##############################################################################
#
# Copyright (c) 2001 Zope Corporation 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.
#
##############################################################################
# This file contains code drawn from CMFCore's CachingPolicyManager.py
"""Header set implementation

$Id: $
"""

__authors__ = 'Geoff Davis <geoff@geoffdavis.net>'
__docformat__ = 'restructuredtext'

from zope.tales.tales import CompilerError

from AccessControl import ClassSecurityInfo
from App.Common import rfc1123_date
from DateTime import DateTime
from Products.PageTemplates.Expressions import getEngine

from Products.CMFCore.utils import getToolByName
from Products.CMFCore import permissions

from Products.Archetypes.atapi import BaseContent
from Products.Archetypes.atapi import DisplayList
from Products.Archetypes.atapi import registerType
from Products.Archetypes.atapi import Schema

from Products.Archetypes.atapi import BooleanField
from Products.Archetypes.atapi import IntegerField
from Products.Archetypes.atapi import StringField
from Products.Archetypes.atapi import TextField
from Products.Archetypes.atapi import LinesField

from Products.Archetypes.atapi import BooleanWidget
from Products.Archetypes.atapi import IntegerWidget
from Products.Archetypes.atapi import SelectionWidget
from Products.Archetypes.atapi import TextAreaWidget
from Products.Archetypes.atapi import StringWidget

from Products.CacheSetup.config import PROJECT_NAME, CACHE_TOOL_ID
from nocatalog import NoCatalog

schema = BaseContent.schema.copy() + Schema((

    TextField(
        'description',
        required=0,
        allowable_content_types = ('text/plain',),
        default='A set of HTTP headers to be assigned with a caching rule',
        write_permission = permissions.ManagePortal,
        widget=TextAreaWidget(
            label='Description',
            cols=60,
            rows=5,
            description='Basic documentation for this caching assignment policy')),

    BooleanField(
        'pageCache',
        default=False,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Cache Templates in Memory',
            description='Should templates with this header set be cached in the page cache?')),

    StringField(
        'lastModified',
        default='yes',
        write_permission = permissions.ManagePortal,
        vocabulary=DisplayList((
            ('yes', 'Yes'), 
            ('no', 'No'), 
            ('delete', 'No, and delete any pre-existing header'))),
        widget=SelectionWidget(
            label='Last-Modified Header',
            description='Should the header set add a Last-Modified header?  Note: There appears '
                        'to be an IE bug that causes incorrect caching behavior when you have both '
                        'a Last-Modified header (used for caching heuristics) and explicit caching '
                        'headers such as max-age=0.  The problem may arise from setting the Expires '
                        'header to the current time.  One workaround is to not set the Last-Modified '
                        'header and to delete any pre-existing Last-Modified header.  Setting Expires '
                        'to a time in the past may also work (this is now the default behavior if '
                        'max-age=0) -- further testing is needed.')),
    # The last_modified argument is used to determine whether to add a
    # Last-Modified header.  last_modified=1 by default.  There appears
    # to be a bug in IE 6 (and possibly other versions) that uses the
    # Last-Modified header plus some heuristics rather than the other
    # explicit caching headers to determine whether to render content
    # from the cache.  If you set, say, max-age=0, must-revalidate and
    # have a Last-Modified header some time in the past, IE will
    # recognize that the page in cache is stale and will request an
    # update from the server BUT if you have a Last-Modified header
    # with an older date, will then ignore the update and render from
    # the cache, so you may want to disable the Last-Modified header
    # when controlling caching using Cache-Control headers.
    #
    # Update: The problem may be because we were setting Expires to
    # the current time when max-age was set to 0.  IE may have Expires
    # override max-age (bad) or something similar.  We are now setting
    # Expires to a time in the past if max-age is 0.

