# Receipt & Invoice System - Complete Implementation Guide
## KSO Chandigarh Management System

### 📋 System Overview

The KSO Chandigarh management system includes a comprehensive receipt and invoice generation, storage, and viewing system. This system handles all financial transactions with professional documentation and audit trails.

---

## 🔧 Technical Architecture

### Backend Components

1. **ReceiptService.php** (`api/services/ReceiptService.php`)
   - Core service for receipt/invoice generation
   - PDF/HTML template rendering
   - File storage management
   - Database integration

2. **API Endpoints** (`api/receipts/index.php`)
   - RESTful API for all receipt operations
   - Authentication required
   - JSON responses

3. **Database Schema** (`database/receipt_invoice_setup.sql`)
   - `receipts` table - Receipt records
   - `invoices` table - Invoice management
   - Foreign key relationships with members and finance tables

4. **Templates**
   - `api/templates/receipts/standard.php` - Professional receipt template
   - `api/templates/invoices/standard.php` - Invoice template

### Frontend Components

1. **Receipt Management Page** (`frontend/pages/receipts.html`)
   - AdminLTE v3 interface
   - Statistics dashboard
   - Receipt listing with filters
   - Modal previews

2. **JavaScript Interface** (`frontend/js/receipts.js`)
   - API integration
   - Dynamic UI updates
   - Real-time filtering
   - Receipt generation

---

## 🚀 Key Features

### ✅ Receipt Generation
- **Automatic Numbering**: Smart receipt numbers with prefixes
  - `KSO-MF-202507XXXX` - Membership Fees
  - `KSO-EF-202507XXXX` - Event Fees
  - `KSO-DN-202507XXXX` - Donations
  - `KSO-OT-202507XXXX` - Other Transactions

- **Professional Templates**: HTML-based with PDF conversion capability
- **Member Integration**: Automatic member data inclusion
- **Transaction Types**: Support for all financial transaction types

### ✅ Invoice Management
- **Invoice Creation**: Generate invoices for upcoming payments
- **Status Tracking**: pending, paid, overdue, cancelled
- **Due Date Management**: Automatic overdue detection
- **Payment Integration**: Link invoices to actual payments

### ✅ Storage & Organization
- **File System**: Organized by year/month structure
  ```
  storage/
  ├── receipts/
  │   ├── 2025/
  │   │   ├── 01/
  │   │   ├── 02/
  │   │   └── ...
  └── invoices/
      └── 2025/
          ├── 01/
          └── ...
  ```

- **Database Records**: Complete audit trail and metadata
- **Duplicate Prevention**: Unique receipt numbers
- **Version Control**: Track generation and updates

### ✅ User Interface
- **Statistics Dashboard**:
  - Total receipts generated
  - Today's receipts
  - Monthly receipts
  - Total amount processed

- **Advanced Filtering**:
  - Search by receipt number, member name
  - Filter by transaction type
  - Date range filtering
  - Status filtering

- **Actions Available**:
  - Generate new receipts
  - View/preview receipts
  - Download receipts
  - Regenerate if needed
  - Email receipts to members

---

## 📊 API Endpoints

### Receipt Management

#### GET `/api/receipts/receipts`
**List receipts with pagination and filters**

**Parameters:**
- `search` - Search term (receipt number, member name)
- `transaction_type` - Filter by type (membership_fee, donation, etc.)
- `year` - Filter by year
- `month` - Filter by month
- `limit` - Number of results (default: 50)
- `offset` - Pagination offset

**Response:**
```json
{
  "success": true,
  "data": [
    {
      "id": 1,
      "receipt_number": "KSO-MF-202507001",
      "member_name": "John Doe",
      "amount": "5000.00",
      "transaction_type": "membership_fee",
      "created_at": "2025-07-10 10:30:00",
      "file_path": "storage/receipts/2025/07/KSO-MF-202507001.html"
    }
  ]
}
```

#### GET `/api/receipts/stats`
**Get receipt statistics**

**Response:**
```json
{
  "success": true,
  "data": {
    "total_receipts": 150,
    "today_receipts": 5,
    "this_month_receipts": 45,
    "total_amount": "750000.00"
  }
}
```

