path: root/portato/plugin.py

# -*- coding: utf-8 -*-
#
# File: portato/plugin.py
# This file is part of the Portato-Project, a graphical portage-frontend.
#
# Copyright (C) 2006-2009 René 'Necoro' Neumann
# This is free software.  You may redistribute copies of it under the terms of
# the GNU General Public License version 2.
# There is NO WARRANTY, to the extent permitted by law.
#
# Written by René 'Necoro' Neumann <necoro@necoro.net>

"""
A module managing the plugins for Portato.
"""

from __future__ import absolute_import
__docformat__ = "restructuredtext"

import os
import os.path as osp
import traceback
from collections import defaultdict
from functools import wraps

from .helper import debug, warning, info, error
from .constants import PLUGIN_DIR
from .backend import system
from . import plugins as plugin_module

class PluginLoadException (Exception):
    """
    Exception signaling a failed plugin loading.
    """
    pass

class Menu (object):
    """
    One single menu entry.

    :IVariables:

        label : string
            The label of the entry. Can have underscores to define the shortcut.

        call
            The function to call, if the entry is clicked.
    """
    __slots__ = ("label", "call")

    def __init__ (self, label, call):
        self.label = label
        self.call = call

class Call (object):
    """
    This class represents an object, which is attached to a specified hook.

    :IVariables:

        plugin : `Plugin`
            The plugin where this call belongs to.

        hook : string
            The name of the corresponding hook.

        call
            The function to call.

        type : string
            This is either ``before``, ``after`` or ``override`` and defines the type of the call:

                before
                    access before the original function
                override
                    access *instead of* the original function. **USE THIS ONLY IF YOU KNOW WHAT YOU ARE DOING**
                after
                    access after the original function has been called

            Default: ``before``

        dep : string
            This defines a plugin which should be executed after/before this one.
            ``"*"`` means all and ``"-*"`` means none.
    """
    __slots__ = ("plugin", "hook", "call", "type", "dep")

    def __init__ (self, plugin, hook, call, type = "before", dep = None):
        self.plugin = plugin
        self.hook = hook
        self.call = call
        self.type = type
        self.dep = dep

class Hook (object):
    """
    Representing a hook with all the `Call` s for the different types.
    """
            
    __slots__ = ("before", "override", "after")

    def __init__ (self):
        self.before = []
        self.override = None
        self.after = []

class Plugin (object):
    """
    This is the main plugin object. It is used where ever a plugin is wanted, and it is the one, which needs to be subclassed by plugin authors.

    :CVariables:

        STAT_DISABLED : status
            Status: Disabled.

        STAT_TEMP_ENABLED : status
            Status: Enabled for this session only.

        STAT_ENABLED : status
            Status: Enabled.

        STAT_TEMP_DISABLED : status
            Status: Disabled for this session only.

        STAT_HARD_DISABLED : status
            Status: Forced disabled by program (i.e. because of errors in the plugin).
    """

    (STAT_DISABLED, STAT_TEMP_ENABLED, STAT_ENABLED, STAT_TEMP_DISABLED) = range(4)
    STAT_HARD_DISABLED = -1

    def __init__ (self, disable = False):
        """
        :param disable: Forcefully disable the plugin
        :type disable: bool
        """
        self.__menus = [] #: List of `Menu`
        self.__calls = [] #: List of `Call`
        self._unresolved_deps = False #: Does this plugin has unresolved dependencies?

        self.status = self.STAT_ENABLED #: The status of this plugin
        
        if disable:
            self.status = self.STAT_HARD_DISABLED

    def _init (self):
        """
        Method called from outside to init the extension parts of this plugin.
        If the current status is `STAT_HARD_DISABLED` or there are unresolved dependencies, the init process is not started.
        """

        for d in self.deps:
            if not system.find_packages(d, pkgSet=system.SET_INSTALLED, with_version = False):
                self._unresolved_deps = True
                break
        
        if self.status != self.STAT_HARD_DISABLED and not self._unresolved_deps:
            self.init()
    
    def init (self):
        """
        This method is called by `_init` and should be overriden by the plugin author.

        :precond: No unresolved deps and the status is not `STAT_HARD_DISABLED`.
        """
        pass

    @property
    def author (self):
        """
        Returns the plugin's author.
        The author is given by the ``__author__`` variable.

        :rtype: string
        """
        return getattr(self, "__author__", "")

    @property
    def description (self):
        """
        Returns the description of this plugin.
        It is given by either a ``__description__`` variable or by the normal class docstring.

        :rtype: string
        """
        if hasattr(self, "__description__"):
            return self.__description__
        else:
            doc = getattr(self, "__doc__", "")

            if not doc or doc == Plugin.__doc__:
                return ""
            else:
                return doc

    @property
    def name (self):
        """
        The name of the plugin. If no ``__name__`` variable is given, the class name is taken.

        :rtype: string
        """
        return getattr(self, "__name__", self.__class__.__name__)

    @property
    def menus (self):
        """
        Returns an iterator over the menus for this plugin.

