#!/usr/bin/env python3

# Libervia: a Salut à Toi frontend
# Copyright (C) 2011-2021 Jérôme Poisson <goffi@goffi.org>

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from __future__ import annotations
import copy
from functools import reduce
import hashlib
import json
import os.path
from pathlib import Path
import time
import traceback
from typing import List, Optional, Union
import urllib.error
import urllib.parse
import urllib.request

from twisted.internet import defer
from twisted.python import failure
from twisted.python.filepath import FilePath
from twisted.web import server
from twisted.web import resource as web_resource
from twisted.web import util as web_util
from twisted.words.protocols.jabber import jid

from libervia.backend.core import exceptions
from libervia.backend.core.i18n import _
from libervia.backend.core.log import getLogger
from libervia.backend.tools.common import date_utils
from libervia.backend.tools.common import utils
from libervia.backend.tools.common import data_format
from libervia.backend.tools.utils import as_deferred
from libervia.frontends.bridge.bridge_frontend import BridgeException

from . import session_iface
from .classes import WebsocketMeta
from .classes import Script
from .constants import Const as C
from .resources import LiberviaRootResource
from .utils import SubPage, quote

log = getLogger(__name__)


class CacheBase(object):
    def __init__(self):
        self._created = time.time()
        self._last_access = self._created

    @property
    def created(self):
        return self._created

    @property
    def last_access(self):
        return self._last_access

    @last_access.setter
    def last_access(self, timestamp):
        self._last_access = timestamp


class CachePage(CacheBase):
    def __init__(self, rendered):
        super(CachePage, self).__init__()
        self._created = time.time()
        self._last_access = self._created
        self._rendered = rendered
        self._hash = hashlib.sha256(rendered).hexdigest()

    @property
    def rendered(self):
        return self._rendered

    @property
    def hash(self):
        return self._hash


class CacheURL(CacheBase):
    def __init__(self, request):
        super(CacheURL, self).__init__()
        try:
            self._data = copy.deepcopy(request.data)
        except AttributeError:
            self._data = {}
        self._template_data = copy.deepcopy(request.template_data)
        self._prepath = request.prepath[:]
        self._postpath = request.postpath[:]
        del self._template_data["csrf_token"]

    def use(self, request):
        self.last_access = time.time()
        request.data = copy.deepcopy(self._data)
        request.template_data.update(copy.deepcopy(self._template_data))
        request.prepath = self._prepath[:]
        request.postpath = self._postpath[:]


class LiberviaPage(web_resource.Resource):
    isLeaf = True  #  we handle subpages ourself
    cache = {}
    #  Set of tuples (service/node/sub_id) of nodes subscribed for caching
    # sub_id can be empty string if not handled by service
    cache_pubsub_sub = set()

    def __init__(
        self, host, vhost_root, root_dir, url, name=None, label=None, redirect=None,
        access=None, dynamic=True, parse_url=None, add_breadcrumb=None,
        prepare_render=None, render=None, template=None, on_data_post=None, on_data=None,
        url_cache=False, replace_on_conflict=False
        ):
        """Initiate LiberviaPage instance

        LiberviaPages are the main resources of Libervia, using easy to set python files
        The non mandatory arguments are the variables found in page_meta.py
        @param host(Libervia): the running instance of Libervia
        @param vhost_root(web_resource.Resource): root resource of the virtual host which
            handle this page.
        @param root_dir(Path): absolute file path of the page
        @param url(unicode): relative URL to the page
            this URL may not be valid, as pages may require path arguments
        @param name(unicode, None): if not None, a unique name to identify the page
            can then be used for e.g. redirection
            "/" is not allowed in names (as it can be used to construct URL paths)
        @param redirect(unicode, None): if not None, this page will be redirected.
            A redirected parameter is used as in self.page_redirect.
            parse_url will not be skipped
            using this redirect parameter is called "full redirection"
            using self.page_redirect is called "partial redirection" (because some
            rendering method can still be used, e.g. parse_url)
        @param access(unicode, None): permission needed to access the page
            None means public access.
            Pages inherit from parent pages: e.g. if a "settings" page is restricted
            to admins, and if "settings/blog" is public, it still can only be accessed by
            admins. See C.PAGES_ACCESS_* for details
        @param dynamic(bool): if True, activate websocket for bidirectional communication
        @param parse_url(callable, None): if set it will be called to handle the URL path
            after this method, the page will be rendered if noting is left in path
            (request.postpath) else a the request will be transmitted to a subpage
        @param add_breadcrumb(callable, None): if set, manage the breadcrumb data for this
            page, otherwise it will be set automatically from page name or label.
        @param prepare_render(callable, None): if set, will be used to prepare the
            rendering. That often means gathering data using the bridge
        @param render(callable, None): if template is not set, this method will be
            called and what it returns will be rendered.
            This method is mutually exclusive with template and must return a unicode
            string.
        @param template(unicode, None): path to the template to render.
            This method is mutually exclusive with render
        @param on_data_post(callable, None): method to call when data is posted
            None if data post is not handled
            "continue" if data post is not handled there, and we must not interrupt
            workflow (i.e. it's handled in "render" method).
            otherwise, on_data_post can return a string with following value:
                - C.POST_NO_CONFIRM: confirm flag will not be set
            on_data_post can raise following exceptions:
                - exceptions.DataError: value is incorrect, message will be displayed
                    as a notification
        @param on_data(callable, None): method to call when dynamic data is sent
            this method is used with Libervia's websocket mechanism
        @param url_cache(boolean): if set, result of parse_url is cached (per profile).
            Useful when costly calls (e.g. network) are done while parsing URL.
        @param replace_on_conflict(boolean): if True, don't raise ConflictError if a
            page of this name already exists, but replace it
        """

        web_resource.Resource.__init__(self)
        self.host = host
        self.vhost_root = vhost_root
        self.root_dir = root_dir
        self.url = url
        self.name = name
        self.label = label
        self.dyn_data = {}
        if name is not None:
            if (name in self.named_pages
                and not (replace_on_conflict and self.named_pages[name].url == url)):
                raise exceptions.ConflictError(
                    _('a Libervia page named "{}" already exists'.format(name)))
            if "/" in name:
                raise ValueError(_('"/" is not allowed in page names'))
            if not name:
                raise ValueError(_("a page name can't be empty"))
            self.named_pages[name] = self
        if access is None:
            access = C.PAGES_ACCESS_PUBLIC
        if access not in (
            C.PAGES_ACCESS_PUBLIC,
            C.PAGES_ACCESS_PROFILE,
            C.PAGES_ACCESS_NONE,
        ):
            raise NotImplementedError(
                _("{} access is not implemented yet").format(access)
            )
        self.access = access
        self.dynamic = dynamic
        if redirect is not None:
            # only page access and name make sense in case of full redirection
            # so we check that rendering methods/values are not set
            if not all(
                lambda x: x is not None
                for x in (parse_url, prepare_render, render, template)
            ):
                raise ValueError(
                    _("you can't use full page redirection with other rendering"
                      "method, check self.page_redirect if you need to use them"))
            self.redirect = redirect
        else:
            self.redirect = None
        self.parse_url = parse_url
        self.add_breadcrumb = add_breadcrumb
        self.prepare_render = prepare_render
        self.template = template
        self.render_method = render
        self.on_data_post = on_data_post
        self.on_data = on_data
        self.url_cache = url_cache
        if access == C.PAGES_ACCESS_NONE:
            # none pages just return a 404, no further check is needed
            return
        if template is not None and render is not None:
            log.error(_("render and template methods can't be used at the same time"))

