Add docker_context_info module (#1039)

* Vendor parts of the Docker SDK for Python

This is a combination of the latest git version
(https://github.com/docker/docker-py/tree/db7f8b8bb67e485a7192846906f600a52e0aa623)
with some fixes to make it compatible with Python 2.7
and adjusting some imports.

* Polishing.

* Fix bug that prevents contexts to be found when no Docker config file is present.

Ref: https://github.com/docker/docker-py/issues/3190

* Linting.

* Fix typos.

* Adjust more to behavior of Docker CLI.

* Add first iteration of docker_context_info module.

* Improvements.

* Add basic CI.

* Add caveat on contexts[].config result.

plugins/module_utils/_api/context/config.py

@@ -0,0 +1,103 @@
+# -*- coding: utf-8 -*-
+# This code is part of the Ansible collection community.docker, but is an independent component.
+# This particular file, and this file only, is based on the Docker SDK for Python (https://github.com/docker/docker-py/)
+#
+# Copyright (c) 2016-2025 Docker, Inc.
+#
+# It is licensed under the Apache 2.0 license (see LICENSES/Apache-2.0.txt in this collection)
+# SPDX-License-Identifier: Apache-2.0
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+import hashlib
+import json
+import os
+
+from ..constants import DEFAULT_UNIX_SOCKET, IS_WINDOWS_PLATFORM
+from ..utils.config import find_config_file, get_default_config_file
+from ..utils.utils import parse_host
+
+METAFILE = "meta.json"
+
+
+def get_current_context_name_with_source():
+    if os.environ.get('DOCKER_HOST'):
+        return "default", "DOCKER_HOST environment variable set"
+    if os.environ.get('DOCKER_CONTEXT'):
+        return os.environ['DOCKER_CONTEXT'], "DOCKER_CONTEXT environment variable set"
+    docker_cfg_path = find_config_file()
+    if docker_cfg_path:
+        try:
+            with open(docker_cfg_path) as f:
+                return json.load(f).get("currentContext", "default"), "configuration file {file}".format(file=docker_cfg_path)
+        except Exception:
+            pass
+    return "default", "fallback value"
+
+
+def get_current_context_name():
+    return get_current_context_name_with_source()[0]
+
+
+def write_context_name_to_docker_config(name=None):
+    if name == 'default':
+        name = None
+    docker_cfg_path = find_config_file()
+    config = {}
+    if docker_cfg_path:
+        try:
+            with open(docker_cfg_path) as f:
+                config = json.load(f)
+        except Exception as e:
+            return e
+    current_context = config.get("currentContext", None)
+    if current_context and not name:
+        del config["currentContext"]
+    elif name:
+        config["currentContext"] = name
+    else:
+        return
+    if not docker_cfg_path:
+        docker_cfg_path = get_default_config_file()
+    try:
+        with open(docker_cfg_path, "w") as f:
+            json.dump(config, f, indent=4)
+    except Exception as e:
+        return e
+
+
+def get_context_id(name):
+    return hashlib.sha256(name.encode('utf-8')).hexdigest()
+
+
+def get_context_dir():
+    docker_cfg_path = find_config_file() or get_default_config_file()
+    return os.path.join(os.path.dirname(docker_cfg_path), "contexts")
+
+
+def get_meta_dir(name=None):
+    meta_dir = os.path.join(get_context_dir(), "meta")
+    if name:
+        return os.path.join(meta_dir, get_context_id(name))
+    return meta_dir
+
+
+def get_meta_file(name):
+    return os.path.join(get_meta_dir(name), METAFILE)
+
+
+def get_tls_dir(name=None, endpoint=""):
+    context_dir = get_context_dir()
+    if name:
+        return os.path.join(context_dir, "tls", get_context_id(name), endpoint)
+    return os.path.join(context_dir, "tls")
+
+
+def get_context_host(path=None, tls=False):
+    host = parse_host(path, IS_WINDOWS_PLATFORM, tls)
+    if host == DEFAULT_UNIX_SOCKET:
+        # remove http+ from default docker socket url
+        if host.startswith("http+"):
+            host = host[5:]
+    return host