"""
Plugin Manager
--------------

A plugin manager class is used to load plugins, manage the list of
loaded plugins, and proxy calls to those plugins.

The plugin managers provided with nose are:

:class:`PluginManager`
    This manager doesn't implement loadPlugins, so it can only work
    with a static list of plugins.

:class:`BuiltinPluginManager`
    This manager loads plugins referenced in ``nose.plugins.builtin``.

:class:`EntryPointPluginManager`
    This manager uses setuptools entrypoints to load plugins.

:class:`DefaultPluginMananger`
    This is the manager class that will be used by default. If
    setuptools is installed, it is a subclass of
    :class:`EntryPointPluginManager` and :class:`BuiltinPluginManager`;
    otherwise, an alias to :class:`BuiltinPluginManager`.

:class:`RestrictedPluginManager`
    This manager is for use in test runs where some plugin calls are
    not available, such as runs started with ``python setup.py test``,
    where the test runner is the default unittest :class:`TextTestRunner`. It
    is a subclass of :class:`DefaultPluginManager`.

Writing a plugin manager
========================

If you want to load plugins via some other means, you can write a
plugin manager and pass an instance of your plugin manager class when
instantiating the :class:`nose.config.Config` instance that you pass to
:class:`TestProgram` (or :func:`main` or :func:`run`).

To implement your plugin loading scheme, implement ``loadPlugins()``,
and in that method, call ``addPlugin()`` with an instance of each plugin
you wish to make available. Make sure to call
``super(self).loadPlugins()`` as well if have subclassed a manager
other than ``PluginManager``.

"""
import inspect
import logging
import os
import sys
from warnings import warn
import nose.config
from nose.failure import Failure
from nose.plugins.base import IPluginInterface
from nose.pyversion import sort_list

try:
    import cPickle as pickle
except:
    import pickle
try:
    from cStringIO import StringIO
except:
    from StringIO import StringIO


__all__ = ['DefaultPluginManager', 'PluginManager', 'EntryPointPluginManager',
           'BuiltinPluginManager', 'RestrictedPluginManager']

log = logging.getLogger(__name__)


class PluginProxy(object):
    """Proxy for plugin calls. Essentially a closure bound to the
    given call and plugin list.

    The plugin proxy also must be bound to a particular plugin
    interface specification, so that it knows what calls are available
    and any special handling that is required for each call.
    """
    interface = IPluginInterface
    def __init__(self, call, plugins):
        try:
            self.method = getattr(self.interface, call)
        except AttributeError:
            raise AttributeError("%s is not a valid %s method"
                                 % (call, self.interface.__name__))
        self.call = self.makeCall(call)
        self.plugins = []
        for p in plugins:
            self.addPlugin(p, call)

    def __call__(self, *arg, **kw):
        return self.call(*arg, **kw)

    def addPlugin(self, plugin, call):
        """Add plugin to my list of plugins to call, if it has the attribute
        I'm bound to.
        """
        meth = getattr(plugin, call, None)
        if meth is not None:
            if call == 'loadTestsFromModule' and \
                    len(inspect.getargspec(meth)[0]) == 2:
                orig_meth = meth
                meth = lambda module, path, **kwargs: orig_meth(module)
            self.plugins.append((plugin, meth))

    def makeCall(self, call):
        if call == 'loadTestsFromNames':
            # special case -- load tests from names behaves somewhat differently
            # from other chainable calls, because plugins return a tuple, only
            # part of which can be chained to the next plugin.
            return self._loadTestsFromNames

        meth = self.method
        if getattr(meth, 'generative', False):
            # call all plugins and yield a flattened iterator of their results
            return lambda *arg, **kw: list(self.generate(*arg, **kw))
        elif getattr(meth, 'chainable', False):
            return self.chain
        else:
            # return a value from the first plugin that returns non-None
            return self.simple

    def chain(self, *arg, **kw):
        """Call plugins in a chain, where the result of each plugin call is
        sent to the next plugin as input. The final output result is returned.
        """
        result = None
        # extract the static arguments (if any) from arg so they can
        # be passed to each plugin call in the chain
        static = [a for (static, a)
                  in zip(getattr(self.method, 'static_args', []), arg)
                  if static]
        for p, meth in self.plugins:
            result = meth(*arg, **kw)
            arg = static[:]
            arg.append(result)
        return result

