ksc-sdk-python/kscore/configloader.py

# Copyright (c) 2012-2013 LiuYC https://github.com/liuyichen/
# Copyright 2012-2016 ksyun.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
import os
import shlex
import copy

from six.moves import configparser

import kscore.exceptions


def multi_file_load_config(*filenames):
    """Load and combine multiple INI configs with profiles.

    This function will take a list of filesnames and return
    a single dictionary that represents the merging of the loaded
    config files.

    If any of the provided filenames does not exist, then that file
    is ignored.  It is therefore ok to provide a list of filenames,
    some of which may not exist.

    Configuration files are **not** deep merged, only the top level
    keys are merged.  The filenames should be passed in order of
    precedence.  The first config file has precedence over the
    second config file, which has precedence over the third config file,
    etc.  The only exception to this is that the "profiles" key is
    merged to combine profiles from multiple config files into a
    single profiles mapping.  However, if a profile is defined in
    multiple config files, then the config file with the highest
    precedence is used.  Profile values themselves are not merged.
    For example::

        FileA              FileB                FileC
        [foo]             [foo]                 [bar]
        a=1               a=2                   a=3
                          b=2

        [bar]             [baz]                [profile a]
        a=2               a=3                  region=e

        [profile a]       [profile b]          [profile c]
        region=c          region=d             region=f

    The final result of ``multi_file_load_config(FileA, FileB, FileC)``
    would be::

        {"foo": {"a": 1}, "bar": {"a": 2}, "baz": {"a": 3},
        "profiles": {"a": {"region": "c"}}, {"b": {"region": d"}},
                    {"c": {"region": "f"}}}

    Note that the "foo" key comes from A, even though it's defined in both
    FileA and FileB.  Because "foo" was defined in FileA first, then the values
    for "foo" from FileA are used and the values for "foo" from FileB are
    ignored.  Also note where the profiles originate from.  Profile "a"
    comes FileA, profile "b" comes from FileB, and profile "c" comes
    from FileC.

    """
    configs = []
    profiles = []
    for filename in filenames:
        try:
            loaded = load_config(filename)
        except kscore.exceptions.ConfigNotFound:
            continue
        profiles.append(loaded.pop('profiles'))
        configs.append(loaded)
    merged_config = _merge_list_of_dicts(configs)
    merged_profiles = _merge_list_of_dicts(profiles)
    merged_config['profiles'] = merged_profiles
    return merged_config


def _merge_list_of_dicts(list_of_dicts):
    merged_dicts = {}
    for single_dict in list_of_dicts:
        for key, value in single_dict.items():
            if key not in merged_dicts:
                merged_dicts[key] = value
    return merged_dicts


def load_config(config_filename):
    """Parse a INI config with profiles.

    This will parse an INI config file and map top level profiles
    into a top level "profile" key.

    If you want to parse an INI file and map all section names to
    top level keys, use ``raw_config_parse`` instead.

    """
    parsed = raw_config_parse(config_filename)
    return build_profile_map(parsed)


def raw_config_parse(config_filename):
    """Returns the parsed INI config contents.

    Each section name is a top level key.

    :returns: A dict with keys for each profile found in the config
        file and the value of each key being a dict containing name
        value pairs found in that profile.

    :raises: ConfigNotFound, ConfigParseError
    """
    config = {}
    path = config_filename
    if path is not None:
        path = os.path.expandvars(path)
        path = os.path.expanduser(path)
        if not os.path.isfile(path):
            raise kscore.exceptions.ConfigNotFound(path=path)
        cp = configparser.RawConfigParser()
        try:
            cp.read(path)
        except configparser.Error:
            raise kscore.exceptions.ConfigParseError(path=path)
        else:
            for section in cp.sections():
                config[section] = {}
                for option in cp.options(section):
                    config_value = cp.get(section, option)
                    if config_value.startswith('\n'):
                        # Then we need to parse the inner contents as
                        # hierarchical.  We support a single level
                        # of nesting for now.
                        try:
                            config_value = _parse_nested(config_value)
                        except ValueError:
                            raise kscore.exceptions.ConfigParseError(
                                path=path)
                    config[section][option] = config_value
    return config


def _parse_nested(config_value):
    # Given a value like this:
    # \n
    # foo = bar
    # bar = baz
    # We need to parse this into
    # {'foo': 'bar', 'bar': 'baz}
    parsed = {}
    for line in config_value.splitlines():
        line = line.strip()
        if not line:
            continue
        # The caller will catch ValueError
        # and raise an appropriate error
        # if this fails.
        key, value = line.split('=', 1)
        parsed[key.strip()] = value.strip()
    return parsed


def build_profile_map(parsed_ini_config):
    """Convert the parsed INI config into a profile map.

    The config file format requires that every profile except the
    default to be prepended with "profile", e.g.::

        [profile test]
        aws_... = foo
        aws_... = bar

        [profile bar]
        aws_... = foo
        aws_... = bar

        # This is *not* a profile
        [preview]
        otherstuff = 1

        # Neither is this
        [foobar]
        morestuff = 2

    The build_profile_map will take a parsed INI config file where each top
    level key represents a section name, and convert into a format where all
    the profiles are under a single top level "profiles" key, and each key in
    the sub dictionary is a profile name.  For example, the above config file
    would be converted from::

        {"profile test": {"aws_...": "foo", "aws...": "bar"},
         "profile bar": {"aws...": "foo", "aws...": "bar"},
         "preview": {"otherstuff": ...},
         "foobar": {"morestuff": ...},
         }

    into::

        {"profiles": {"test": {"aws_...": "foo", "aws...": "bar"},
                      "bar": {"aws...": "foo", "aws...": "bar"},
         "preview": {"otherstuff": ...},
         "foobar": {"morestuff": ...},
        }

    If there are no profiles in the provided parsed INI contents, then
    an empty dict will be the value associated with the ``profiles`` key.

    .. note::

        This will not mutate the passed in parsed_ini_config.  Instead it will
        make a deepcopy and return that value.

    """
    parsed_config = copy.deepcopy(parsed_ini_config)
    profiles = {}
    final_config = {}
    for key, values in parsed_config.items():
        if key.startswith("profile"):
            try:
                parts = shlex.split(key)
            except ValueError:
                continue
            if len(parts) == 2:
                profiles[parts[1]] = values
        elif key == 'default':
            # default section is special and is considered a profile
            # name but we don't require you use 'profile "default"'
            # as a section.
            profiles[key] = values
        else:
            final_config[key] = values
    final_config['profiles'] = profiles
    return final_config