thermal.py

#!/usr/bin/env python3

# Markdown to Sparkfun Thermal Printer (Model: CSN-A2) script
# Copyright 2020 Stu Donnan
# License: Public Domain

import sys
import argparse
import binascii
import bs4
import markdown
import serial
import struct
import textwrap
import time

# Constants for thermal printer communication

ESC = b"\x1B"
GS = b"\x1D"

WIDTH = 32
LINE = 30

FMT_EMPH = 1 << 3
FMT_DBLH = 1 << 4
FMT_DBLW = 1 << 5
FMT_DELL = 1 << 6
FMT_UNDL = 1 << 7


class Printer:
    '''Class for thermal printer interface'''

    def __init__(self, port, baud=19200):
        self.port = serial.Serial(port, baudrate=baud)
        self.port.flush()
        self.command(ESC, '@')

    def command(self, cmd, char, *args):
        raw = cmd
        raw += struct.pack('B', ord(char))
        for arg in args:
            try:
                raw += arg.encode('ASCII')
            except:
                raw += struct.pack('B', arg)
        # print(binascii.hexlify(raw))
        self.port.write(raw)

    def text(self, s):
        self.port.write(str(s).encode('cp437'))

    def println(self, s):
        for line in s.split('\n'):
            self.text(line + '\n')

    def print_and_feed(self, s, n):
        self.text(s)
        self.command(ESC, 'J', n)

    def set_fmt(self, fmt):
        self.command(ESC, '!', fmt)

    def set_reverse(self, reverse=True):
        self.command(GS, 'B', 1 if reverse else 0)


def fmt_p(s):
    '''Format an HTML paragraph'''
    return (0, textwrap.fill(s, WIDTH))


def fmt_h1(s):
    '''Format an HTML heading 1'''
    return (FMT_DBLH | FMT_DBLW, textwrap.fill(s, WIDTH/2))


def fmt_hx(s):
    '''Format an HTML heading > 1'''
    return (FMT_EMPH | FMT_UNDL, textwrap.fill(s, WIDTH))


def fmt_ul(i):
    '''Format an HTML unordered list'''
    items = []
    w = textwrap.TextWrapper(
        drop_whitespace=True, initial_indent='', subsequent_indent='  ', width=WIDTH)
    for child in i:
        if child.name == 'li' and child.text:
            items.append(w.fill('· ' + child.text.strip()))
    return (0, '\n'.join(items))


def fmt_ol(i):
    '''Format an HTML ordered list'''
    items = []
    count = 1
    w = textwrap.TextWrapper(
        drop_whitespace=True, initial_indent='', subsequent_indent='  ', width=WIDTH)
    for child in i:
        if child.name == 'li' and child.text:
            items.append(w.fill('{}. '.format(count) + child.text.strip()))
            count += 1
    return (0, '\n'.join(items))


def fmt_block(s):
    '''Format an HTML quote block'''
    w = textwrap.TextWrapper(
        drop_whitespace=True, initial_indent='> ', subsequent_indent='| ', width=WIDTH)
    return (0, w.fill(s))


def fmt(item):
    '''Format an HTML item'''
    if not item.name:
        return (0, None)
    if item.name == 'h1':
        return fmt_h1(item.text)
    elif item.name.startswith('h'):
        return fmt_hx(item.text)
    elif item.name == 'p':
        return fmt_p(item.text)
    elif item.name == 'ul':
        return fmt_ul(item)
    elif item.name == 'ol':
        return fmt_ol(item)
    elif item.name == 'blockquote':
        return fmt_block(item.text.strip())
    else:
        if item.text:
            return fmt_p(item.text)
        return (0, None)


if __name__ == '__main__':

    parser = argparse.ArgumentParser(
        description='Print markdown to thermal printer')
    parser.add_argument('--verbose', '-v', action='store_true',
                        help='Generate more output')
    parser.add_argument('--trial', '-t', action='store_true',
                        help='Dont actually print, use with -v for preview')
    parser.add_argument('--device', '-d', default='/dev/ttyUSB0',
                        help='Serial device for printer')
    parser.add_argument('--baudrate', '-b', type=int,
                        default=19200, help='Serial device baudrate')
    parser.add_argument('infile', nargs='?',
                        type=argparse.FileType('r'), default=sys.stdin)

    args = parser.parse_args()

    md = args.infile.read()
    html = markdown.markdown(md)
    soup = bs4.BeautifulSoup(html, 'lxml')

    if args.verbose:
        print('-- HTML --')
        print(html)
        print('')
        print('-- Formatted --')

    if not args.trial:
        p = Printer(args.device, args.baudrate)

    for item in soup.body.children:
        f, s = fmt(item)
        if s:
            if args.verbose:
                print(s)
                print()
            if not args.trial:
                p.set_fmt(f)
                p.print_and_feed(s, 2 * LINE)
                p.set_fmt(0)

    if not args.trial:
        p.print_and_feed('', 2 * LINE)