        # if not None, next rendering will be cached
        #  it must then contain a list of the the keys to use (without the page instance)
        # e.g. [C.SERVICE_PROFILE, "pubsub", server@example.tld, pubsub_node]
        self._do_cache = None

    def __str__(self):
        return "LiberviaPage {name} at {url} (vhost: {vhost_root})".format(
            name=self.name or "<anonymous>", url=self.url, vhost_root=self.vhost_root)

    @property
    def named_pages(self):
        return self.vhost_root.named_pages

    @property
    def uri_callbacks(self):
        return self.vhost_root.uri_callbacks

    @property
    def pages_redirects(self):
        return self.vhost_root.pages_redirects

    @property
    def cached_urls(self):
        return self.vhost_root.cached_urls

    @property
    def main_menu(self):
        return self.vhost_root.main_menu

    @property
    def default_theme(self):
        return self.vhost_root.default_theme


    @property
    def site_themes(self):
        return self.vhost_root.site_themes

    @staticmethod
    def create_page(host, meta_path, vhost_root, url_elts, replace_on_conflict=False):
        """Create a LiberviaPage instance

        @param meta_path(Path): path to the page_meta.py file
        @param vhost_root(resource.Resource): root resource of the virtual host
        @param url_elts(list[unicode]): list of path element from root site to this page
        @param replace_on_conflict(bool): same as for [LiberviaPage]
        @return (tuple[dict, LiberviaPage]): tuple with:
            - page_data: dict containing data of the page
            - libervia_page: created resource
        """
        dir_path = meta_path.parent
        page_data = {"__name__": ".".join(["page"] + url_elts)}
        # we don't want to force the presence of __init__.py
        # so we use execfile instead of import.
        # TODO: when moved to Python 3, __init__.py is not mandatory anymore
        #       so we can switch to import
        exec(compile(open(meta_path, "rb").read(), meta_path, 'exec'), page_data)
        return page_data, LiberviaPage(
            host=host,
            vhost_root=vhost_root,
            root_dir=dir_path,
            url="/" + "/".join(url_elts),
            name=page_data.get("name"),
            label=page_data.get("label"),
            redirect=page_data.get("redirect"),
            access=page_data.get("access"),
            dynamic=page_data.get("dynamic", True),
            parse_url=page_data.get("parse_url"),
            add_breadcrumb=page_data.get("add_breadcrumb"),
            prepare_render=page_data.get("prepare_render"),
            render=page_data.get("render"),
            template=page_data.get("template"),
            on_data_post=page_data.get("on_data_post"),
            on_data=page_data.get("on_data"),
            url_cache=page_data.get("url_cache", False),
            replace_on_conflict=replace_on_conflict
        )

    @staticmethod
    def create_browser_data(
        vhost_root,
        resource: Optional[LiberviaPage],
        browser_path: Path,
        path_elts: Optional[List[str]],
        engine: str = "brython"
    ) -> None:
        """create and store data for browser dynamic code"""
        dyn_data = {
            "path": browser_path,
            "url_hash": (
                hashlib.sha256('/'.join(path_elts).encode()).hexdigest()
                if path_elts is not None else None
            ),
        }
        browser_meta_path = browser_path / C.PAGES_BROWSER_META_FILE
        if browser_meta_path.is_file():
            with browser_meta_path.open() as f:
                browser_meta = json.load(f)
            utils.recursive_update(vhost_root.browser_modules, browser_meta)
            if resource is not None:
                utils.recursive_update(resource.dyn_data, browser_meta)

        init_path = browser_path / '__init__.py'
        if init_path.is_file():
            vhost_root.browser_modules.setdefault(
                engine, []).append(dyn_data)
            if resource is not None:
                resource.dyn_data[engine] = dyn_data
        elif path_elts is None:
            try:
                next(browser_path.glob('*.py'))
            except StopIteration:
                # no python file, nothing for Brython
                pass
            else:
                vhost_root.browser_modules.setdefault(
                    engine, []).append(dyn_data)


    @classmethod
    def import_pages(cls, host, vhost_root, root_path=None, _parent=None, _path=None,
        _extra_pages=False):
        """Recursively import Libervia pages

        @param host(Libervia): Libervia instance
        @param vhost_root(LiberviaRootResource): root of this VirtualHost
        @param root_path(Path, None): use this root path instead of vhost_root's one
            Used to add default site pages to external sites
        @param _parent(Resource, None): _parent page. Do not set yourself, this is for
            internal use only
        @param _path(list(unicode), None): current path. Do not set yourself, this is for
            internal use only
        @param _extra_pages(boolean): set to True when extra pages are used (i.e.
            root_path is set). Do not set yourself, this is for internal use only
        """
        if _path is None:
            _path = []
        if _parent is None:
            if root_path is None:
                root_dir = vhost_root.site_path / C.PAGES_DIR
            else:
                root_dir = root_path / C.PAGES_DIR
                _extra_pages = True
            _parent = vhost_root
            root_browser_path = root_dir / C.PAGES_BROWSER_DIR
            if root_browser_path.is_dir():
                cls.create_browser_data(vhost_root, None, root_browser_path, None)
        else:
            root_dir = _parent.root_dir

        for d in os.listdir(root_dir):
            dir_path = root_dir / d
            if not dir_path.is_dir():
                continue
            if _extra_pages and d in _parent.children:
                log.debug(_("[{host_name}] {path} is already present, ignoring it")
                    .format(host_name=vhost_root.host_name, path='/'.join(_path+[d])))
                continue
            meta_path = dir_path / C.PAGES_META_FILE
            if meta_path.is_file():
                new_path = _path + [d]
                try:
                    page_data, resource = cls.create_page(
                        host, meta_path, vhost_root, new_path)
                except exceptions.ConflictError as e:
                    if _extra_pages:
                        # extra pages are discarded if there is already an existing page
                        continue
                    else:
                        raise e
                _parent.putChild(str(d).encode(), resource)
                log_msg = ("[{host_name}] Added /{path} page".format(
                    host_name=vhost_root.host_name,
                    path="[…]/".join(new_path)))
                if _extra_pages:
                    log.debug(log_msg)
                else:
                    log.info(log_msg)
                if "uri_handlers" in page_data:
                    if not isinstance(page_data, dict):
                        log.error(_("uri_handlers must be a dict"))
                    else:
                        for uri_tuple, cb_name in page_data["uri_handlers"].items():
                            if len(uri_tuple) != 2 or not isinstance(cb_name, str):
                                log.error(_("invalid uri_tuple"))
                                continue
                            if not _extra_pages:
                                log.info(_("setting {}/{} URIs handler")
                                         .format(*uri_tuple))
                            try:
                                cb = page_data[cb_name]
                            except KeyError:
                                log.error(_("missing {name} method to handle {1}/{2}")
                                          .format(name=cb_name, *uri_tuple))
                                continue
                            else:
                                resource.register_uri(uri_tuple, cb)

