A sample application that shows one potential way to implement a simple "plugin architecture" in Python.
The app dynamically loads plugins from a directory.
This makes it easy to drop new plugins into the app
by just copying it to the plugins directory.
Two types of plugins are supported: commands and hooks.
A command is mapped to a command-line argument. A command typically takes text input (stdin) and/or command-line arguments and provides text output (stdout).
A hook is an "aspect-oriented" type plugin that could be used for cross-cutting concerns. I.e., a hook could be applied to any number of commands. An example would be a hook that prints/logs the input or output of a command for debugging purposes.
TODO: separate commands with some delimiter like ':' to allow passing args to each command.
TODO: allow a hook to specify filters for the commands it should be applied to, e.g. either by command name or command-line arguments.
TODO: consider getting rid of the base classes and just use a convention for the command/hook interfaces.