# Phase 14: Customer Management - COMPLETE ✅

## Overview
Phase 14 implements comprehensive customer management with CRUD operations, search functionality, price list linking, and tax exemption support. The system supports both B2C and B2B customers, with optional customer assignment to sales.

## Implementation Details

### 1. Customer Service
**File:** `server/modules/customers/services/index.js`

Implemented the following functions:

#### createCustomer
Creates a new customer:
- Validates required fields (name)
- Validates customer_type (B2C or B2B)
- Validates credit_limit (non-negative)
- Validates price_list_id if provided
- Creates customer with all fields
- Returns created customer with associations

#### getCustomer
Retrieves a customer by ID with associations:
- Includes price list
- Includes tax exemptions
- Returns customer with all related data

#### updateCustomer
Updates an existing customer:
- Validates customer exists
- Updates provided fields only (partial update)
- Validates price_list_id if provided
- Validates all updated fields
- Returns updated customer with associations

#### deleteCustomer
Soft deletes a customer:
- Sets active status to false
- Preserves customer data for historical sales
- Does not delete customer record

#### listCustomers
Lists customers with optional filters and pagination:
- Supports filtering by customer_type, active status, price_list_id
- Supports search by name or KRA PIN
- Defaults to active customers only
- Paginated results with metadata
- Ordered by creation date descending

#### searchCustomers
Searches customers by name or KRA PIN:
- Searches in customer name and KRA PIN fields
- Returns only active customers
- Supports limit option
- Ordered by name ascending
- Returns array of matching customers

### 2. Controllers
**File:** `server/modules/customers/controllers/index.js`

Implemented controllers for:
- createCustomer: Creates a new customer
- getCustomer: Retrieves customer by ID
- updateCustomer: Updates existing customer
- deleteCustomer: Soft deletes customer
- listCustomers: Lists customers with filters
- searchCustomers: Searches customers

All controllers:
- Use asyncHandler for error handling
- Extract data from request (body, params, query)
- Call appropriate service functions
- Return standardized responses
- Log operations

### 3. Validations
**File:** `server/modules/customers/validations/index.js`

Implemented comprehensive validation rules for:
- createCustomer:
  - name (required, 1-150 chars)
  - customer_type (optional, B2C or B2B)
  - kra_pin (optional, max 20 chars)
  - credit_limit (optional, non-negative)
  - price_list_id (optional, positive integer)
- getCustomer: customer ID (required, positive integer)
- updateCustomer: All fields optional with appropriate validation
- deleteCustomer: customer ID (required, positive integer)
- listCustomers: Optional filters (customer_type, active, price_list_id, search, page, limit)
- searchCustomers: q (required), limit (optional, 1-100)

### 4. Routes
**File:** `server/modules/customers/routes/index.js`

Implemented RESTful routes:
- `POST /api/customers` - Create customer (manager, system_admin)
- `GET /api/customers` - List customers (authenticated)
- `GET /api/customers/search` - Search customers (authenticated)
- `GET /api/customers/:id` - Get customer by ID (authenticated)
- `PUT /api/customers/:id` - Update customer (manager, system_admin)
- `DELETE /api/customers/:id` - Delete customer (manager, system_admin)

All routes:
- Use authentication middleware
- Use role-based access control where appropriate
- Include request validation
- Have Swagger documentation

### 5. Routes Integration
**File:** `server/routes/index.js`

Added customer routes to main routes file:
- `router.use('/customers', customerRoutes)`

### 6. Integration with Existing Systems

#### Sales Integration
**Already implemented in Phase 4:**
- Sales already support optional customer_id
- Sales service validates customer if provided
- Customer lookup integrated in sales workflow

#### Price List Integration
**Already implemented in Phase 7B:**
- Customer model has price_list_id field
- Customers can be assigned to price lists
- Price list service supports customer-specific pricing
- getPriceForCustomer function uses customer's price_list_id

#### Tax Exemption Integration
**Already implemented in Phase 7C:**
- TaxExemption model has customer_id field
- Customer model has taxExemptions association
- Tax calculation service checks customer exemptions
- checkTaxExemption function supports customer exemptions

## Key Features

### 1. Customer Types
- **B2C**: Walk-in customers (default)
- **B2B**: Business customers with credit limits

### 2. Soft Delete
- Customers are soft deleted (active = false)
- Preserves historical sales data
- Can be reactivated if needed

### 3. Search Functionality
- Search by name or KRA PIN
- Case-insensitive partial matching
- Fast lookup for sales workflow

### 4. Price List Assignment
- Customers can be assigned to price lists
- Supports customer-specific pricing
- Price list validated before assignment

### 5. Credit Limit Management
- Credit limits for B2B customers
- Tracks credit limit per customer
- Default credit limit is 0

### 6. Tax Exemption Support
- Customers can have tax exemptions
- Exemptions checked during tax calculation
- Linked via TaxExemption model

## API Endpoints Summary

### Customer Endpoints
- `POST /api/customers` - Create customer
- `GET /api/customers` - List customers
- `GET /api/customers/search` - Search customers
- `GET /api/customers/:id` - Get customer by ID
- `PUT /api/customers/:id` - Update customer
- `DELETE /api/customers/:id` - Delete customer (soft delete)

## Testing Checklist

- [x] Create customer (B2C)
- [x] Create customer (B2B)
- [x] Get customer by ID
- [x] Update customer
- [x] Soft delete customer
- [x] List customers with filters
- [x] Search customers by name
- [x] Search customers by KRA PIN
- [x] Link customer to price list
- [x] Remove price list from customer
- [x] Customer integration with sales
- [x] Customer tax exemptions (already implemented in Phase 7C)

## Dependencies

- Phase 7B: Pricing (PriceList model - price_list_id field already exists in Customer model)
- Phase 7C: Taxes (TaxExemption model - customer_id field already exists)

## Notes

1. **Optional Customers**: Customers are optional for sales (walk-in sales don't require customers)
2. **Price List Linking**: Customers link to price lists via price_list_id field (already in model)
3. **Tax Exemptions**: Customer tax exemptions supported via TaxExemption model (already implemented in Phase 7C)
4. **Sales Integration**: Sales already support customer_id (implemented in Phase 4)
5. **Soft Delete**: Customers are soft deleted to preserve historical data
6. **Search**: Fast search by name or KRA PIN for sales workflow

## Next Steps

Phase 14 is complete. The customer management system is fully functional with CRUD operations, search, price list linking, and tax exemption support. All endpoints are operational and integrated with sales, pricing, and tax systems.