                LiberviaPage.import_pages(
                    host, vhost_root, _parent=resource, _path=new_path,
                    _extra_pages=_extra_pages)
                # now we check if there is some code for browser
                browser_path = dir_path / C.PAGES_BROWSER_DIR
                if browser_path.is_dir():
                    cls.create_browser_data(vhost_root, resource, browser_path, new_path)

    @classmethod
    def on_file_change(
        cls,
        host,
        file_path: FilePath,
        flags: List[str],
        site_root: LiberviaRootResource,
        site_path: Path
    ) -> None:
        """Method triggered by file_watcher when something is changed in files

        This method is used in dev mode to reload pages when needed
        @param file_path: path of the file which triggered the event
        @param flags: human readable flags of the event (from
            internet.inotify)
        @param site_root: root of the site
        @param site_path: absolute path of the site
        """
        if flags == ['create']:
            return
        path = Path(file_path.path.decode())
        base_name = path.name
        if base_name != "page_meta.py":
            # we only handle libervia pages
            return

        log.debug("{flags} event(s) received for {file_path}".format(
            flags=", ".join(flags), file_path=file_path))

        dir_path = path.parent

        if dir_path == site_path:
            return

        if not site_path in dir_path.parents:
            raise exceptions.InternalError("watched file should be in a subdirectory of site path")

        path_elts = list(dir_path.relative_to(site_path).parts)

        if path_elts[0] == C.PAGES_DIR:
            # a page has been modified
            del path_elts[0]
            if not path_elts:
                # we need at least one element to parse
                return
            # we retrieve page by starting from site root and finding each path element
            parent = page = site_root
            new_page = False
            for idx, child_name in enumerate(path_elts):
                child_name = child_name.encode()
                try:
                    try:
                        page = page.original.children[child_name]
                    except AttributeError:
                        page = page.children[child_name]
                except KeyError:
                    if idx != len(path_elts)-1:
                        # a page has been created in a subdir when one or more
                        # page_meta.py are missing on the way
                        log.warning(_("Can't create a page at {path}, missing parents")
                                    .format(path=path))
                        return
                    new_page = True
                else:
                    if idx<len(path_elts)-1:
                        try:
                            parent = page.original
                        except AttributeError:
                            parent = page

            try:
                # we (re)create a page with the new/modified code
                __, resource = cls.create_page(host, path, site_root, path_elts,
                                              replace_on_conflict=True)
                if not new_page:
                    try:
                        resource.children = page.original.children
                    except AttributeError:
                        # FIXME: this .original handling madness is due to EncodingResourceWrapper
                        #        EncodingResourceWrapper should probably be removed
                        resource.children = page.children
            except Exception as e:
                log.warning(_("Can't create page: {reason}").format(reason=e))
            else:
                url_elt = path_elts[-1].encode()
                if not new_page:
                    # the page was already existing, we remove it
                    del parent.children[url_elt]
                # we can now add the new page
                parent.putChild(url_elt, resource)

                # is there any browser data to create?
                browser_path = resource.root_dir / C.PAGES_BROWSER_DIR
                if browser_path.is_dir():
                    cls.create_browser_data(
                        resource.vhost_root,
                        resource,
                        browser_path,
                        resource.url.split('/')
                    )

                if new_page:
                    log.info(_("{page} created").format(page=resource))
                else:
                    log.info(_("{page} reloaded").format(page=resource))

    def check_csrf(self, request):
        session = self.host.get_session_data(
            request, session_iface.IWebSession
        )
        if session.profile is None:
            # CSRF doesn't make sense when no user is logged
            log.debug("disabling CSRF check because service profile is used")
            return
        csrf_token = session.csrf_token
        given_csrf = request.getHeader("X-Csrf-Token")
        if given_csrf is None:
            try:
                given_csrf = self.get_posted_data(request, "csrf_token")
            except KeyError:
                pass
        if given_csrf is None or given_csrf != csrf_token:
            log.warning(
                _("invalid CSRF token, hack attempt? URL: {url}, IP: {ip}").format(
                    url=request.uri, ip=request.getClientIP()
                )
            )
            self.page_error(request, C.HTTP_FORBIDDEN)

    def expose_to_scripts(
        self,
        request: server.Request,
        **kwargs: str
    ) -> None:
        """Make a local variable available to page script as a global variable

        No check is done for conflicting name, use this carefully
        """
        template_data = request.template_data
        scripts = template_data.setdefault("scripts", utils.OrderedSet())
        for name, value in kwargs.items():
            if value is None:
                value = "null"
            elif isinstance(value, str):
                # FIXME: workaround for subtype used by python-dbus (dbus.String)
                #   to be removed when we get rid of python-dbus
                value = repr(str(value))
            else:
                value = repr(value)
            scripts.add(Script(content=f"var {name}={value};"))

    def register_uri(self, uri_tuple, get_uri_cb):
        """Register a URI handler

        @param uri_tuple(tuple[unicode, unicode]): type or URIs handler
            type/subtype as returned by tools/common/parse_xmpp_uri
            or type/None to handle all subtypes
        @param get_uri_cb(callable): method which take uri_data dict as only argument
            and return absolute path with correct arguments or None if the page
            can't handle this URL
        """
        if uri_tuple in self.uri_callbacks:
            log.info(_("{}/{} URIs are already handled, replacing by the new handler")
                .format( *uri_tuple))
        self.uri_callbacks[uri_tuple] = (self, get_uri_cb)

    def config_get(self, key, default=None, value_type=None):
        return self.host.config_get(self.vhost_root, key=key, default=default,
                                   value_type=value_type)

    def get_build_path(self, session_data):
        return session_data.cache_dir + self.vhost.site_name

    def get_page_by_name(self, name):
        return self.vhost_root.get_page_by_name(name)

    def get_page_path_from_uri(self, uri):
        return self.vhost_root.get_page_path_from_uri(uri)

    def get_page_redirect_url(self, request, page_name="login", url=None):
        """generate URL for a page with redirect_url parameter set

        mainly used for login page with redirection to current page
        @param request(server.Request): current HTTP request
        @param page_name(unicode): name of the page to go
        @param url(None, unicode): url to redirect to
            None to use request path (i.e. current page)
        @return (unicode): URL to use
        """
        return "{root_url}?redirect_url={redirect_url}".format(
            root_url=self.get_page_by_name(page_name).url,
            redirect_url=urllib.parse.quote_plus(request.uri)
            if url is None
            else url.encode("utf-8"),
        )

    def get_url(self, *args: str, **kwargs: str) -> str:
        """retrieve URL of the page set arguments