        :rtype: iter<`Menu`>
        """
        return iter(self.__menus)

    @property
    def calls (self):
        """
        Returns an iterator over the registered calls for this plugin.

        :rtype: iter<`Call`>
        """
        return iter(self.__calls)

    @property
    def deps (self):
        """
        Returns an iterator of the dependencies or ``[]`` if there are none.
        The dependencies are given in the ``__dependency__`` variable.

        :rtype: [] or iter<string>
        """
        if hasattr(self, "__dependency__"):
            return iter(self.__dependency__)
        else:
            return []

    @property
    def enabled (self):
        """
        Returns ``True`` if the plugin is enabled.

        :rtype: boolean
        :see: `status`
        """
        return (self.status in (self.STAT_ENABLED, self.STAT_TEMP_ENABLED))
    
    def add_menu (self, label, callable):
        """
        Adds a new menu item for this plugin.

        :see: `Menu`
        """
        self.__menus.append(Menu(label, callable))

    def add_call (self, hook, callable, type = "before", dep = None):
        """
        Adds a new call for this plugin.

        :see: `Call`
        """
        self.__calls.append(Call(self, hook, callable, type, dep))


class PluginQueue (object):
    """
    Class managing and loading the plugins.
    
    :IVariables:

        plugins : `Plugin` []
            The list of managed plugins.

        hooks : string -> `Hook`
            For each hook name map to a `Hook` object holding the corresponding `Call` objects.
    """

    def __init__ (self):
        """
        Constructor.
        """

        self.plugins = []
        self.hooks = defaultdict(Hook)

    def get_plugins (self, list_disabled = True):
        """
        Returns the plugins.

        :param list_disabled: Also list disabled plugins.
        :type list_disabled: boolean

        :rtype: iter<`Plugin`>
        """
        return (x for x in self.plugins if (x.enabled or list_disabled))

    def load (self):
        """
        Load the plugins.
        
        This method scans the `portato.constants.PLUGIN_DIR` for python modules and tries to load them. If the modules are real plugins,
        they have called `register` and thus the plugins are added.
        """

        # look them up
        plugins = []
        for f in os.listdir(PLUGIN_DIR):
            path = osp.join(PLUGIN_DIR, f)
            if osp.isdir(path):
                if osp.isfile(osp.join(path, "__init__.py")):
                    plugins.append(f)
                else:
                    debug("'%s' is not a plugin: __init__.py missing", path)
            else:
                if f.endswith(".py"):
                    plugins.append(f[:-3])
                elif f.endswith(".pyc") or f.endswith(".pyo"):
                    pass # ignore .pyc and .pyo
                else:
                    debug("'%s' is not a plugin: not a .py file", path)

        # some magic ...
        plugin_module.__path__.insert(0, PLUGIN_DIR.rstrip("/")) # make the plugins loadable as "portato.plugins.name"
        # add Plugin and register to the builtins, so the plugins always have the correct version :)
        plugin_module.__builtins__["Plugin"] = Plugin
        plugin_module.__builtins__["register"] = register

        for p in plugins: # import them
            try:
                exec "from portato.plugins import %s" % p in {}
            except PluginLoadException, e:
                error(_("Loading plugin '%(plugin)s' failed: %(error)s"), {"plugin" : p, "error" : e.message})
            except:
                tb = traceback.format_exc()
                error(_("Loading plugin '%(plugin)s' failed: %(error)s"), {"plugin" : p, "error" : tb})

        self._organize()

    def add (self, plugin, disable = False):
        """
        Adds a plugin to the internal list.

        :Parameters:

            plugin : `Plugin`
                ``Plugin`` subclass or instance to add. If a class is passed, it is instantiated.

            disable : boolean
                Disable the plugin.

        :raise PluginLoadException: passed plugin is not of class `Plugin`
        """

        if callable(plugin) and Plugin in plugin.__bases__:
            p = plugin(disable = disable) # need an instance and not the class
        elif isinstance(plugin, Plugin):
            p = plugin
            if disable:
                p.status = p.STAT_HARD_DISABLED
        else:
            raise PluginLoadException, "Is neither a subclass nor an instance of Plugin."

        p._init()

        self.plugins.append(p)
        
        if p.status == p.STAT_HARD_DISABLED:
            msg = _("Plugin is disabled!")
        elif p._unresolved_deps:
            msg = _("Plugin has unresolved dependencies - disabled!")
        else:
            msg = ""
        
        info("%s %s", _("Plugin '%s' loaded.") % p.name, msg)

    def hook (self, hook, *hargs, **hkwargs):
        """
        The decorator to use in the program.
        All parameters except ``hook`` are passed to plugins.

