added plugin manager

src/manjaro_hello.py

@@ -9,6 +9,13 @@ import subprocess
 import sys
 import webbrowser
 
+import imp
+import logging
+import collections
+
+logging.basicConfig(level=logging.DEBUG)
+
+
 try:
     from applications.alpm import Alpm
     from applications.app_data import AppData
@@ -29,6 +36,114 @@ gi.require_version("Gtk", "3.0")
 from gi.repository import Gtk, GdkPixbuf
 
 
+class PluginManager:
+    """
+    A simple plugin manager
+    """
+
+    def __init__(self, plugin_folder, main_module='__init__', log=logging):
+        self.logging = log
+        self.plugin_folder = plugin_folder
+        self.main_module = main_module
+        self.loaded_plugins = collections.OrderedDict({})
+
+        __author__ = "Michael E. Cotterell"
+        __email__ = "mepcotterell@gmail.com"
+        __copyright__ = "Copyright 2013, Michael E. Cotterell"
+        __license__ = "MIT"
+
+    def get_available_plugins(self):
+        """
+        Returns a dictionary of plugins available in the plugin folder
+        """
+        plugins = {}
+        for possible in os.listdir(self.plugin_folder):
+            location = os.path.join(self.plugin_folder, possible)
+            if os.path.isdir(location) and self.main_module + '.py' in os.listdir(location):
+                info = imp.find_module(self.main_module, [location])
+                plugins[possible] = {
+                    'name': possible,
+                    'info': info
+                }
+        return plugins
+
+    def get_loaded_plugins(self):
+        """
+        Returns a dictionary of the loaded plugin modules
+        """
+        return self.loaded_plugins.copy()
+
+    def load_plugin(self, plugin_name):
+        """
+        Loads a plugin module
+        :param plugin_name:
+        """
+        plugins = self.get_available_plugins()
+        if plugin_name in plugins:
+            if plugin_name not in self.loaded_plugins:
+                module = imp.load_module(self.main_module, *plugins[plugin_name]['info'])
+                self.loaded_plugins[plugin_name] = {
+                    'name': plugin_name,
+                    'info': plugins[plugin_name]['info'],
+                    'module': module
+                }
+                self.logging.info('plugin "%s" loaded' % plugin_name)
+            else:
+                self.logging.warn('plugin "%s" already loaded' % plugin_name)
+        else:
+            self.logging.error('cannot locate plugin "%s"' % plugin_name)
+            raise Exception('cannot locate plugin "%s"' % plugin_name)
+
+    def unload_plugin(self, plugin_name):
+        """
+        Unloads a plugin module
+        :param plugin_name:
+        """
+        del self.loaded_plugins[plugin_name]
+        self.logging.info('plugin "%s" unloaded' % plugin_name)
+
+    def execute_action_hook(self, hook_name, hook_params=None):
+        """
+        Executes action hook functions of the form action_hook_name contained in
+        the loaded plugin modules.
+        :param hook_name:
+        :param hook_params:
+        """
+        if hook_params is None:
+            hook_params = {}
+        for key, plugin_info in self.loaded_plugins.items():
+            module = plugin_info['module']
+            hook_func_name = 'action_%s' % hook_name
+            if hasattr(module, hook_func_name):
+                hook_func = getattr(module, hook_func_name)
+                hook_func(hook_params)
+
+    def execute_filter_hook(self, hook_name, hook_params=None):
+        """
+        Filters the hook_params through filter hook functions of the form
+        filter_hook_name contained in the loaded plugin modules.
+        :param hook_name:
+        :param hook_params:
+        :return:
+        """
+        if hook_params is None:
+            hook_params = {}
+        hook_params_keys = hook_params.keys()
+        for key, plugin_info in self.loaded_plugins.items():
+            module = plugin_info['module']
+            hook_func_name = 'filter_%s' % hook_name
+            if hasattr(module, hook_func_name):
+                hook_func = getattr(module, hook_func_name)
+                hook_params = hook_func(hook_params)
+                for nkey in hook_params_keys:
+                    if nkey not in hook_params.keys():
+                        msg = 'function "%s" in plugin "%s" is missing "%s" in the dict it returns' % (
+                         hook_func_name, plugin_info['name'], nkey)
+                        self.logging.error(msg)
+                        raise Exception(msg)
+        return hook_params
+
+
 class Hello(Gtk.Window):
     """Hello"""