markdown_parser.py

from funcparserlib.lexer import make_tokenizer, Token, LexerError
from funcparserlib.parser import some, a, maybe, many, finished, skip, \
    forward_decl, NoParseError


const = lambda x: lambda _: x
tokval = lambda x: x.value
toktype = lambda t: some(lambda x: x.type == t) >> tokval
op = lambda s: a(Token('Op', s)) >> tokval
op_ = lambda s: skip(op(s))
nop = lambda s: some(lambda t: t.type == 'Op' and t.value != s) >> tokval
nop_ = lambda s: skip(nop(s))


class Tokenizer(object):
    tokens = [
        ('Op', (r'`|~~|\*\*\*|\*\*|\*|######|#####|####|###|##|#|/-|-/',)),
        ('Text', (r'([^~\\#`*@$\n]|\\[^\n])+',)),
    ]

    def __call__(self, s):
        return list(make_tokenizer(self.tokens)(s))


class Parser(object):
    tokenizer = Tokenizer()

    inlines = forward_decl()

    text = toktype('Text')

    plain_text_code = many(toktype('Text') | nop('`')) >> ''.join
    inline_code = op_('`') + plain_text_code + op_('`') >> (lambda x: '<code>' + x + '</code>')

    emphasis = op_('*') + inlines + op_('*') >> (lambda x: '<em>' + x + '</em>')
    double_emphasis = op_('**') + inlines + op_('**') >> (lambda x: '<strong>' + x + '</strong>')
    triple_emphasis = op_('***') + inlines + op_('***') >> (lambda x: '<u>' + x + '</u>')

    strike = op_('~~') + inlines + op_('~~') >> (lambda x: '<s>' + x + '</s>')

    cite = op_('/-') + inlines + op_('-/') >> (lambda x: '<cite>' + x + '</cite>')

    inlines.define(
        triple_emphasis
        |
        double_emphasis
        |
        emphasis
        |
        strike
        |
        inline_code
        |
        text
    )

    start = many(inlines) >> ''.join

    def __call__(self, s):
        return self.start.parse(self.tokenizer(s))

parser = Parser()
print(parser(input()))