From c88fccd6ec09cb64ff3ee80e314734ed80dea482 Mon Sep 17 00:00:00 2001
From: Diego Garcia <drgarcia1986@gmail.com>
Date: Tue, 1 Oct 2019 18:45:01 -0300
Subject: [PATCH] Change import dynamic reader mechanism to simplify to custom
 dynamic readers

---
 README.rst                                    | 39 ++++++++++++++++++
 simple_settings/dynamic_settings/__init__.py  | 40 +++++++++++++++----
 .../dynamic_settings/test_dynamic_settings.py |  2 +-
 3 files changed, 72 insertions(+), 9 deletions(-)

diff --git a/README.rst b/README.rst
index e97213e..cf2a972 100644
--- a/README.rst
+++ b/README.rst
@@ -541,6 +541,45 @@ the ``DYNAMIC_SETTINGS`` special setting with the ``memcached`` backend
     To install with memcached dependencies use: ``pip install simple-settings[memcached]``
 
 
+Custom
+^^^^^^
+You can easily create your own dynamic settings reader. To do that you need to
+create a class than inherit from ``simple_settings.dynamic_settings.base.BaseReader``
+and implement ``_get`` and ``_set`` methods, f.ex:
+
+.. code:: python
+
+   from simple_settings.dynamic_settings.base import BaseReader
+
+
+   class Reader(BaseReader):
+
+       def __init__(self, conf):
+           super(Reader, self).__init__(conf)
+           self._dict = {}
+
+       def _get(self, key):
+           return self._dict.get(key)
+
+       def _set(self, key, value):
+           self._dict[key] = value
+
+..
+
+To use it, just configure ``SIMPLE_SETINGS`` special setting with the full path
+of the reader, f.ex:
+
+.. code:: python
+
+   'SIMPLE_SETTINGS': {
+       'DYNAMIC_SETTINGS': {
+         'backend': 'path.of.module.ClassName'
+       }
+   }
+..
+
+Any other config of dynamic settings will be pass to reader backend on argument ``config``
+
 Utils
 -----
 
diff --git a/simple_settings/dynamic_settings/__init__.py b/simple_settings/dynamic_settings/__init__.py
index 1bb458d..d610d42 100644
--- a/simple_settings/dynamic_settings/__init__.py
+++ b/simple_settings/dynamic_settings/__init__.py
@@ -7,14 +7,26 @@
 )
 
 DYNAMIC_SETTINGS_MAPPING = {
-    'consul': 'simple_settings.dynamic_settings.consul_reader',
-    'database': 'simple_settings.dynamic_settings.database_reader',
-    'memcached': 'simple_settings.dynamic_settings.memcached_reader',
-    'redis': 'simple_settings.dynamic_settings.redis_reader',
-    's3': 'simple_settings.dynamic_settings.s3_reader'
+    'consul': 'simple_settings.dynamic_settings.consul_reader.Reader',
+    'database': 'simple_settings.dynamic_settings.database_reader.Reader',
+    'memcached': 'simple_settings.dynamic_settings.memcached_reader.Reader',
+    'redis': 'simple_settings.dynamic_settings.redis_reader.Reader',
+    's3': 'simple_settings.dynamic_settings.s3_reader.Reader'
 }
 
 
+class InvalidDynamicSettingsReaderPath(RuntimeError):
+
+    def __init__(self, path):
+        super(InvalidDynamicSettingsReaderPath, self).__init__(self)
+        self.path = path
+
+    def __str__(self):
+        return 'The path of dynamic settings reader [{}] are invalid'.format(
+            self.path
+        )
+
+
 def get_dynamic_reader(settings_dict):
     dynamic_settings_conf = (
         settings_dict.get(SPECIAL_SETTINGS_KEY, {}).get(DYNAMIC_SETTINGS_KEY)
@@ -26,7 +38,19 @@ def get_dynamic_reader(settings_dict):
     if reader_backend in DYNAMIC_SETTINGS_MAPPING:
         reader_backend = DYNAMIC_SETTINGS_MAPPING[reader_backend]
 
-    reader_module = importlib.import_module(reader_backend)
-    reader = reader_module.Reader(dynamic_settings_conf)
+    reader_class = get_dynamic_reader_class(reader_backend)
+    return reader_class(dynamic_settings_conf)
+
+
+def get_dynamic_reader_class(reader_backend_path):
+    try:
+        module_path, class_name = reader_backend_path.rsplit('.', 1)
+    except ValueError:
+        raise InvalidDynamicSettingsReaderPath(reader_backend_path)
+
+    reader_module = importlib.import_module(module_path)
 
-    return reader
+    try:
+        return getattr(reader_module, class_name)
+    except AttributeError:
+        raise InvalidDynamicSettingsReaderPath(reader_backend_path)
diff --git a/tests/dynamic_settings/test_dynamic_settings.py b/tests/dynamic_settings/test_dynamic_settings.py
index 30ce7ad..b2e8065 100644
--- a/tests/dynamic_settings/test_dynamic_settings.py
+++ b/tests/dynamic_settings/test_dynamic_settings.py
@@ -25,7 +25,7 @@ class TestDynamicSettings(object):
     def settings_dict(self):
         return {
             'SIMPLE_SETTINGS': {
-                'DYNAMIC_SETTINGS': {'backend': __name__}
+                'DYNAMIC_SETTINGS': {'backend': '{}.Reader'.format(__name__)}
             }
         }