multiconf.py

r"""
Multiconf allows the reading of platform and or host specific values from Sublime settings.

Multiconf is a module that allows you to read platforma and/or host
specific configuration values to be used by Sublime Text 2 plugins.

Using this module's `get` function, allows the user to replace any settings
value in a '.settings' file with a dictionary containing multiple values.

Mulitconf does this by using a dictionary with a special identifier
"#multiconf#"  and a list of dictionaries identified by a qualifier of the form

    "<qualifier name>:<qualifier value>[;<qualifier name>:<qualifier value>]..."

For example, the following setting

    "user_home": "/home"

would result in `get("user_home")` returning the value "/home" but it could also
be replaced with

    "user_home":  {
                    "#multiconf#": [
                        {"os:windows": "C:\\Users"},
                        {"os:linux;host:his_pc": "/home"},
                        {"os:linux;host:her_pc": "/home/her/special"}
                    ]
    }

Now the same configuration file will provide different values depending on the
machine it's on. On an MS Windows machine the value returned by `get` will be
"C:\\Users", and on a Linux machine with the host name 'his_pc' the value will be
"/home".

-----

Thanks to: biermeester and matthjes for their ideas and contributions

-----

Licensed under MIT.

Copyright (C) 2012 - 2017 Isaac Muse

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
documentation files (the "Software"), to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and
to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of
the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
"""
import socket
import sublime
import re

__version__ = "1.0"

__CURRENT_HOSTNAME = socket.gethostname().lower()

QUALIFIERS = r"""([A-Za-z\d_]*):([^;]*)(?:;|$)"""


def get(settings_obj, key, default=None, callback=None):
    """
    Return a Sublime Text plugin setting value.

    Parameters:
      settings_obj - a sublime.Settings object or a dictionary containing
                     settings
      key          - the name of the setting
      default      - the default value to return if the key value is not found.
      callback     - a callback function that, if provided, will be called with
                     the found and default values as parameters.

    """

    # Parameter validation
    if not isinstance(settings_obj, (dict, sublime.Settings)):
        raise AttributeError("Invalid settings object")
    if not isinstance(key, str):
        raise AttributeError("Invalid callback function")
    if callback is not None and not hasattr(callback, '__call__'):
        raise AttributeError("Invalid callback function")

    setting = settings_obj.get(key, default)
    final_val = None

    if isinstance(setting, dict) and "#multiconf#" in setting:
        reject_item = False
        for entry in setting["#multiconf#"]:
            reject_item = False if isinstance(entry, dict) and len(entry) else True

            k, v = entry.popitem()

            if reject_item:
                continue

            for qual in re.compile(QUALIFIERS).finditer(k):
                if Qualifications.exists(qual.group(1)):
                    reject_item = not Qualifications.eval_qual(qual.group(1), qual.group(2))
                else:
                    reject_item = True
                if reject_item:
                    break

            if not reject_item:
                final_val = v
                break

        if reject_item:
            final_val = default
    else:
        final_val = setting

    return callback(final_val, default) if callback else final_val


class QualException(Exception):
    """Qualification exception."""

    pass


class Qualifications(object):
    """Qualifications."""

    __qualifiers = {}

    @classmethod
    def add_qual(cls, key, callback):
        """Add a qualifier."""

        if isinstance(key, str) and re.match(r"^[a-zA-Z][a-zA-Z\d_]*$", key) is None:
            raise QualException("'%s' is not a valid function name." % key)
        if not hasattr(callback, '__call__'):
            raise QualException("Bad function callback.")
        if key in cls.__qualifiers:
            raise QualException("'%s' qualifier already exists." % key)

        cls.__qualifiers[key] = callback

    @classmethod
    def exists(cls, key):
        """See if qualifieer exists."""

        return (key in cls.__qualifiers)

    @classmethod
    def eval_qual(cls, key, value):
        """
        Evaluate the qualifier.

        See if key is in the qualifier list,
        and if so, test the value.
        """

        try:
            return cls.__qualifiers[key](value)
        except Exception:
            raise QualException("Failed to execute %s qualifier" % key)


def _host_match(h):
    """Check if the host matches the input."""

    return (h.lower() == __CURRENT_HOSTNAME)


def _os_match(os):
    """See if the OS platform matches the input."""

    return (os == sublime.platform())


Qualifications.add_qual("host", _host_match)
Qualifications.add_qual("os", _os_match)