#!/usr/bin/python
# Terminator by Chris Jones <cmsj@tenshu.net>
# GPL v2 only
"""plugin.py - Base plugin system
   Inspired by Armin Ronacher's post at
   http://lucumr.pocoo.org/2006/7/3/python-plugin-system
   Used with permission (the code in that post is to be
   considered BSD licenced, per the authors wishes)

>>> registry = PluginRegistry()
>>> registry.instances
{}
>>> registry.load_plugins(True)
>>> plugins = registry.get_plugins_by_capability('test')
>>> len(plugins)
1
>>> plugins[0] #doctest: +ELLIPSIS
<testplugin.TestPlugin object at 0x...>
>>> registry.get_plugins_by_capability('this_should_not_ever_exist')
[]
>>> plugins[0].do_test()
'TestPluginWin'

"""

import sys
import os
import borg
from config import Config
from util import dbg, err, get_config_dir

class Plugin(object):
    """Definition of our base plugin class"""
    capabilities = None
    is_permanent = None

    def __init__(self):
        """Class initialiser."""
        pass

class PluginRegistry(borg.Borg):
    """Definition of a class to store plugin instances"""
    available_plugins = None
    instances = None
    path = None
    done = None

    def __init__(self):
        """Class initialiser"""
        borg.Borg.__init__(self, self.__class__.__name__)
        self.prepare_attributes()

    def prepare_attributes(self):
        """Prepare our attributes"""
        if not self.instances:
            self.instances = {}
        if not self.path:
            self.path = []
            (head, _tail) = os.path.split(borg.__file__)
            self.path.append(os.path.join(head, 'plugins'))
            self.path.append(os.path.join(get_config_dir(), 'plugins'))
            dbg('PluginRegistry::prepare_attributes: Plugin path: %s' % 
                self.path)
        if not self.done:
            self.done = False
        if not self.available_plugins:
            self.available_plugins = {}

    def load_plugins(self, testing=False):
        """Load all plugins present in the plugins/ directory in our module"""
        if self.done:
            dbg('PluginRegistry::load_plugins: Already loaded')
            return

        config = Config()

        for plugindir in self.path:
            sys.path.insert(0, plugindir)
            try:
                files = os.listdir(plugindir)
            except OSError:
                sys.path.remove(plugindir)
                continue
            for plugin in files:
                pluginpath = os.path.join(plugindir, plugin)
                if os.path.isfile(pluginpath) and plugin[-3:] == '.py':
                    dbg('PluginRegistry::load_plugins: Importing plugin %s' % 
                        plugin)
                    try:
                        module = __import__(plugin[:-3], None, None, [''])
                        for item in getattr(module, 'AVAILABLE'):
                            if item not in self.available_plugins.keys():
                                func = getattr(module, item)
                                self.available_plugins[item] = func

                            if not testing and item not in config['enabled_plugins']:
                                dbg('plugin %s not enabled, skipping' % item)
                                continue
                            if item not in self.instances:
                                self.instances[item] = func()
                    except Exception, ex:
                        err('PluginRegistry::load_plugins: Importing plugin %s \
failed: %s' % (plugin, ex))

        self.done = True

    def get_plugins_by_capability(self, capability):
        """Return a list of plugins with a particular capability"""
        result = []
        dbg('PluginRegistry::get_plugins_by_capability: searching %d plugins \
for %s' % (len(self.instances), capability))
        for plugin in self.instances:
            if capability in self.instances[plugin].capabilities:
                result.append(self.instances[plugin])
        return result

    def get_all_plugins(self):
        """Return all plugins"""
        return(self.instances)

    def get_available_plugins(self):
        """Return a list of all available plugins whether they are enabled or
        disabled"""
        return(self.available_plugins.keys())

    def is_enabled(self, plugin):
        """Return a boolean value indicating whether a plugin is enabled or
        not"""
        return(self.instances.has_key(plugin))

    def is_permanent(self, plugin):
        """Return a boolean value indicating whether a plugin is believed to be
        permanent. This is impossible to determine for plugins that haven't
        been loaded, so they will report as not being permanent until they are
        loaded"""
        if plugin not in self.instances:
            return(False)
        else:
            return(self.instances[plugin].is_permanent)

    def enable(self, plugin):
        """Enable a plugin"""
        dbg("Enabling %s" % plugin)
        if plugin not in self.instances:
            self.instances[plugin] = self.available_plugins[plugin]()

    def disable(self, plugin):
        """Disable a plugin"""
        if self.instances[plugin].is_permanent:
            dbg("Refusing to disable permanent plugin %s" % plugin)
        else:
            dbg("Disabling %s" % plugin)
            del(self.instances[plugin])

# This is where we should define a base class for each type of plugin we
# support

# URLHandler - This adds a regex match to the Terminal widget and provides a
#               callback to turn that into a URL.
class URLHandler(Plugin):
    """Base class for URL handlers"""
    capabilities = ['url_handler']
    handler_name = None
    match = None
    is_permanent = True

    def callback(self, url):
        """Callback to transform the enclosed URL"""
        raise NotImplementedError

# MenuItem - This is able to execute code during the construction of the
#             context menu of a Terminal.
class MenuItem(Plugin):
    """Base class for menu items"""
    capabilities = ['terminal_menu']

    def callback(self, menuitems, menu, terminal):
        """Callback to transform the enclosed URL"""
        raise NotImplementedError