rpn-cli 1.0.0

Command line reverse polish notation calculator.
Documentation 
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#!/usr/bin/env python3
import os
import re
import subprocess
import sys
from itertools import zip_longest

def read_olds(reader):
    for line in reader:
        if re.search(r'^```$', line):
            break
        yield line

def read_news():
    command = ['rpn', '--command', 'help']
    process = subprocess.Popen(command, stdout=subprocess.PIPE, text=True)
    for line in process.stdout:
        yield f'  {line}'

def replace_help(reader, writer):
    dirty = False
    olds = read_olds(reader)
    news = read_news()
    for old, new in zip_longest(olds, news):
        if new is not None:
            print(new, end='', file=writer)
            dirty |= (new != old)
        elif old is not None:
            dirty = True
    print('```', file=writer)
    return dirty

def modify_stream(reader, writer):
    dirty = False
    quoted = False
    for line in reader:
        print(line, end='', file=writer)
        if quoted:
            if re.search(r'^dec> help$', line):
                dirty |= replace_help(reader, writer)
                quoted = False
            elif re.search(r'^```$', line):
                quoted = False
        else:
            if re.search(r'^```$', line):
                quoted = True
    return dirty

def modify_paths(paths):
    if paths:
        for path in paths:
            temp = f'{path}.___'
            with open(path, 'r') as reader:
                with open(temp, 'w') as writer:
                    dirty = modify_stream(reader, writer)
            if dirty:
                print(path)
                os.rename(temp, path)
            else:
                os.remove(temp)
    else:
        modify_stream(sys.stdin, sys.stdout)

paths = sys.argv[1:]
modify_paths(paths)