# Invoice Generator - Project Documentation

## Project Overview

A Node.js command-line application for generating professional PDF invoices. The system uses a data-driven approach where all business information (senders, clients, products) is stored in JSON files, making it easy to maintain without code changes.

## Architecture

### Core Components

```
invoice/
├── index.js              # Main application entry point
├── data/                 # JSON data files
│   ├── sender.json       # Company/sender profiles
│   ├── client.json       # Client information
│   ├── products.json     # Product/service catalog
│   └── invoices.json     # Invoice ledger (auto-generated)
├── invoice/              # Generated PDF output
│   └── <sender_name>/    # Organized by sender
└── test/
    └── invoice.test.js   # Unit tests
```

### Dependencies

**Production:**

- `easyinvoice` (v3.0.47) - PDF generation library
- `inquirer` (v8.2.4) - Interactive command-line prompts
- `yargs` (v17.7.2) - Command-line argument parsing

**Development:**

- `jest` (v29.7.0) - Testing framework

## Data Flow

### 1. Data Loading

```javascript
// Loads all JSON files from data/ directory
const senders = loadJson(FILES.SENDERS);
const clients = loadJson(FILES.CLIENTS);
const productsData = loadJson(FILES.PRODUCTS);
```

### 2. User Input Processing

- **Interactive Mode**: Uses `inquirer` prompts for sender, client, and product selection
- **Non-Interactive Mode**: Processes command-line arguments via `yargs`
- **Test Mode**: Automatically selects first available options

### 3. Invoice Generation Process

```mermaid
graph TD
    A[Load Data] --> B[Validate Inputs]
    B --> C[Generate Preview PDF]
    C --> D[User Review]
    D --> E{Proceed?}
    E -->|Yes| F[Generate Production PDF]
    E -->|No| G[Keep Preview Only]
    F --> H[Save to Ledger]
    H --> I[Update invoices.json]
```

### 4. File Output

- **Preview**: `invoice/<sender>/<client>_<year>-DEV-PREVIEW.pdf`
- **Production**: `invoice/<sender>/<client>_<year>-<sequence>.pdf`

## Key Functions

### `getNextInvoiceNumber(year, invoicesData)`

- Generates sequential invoice numbers (YYYY-0001, YYYY-0002...)
- Resets numbering annually
- Handles unordered invoice numbers correctly

### `createInvoice(invoiceData, invoiceFilePath)`

- Uses `easyinvoice` library to generate PDF
- Creates directory structure if needed
- Returns success/failure status

### `saveInvoiceRecord(invoiceData, invoiceProducts)`

- Calculates totals (subtotal, tax, grand total)
- Appends invoice record to `invoices.json`
- Persists `dueDate` from `invoiceData.information.dueDate` when set, for accurate future `--print` output
- Maintains complete invoice history

## Data Schema

### Sender Schema

```json
{
  "company": "string",
  "contactName": "string (optional)",
  "phone": "string (optional)",
  "email": "string (optional)",
  "address": "string",
  "zip": "string",
  "city": "string",
  "country": "string",
  "taxName": "string (optional)",
  "taxNumber": "string (optional)",
  "paymentInfo": "string (optional)"
}
```

### Client Schema

```json
{
  "company": "string",
  "address": "string",
  "zip": "string",
  "city": "string",
  "country": "string",
  "invoiceFileName": "string (optional)"
}
```

### Product Schema

```json
{
  "description": "string",
  "price": "number",
  "taxRate": "number (optional, default 0)"
}
```

### Invoice Record Schema

```json
{
  "number": "string (YYYY-0001 or custom e.g. 2026-LFSU01)",
  "date": "string (YYYY-MM-DD)",
  "dueDate": "string (YYYY-MM-DD, optional — see Due dates below)",
  "sender": "string (must match sender.json company name)",
  "client": "string (must match client.json company name)",
  "products": [
    {
      "description": "string",
      "price": "number",
      "quantity": "number",
      "taxRate": "number"
    }
  ],
  "subtotal": "number",
  "taxTotal": "number",
  "total": "number"
}
```

**Due dates:** When you run `node index.js --print <number>`, the PDF due date is taken from `dueDate` if present. Otherwise it defaults to `date` plus 14 days. New production invoices still compute due as “today + 14” in the UI flow; `saveInvoiceRecord` stores that value on the ledger row as `dueDate` when present so reprints stay consistent. You can edit `dueDate` in `invoices.json` for any row (for example, payment terms through end of month).