#### POST `/api/receipts/generate`
**Generate new receipt**

**Payload:**
```json
{
  "transaction_id": 123,
  "template": "standard"
}
```

**Response:**
```json
{
  "success": true,
  "data": {
    "receipt_id": 456,
    "receipt_number": "KSO-MF-202507002",
    "file_path": "storage/receipts/2025/07/KSO-MF-202507002.html"
  }
}
```

#### GET `/api/receipts/view/{id}`
**View specific receipt**

#### DELETE `/api/receipts/{id}`
**Delete receipt (admin only)**

### Invoice Management

#### GET `/api/receipts/invoices`
**List invoices**

#### POST `/api/receipts/invoices`
**Create new invoice**

#### PUT `/api/receipts/invoices/{id}`
**Update invoice**

#### POST `/api/receipts/invoices/{id}/pay`
**Mark invoice as paid**

---

## 🗄️ Database Schema

### Receipts Table
```sql
CREATE TABLE `receipts` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `receipt_number` varchar(50) NOT NULL UNIQUE,
  `transaction_id` int(11) NOT NULL,
  `member_id` int(11) NOT NULL,
  `transaction_type` enum('membership_fee','donation','event_fee','other') NOT NULL,
  `amount` decimal(10,2) NOT NULL,
  `file_path` varchar(500) NOT NULL,
  `file_type` enum('pdf','html') DEFAULT 'html',
  `generated_by` int(11) NOT NULL,
  `created_at` datetime DEFAULT CURRENT_TIMESTAMP,
  `updated_at` datetime DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  FOREIGN KEY (`transaction_id`) REFERENCES `finance` (`id`),
  FOREIGN KEY (`member_id`) REFERENCES `members` (`id`),
  FOREIGN KEY (`generated_by`) REFERENCES `admins` (`id`)
);
```

### Invoices Table
```sql
CREATE TABLE `invoices` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `invoice_number` varchar(50) NOT NULL UNIQUE,
  `member_id` int(11) NOT NULL,
  `total_amount` decimal(10,2) NOT NULL,
  `due_date` date NOT NULL,
  `status` enum('pending','paid','overdue','cancelled') DEFAULT 'pending',
  `items` json NOT NULL,
  `file_path` varchar(500) DEFAULT NULL,
  `payment_transaction_id` int(11) DEFAULT NULL,
  `paid_amount` decimal(10,2) DEFAULT 0.00,
  `paid_date` datetime DEFAULT NULL,
  `notes` text DEFAULT NULL,
  `created_by` int(11) NOT NULL,
  `created_at` datetime DEFAULT CURRENT_TIMESTAMP,
  `updated_at` datetime DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  FOREIGN KEY (`member_id`) REFERENCES `members` (`id`),
  FOREIGN KEY (`created_by`) REFERENCES `admins` (`id`)
);
```

---

## 🎨 Templates

### Receipt Template Features
- **Professional Design**: Clean, organized layout
- **Organization Branding**: KSO Chandigarh logo and details
- **Member Information**: Complete member details
- **Transaction Details**: Amount, type, date, method
- **Receipt Number**: Unique, trackable identifier
- **Authorized Signatures**: Digital signature space
- **Terms & Conditions**: Payment terms and policies

### Template Customization
Templates are PHP-based with embedded CSS for styling. Key sections:

1. **Header Section**: Organization details and logo
2. **Receipt Information**: Number, date, member details
3. **Transaction Details**: Itemized breakdown
4. **Footer**: Terms, signatures, contact information

---

## 🔒 Security Features

### Access Control
- **Authentication Required**: All API endpoints require admin login
- **Role-Based Access**: Different permissions for different admin roles
- **Session Management**: Secure session handling

### Data Protection
- **Input Validation**: All inputs sanitized and validated
- **SQL Injection Prevention**: Prepared statements throughout
- **File Path Security**: Controlled file storage locations
- **XSS Prevention**: Output escaping for all user data

