# Copyright 2019, David Wilson
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
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# 1. Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
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# 3. Neither the name of the copyright holder nor the names of its contributors
# may be used to endorse or promote products derived from this software without
# specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# POSSIBILITY OF SUCH DAMAGE.

from __future__ import absolute_import, division, print_function
__metaclass__ = type

import os.path
import sys

try:
    import ansible_mitogen.connection
except ImportError:
    base_dir = os.path.dirname(__file__)
    sys.path.insert(0, os.path.abspath(os.path.join(base_dir, '../../..')))
    del base_dir

import ansible_mitogen.connection
import ansible_mitogen.process

viewkeys = getattr(dict, 'viewkeys', dict.keys)


def dict_diff(old, new):
    """
    Return a dict representing the differences between the dicts `old` and
    `new`. Deleted keys appear as a key with the value :data:`None`, added and
    changed keys appear as a key with the new value.
    """
    old_keys = viewkeys(old)
    new_keys = viewkeys(dict(new))
    out = {}
    for key in new_keys - old_keys:
        out[key] = new[key]
    for key in old_keys - new_keys:
        out[key] = None
    for key in old_keys & new_keys:
        if old[key] != new[key]:
            out[key] = new[key]
    return out


class Connection(ansible_mitogen.connection.Connection):
    transport = 'local'

    def get_default_cwd(self):
        # https://github.com/ansible/ansible/issues/14489
        return self.loader_basedir

    def get_default_env(self):
        """
        Vanilla Ansible local commands execute with an environment inherited
        from WorkerProcess, we must emulate that.
        """
        return dict_diff(
            old=ansible_mitogen.process.MuxProcess.cls_original_env,
            new=os.environ,
        )