        @param *args: arguments to add to the URL as path elements empty or None
            arguments will be ignored
        @param **kwargs: query parameters
        """
        url_args = [quote(a) for a in args if a]

        if self.name is not None and self.name in self.pages_redirects:
            #  we check for redirection
            redirect_data = self.pages_redirects[self.name]
            args_hash = tuple(args)
            for limit in range(len(args), -1, -1):
                current_hash = args_hash[:limit]
                if current_hash in redirect_data:
                    url_base = redirect_data[current_hash]
                    remaining = args[limit:]
                    remaining_url = "/".join(remaining)
                    url = urllib.parse.urljoin(url_base, remaining_url)
                    break
            else:
                url = os.path.join(self.url, *url_args)
        else:
            url = os.path.join(self.url, *url_args)

        if kwargs:
            encoded = urllib.parse.urlencode(
                {k: v for k, v in kwargs.items()}
            )
            url +=  f"?{encoded}"

        return self.host.check_redirection(
            self.vhost_root,
            url
        )

    def get_current_url(self, request):
        """retrieve URL used to access this page

        @return(unicode): current URL
        """
        # we get url in the following way (splitting request.path instead of using
        # request.prepath) because request.prepath may have been modified by
        # redirection (if redirection args have been specified), while path reflect
        # the real request

        # we ignore empty path elements (i.e. double '/' or '/' at the end)
        path_elts = [p for p in request.path.decode('utf-8').split("/") if p]

        if request.postpath:
            if not request.postpath[-1]:
                #  we remove trailing slash
                request.postpath = request.postpath[:-1]
            if request.postpath:
                #  get_sub_page_url must return subpage from the point where
                # the it is called, so we have to remove remanining
                # path elements
                path_elts = path_elts[: -len(request.postpath)]

        return "/" + "/".join(path_elts)

    def get_param_url(self, request, **kwargs):
        """use URL of current request but modify the parameters in query part

        **kwargs(dict[str, unicode]): argument to use as query parameters
        @return (unicode): constructed URL
        """
        current_url = self.get_current_url(request)
        if kwargs:
            encoded = urllib.parse.urlencode(
                {k: v for k, v in kwargs.items()}
            )
            current_url = current_url + "?" + encoded
        return current_url

    def get_sub_page_by_name(self, subpage_name, parent=None):
        """retrieve a subpage and its path using its name

        @param subpage_name(unicode): name of the sub page
            it must be a direct children of parent page
        @param parent(LiberviaPage, None): parent page
            None to use current page
        @return (tuple[str, LiberviaPage]): page subpath and instance
        @raise exceptions.NotFound: no page has been found
        """
        if parent is None:
            parent = self
        for path, child in parent.children.items():
            try:
                child_name = child.name
            except AttributeError:
                #  LiberviaPages have a name, but maybe this is an other Resource
                continue
            if child_name == subpage_name:
                return path.decode('utf-8'), child
        raise exceptions.NotFound(
            _("requested sub page has not been found ({subpage_name})").format(
            subpage_name=subpage_name))

    def get_sub_page_url(self, request, page_name, *args):
        """retrieve a page in direct children and build its URL according to request

        request's current path is used as base (at current parsing point,
        i.e. it's more prepath than path).
        Requested page is checked in children and an absolute URL is then built
        by the resulting combination.
        This method is useful to construct absolute URLs for children instead of
        using relative path, which may not work in subpages, and are linked to the
        names of directories (i.e. relative URL will break if subdirectory is renamed
        while get_sub_page_url won't as long as page_name is consistent).
        Also, request.path is used, keeping real path used by user,
        and potential redirections.
        @param request(server.Request): current HTTP request
        @param page_name(unicode): name of the page to retrieve
            it must be a direct children of current page
        @param *args(list[unicode]): arguments to add as path elements
            if an arg is None, it will be ignored
        @return (unicode): absolute URL to the sub page
        """
        current_url = self.get_current_url(request)
        path, child = self.get_sub_page_by_name(page_name)
        return os.path.join(
            "/", current_url, path, *[quote(a) for a in args if a is not None]
        )

    def get_url_by_names(self, named_path):
        """Retrieve URL from pages names and arguments

        @param named_path(list[tuple[unicode, list[unicode]]]): path to the page as a list
            of tuples of 2 items:
                - first item is page name
                - second item is list of path arguments of this page
        @return (unicode): URL to the requested page with given path arguments
        @raise exceptions.NotFound: one of the page was not found
        """
        current_page = None
        path = []
        for page_name, page_args in named_path:
            if current_page is None:
                current_page = self.get_page_by_name(page_name)
                path.append(current_page.get_url(*page_args))
            else:
                sub_path, current_page = self.get_sub_page_by_name(
                    page_name, parent=current_page
                )
                path.append(sub_path)
                if page_args:
                    path.extend([quote(a) for a in page_args])
        return self.host.check_redirection(self.vhost_root, "/".join(path))

    def get_url_by_path(self, *args):
        """Generate URL by path

        this method as a similar effect as get_url_by_names, but it is more readable
        by using SubPage to get pages instead of using tuples
        @param *args: path element:
            - if unicode, will be used as argument
            - if util.SubPage instance, must be the name of a subpage
        @return (unicode): generated path
        """
        args = list(args)
        if not args:
            raise ValueError("You must specify path elements")
        # root page is the one needed to construct the base of the URL
        # if first arg is not a SubPage instance, we use current page
        if not isinstance(args[0], SubPage):
            root = self
        else:
            root = self.get_page_by_name(args.pop(0))
        # we keep track of current page to check subpage
        current_page = root
        url_elts = []
        arguments = []
        while True:
            while args and not isinstance(args[0], SubPage):
                arguments.append(quote(args.pop(0)))
            if not url_elts:
                url_elts.append(root.get_url(*arguments))
            else:
                url_elts.extend(arguments)
            if not args:
                break
            else:
                path, current_page = current_page.get_sub_page_by_name(args.pop(0))
                arguments = [path]
        return self.host.check_redirection(self.vhost_root, "/".join(url_elts))

    def getChildWithDefault(self, path, request):
        # we handle children ourselves
        raise exceptions.InternalError(
            "this method should not be used with LiberviaPage"
        )

    def next_path(self, request):
        """get next URL path segment, and update request accordingly

        will move first segment of postpath in prepath
        @param request(server.Request): current HTTP request
        @return (unicode): unquoted segment
        @raise IndexError: there is no segment left
        """
        pathElement = request.postpath.pop(0)
        request.prepath.append(pathElement)
        return urllib.parse.unquote(pathElement.decode('utf-8'))

    def _filter_path_value(self, value, handler, name, request):
        """Modify a path value according to handler (see [get_path_args])"""
        if handler in ("@", "@jid") and value == "@":
            value = None

        if handler in ("", "@"):
            if value is None:
                return ""
        elif handler in ("jid", "@jid"):
            if value:
                try:
                    return jid.JID(value)
                except (RuntimeError, jid.InvalidFormat):
                    log.warning(_("invalid jid argument: {value}").format(value=value))
                    self.page_error(request, C.HTTP_BAD_REQUEST)
            else:
                return ""
        else:
            return handler(self, value, name, request)

        return value

    def get_path_args(self, request, names, min_args=0, **kwargs):
        """get several path arguments at once

