##############################################################################
#
# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Hooks for getting and setting a site in the thread global namespace.
"""
__docformat__ = 'restructuredtext'

import contextlib
import threading

from zope.component._compat import ZOPE_SECURITY_NOT_AVAILABLE_EX

try:
    from zope.security.proxy import removeSecurityProxy
except ZOPE_SECURITY_NOT_AVAILABLE_EX: # pragma: no cover
    def removeSecurityProxy(x):
        return x

from zope.component.globalregistry import getGlobalSiteManager
from zope.interface.interfaces import ComponentLookupError
from zope.interface.interfaces import IComponentLookup

__all__ = [
    'setSite',
    'getSite',
    'site',
    'getSiteManager',
    'setHooks',
    'resetHooks',
]

class read_property(object):
    """Descriptor for property-like computed attributes.

    Unlike the standard 'property', this descriptor allows assigning a
    value to the instance, shadowing the property getter function.
    """
    def __init__(self, func):
        self.func = func

    def __get__(self, inst, cls):
        if inst is None:
            return self

        return self.func(inst)

class SiteInfo(threading.local):
    site = None
    sm = getGlobalSiteManager()

    @read_property
    def adapter_hook(self):
        adapter_hook = self.sm.adapters.adapter_hook
        self.adapter_hook = adapter_hook
        return adapter_hook

siteinfo = SiteInfo()

def setSite(site=None):
    if site is None:
        sm = getGlobalSiteManager()
    else:

        # We remove the security proxy because there's no way for
        # untrusted code to get at it without it being proxied again.

        # We should really look look at this again though, especially
        # once site managers do less.  There's probably no good reason why
        # they can't be proxied.  Well, except maybe for performance.

        site = removeSecurityProxy(site)
        # The getSiteManager method is defined by IPossibleSite.
        sm = site.getSiteManager()

    siteinfo.site = site
    siteinfo.sm = sm
    try:
        del siteinfo.adapter_hook
    except AttributeError:
        pass

def getSite():
    return siteinfo.site


@contextlib.contextmanager
def site(site):
    """
    site(site) -> None

    Context manager that sets *site* as the current site for the
    duration of the ``with`` body.
    """
    old_site = getSite()
    setSite(site)
    try:
        yield
    finally:
        setSite(old_site)


def getSiteManager(context=None):
    """A special hook for getting the site manager.

    Here we take the currently set site into account to find the appropriate
    site manager.
    """
    if context is None:
        return siteinfo.sm

    # We remove the security proxy because there's no way for
    # untrusted code to get at it without it being proxied again.

    # We should really look look at this again though, especially
    # once site managers do less.  There's probably no good reason why
    # they can't be proxied.  Well, except maybe for performance.
    sm = IComponentLookup(
        context, getGlobalSiteManager())
    sm = removeSecurityProxy(sm)
    return sm


def adapter_hook(interface, object, name='', default=None):
    try:
        return siteinfo.adapter_hook(interface, object, name, default)
    except ComponentLookupError:
        return default


def setHooks():
    """
    Make `zope.component.getSiteManager` and interface adaptation
    respect the current site.

    Most applications will want to be sure te call this early in their
    startup sequence. Test code that uses these APIs should also arrange to
    call this.

    .. seealso:: :mod:`zope.component.testlayer`
    """
    from zope.component import _api
    _api.adapter_hook.sethook(adapter_hook)
    _api.getSiteManager.sethook(getSiteManager)

def resetHooks():
    """
    Reset `zope.component.getSiteManager` and interface adaptation to
    their original implementations that are unaware of the current
    site.

    Use caution when calling this; most code will not need to call
    this. If code using the global API executes following this, it
    will most likely use the base global component registry instead of
    a site-specific registry it was expected. This can lead to
    failures in adaptation and utility lookup.
    """
    # Reset hookable functions to original implementation.
    from zope.component import _api
    _api.adapter_hook.reset()
    _api.getSiteManager.reset()
    # be sure the old adapter hook isn't cached, since
    # it is derived from the SiteManager
    try:
        del siteinfo.adapter_hook
    except AttributeError:
        pass

# Clear the site thread global
clearSite = setSite
try:
    from zope.testing.cleanup import addCleanUp
except ImportError: #pragma NO COVER
    pass
else:
    addCleanUp(resetHooks)
