from logging import info

from landscape.log import format_object


class PluginConfigError(Exception):
"""There was an error registering or configuring a plugin."""


class PluginRegistry(object):
"""A central integration point for plugins."""

def __init__(self):
self._plugins = []
self._plugin_names = {}

def add(self, plugin):
"""Register a plugin.

The plugin's C{register} method will be called with this registry as
its argument.

If the plugin has a C{plugin_name} attribute, it will be possible to
look up the plugin later with L{get_plugin}.
"""
info("Registering plugin %s.", format_object(plugin))
self._plugins.append(plugin)
if hasattr(plugin, "plugin_name"):
self._plugin_names[plugin.plugin_name] = plugin
plugin.register(self)

def get_plugins(self):
"""Get the list of plugins."""
return self._plugins

def get_plugin(self, name):
"""Get a particular plugin by name."""
return self._plugin_names[name]


class Plugin(object):
"""A convenience for writing plugins.

This provides a register method which will set up a bunch of
reactor handlers in the idiomatic way.

If C{run} is defined on subclasses, it will be called every C{run_interval}
seconds after being registered.

@cvar run_interval: The interval, in seconds, to execute the
C{run} method. If set to C{None}, then C{run} will not be
scheduled.
"""

run_interval = 5

def register(self, registry):
self.registry = registry
if hasattr(self, "run") and self.run_interval is not None:
registry.reactor.call_every(self.run_interval, self.run)