themattrix/bashup

# pylint: disable=pointless-statement,expression-not-assigned,too-few-public-methods

import collections

import pyparsing as pp


# Enable memoization to speed up the parser.
pp.ParserElement.enablePackrat()


#
# Public Constants
#

PRINTABLES_PLUS_WHITESPACE = pp.printables + '\n\r\t '


#
# Private Parser Creators
#

def __any_except(exclude_chars):
    return pp.Word(PRINTABLES_PLUS_WHITESPACE, excludeChars=exclude_chars)


def __enclosed(start_str, end_str):
    def __generate_match_first():
        yield PAREN_SUBSHELL
        if start_str != '`':
            yield BACKTICK_SUBSHELL
        yield VARIABLE
        yield QUOTED_STRING
        yield __any_except('"\'$`' + end_str)('other')
        yield pp.Literal('$')('non_variable')

    match_first = pp.MatchFirst(list(__generate_match_first()))

    return pp.Group(
        pp.Literal(start_str)('start') +
        pp.Group(pp.ZeroOrMore(match_first))('body') +
        pp.Literal(end_str)('end'))


def __value(quoted):
    return (
        CAPTURING_SUBSHELL |
        VARIABLE |
        __any_except('"' if quoted else '"\'$`\n\r\t ;,{([#!&<>|')(
            'quoted_extras' if quoted else 'unquoted_extras'))


#
# Forward-Declarations
#

DOUBLE_QUOTED_STRING_UNCOMBINED = pp.Forward()
VARIABLE = pp.Forward()
BACKTICK_SUBSHELL = pp.Forward()
PAREN_SUBSHELL = pp.Forward()


#
# Public Parsers
#

NAME = pp.Word(pp.alphas + '_', pp.alphanums + '_')

SINGLE_QUOTED_STRING = (
    pp.QuotedString("'", multiline=True, unquoteResults=False)
)('single_quoted_string')

QUOTED_STRING = (SINGLE_QUOTED_STRING | DOUBLE_QUOTED_STRING_UNCOMBINED)
STRING_ESCAPED = pp.Word('\\', '\\"$`', exact=2)
SPECIAL_NAME = pp.Word(pp.nums + '#*@-!?_$', exact=1).leaveWhitespace()

SIMPLE_VARIABLE = pp.Group(
    pp.Literal('$')('start') +
    (NAME | SPECIAL_NAME)('name')
)('simple_variable')

EXPANDED_VARIABLE = __enclosed('${', '}')('expanded_variable')
PAREN_SUBSHELL << __enclosed('$(', ')')('paren_subshell')
BACKTICK_SUBSHELL << __enclosed('`', '`')('backtick_subshell')
CAPTURING_SUBSHELL = (PAREN_SUBSHELL | BACKTICK_SUBSHELL)
VARIABLE << (EXPANDED_VARIABLE | SIMPLE_VARIABLE)

STRING_COMPONENT = (
    STRING_ESCAPED('string_escaped') |
    __any_except('"$`\\')('string_other') |
    __value(quoted=True))

DOUBLE_QUOTED_STRING_UNCOMBINED << pp.Group(
    pp.Literal('"')('start') +
    pp.Group(pp.ZeroOrMore(STRING_COMPONENT))('body') +
    pp.Literal('"')('end'))('double_quoted_string')

DOUBLE_QUOTED_STRING = (
    pp.originalTextFor(pp.Combine(DOUBLE_QUOTED_STRING_UNCOMBINED))
    .leaveWhitespace()
    .parseWithTabs())

VALUE = pp.Group(pp.OneOrMore(
    SINGLE_QUOTED_STRING |
    DOUBLE_QUOTED_STRING |
    __value(quoted=False) |
    ('$' + (pp.StringEnd() | pp.LineEnd() | ~SPECIAL_NAME))))

FN_DEFAULT_VALUE = (
    pp.Literal('=').suppress() +
    pp.originalTextFor(VALUE)
)('value')

FN_PARAMETER = pp.Group(
    NAME('name') +
    pp.Optional(FN_DEFAULT_VALUE)
)('parameter')

FN_PARAMETER_LIST = (
    pp.delimitedList(FN_PARAMETER)
)('parameter_list')

FN = pp.Group(
    pp.Literal('@fn').suppress() +
    NAME('name') +
    pp.Optional(FN_PARAMETER_LIST) +
    pp.Literal('{').suppress()
)('fn')


#
# Specifications
#

# noinspection PyClassHasNoInit
class FnSpec(collections.namedtuple('FnSpec', ('name', 'args'))):
    __slots__ = ()

    @classmethod
    def from_parse_result(cls, fn_parse_result):
        name = fn_parse_result['fn']['name']
        args = tuple(
            FnArgSpec.from_list(arg) for arg
            in fn_parse_result['fn'].get('parameter_list', _EMPTY).asList())
        return cls(name=name, args=args)


# noinspection PyClassHasNoInit
class FnArgSpec(collections.namedtuple('FnArgSpec', ('name', 'value'))):
    __slots__ = ()

    @classmethod
    def from_list(cls, name_and_maybe_value):
        nv = name_and_maybe_value
        return cls(name=nv[0], value=nv[1] if len(nv) > 1 else None)


#
# Private Helpers
#

class _Empty(object):
    # noinspection PyPep8Naming
    @staticmethod
    def asList():  # pylint: disable=invalid-name
        return []


_EMPTY = _Empty()