    BooleanField(
        'etag',
        default=True,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='ETag Header',
            description='Should the header set add an ETag header?')),

    BooleanField(
        'enable304s',
        default=True,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Enable 304s',
            description='Should objects that support conditional GET handling with ETags '
                        '(FSPageTemplates) be allowed to return a 304 Not Modified HTTP status?')),

    BooleanField(
        'vary',
        default=True,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Vary Header',
            description='Should the header set add a Vary header?')),

    IntegerField(
        'maxAge',
        default=None,
        write_permission = permissions.ManagePortal,
        widget=IntegerWidget(
            label='Cache-Control Header: max-age',
            size=6,
            description='The amount of time in seconds that a page can be cached on a '
                        'client without revalidation.  Also used to set the Expires header '
                        '(HTTP 1.0).  If left blank, no max-age token will be added and no '
                        'Expires header will be set.')),

    IntegerField(
        'sMaxAge',
        default=None,
        write_permission = permissions.ManagePortal,
        widget=IntegerWidget(
            label='Cache-Control Header: s-maxage',
            size=6,
            description='The amount of time in seconds that a page can be cached in a proxy '
                        'cache without revalidation.  If left blank, no s-maxage token will '
                        'be added.  If you do not indicate that you have a purgeable proxy '
                        'server available (e.g. squid), the s-maxage token will not be added.')),

    BooleanField(
        'mustRevalidate',
        default=False,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Cache-Control Header: must-revalidate',
            description='Must objects be revalidated with the server (by a conditional GET) '
                        'once they have expired in the client?')),

    BooleanField(
        'proxyRevalidate',
        default=False,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Cache-Control Header: proxy-revalidate',
            description='Must objects be revalidated with the server once they have expired '
                        'in the proxy cache?')),

    BooleanField(
        'noCache',
        default=False,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Cache-Control Header: no-cache',
            description='If no-cache is set, objects may be cached, but the cache must '
                        'revalidate with the server before serving the cached version. '
                        'Setting no-cache also causes a Pragma: no-cache (HTTP 1.0) header '
                        'to be sent. (Caution: There is a Microsoft IE bug with HTTPS and '
                        'no-cache so this token should probably be avoided if the server '
                        'supports SSL connections)')),

    BooleanField(
        'noStore',
        default=False,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Cache-Control Header: no-store',
            description='If no-store is set, objects may not be stored in a cache. '
                        '(Caution: There is a Microsoft IE bug with HTTPS and no-store '
                        'so this token should probably be avoided if the server '
                        'supports SSL connections)')),

    BooleanField(
        'public',
        default=False,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Cache-Control Header: public',
            description='If the public flag is set, proxy caches may cache a page even '
                        'in the presence of things like Authentication headers that would '
                        'otherwise prevent them from doing so.')),

    BooleanField(
        'private',
        default=False,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Cache-Control Header: private',
            description='If the private flag is set, shared HTTP 1.1-compliant proxy caches '
                        'will not cache a page.  The non-shared browser cache, however, may '
                        'cache a page with the private flag.')),

    BooleanField(
        'noTransform',
        default=False,
        write_permission = permissions.ManagePortal,
        widget=BooleanWidget(
            label='Cache-Control Header: no-transform',
            description='The no-transform flag tells intermediate proxies not to alter the '
                        'content in transit (e.g. tell proxies to mobile phones not to '
                        'downsample images, etc)')),

    IntegerField(
        'preCheck',
        default=None,
        write_permission = permissions.ManagePortal,
        widget=IntegerWidget(
            label='Cache-Control Header: pre-check',
            description='<strong>IE-ONLY:</strong> '
                        'The pre-check flag is a Microsoft IE Cache-Control extension. '
                        'See http://msdn.microsoft.com/workshop/author/perf/perftips.asp for details. '
                        'IE 5+ will send some cache directives unless pre-check and post-check '
                        'are set to 0.')),

    IntegerField(
        'postCheck',
        default=None,
        write_permission = permissions.ManagePortal,
        widget=IntegerWidget(
            label='Cache-Control Header: post-check',
            description='<strong>IE-ONLY:</strong> '
                        'The post-check flag is a Microsoft IE Cache-Control extension. '
                        'See http://msdn.microsoft.com/workshop/author/perf/perftips.asp for details. '
                        'IE 5+ will send some cache directives unless pre-check and post-check '
                        'are set to 0.')),