        Arguments will be put in request data.
        Missing arguments will have None value
        @param names(list[unicode]): list of arguments to get
        @param min_args(int): if less than min_args are found, PageError is used with
            C.HTTP_BAD_REQUEST
            Use 0 to ignore
        @param **kwargs: special value or optional callback to use for arguments
            names of the arguments must correspond to those in names
            special values may be:
                - '': use empty string instead of None when no value is specified
                - '@': if value of argument is empty or '@', empty string will be used
                - 'jid': value must be converted to jid.JID if it exists, else empty
                    string is used
                - '@jid': if value of arguments is empty or '@', empty string will be
                    used, else it will be converted to jid
        """
        data = self.get_r_data(request)

        for idx, name in enumerate(names):
            if name[0] == "*":
                value = data[name[1:]] = []
                while True:
                    try:
                        value.append(self.next_path(request))
                    except IndexError:
                        idx -= 1
                        break
                    else:
                        idx += 1
            else:
                try:
                    value = data[name] = self.next_path(request)
                except IndexError:
                    data[name] = None
                    idx -= 1
                    break

        values_count = idx + 1
        if values_count < min_args:
            log.warning(_("Missing arguments in URL (got {count}, expected at least "
                          "{min_args})").format(count=values_count, min_args=min_args))
            self.page_error(request, C.HTTP_BAD_REQUEST)

        for name in names[values_count:]:
            data[name] = None

        for name, handler in kwargs.items():
            if name[0] == "*":
                data[name] = [
                    self._filter_path_value(v, handler, name, request) for v in data[name]
                ]
            else:
                data[name] = self._filter_path_value(data[name], handler, name, request)

    ## Pagination/Filtering ##

    def get_pubsub_extra(self, request, page_max=10, params=None, extra=None,
        order_by=C.ORDER_BY_CREATION):
        """Set extra dict to retrieve PubSub items corresponding to URL parameters

        Following parameters are used:
            - after: set rsm_after with ID of item
            - before: set rsm_before with ID of item
        @param request(server.Request): current HTTP request
        @param page_max(int): required number of items per page
        @param params(None, dict[unicode, list[unicode]]): params as returned by
            self.get_all_posted_data.
            None to parse URL automatically
        @param extra(None, dict): extra dict to use, or None to use a new one
        @param order_by(unicode, None): key to order by
            None to not specify order
        @return (dict): fill extra data
        """
        if params is None:
            params = self.get_all_posted_data(request, multiple=False)
        if extra is None:
            extra = {}
        else:
            assert not {"rsm_max", "rsm_after", "rsm_before",
                        C.KEY_ORDER_BY}.intersection(list(extra.keys()))
        extra["rsm_max"] = params.get("page_max", str(page_max))
        if order_by is not None:
            extra[C.KEY_ORDER_BY] = order_by
        if 'after' in params:
            extra['rsm_after'] = params['after']
        elif 'before' in params:
            extra['rsm_before'] = params['before']
        else:
            # RSM returns list in order (oldest first), but we want most recent first
            # so we start by the end
            extra['rsm_before'] = ""
        return extra

    def set_pagination(self, request: server.Request, pubsub_data: dict) -> None:
        """Add to template_data if suitable

        "previous_page_url" and "next_page_url" will be added using respectively
        "before" and "after" URL parameters
        @param request: current HTTP request
        @param pubsub_data: pubsub metadata
        """
        template_data = request.template_data
        extra = {}
        try:
            rsm = pubsub_data["rsm"]
            last_id = rsm["last"]
        except KeyError:
            # no pagination available
            return

        # if we have a search query, we must keep it
        search = self.get_posted_data(request, 'search', raise_on_missing=False)
        if search is not None:
            extra['search'] = search.strip()

        # same for page_max
        page_max = self.get_posted_data(request, 'page_max', raise_on_missing=False)
        if page_max is not None:
            extra['page_max'] = page_max

        if rsm.get("index", 1) > 0:
            # We only show previous button if it's not the first page already.
            # If we have no index, we default to display the button anyway
            # as we can't know if we are on the first page or not.
            first_id = rsm["first"]
            template_data['previous_page_url'] = self.get_param_url(
                request, before=first_id, **extra)
        if not pubsub_data["complete"]:
            # we also show the page next button if complete is None because we
            # can't know where we are in the feed in this case.
            template_data['next_page_url'] = self.get_param_url(
                request, after=last_id, **extra)


    ## Cache handling ##

    def _set_cache_headers(self, request, cache):
        """Set ETag and Last-Modified HTTP headers, used for caching"""
        request.setHeader("ETag", cache.hash)
        last_modified = self.host.get_http_date(cache.created)
        request.setHeader("Last-Modified", last_modified)

    def _check_cache_headers(self, request, cache):
        """Check if a cache condition is set on the request

        if condition is valid, C.HTTP_NOT_MODIFIED is returned
        """
        etag_match = request.getHeader("If-None-Match")
        if etag_match is not None:
            if cache.hash == etag_match:
                self.page_error(request, C.HTTP_NOT_MODIFIED, no_body=True)
        else:
            modified_match = request.getHeader("If-Modified-Since")
            if modified_match is not None:
                modified = date_utils.date_parse(modified_match)
                if modified >= int(cache.created):
                    self.page_error(request, C.HTTP_NOT_MODIFIED, no_body=True)

    def check_cache_subscribe_cb(self, sub_id, service, node):
        self.cache_pubsub_sub.add((service, node, sub_id))

    def check_cache_subscribe_eb(self, failure_, service, node):
        log.warning(_("Can't subscribe to node: {msg}").format(msg=failure_))
        # FIXME: cache must be marked as unusable here

    def ps_node_watch_add_eb(self, failure_, service, node):
        log.warning(_("Can't add node watched: {msg}").format(msg=failure_))

    def use_cache(self, request: server.Request) -> bool:
        """Indicate if the cache should be used

        test request header to see if it is requested to skip the cache
        @return: True if cache should be used
        """
        return request.getHeader('cache-control') != 'no-cache'

    def check_cache(self, request, cache_type, **kwargs):
        """check if a page is in cache and return cached version if suitable

        this method may perform extra operation to handle cache (e.g. subscribing to a
        pubsub node)
        @param request(server.Request): current HTTP request
        @param cache_type(int): on of C.CACHE_* const.
        @param **kwargs: args according to cache_type:
            C.CACHE_PUBSUB:
                service: pubsub service
                node: pubsub node
                short: short name of feature (needed if node is empty to find namespace)

