gremlin-python/src/main/python/gremlin_python/structure/io/util.py

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# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
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# KIND, either express or implied.  See the License for the
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import re
from threading import Lock

from gremlin_python.statics import SingleByte


class SymbolUtil:
    camel_pattern = re.compile(r'(?<!^)(?=[A-Z])')

    @classmethod
    def to_snake_case(cls, symbol):
        return cls.camel_pattern.sub('_', symbol).lower()

    @classmethod
    def to_camel_case(cls, symbol):
        u = ''
        first = True
        for segment in symbol.split('_'):
            u += segment if first else segment.title()
            first = False

        return u


class HashableDict(dict):
    def __hash__(self):
        try:
            return hash(tuple(sorted(self.items())))
        except:
            return hash(tuple(sorted(str(x) for x in self.items())))

    @classmethod
    def of(cls, o):
        if isinstance(o, (tuple, set, list)):
            return tuple([cls.of(e) for e in o])
        elif not isinstance(o, (dict, HashableDict)):
            return o

        new_o = HashableDict()
        for k, v in o.items():
            if isinstance(k, (set, list)):
                new_o[tuple(k)] = cls.of(v)
            else:
                new_o[k] = cls.of(v)
        return new_o


# referenced python singleton from https://refactoring.guru/design-patterns/singleton/python/example#example-1--main-py,
# might need some refactoring
class SingletonMeta(type):

    _instances = {}
    _lock: Lock = Lock()

    def __call__(cls, *args, **kwargs):
        with cls._lock:
            if cls not in cls._instances:
                instance = super().__call__(*args, **kwargs)
                cls._instances[cls] = instance
        return cls._instances[cls]


class Marker(metaclass=SingletonMeta):
    _value: SingleByte

    def __init__(self, value: SingleByte) -> None:
        self._value = value

    @staticmethod
    def end_of_stream():
        return Marker(SingleByte(0))

    def get_value(self):
        return self._value

    @classmethod
    def of(cls, val):
        if val != 0:
            raise ValueError
        return cls.end_of_stream()