    IntegerField(
        'staleWhileRevalidate',
        default=None,
        write_permission = permissions.ManagePortal,
        widget=IntegerWidget(
            label='Cache-Control Header: stale-while-revalidate',
            size=6,
            description='<strong>EXPERIMENTAL:</strong> '
                        'The amount of time in seconds that a stale page may be served from a proxy '
                        'cache while the proxy revalidates the page asynchronously. '
                        'See http://www.mnot.net/blog/2007/12/12/stale for details.')),

    IntegerField(
        'staleIfError',
        default=None,
        write_permission = permissions.ManagePortal,
        widget=IntegerWidget(
            label='Cache-Control Header: stale-if-error',
            size=6,
            description='<strong>EXPERIMENTAL:</strong> '
                        'The amount of time in seconds that a stale page may be served from a proxy '
                        'cache if revalidation results in an error. '
                        'See http://www.mnot.net/blog/2007/12/12/stale for details')),

    LinesField(
        'extraHeader',
        write_permission = permissions.ManagePortal,
        widget=StringWidget(
            macro_edit='extraHeaderWidget',
            label='Extra Response Header',
            size=80,
            description='<strong>EXPERIMENTAL:</strong> '
                        'An extra header that will be added to the response. '
                        'Two header types are allowed: "Surrogate-Control: &lt;value&gt;" '
                        'and "X-&lt;name&gt'': &lt;value&gt;". '
                        'Enter the entire header line like so: "X-My-Header: Hello World" ')),


))

schema['id'].widget.ignore_visible_ids=True                       
schema['id'].widget.description="Should not contain spaces, underscores or mixed case. An 'X-Header-Set-Id' header with this id will be added."

class HeaderSet(NoCatalog, BaseContent):
    """A content object used for setting a set of response headers for a page"""

    security = ClassSecurityInfo()
    archetype_name = 'Response Header Set'
    portal_type = meta_type = 'HeaderSet'
    schema = schema
    global_allow = 0
    _at_rename_after_creation = True

    actions = (
        {'action':      'string:$object_url',
         'category':    'object',
         'id':          'view',
         'name':        'Cache Setup',
         'permissions': (permissions.ManagePortal,),
         'visible':     False},
    )

    aliases = {
        '(Default)':    'cache_policy_item_config',
        'view' :        'cache_policy_item_config',
        'edit' :        'cache_policy_item_config'
    }

    def setExtraHeader(self, value):
        """Clean up syntax to make a valid header"""
        if isinstance(value, basestring):
            value = value.split()
        value = " ".join(value) + ':'
        key, value = [v.strip() for v in value.split(':')[:2]]
        if key and value == '':
            # Lines field doesn't like empty strings
            value = 'blank'
        key = ''.join([k.isalnum() and k.lower() or '-' for k in key])
        if key and not key.startswith('x-') and key != 'surrogate-control':
            key = 'x-' + key
        # Convert to standard HTTP header case style
        # Copied from ZServer.HTTPResponse
        key="%s%s" % (key[:1].upper(), key[1:])
        start=0
        l=key.find('-',start)
        while l >= start:
            key="%s-%s%s" % (key[:l],key[l+1:l+2].upper(),key[l+2:])
            start=l+1
            l=key.find('-',start)
        self.getField('extraHeader').set(self, (key, value))

    def _validate_expression(self, expression):
        try:
            getEngine().compile(expression)
        except CompilerError, e:
            return 'Bad expression:', str(e)
        except:
            raise

    def getLastModifiedValue(self, expr_context):
        if not self.getLastModified() == 'yes':
            return None # no last-modified value if disabled
        rule = expr_context.vars['rule']
        return rule.getLastModified(expr_context)

    def getVaryValue(self, expr_context):
        if not self.getVary():
            return None # no Vary value if disabled
        rule = expr_context.vars['rule']
        return rule.getVary(expr_context)