    def generate(self, *arg, **kw):
        """Call all plugins, yielding each item in each non-None result.
        """
        for p, meth in self.plugins:
            result = None
            try:
                result = meth(*arg, **kw)
                if result is not None:
                    for r in result:
                        yield r
            except (KeyboardInterrupt, SystemExit):
                raise
            except:
                exc = sys.exc_info()
                yield Failure(*exc)
                continue

    def simple(self, *arg, **kw):
        """Call all plugins, returning the first non-None result.
        """
        for p, meth in self.plugins:
            result = meth(*arg, **kw)
            if result is not None:
                return result

    def _loadTestsFromNames(self, names, module=None):
        """Chainable but not quite normal. Plugins return a tuple of
        (tests, names) after processing the names. The tests are added
        to a suite that is accumulated throughout the full call, while
        names are input for the next plugin in the chain.
        """
        suite = []
        for p, meth in self.plugins:
            result = meth(names, module=module)
            if result is not None:
                suite_part, names = result
                if suite_part:
                    suite.extend(suite_part)
        return suite, names


class NoPlugins(object):
    """Null Plugin manager that has no plugins."""
    interface = IPluginInterface
    def __init__(self):
        self._plugins = self.plugins = ()

    def __iter__(self):
        return ()

    def _doNothing(self, *args, **kwds):
        pass

    def _emptyIterator(self, *args, **kwds):
        return ()

    def __getattr__(self, call):
        method = getattr(self.interface, call)
        if getattr(method, "generative", False):
            return self._emptyIterator
        else:
            return self._doNothing

    def addPlugin(self, plug):
        raise NotImplementedError()

    def addPlugins(self, plugins):
        raise NotImplementedError()

    def configure(self, options, config):
        pass

    def loadPlugins(self):
        pass

    def sort(self):
        pass


class PluginManager(object):
    """Base class for plugin managers. Does not implement loadPlugins, so it
    may only be used with a static list of plugins.

    The basic functionality of a plugin manager is to proxy all unknown
    attributes through a ``PluginProxy`` to a list of plugins.

    Note that the list of plugins *may not* be changed after the first plugin
    call.
    """
    proxyClass = PluginProxy

    def __init__(self, plugins=(), proxyClass=None):
        self._plugins = []
        self._proxies = {}
        if plugins:
            self.addPlugins(plugins)
        if proxyClass is not None:
            self.proxyClass = proxyClass

    def __getattr__(self, call):
        try:
            return self._proxies[call]
        except KeyError:
            proxy = self.proxyClass(call, self._plugins)
            self._proxies[call] = proxy
        return proxy

    def __iter__(self):
        return iter(self.plugins)

    def addPlugin(self, plug):
        # allow, for instance, plugins loaded via entry points to
        # supplant builtin plugins.
        new_name = getattr(plug, 'name', object())
        self._plugins[:] = [p for p in self._plugins
                            if getattr(p, 'name', None) != new_name]
        self._plugins.append(plug)

    def addPlugins(self, plugins):
        for plug in plugins:
            self.addPlugin(plug)

    def configure(self, options, config):
        """Configure the set of plugins with the given options
        and config instance. After configuration, disabled plugins
        are removed from the plugins list.
        """
        log.debug("Configuring plugins")
        self.config = config
        cfg = PluginProxy('configure', self._plugins)
        cfg(options, config)
        enabled = [plug for plug in self._plugins if plug.enabled]
        self.plugins = enabled
        self.sort()
        log.debug("Plugins enabled: %s", enabled)

    def loadPlugins(self):
        pass

    def sort(self):
        return sort_list(self._plugins, lambda x: getattr(x, 'score', 1), reverse=True)

    def _get_plugins(self):
        return self._plugins

    def _set_plugins(self, plugins):
        self._plugins = []
        self.addPlugins(plugins)

    plugins = property(_get_plugins, _set_plugins, None,
                       """Access the list of plugins managed by
                       this plugin manager""")


class ZeroNinePlugin:
    """Proxy for 0.9 plugins, adapts 0.10 calls to 0.9 standard.
    """
    def __init__(self, plugin):
        self.plugin = plugin

    def options(self, parser, env=os.environ):
        self.plugin.add_options(parser, env)

