Started building Microscope plugin system

openflexure_microscope/plugins/loader.py

@@ -0,0 +1,116 @@
+import importlib
+import os
+import warnings
+import logging
+
+MAIN_MODULE = '__init__'
+HERE = os.path.abspath(os.path.dirname(__file__))
+DEFAULT_PLUGIN_PATH = os.path.join(HERE, 'default')
+
+
+def search_plugin_dirs(plugin_dirs, include_default=True):
+    """
+    Search through, and load from, a list of plugin directories.
+
+    Args:
+        plugin_dirs (list): List of strings of plugin directories.
+        include_default (bool): Also load plugins from the module default directory (DEFAULT_PLUGIN_PATH)
+    """
+    global DEFAULT_PLUGIN_PATH
+
+    if include_default:  # If including default plugins
+        plugin_dirs.append(DEFAULT_PLUGIN_PATH)  # Add default directory to the search paths
+
+    logging.debug(plugin_dirs)
+
+    plugins = []  # List of loaded plugins
+    for plugin_dir in plugin_dirs:  # For each plugin directory
+        logging.debug("Searching {}".format(plugin_dir))
+        plugins.extend(find_plugins(plugin_dir))  # Find plugin folders, and load into list
+
+    return plugins
+
+
+def find_plugins(plugin_dir):
+    """
+    Find all plugins residing within a directory
+
+    Args:
+        plugin_dir (str): String of directory to be searched
+    """
+    plugins = []
+    plugins_folders = os.listdir(plugin_dir)
+
+    loader_details = (
+        importlib.machinery.SourceFileLoader,
+        importlib.machinery.SOURCE_SUFFIXES
+    )
+
+    for i in plugins_folders:
+        plugin_folder = os.path.join(plugin_dir, i)
+        logging.info(plugin_folder)
+
+        if not os.path.isdir(plugin_folder):
+            continue
+        if not MAIN_MODULE + '.py' in os.listdir(plugin_folder):
+            continue
+
+        module_spec = importlib.machinery.FileFinder(plugin_folder, loader_details).find_spec(MAIN_MODULE)
+
+        plugins.append(module_spec)
+    return plugins
+
+
+def load_plugin(module_spec):
+    """
+    Load a source file from a given spec.
+
+    Args:
+        module_spec: Module spec of module to be returned
+    """
+    module = importlib.util.module_from_spec(module_spec)
+    module_spec.loader.exec_module(module)
+    return module
+
+
+class PluginMount(object):
+    """
+    A mount-point for all loaded plugins. Attaches to a Microscope object.
+
+    Args:
+        parent (:py:class:`openflexure_microscope.microscope.Microscope`): The parent Microscope object to attach to.
+    """
+    def __init__(self, parent):
+        self.parent = parent
+        print("Creating plugin mount")
+
+    def attach(self, plugin_module):
+        if not hasattr(plugin_module, 'PLUGINS') or not isinstance(plugin_module.PLUGINS, dict):
+            raise Exception("No falid PLUGINS dictionary found in {}".format(plugin_module))
+
+        for plugin_name, plugin_class in plugin_module.PLUGINS.items():
+
+            plugin_object = plugin_class()
+            if hasattr(self, plugin_name):
+                warnings.warn("A plugin named {} has already been loaded. Skipping {}.".format(plugin_name, plugin_class))
+            else:
+                setattr(self, plugin_name, plugin_object)
+
+                # Grant plugin access to the hardware
+                assert(isinstance(plugin_object, MicroscopePlugin))
+                plugin_object.camera = self.parent.camera
+                plugin_object.stage = self.parent.stage
+
+                print("Adding plugin: {}".format(plugin_name))
+
+
+class MicroscopePlugin():
+    """
+    Parent class for all microscope plugins.
+
+    Initially only defines an empty object for camera and stage. All plugins
+    must be an instance of this class to successfully attach to PluginMount.
+    """
+    def __init__(self):
+        self.camera = None  #: :py:class:`openflexure_microscope.camera.pi.StreamingCamera`: Picamera object
+        self.stage = None  #: :py:class:`openflexure_stage.stage.OpenFlexureStage`: OpenFlexure stage object