    def getPageCacheKey(self, expr_context):
        # Return a cache key for use with PageCacheManager
        if not self.getPageCache():
            return None
        return self._getEtagValue(expr_context)

    def _getEtagValue(self, expr_context):
        rule = expr_context.vars['rule']
        request = expr_context.vars['request']
        object = expr_context.vars['object']
        view = expr_context.vars['view']
        member = expr_context.vars['member']
        return rule.getEtag(request, object, view, member)

    def getEtagValue(self, expr_context):
        if not self.getEtag():
            return None # no etag if disabled
        return self._getEtagValue(expr_context)

    def getHeaders(self, expr_context):
        """Returns a list of caching headers in (key, value) tuples"""
        pcs = getToolByName(self, CACHE_TOOL_ID)
        headers_to_add = []
        headers_to_remove = []

        last_modified = self.getLastModified()
        if last_modified == 'yes':
            mod_time = self.getLastModifiedValue(expr_context)
            if type(mod_time) is type(''):
                mod_time = DateTime(mod_time)
            if mod_time is not None:
                mod_time_st = rfc1123_date(mod_time.timeTime())
                headers_to_add.append(('Last-modified', mod_time_st))
        elif last_modified == 'delete':
            headers_to_remove.append('Last-modified')

        if self.getEtag():
            etag = self.getEtagValue(expr_context)
            if etag is not None:
                headers_to_add.append(('ETag', etag))

        vary = self.getVaryValue(expr_context)
        if vary:
            if pcs.getGzip() in ('accept-encoding', 'accept-encoding+user-agent'):
                # Zope adds Accept-Encoding automatically
                vary = ', '.join([v.strip() for v in vary.split(',') if v.strip() != 'Accept-Encoding'])
            if vary:
                headers_to_add.append(('Vary', vary))

        # a list of cache-control tokens
        control = []

        max_age = self.getMaxAge()
        if max_age is not None:
            now = expr_context.vars['time']
            if max_age > 0:
                expiration_time = now.timeTime() + max_age
            else:
                # immediate expiration requires that the client clock be precisely synchronized
                # since this is not guaranteed, we'll set the expiration time to 10 years ago
                expiration_time = now.timeTime() - 10*365*24*3600
            exp_time_st = rfc1123_date(expiration_time)
            headers_to_add.append(('Expires', exp_time_st))
            control.append('max-age=%d' % max_age)

        s_max_age = self.getSMaxAge()
        if s_max_age is not None:
            control.append('s-maxage=%d' % s_max_age)

        if self.getNoCache():
            control.append('no-cache')
            # The following is for HTTP 1.0 clients
            headers_to_add.append(('Pragma', 'no-cache'))

        if self.getNoStore():
            control.append('no-store')

        if self.getPublic():
            control.append('public')

        if self.getPrivate():
            control.append('private')

        if self.getMustRevalidate():
            control.append('must-revalidate')

        if self.getProxyRevalidate():
            control.append('proxy-revalidate')

        if self.getNoTransform():
            control.append('no-transform')

        pre_check = self.getPreCheck()
        if pre_check is not None:
            control.append('pre-check=%d' % pre_check)

        post_check = self.getPostCheck()
        if post_check is not None:
            control.append('post-check=%d' % post_check)

        stale_while_revalidate = self.getStaleWhileRevalidate()
        if stale_while_revalidate is not None:
            control.append('stale-while-revalidate=%d' % stale_while_revalidate)

        stale_if_error = self.getStaleIfError()
        if stale_if_error is not None:
            control.append('stale-if-error=%d' % stale_if_error)

        if control:
            headers_to_add.append(('Cache-control', ', '.join(control)))

        extra = self.getExtraHeader()
        if extra is not ():
            headers_to_add.append(extra)

        # add debugging information
        rule = expr_context.vars['rule']
        headers_to_add.append(('X-Caching-Rule-Id', rule.getId()))
        headers_to_add.append(('X-Header-Set-Id', self.getId()))

        return (headers_to_add, headers_to_remove)

registerType(HeaderSet, PROJECT_NAME)