## Command-Line Interface

### Available Commands

```bash
npm start                    # Interactive mode
npm run generate            # Non-interactive mode
npm test                    # Run unit tests
npm run test-invoice        # Test mode (dev only)
```

### Reprinting from the ledger (no prompts, no ledger changes)

```bash
node index.js --print <invoice-number>
```

Looks up `invoice-number` in `data/invoices.json`, resolves sender and client by matching `company` strings to `sender.json` / `client.json`, and writes `invoice/<senderKey>/<filename>_<number>.pdf`. The client’s optional `invoiceFileName` is used as the filename prefix when set (for example `limmud_fsuc_2026-LFSU01.pdf`).

### Command-Line Options

```bash
--interactive               # Force interactive mode
--print <invoice-number>    # PDF only from invoices.json; does not append ledger
--sender <key>             # Sender key from sender.json
--client <key>             # Client key from client.json
--products <key1> <key2>   # Product keys from products.json
--test                     # Test mode (uses first available options)
--help                     # Show help
```

## Testing Strategy

### Unit Tests (`test/invoice.test.js`)

- **Invoice Numbering**: Tests sequential numbering logic
- **Year Reset**: Verifies numbering resets annually
- **Unordered Numbers**: Handles gaps in invoice sequence

### Test Coverage

- `getNextInvoiceNumber()` function
- Edge cases for invoice numbering
- Year boundary scenarios

## Error Handling

### File System Errors

- Missing JSON files trigger helpful error messages
- Invalid JSON syntax is caught and reported
- Directory creation failures are handled gracefully

### Data Validation

- Invalid sender/client/product keys are rejected
- Missing required fields trigger validation errors
- Tax rate calculations handle missing values

### PDF Generation Errors

- `easyinvoice` failures are caught and logged
- File write errors are handled with user feedback

## Configuration Options

### Currency

- Default: CAD (Canadian Dollar)
- Set in `commonData.settings.currency`

### Tax Configuration

- Per-product tax rates in `products.json`
- Tax name customization in `sender.json`
- Automatic tax calculations

### Payment Information

- Custom payment instructions in `sender.paymentInfo`
- Rendered in invoice footer
- Supports HTML formatting

## File Organization

### Input Files (`data/`)

- **sender.json**: Company profiles and tax information
- **client.json**: Client contact details
- **products.json**: Service/product catalog with pricing
- **invoices.json**: Auto-generated invoice ledger

### Output Files (`invoice/`)

- Organized by sender name
- Preview files marked with `-DEV-PREVIEW`
- Production files with sequential numbering
- Automatic directory creation

## Development Workflow

### Adding New Data

1. Edit appropriate JSON file in `data/`
2. Use interactive mode to test: `npm start`
3. Verify preview generation
4. Create production invoice if satisfied

### Testing Changes

1. Run unit tests: `npm test`
2. Test invoice generation: `npm run test-invoice`
3. Verify file output structure
4. Check ledger updates

### Code Modifications

- Main logic in `index.js`
- Test cases in `test/invoice.test.js`
- Data validation in main function
- Error handling throughout

## Security Considerations

- No external API calls
- Local file system only
- No sensitive data in code
- JSON validation for data integrity
- Error boundaries prevent crashes

## Performance

- Minimal dependencies
- Synchronous file operations
- No database overhead
- Fast PDF generation
- Efficient JSON parsing

## Changelog (May 2026)

- **`--print`**: Regenerate PDFs from `data/invoices.json` without modifying the ledger.
- **Optional ledger `dueDate`**: Overrides the default “invoice date + 14 days” when printing; stored on new rows when production creates `information.dueDate`.
- **Data**: Client `limmud_fsu_canada` (Limmud FSU Canada) with `invoiceFileName` for PDF naming; product `cruise_event_av_it` ($500 + 13% HST); sample invoice `2026-LFSU01` (Levkin Inc. → Limmud FSU Canada).
- **Sender**: Optional `contactName`, `phone`, and `email` on `levkin` in `sender.json` (and schema support for other senders).

## Future Enhancements

### Potential Features

- Multiple currency support
- Invoice templates
- Email integration
- Export to accounting software
- Invoice status tracking
- Payment reminders

### Technical Improvements

- TypeScript migration
- Database integration
- Web interface
- API endpoints
- Docker containerization