### Audit Trail
- **Complete Logging**: All receipt operations logged
- **User Tracking**: Track who generated each receipt
- **Timestamp Records**: Creation and modification timestamps
- **Change History**: Track all modifications

---

## 📱 Frontend Usage

### Accessing Receipt Management
1. Login to admin panel
2. Navigate to "Finance" → "Receipts" in sidebar
3. View dashboard with statistics

### Generating Receipts
1. Go to Finance → Transactions
2. Find the transaction
3. Click "Generate Receipt" button
4. Receipt is automatically created and stored

### Viewing Receipts
1. Go to Receipt Management page
2. Use search/filters to find specific receipts
3. Click "View" to preview in modal
4. Click "Download" to get file

### Managing Invoices
1. Access Invoice section
2. Create new invoices for upcoming payments
3. Track payment status
4. Generate receipts when paid

---

## 🚀 Advanced Features

### Batch Operations
- **Bulk Receipt Generation**: Generate multiple receipts at once
- **Batch Email**: Send receipts to multiple members
- **Mass Updates**: Update multiple records simultaneously

### Reporting
- **Financial Reports**: Revenue reports with receipt data
- **Member Reports**: Individual member payment history
- **Audit Reports**: Complete transaction audit trails

### Integration
- **Email Integration**: Automatic email sending with EmailService
- **Member Portal**: Members can view their own receipts
- **Payment Gateway**: Future integration with online payments

---

## 🔧 Installation & Setup

### 1. Database Setup
```sql
-- Run the receipt/invoice setup script
SOURCE database/receipt_invoice_setup.sql;
```

### 2. Directory Creation
```bash
# Create storage directories
mkdir -p storage/receipts
mkdir -p storage/invoices
chmod 755 storage/receipts storage/invoices
```

### 3. Service Configuration
Update `api/config.php` with proper paths and settings.

### 4. Frontend Integration
Ensure AdminLTE v3 assets are properly loaded and sidebar includes receipt navigation.

---

## 🐛 Troubleshooting

### Common Issues

#### Receipt Generation Fails
- **Check**: Database connection
- **Verify**: Transaction exists in finance table
- **Ensure**: Storage directory permissions
- **Validate**: Member data completeness

#### Template Rendering Issues
- **Check**: PHP template syntax
- **Verify**: Variable data availability
- **Ensure**: CSS/styling is correct
- **Test**: Template in isolation

#### File Storage Problems
- **Check**: Directory permissions (755)
- **Verify**: Disk space availability
- **Ensure**: Proper path configuration
- **Test**: Manual file creation

### Error Logging
All errors are logged to PHP error log. Check:
- Receipt generation errors
- Template rendering issues
- Database operation failures
- File system problems

---

## 📈 Future Enhancements

### Phase 2 Features
- **True PDF Generation**: Integrate TCPDF or mPDF library
- **Custom Templates**: Template editor for admins
- **Scheduled Invoices**: Automatic recurring invoice generation
- **Payment Reminders**: Automated email reminders for overdue invoices
- **Mobile App**: Mobile interface for receipt viewing

### Integration Opportunities
- **QR Codes**: Add QR codes to receipts for verification
- **Digital Signatures**: Electronic signature capability
- **Blockchain**: Receipt verification on blockchain
- **Analytics**: Advanced financial analytics and insights

---

## 📞 Support & Documentation

### Related Documentation
- `EMAIL_FUNCTIONALITY_COMPLETE_GUIDE.md` - Email integration
- `SQL_SCHEMA_ALIGNMENT_COMPLETE.md` - Database structure
- `ADMINLTE_V3_DASHBOARD_FINAL_STATUS.md` - Frontend framework

### File Locations
- **Backend**: `api/services/ReceiptService.php`
- **Frontend**: `frontend/pages/receipts.html`
- **API**: `api/receipts/index.php`
- **Templates**: `api/templates/receipts/`
- **Database**: `database/receipt_invoice_setup.sql`

---

*Last Updated: July 10, 2025*
*Version: 1.0 - Production Ready*