        :param hook: the name of the hook
        :type hook: string
        """

        def hook_decorator (func):
            """
            The real decorator.
            """
            h = self.hooks[hook]

            active = Hook()

            # remove disabled
            for type in ("before", "after"):
                calls = getattr(h, type)
                aCalls = getattr(active, type)
                for call in calls:
                    if call.plugin.enabled:
                        aCalls.append(call)

            if h.override and h.override.plugin.enabled:
                active.override = h.override

            @wraps(func)
            def wrapper (*args, **kwargs):
                ret = None

                # before
                for call in active.before:
                    debug("Accessing hook '%(hook)s' of plugin '%(plugin)s' (before).", {"hook" : hook, "plugin": call.plugin.name})
                    call.call(*hargs, **hkwargs)
                
                if active.override: # override
                    info(_("Overriding hook '%(hook)s' with plugin '%(plugin)s'."), {"hook": hook, "plugin": active.override.plugin.name})
                    ret = active.override.call(*hargs, **hkwargs)
                else: # normal
                    ret = func(*args, **kwargs)

                # after
                for call in active.after:
                    debug("Accessing hook '%(hook)s' of plugin '%(plugin)s' (after).", {"hook": hook, "plugin": call.plugin.name})
                    call.call(*hargs, **hkwargs)

                return ret

            return wrapper

        return hook_decorator

    def _organize (self):
        """
        Organizes the lists of `Call` in a way, that all dependencies are fullfilled.
        """
        unresolved_before = defaultdict(list)
        unresolved_after = defaultdict(list)
        star_before = defaultdict(Hook) # should be _before_ all other
        star_after = defaultdict(Hook) # should be _after_ all other

        for plugin in self.plugins: # plugins
            for call in plugin.calls: # hooks in plugin
                if call.type == "before":
                    if call.dep is None: # no dependency -> straight add
                        self.hooks[call.hook].before.append(call)
                    elif call.dep == "*":
                        self.hooks[call.hook].before.insert(0, call)
                    elif call.dep == "-*":
                        star_before[call.hook].append(call)
                    else:
                        named = [x.plugin.name for x in self.hooks[call.hook].before]
                        if call.dep in named:
                            self.hooks[call.hook].before.insert(named.index(call.dep), call)
                        else:
                            unresolved_before[call.hook].append(call)

                elif call.type == "after":
                    if call.dep is None: # no dependency -> straight add
                        self.hooks[call.hook].after.append(call)
                    elif call.dep == "*":
                        star_after[call.hook].append(call)
                    elif call.dep == "-*":
                        self.hooks[call.hook].after.insert(0, call)
                    else:
                        named = [x.plugin.name for x in self.hooks[call.hook].after]
                        if call.dep in named:
                            self.hooks[call.hook].after.insert(named.index(call.dep)+1, call)
                        else:
                            unresolved_after[call.hook].append(call)
                
                # type = "override"
                elif call.type == "override":
                    if self.hooks[call.hook].override:
                        warning(_("For hook '%(hook)s' an override is already defined by plugin '%(plugin)s'!"), {"hook": call.hook, "plugin": self.hooks[call.hook].override.plugin.name})
                        warning(_("It is now replaced by the one from plugin '%s'!"), call.plugin.name)
                    
                    self.hooks[call.hook].override = call
                    continue
        
        self._resolve_unresolved(unresolved_before, unresolved_after)

        for hook, calls in star_before.iteritems():
            self.hooks[hook].before.extend(calls) # append the list

        for hook, calls in star_after.iteritems():
            self.hooks[hook].after.extend(calls) # append the list


    def _resolve_unresolved (self, before, after):
        def resolve(hook, list, type, add):
            if not list:
                return
            
            callList = getattr(self.hooks[hook], type)
            named = [x.plugin.name for x in callList]

            while list and named:
                newNamed = [] # use newNamed, so in each iteration only the plugins inserted last are searched
                for call in list[:]:
                    if call.dep in named:
                        callList.insert(named.index(call.dep)+add, call)
                        list.remove(call)
                        newNamed.append(call.plugin.name)

                named = newNamed

            for l in list:
                callList.append(l)
                info(_("Dependant '%(dep)s' for '%(hook)s' in plugin '%(plugin)s' not found! Adding nevertheless."), {"hook": hook, "plugin": l.plugin.name, "dep": l.dep})

        for hook in before:
            resolve(hook, before[hook], "before", 0)
        
        for hook in after:
            resolve(hook, after[hook], "after", 1)


__plugins = None

def load_plugins():
    """
    Loads the plugins.
    """
    
    global __plugins
    if __plugins is None:
        __plugins = PluginQueue()
        __plugins.load()
    

def get_plugin_queue():
    """
    Returns the actual `PluginQueue`. If it is ``None``, they are not being loaded yet.

    :rtype: `PluginQueue` or ``None``"""
    return __plugins

def hook(hook, *args, **kwargs):
    """
    Shortcut to `PluginQueue.hook`. If no `PluginQueue` is loaded, this does nothing.
    """
    if __plugins is None:
        def pseudo_decorator(f):
            return f
        return pseudo_decorator
    else:
        return __plugins.hook(hook, *args, **kwargs)

def register (plugin, disable = False):
    """
    Registers a plugin.

    :see: `PluginQueue.add`
    """
    if __plugins is not None:
        __plugins.add(plugin, disable)