        """
        if request.postpath:
            #  we are not on the final page, no need to go further
            return

        if request.uri != request.path:
            # we don't cache page with query arguments as there can be a lot of variants
            # influencing page results (e.g. search terms)
            log.debug("ignoring cache due to query arguments")

        no_cache = not self.use_cache(request)

        profile = self.get_profile(request) or C.SERVICE_PROFILE

        if cache_type == C.CACHE_PUBSUB:
            service, node = kwargs["service"], kwargs["node"]
            if not node:
                try:
                    short = kwargs["short"]
                    node = self.host.ns_map[short]
                except KeyError:
                    log.warning(_('Can\'t use cache for empty node without namespace '
                                  'set, please ensure to set "short" and that it is '
                                  'registered'))
                    return
            if profile != C.SERVICE_PROFILE:
                #  only service profile is cached for now
                return
            session_data = self.host.get_session_data(request, session_iface.IWebSession)
            locale = session_data.locale
            if locale == C.DEFAULT_LOCALE:
                # no need to duplicate cache here
                locale = None
            try:
                cache = (self.cache[profile][cache_type][service][node]
                         [self.vhost_root][request.uri][locale][self])
            except KeyError:
                # no cache yet, let's subscribe to the pubsub node
                d1 = self.host.bridge_call(
                    "ps_subscribe", service.full(), node, "", profile
                )
                d1.addCallback(self.check_cache_subscribe_cb, service, node)
                d1.addErrback(self.check_cache_subscribe_eb, service, node)
                d2 = self.host.bridge_call("ps_node_watch_add", service.full(), node, profile)
                d2.addErrback(self.ps_node_watch_add_eb, service, node)
                self._do_cache = [self, profile, cache_type, service, node,
                                  self.vhost_root, request.uri, locale]
                #  we don't return the Deferreds as it is not needed to wait for
                # the subscription to continue with page rendering
                return
            else:
                if no_cache:
                    del (self.cache[profile][cache_type][service][node]
                         [self.vhost_root][request.uri][locale][self])
                    log.debug(f"cache removed for {self}")
                    return

        else:
            raise exceptions.InternalError("Unknown cache_type")
        log.debug("using cache for {page}".format(page=self))
        cache.last_access = time.time()
        self._set_cache_headers(request, cache)
        self._check_cache_headers(request, cache)
        request.write(cache.rendered)
        request.finish()
        raise failure.Failure(exceptions.CancelError("cache is used"))

    def _cache_url(self, request, profile):
        self.cached_urls.setdefault(profile, {})[request.uri] = CacheURL(request)

    @classmethod
    def on_node_event(cls, host, service, node, event_type, items, profile):
        """Invalidate cache for all pages linked to this node"""
        try:
            cache = cls.cache[profile][C.CACHE_PUBSUB][jid.JID(service)][node]
        except KeyError:
            log.info(_(
                "Removing subscription for {service}/{node}: "
                "the page is not cached").format(service=service, node=node))
            d1 = host.bridge_call("ps_unsubscribe", service, node, profile)
            d1.addErrback(
                lambda failure_: log.warning(
                    _("Can't unsubscribe from {service}/{node}: {msg}").format(
                        service=service, node=node, msg=failure_)))
            d2 = host.bridge_call("ps_node_watch_add", service, node, profile)
            # TODO: check why the page is not in cache, remove subscription?
            d2.addErrback(
                lambda failure_: log.warning(
                    _("Can't remove watch for {service}/{node}: {msg}").format(
                        service=service, node=node, msg=failure_)))
        else:
            cache.clear()

    # identities

    async def fill_missing_identities(
        self,
        request: server.Request,
        entities: List[Union[str, jid.JID, None]],
    ) -> None:
        """Check if all entities have an identity cache, get missing ones from backend

        @param request: request with a plugged profile
        @param entities: entities to check, None or empty strings will be filtered
        """
        entities = {str(e) for e in entities if e}
        profile = self.get_profile(request) or C.SERVICE_PROFILE
        identities = self.host.get_session_data(
            request,
            session_iface.IWebSession
        ).identities
        for e in entities:
            if e not in identities:
                id_raw = await self.host.bridge_call(
                    'identity_get', e, [], True, profile)
                identities[e] = data_format.deserialise(id_raw)

    # signals, server => browser communication

    def delegate_to_resource(self, request, resource):
        """continue workflow with Twisted Resource"""
        buf = resource.render(request)
        if buf == server.NOT_DONE_YET:
            pass
        else:
            request.write(buf)
            request.finish()
        raise failure.Failure(exceptions.CancelError("resource delegation"))

    def http_redirect(self, request, url):
        """redirect to an URL using HTTP redirection

        @param request(server.Request): current HTTP request
        @param url(unicode): url to redirect to
        """
        web_util.redirectTo(url.encode("utf-8"), request)
        request.finish()
        raise failure.Failure(exceptions.CancelError("HTTP redirection is used"))

    def redirect_or_continue(self, request, redirect_arg="redirect_url"):
        """Helper method to redirect a page to an url given as arg

        if the arg is not present, the page will continue normal workflow
        @param request(server.Request): current HTTP request
        @param redirect_arg(unicode): argument to use to get redirection URL
        @interrupt: redirect the page to requested URL
        @interrupt page_error(C.HTTP_BAD_REQUEST): empty or non local URL is used
        """
        redirect_arg = redirect_arg.encode('utf-8')
        try:
            url = request.args[redirect_arg][0].decode('utf-8')
        except (KeyError, IndexError):
            pass
        else:
            #  a redirection is requested
            if not url or url[0] != "/":
                # we only want local urls
                self.page_error(request, C.HTTP_BAD_REQUEST)
            else:
                self.http_redirect(request, url)

    def page_redirect(self, page_path, request, skip_parse_url=True, path_args=None):
        """redirect a page to a named page

        the workflow will continue with the workflow of the named page,
        skipping named page's parse_url method if it exist.
        If you want to do a HTTP redirection, use http_redirect
        @param page_path(unicode): path to page (elements are separated by "/"):
            if path starts with a "/":
                path is a full path starting from root
            else:
                - first element is name as registered in name variable
                - following element are subpages path
            e.g.: "blog" redirect to page named "blog"
                  "blog/atom.xml" redirect to atom.xml subpage of "blog"
                  "/common/blog/atom.xml" redirect to the page at the given full path
        @param request(server.Request): current HTTP request
        @param skip_parse_url(bool): if True, parse_url method on redirect page will be
            skipped
        @param path_args(list[unicode], None): path arguments to use in redirected page
        @raise KeyError: there is no known page with this name
        """
        # FIXME: render non LiberviaPage resources
        path = page_path.rstrip("/").split("/")
        if not path[0]:
            redirect_page = self.vhost_root
        else:
            redirect_page = self.named_pages[path[0]]

        for subpage in path[1:]:
            subpage = subpage.encode('utf-8')
            if redirect_page is self.vhost_root:
                redirect_page = redirect_page.children[subpage]
            else:
                redirect_page = redirect_page.original.children[subpage]

        if path_args is not None:
            args = [quote(a).encode() for a in path_args]
            request.postpath = args + request.postpath

        if self._do_cache:
            # if cache is needed, it will be handled by final page
            redirect_page._do_cache = self._do_cache
            self._do_cache = None

        defer.ensureDeferred(
            redirect_page.render_page(request, skip_parse_url=skip_parse_url)
        )
        raise failure.Failure(exceptions.CancelError("page redirection is used"))

    def page_error(self, request, code=C.HTTP_NOT_FOUND, no_body=False):
        """generate an error page and terminate the request

