter prices
    ↓
Save → API call to create SupplierPriceList entries
    ↓
Modal closes, product list updates
    ↓
User can proceed to next step
```

### Implementation Checklist

- [ ] Create useSupplierPriceLists hook
- [ ] Create useCreateSupplierPriceList hook
- [ ] Create useUpdateSupplierPriceList hook
- [ ] Create useDeleteSupplierPriceList hook
- [ ] Add product management UI to SuppliersSetupStep
- [ ] Create product selector modal component
- [ ] Add price entry form
- [ ] Integrate with backend API
- [ ] Add validation (price > 0, unit required)
- [ ] Test create/update/delete flow
- [ ] Test navigation (can proceed after products added)

### Benefits After Implementation
✅ Automatic PO creation will work
✅ System knows which supplier supplies what
✅ System knows current prices
✅ Can calculate PO totals automatically
✅ Can optimize procurement based on prices
✅ Can track price changes over time
✅ Foundation for supplier performance analysis