Autoparts-DB/pos/services/thermal_printer.py

"""ESC/POS thermal printer commands for 58mm and 80mm printers.

Generates raw ESC/POS byte commands that can be sent to a thermal printer
via USB, serial, or network connection.
"""

# ESC/POS command constants
ESC = b'\x1b'
GS = b'\x1d'
INIT = ESC + b'@'           # Initialize printer
CUT = GS + b'V' + b'\x00'  # Full cut
PARTIAL_CUT = GS + b'V' + b'\x01'
FEED = ESC + b'd'           # Feed N lines
ALIGN_LEFT = ESC + b'a' + b'\x00'
ALIGN_CENTER = ESC + b'a' + b'\x01'
ALIGN_RIGHT = ESC + b'a' + b'\x02'
BOLD_ON = ESC + b'E' + b'\x01'
BOLD_OFF = ESC + b'E' + b'\x00'
DOUBLE_HEIGHT = ESC + b'!' + b'\x10'
NORMAL_SIZE = ESC + b'!' + b'\x00'
LARGE_SIZE = ESC + b'!' + b'\x30'  # Double width + double height


def generate_ticket(sale_data, business_info, width=80):
    """Generate ESC/POS bytes for a sale ticket.

    Args:
        sale_data: dict with sale info (items, totals, payment, folio)
        business_info: dict with business name, RFC, address
        width: 58 or 80 (mm)

    Returns: bytes ready to send to printer
    """
    chars = 32 if width == 58 else 48  # characters per line
    buf = bytearray()
    buf += INIT

    # Header: business name (centered, bold, large)
    buf += ALIGN_CENTER
    buf += LARGE_SIZE
    buf += (business_info.get('name', 'NEXUS POS') + '\n').encode('cp437', errors='replace')
    buf += NORMAL_SIZE
    buf += (business_info.get('rfc', '') + '\n').encode('cp437', errors='replace')
    buf += (business_info.get('address', '') + '\n').encode('cp437', errors='replace')
    buf += b'\n'

    # Folio + date
    buf += ALIGN_LEFT
    buf += BOLD_ON
    folio = sale_data.get('folio', 'N/A')
    date = sale_data.get('date', '')
    buf += f'Folio: {folio}\n'.encode('cp437', errors='replace')
    buf += BOLD_OFF
    buf += f'Fecha: {date}\n'.encode('cp437', errors='replace')
    buf += f'Cajero: {sale_data.get("employee", "")}\n'.encode('cp437', errors='replace')
    if sale_data.get('customer'):
        buf += f'Cliente: {sale_data["customer"]}\n'.encode('cp437', errors='replace')
    buf += ('-' * chars + '\n').encode()

    # Column header
    buf += BOLD_ON
    hdr = _format_line('Cant  Descripcion', 'Importe', chars)
    buf += (hdr + '\n').encode('cp437', errors='replace')
    buf += BOLD_OFF
    buf += ('-' * chars + '\n').encode()

    # Items
    for item in sale_data.get('items', []):
        name = item.get('name', '')[:chars - 10]
        qty = item.get('quantity', 1)
        subtotal = item.get('subtotal', 0)
        buf += f'{qty}x {name}\n'.encode('cp437', errors='replace')
        buf += ALIGN_RIGHT
        buf += f'${subtotal:,.2f}\n'.encode('cp437', errors='replace')
        buf += ALIGN_LEFT

    buf += ('-' * chars + '\n').encode()

    # Totals
    buf += ALIGN_RIGHT
    buf += _total_line('Subtotal:', sale_data.get('subtotal', 0), chars).encode('cp437', errors='replace')
    if sale_data.get('discount_total', 0) > 0:
        buf += _total_line('Descuento:', -sale_data['discount_total'], chars).encode('cp437', errors='replace')
    buf += _total_line('IVA 16%:', sale_data.get('tax_total', 0), chars).encode('cp437', errors='replace')
    buf += BOLD_ON + DOUBLE_HEIGHT
    buf += _total_line('TOTAL:', sale_data.get('total', 0), chars).encode('cp437', errors='replace')
    buf += NORMAL_SIZE + BOLD_OFF

    # Payment
    buf += ALIGN_LEFT
    buf += f'\nPago: {sale_data.get("payment_method", "Efectivo")}\n'.encode('cp437', errors='replace')
    if sale_data.get('amount_paid'):
        buf += f'Recibido: ${sale_data["amount_paid"]:,.2f}\n'.encode('cp437', errors='replace')
    if sale_data.get('change_given'):
        buf += f'Cambio: ${sale_data["change_given"]:,.2f}\n'.encode('cp437', errors='replace')

    # Footer
    buf += b'\n'
    buf += ALIGN_CENTER
    buf += 'Gracias por su compra!\n'.encode('cp437', errors='replace')
    buf += 'Nexus Autoparts POS\n'.encode('cp437', errors='replace')
    buf += b'\n\n\n'
    buf += PARTIAL_CUT

    return bytes(buf)


def _format_line(left, right, width):
    """Pad a left-right line to fill the ticket width."""
    space = width - len(left) - len(right)
    if space < 1:
        space = 1
    return left + ' ' * space + right


def _total_line(label, amount, width):
    """Format a totals line like 'Subtotal:        $1,234.56'."""
    val = f'${abs(amount):,.2f}' if amount >= 0 else f'-${abs(amount):,.2f}'
    return _format_line(label, val, width) + '\n'