        @param request(server.Request): HTTP request
        @param core(int): error code to use
        @param no_body: don't write body if True
        """
        if self._do_cache is not None:
            # we don't want to cache error pages
            self._do_cache = None
        request.setResponseCode(code)
        if no_body:
            request.finish()
        else:
            template = "error/" + str(code) + ".html"
            template_data = request.template_data
            session_data = self.host.get_session_data(request, session_iface.IWebSession)
            if session_data.locale is not None:
                template_data['locale'] = session_data.locale
            if self.vhost_root.site_name:
                template_data['site'] = self.vhost_root.site_name

            rendered = self.host.renderer.render(
                template,
                theme=session_data.theme or self.default_theme,
                media_path=f"/{C.MEDIA_DIR}",
                build_path=f"/{C.BUILD_DIR}/",
                site_themes=self.site_themes,
                error_code=code,
                **template_data
            )

            self.write_data(rendered, request)
        raise failure.Failure(exceptions.CancelError("error page is used"))

    def write_data(self, data, request):
        """write data to transport and finish the request"""
        if data is None:
            self.page_error(request)
        data_encoded = data.encode("utf-8")

        if self._do_cache is not None:
            redirected_page = self._do_cache.pop(0)
            cache = reduce(lambda d, k: d.setdefault(k, {}), self._do_cache, self.cache)
            page_cache = cache[redirected_page] = CachePage(data_encoded)
            self._set_cache_headers(request, page_cache)
            log.debug(_("{page} put in cache for [{profile}]")
                .format( page=self, profile=self._do_cache[0]))
            self._do_cache = None
            self._check_cache_headers(request, page_cache)

        try:
            request.write(data_encoded)
        except AttributeError:
            log.warning(_("Can't write page, the request has probably been cancelled "
                          "(browser tab closed or reloaded)"))
            return
        request.finish()

    def _subpages_handler(self, request):
        """render subpage if suitable

        this method checks if there is still an unmanaged part of the path
        and check if it corresponds to a subpage. If so, it render the subpage
        else it render a NoResource.
        If there is no unmanaged part of the segment, current page workflow is pursued
        """
        if request.postpath:
            subpage = self.next_path(request).encode('utf-8')
            try:
                child = self.children[subpage]
            except KeyError:
                self.page_error(request)
            else:
                child.render(request)
                raise failure.Failure(exceptions.CancelError("subpage page is used"))

    def _prepare_dynamic(self, request):
        session_data = self.host.get_session_data(request, session_iface.IWebSession)
        # we need to activate dynamic page
        # we set data for template, and create/register token
        # socket_token = str(uuid.uuid4())
        socket_url = self.host.get_websocket_url(request)
        # as for CSRF, it is important to not let the socket token if we use the service
        # profile, as those pages can be cached, and then the token leaked.
        socket_token = '' if session_data.profile is None else session_data.ws_token
        socket_debug = C.bool_const(self.host.debug)
        request.template_data["websocket"] = WebsocketMeta(
            socket_url, socket_token, socket_debug
        )
        # we will keep track of handlers to remove
        request._signals_registered = []
        # we will cache registered signals until socket is opened
        request._signals_cache = []

    def _render_template(self, request):
        template_data = request.template_data

        # if confirm variable is set in case of successfuly data post
        session_data = self.host.get_session_data(request, session_iface.IWebSession)
        template_data['identities'] = session_data.identities
        if session_data.pop_page_flag(self, C.FLAG_CONFIRM):
            template_data["confirm"] = True
        notifs = session_data.pop_page_notifications(self)
        if notifs:
            template_data["notifications"] = notifs
        if session_data.jid is not None:
            template_data["own_jid"] = session_data.jid
        if session_data.locale is not None:
            template_data['locale'] = session_data.locale
        if session_data.guest:
            template_data['guest_session'] = True
        if self.vhost_root.site_name:
            template_data['site'] = self.vhost_root.site_name
        if self.dyn_data:
            for data in self.dyn_data.values():
                try:
                    scripts = data['scripts']
                except KeyError:
                    pass
                else:
                    template_data.setdefault('scripts', utils.OrderedSet()).update(scripts)
                template_data.update(data.get('template', {}))
        data_common = self.vhost_root.dyn_data_common
        common_scripts = data_common['scripts']
        if common_scripts:
            template_data.setdefault('scripts', utils.OrderedSet()).update(common_scripts)
            if "template" in data_common:
                for key, value in data_common["template"].items():
                    if key not in template_data:
                        template_data[key] = value

        theme = session_data.theme or self.default_theme
        self.expose_to_scripts(
            request,
            cache_path=session_data.cache_dir,
            templates_root_url=str(self.vhost_root.get_front_url(theme)),
            profile=session_data.profile)

        uri = request.uri.decode()
        try:
            template_data["current_page"] = next(
                m[0] for m in self.main_menu if uri.startswith(m[1])
            )
        except StopIteration:
            pass

        return self.host.renderer.render(
            self.template,
            theme=theme,
            site_themes=self.site_themes,
            page_url=self.get_url(),
            media_path=f"/{C.MEDIA_DIR}",
            build_path=f"/{C.BUILD_DIR}/",
            cache_path=session_data.cache_dir,
            main_menu=self.main_menu,
            **template_data)

    def _on_data_post_redirect(self, ret, request):
        """called when page's on_data_post has been done successfuly

