# Copyright 2017-2020 Palantir Technologies, Inc.
# Copyright 2021- Python Language Server Contributors.

import functools
import re

_RE_FIRST_CAP = re.compile('(.)([A-Z][a-z]+)')
_RE_ALL_CAP = re.compile('([a-z0-9])([A-Z])')


class MethodDispatcher:
    """JSON RPC dispatcher that calls methods on itself.

    Method names are computed by converting camel case to snake case, slashes with double underscores, and removing
    dollar signs.
    """

    def __getitem__(self, item):
        method_name = f'm_{_method_to_string(item)}'
        if hasattr(self, method_name):
            method = getattr(self, method_name)

            @functools.wraps(method)
            def handler(params):
                return method(**(params or {}))

            return handler
        raise KeyError()


def _method_to_string(method):
    return _camel_to_underscore(method.replace("/", "__").replace("$", ""))


def _camel_to_underscore(string):
    s1 = _RE_FIRST_CAP.sub(r'\1_\2', string)
    return _RE_ALL_CAP.sub(r'\1_\2', s1).lower()