    def addError(self, test, err):
        if not hasattr(self.plugin, 'addError'):
            return
        # switch off to addSkip, addDeprecated if those types
        from nose.exc import SkipTest, DeprecatedTest
        ec, ev, tb = err
        if issubclass(ec, SkipTest):
            if not hasattr(self.plugin, 'addSkip'):
                return
            return self.plugin.addSkip(test.test)
        elif issubclass(ec, DeprecatedTest):
            if not hasattr(self.plugin, 'addDeprecated'):
                return
            return self.plugin.addDeprecated(test.test)
        # add capt
        capt = test.capturedOutput
        return self.plugin.addError(test.test, err, capt)

    def loadTestsFromFile(self, filename):
        if hasattr(self.plugin, 'loadTestsFromPath'):
            return self.plugin.loadTestsFromPath(filename)

    def addFailure(self, test, err):
        if not hasattr(self.plugin, 'addFailure'):
            return
        # add capt and tbinfo
        capt = test.capturedOutput
        tbinfo = test.tbinfo
        return self.plugin.addFailure(test.test, err, capt, tbinfo)

    def addSuccess(self, test):
        if not hasattr(self.plugin, 'addSuccess'):
            return
        capt = test.capturedOutput
        self.plugin.addSuccess(test.test, capt)

    def startTest(self, test):
        if not hasattr(self.plugin, 'startTest'):
            return
        return self.plugin.startTest(test.test)

    def stopTest(self, test):
        if not hasattr(self.plugin, 'stopTest'):
            return
        return self.plugin.stopTest(test.test)

    def __getattr__(self, val):
        return getattr(self.plugin, val)


class EntryPointPluginManager(PluginManager):
    """Plugin manager that loads plugins from the `nose.plugins` and
    `nose.plugins.0.10` entry points.
    """
    entry_points = (('nose.plugins.0.10', None),
                    ('nose.plugins', ZeroNinePlugin))

    def loadPlugins(self):
        """Load plugins by iterating the `nose.plugins` entry point.
        """
        super(EntryPointPluginManager, self).loadPlugins()
        from pkg_resources import iter_entry_points

        loaded = {}
        for entry_point, adapt in self.entry_points:
            for ep in iter_entry_points(entry_point):
                if ep.name in loaded:
                    continue
                loaded[ep.name] = True
                log.debug('%s load plugin %s', self.__class__.__name__, ep)
                try:
                    plugcls = ep.load()
                except KeyboardInterrupt:
                    raise
                except Exception, e:
                    # never want a plugin load to kill the test run
                    # but we can't log here because the logger is not yet
                    # configured
                    warn("Unable to load plugin %s: %s" % (ep, e),
                         RuntimeWarning)
                    continue
                if adapt:
                    plug = adapt(plugcls())
                else:
                    plug = plugcls()
                self.addPlugin(plug)


class BuiltinPluginManager(PluginManager):
    """Plugin manager that loads plugins from the list in
    `nose.plugins.builtin`.
    """
    def loadPlugins(self):
        """Load plugins in nose.plugins.builtin
        """
        from nose.plugins import builtin
        for plug in builtin.plugins:
            self.addPlugin(plug())
        super(BuiltinPluginManager, self).loadPlugins()

try:
    import pkg_resources
    class DefaultPluginManager(BuiltinPluginManager, EntryPointPluginManager):
        pass
except ImportError:
    DefaultPluginManager = BuiltinPluginManager


class RestrictedPluginManager(DefaultPluginManager):
    """Plugin manager that restricts the plugin list to those not
    excluded by a list of exclude methods. Any plugin that implements
    an excluded method will be removed from the manager's plugin list
    after plugins are loaded.
    """
    def __init__(self, plugins=(), exclude=(), load=True):
        DefaultPluginManager.__init__(self, plugins)
        self.load = load
        self.exclude = exclude
        self.excluded = []
        self._excludedOpts = None

    def excludedOption(self, name):
        if self._excludedOpts is None:
            from optparse import OptionParser
            self._excludedOpts = OptionParser(add_help_option=False)
            for plugin in self.excluded:
                plugin.options(self._excludedOpts, env={})
        return self._excludedOpts.get_option('--' + name)

    def loadPlugins(self):
        if self.load:
            DefaultPluginManager.loadPlugins(self)
        allow = []
        for plugin in self.plugins:
            ok = True
            for method in self.exclude:
                if hasattr(plugin, method):
                    ok = False
                    self.excluded.append(plugin)
                    break
            if ok:
                allow.append(plugin)
        self.plugins = allow