        This will do a Post/Redirect/Get pattern.
        this method redirect to the same page or to request.data['post_redirect_page']
        post_redirect_page can be either a page or a tuple with page as first item, then
        a list of unicode arguments to append to the url.
        if post_redirect_page is not used, initial request.uri (i.e. the same page as
        where the data have been posted) will be used for redirection.
        HTTP status code "See Other" (303) is used as it is the recommanded code in
        this case.
        @param ret(None, unicode, iterable): on_data_post return value
            see LiberviaPage.__init__ on_data_post docstring
        """
        if ret is None:
            ret = ()
        elif isinstance(ret, str):
            ret = (ret,)
        else:
            ret = tuple(ret)
            raise NotImplementedError(
                _("iterable in on_data_post return value is not used yet")
            )
        session_data = self.host.get_session_data(request, session_iface.IWebSession)
        request_data = self.get_r_data(request)
        if "post_redirect_page" in request_data:
            redirect_page_data = request_data["post_redirect_page"]
            if isinstance(redirect_page_data, tuple):
                redirect_page = redirect_page_data[0]
                redirect_page_args = redirect_page_data[1:]
                redirect_uri = redirect_page.get_url(*redirect_page_args)
            else:
                redirect_page = redirect_page_data
                redirect_uri = redirect_page.url
        else:
            redirect_page = self
            redirect_uri = request.uri

        if not C.POST_NO_CONFIRM in ret:
            session_data.set_page_flag(redirect_page, C.FLAG_CONFIRM)
        request.setResponseCode(C.HTTP_SEE_OTHER)
        request.setHeader(b"location", redirect_uri)
        request.finish()
        raise failure.Failure(exceptions.CancelError("Post/Redirect/Get is used"))

    async def _on_data_post(self, request):
        self.check_csrf(request)
        try:
            ret = await as_deferred(self.on_data_post, self, request)
        except exceptions.DataError as e:
            # something is wrong with the posted data, we re-display the page with a
            # warning notification
            session_data = self.host.get_session_data(request, session_iface.IWebSession)
            session_data.set_page_notification(self, str(e), C.LVL_WARNING)
            request.setResponseCode(C.HTTP_SEE_OTHER)
            request.setHeader("location", request.uri)
            request.finish()
            raise failure.Failure(exceptions.CancelError("Post/Redirect/Get is used"))
        else:
            if ret != "continue":
                self._on_data_post_redirect(ret, request)

    def get_posted_data(
            self,
            request: server.Request,
            keys,
            multiple: bool = False,
            raise_on_missing: bool = True,
            strip: bool = True
    ):
        """Get data from a POST request or from URL's query part and decode it

        @param request: request linked to the session
        @param keys(unicode, iterable[unicode]): name of the value(s) to get
            unicode to get one value
            iterable to get more than one
        @param multiple: True if multiple values are possible/expected
            if False, the first value is returned
        @param raise_on_missing: raise KeyError on missing key if True
            else use None for missing values
        @param strip: if True, apply "strip()" on values
        @return (iterator[unicode], list[iterator[unicode], unicode, list[unicode]):
            values received for this(these) key(s)
        @raise KeyError: one specific key has been requested, and it is missing
        """
        #  FIXME: request.args is already unquoting the value, it seems we are doing
        #         double unquote
        if isinstance(keys, str):
            keys = [keys]

        keys = [k.encode('utf-8') for k in keys]

        ret = []
        for key in keys:
            gen = (urllib.parse.unquote(v.decode("utf-8"))
                                        for v in request.args.get(key, []))
            if multiple:
                ret.append(gen.strip() if strip else gen)
            else:
                try:
                    v = next(gen)
                except StopIteration:
                    if raise_on_missing:
                        raise KeyError(key)
                    else:
                        ret.append(None)
                else:
                    ret.append(v.strip() if strip else v)

        if len(keys) == 1:
            return ret[0]
        else:
            return ret

    def get_all_posted_data(self, request, except_=(), multiple=True):
        """get all posted data

        @param request(server.Request): request linked to the session
        @param except_(iterable[unicode]): key of values to ignore
            csrf_token will always be ignored
        @param multiple(bool): if False, only the first values are returned
        @return (dict[unicode, list[unicode]]): post values
        """
        except_ = tuple(except_) + ("csrf_token",)
        ret = {}
        for key, values in request.args.items():
            key = key.decode('utf-8')
            key = urllib.parse.unquote(key)
            if key in except_:
                continue
            values = [v.decode('utf-8') for v in values]
            if not multiple:
                ret[key] = urllib.parse.unquote(values[0])
            else:
                ret[key] = [urllib.parse.unquote(v) for v in values]
        return ret

    def get_profile(self, request):
        """Helper method to easily get current profile

        @return (unicode, None): current profile
            None if no profile session is started
        """
        web_session = self.host.get_session_data(request, session_iface.IWebSession)
        return web_session.profile

    def get_jid(self, request):
        """Helper method to easily get current jid

        @return: current jid
        """
        web_session = self.host.get_session_data(request, session_iface.IWebSession)
        return web_session.jid


    def get_r_data(self, request):
        """Helper method to get request data dict

        this dictionnary if for the request only, it is not saved in session
        It is mainly used to pass data between pages/methods called during request
        workflow
        @return (dict): request data
        """
        try:
            return request.data
        except AttributeError:
            request.data = {}
            return request.data

    def get_page_data(self, request, key):
        """Helper method to retrieve reload resistant data"""
        web_session = self.host.get_session_data(request, session_iface.IWebSession)
        return web_session.get_page_data(self, key)

    def set_page_data(self, request, key, value):
        """Helper method to set reload resistant data"""
        web_session = self.host.get_session_data(request, session_iface.IWebSession)
        return web_session.set_page_data(self, key, value)

    def handle_search(self, request, extra):
        """Manage Full-Text Search

        Check if "search" query argument is present, and add MAM filter for it if
        necessary.
        If used, the "search" variable will also be available in template data, thus
        frontend can display some information about it.
        """
        search = self.get_posted_data(request, 'search', raise_on_missing=False)
        if search is not None:
            search = search.strip()
            if search:
                try:
                    extra[f'mam_filter_{self.host.ns_map["fulltextmam"]}'] = search
                except KeyError:
                    log.warning(_("Full-text search is not available"))
                else:
                    request.template_data['search'] = search

    def _check_access(self, request):
        """Check access according to self.access

        if access is not granted, show a HTTP_FORBIDDEN page_error and stop request,
        else return data (so it can be inserted in deferred chain
        """
        if self.access == C.PAGES_ACCESS_PUBLIC:
            pass
        elif self.access == C.PAGES_ACCESS_PROFILE:
            profile = self.get_profile(request)
            if not profile:
                # registration allowed, we redirect to login page
                login_url = self.get_page_redirect_url(request)
                self.http_redirect(request, login_url)

    def set_best_locale(self, request):
        """Guess the best locale when it is not specified explicitly by user

        This method will check "accept-language" header, and set locale to first
        matching value with available translations.
        """
        accept_language = request.getHeader("accept-language")
        if not accept_language:
            return
        accepted = [a.strip() for a in accept_language.split(',')]
        available = [str(l) for l in self.host.renderer.translations]
        for lang in accepted:
            lang = lang.split(';')[0].strip().lower()
            if not lang:
                continue
            for a in available:
                if a.lower().startswith(lang):
                    session_data = self.host.get_session_data(request,
                                                            session_iface.IWebSession)
                    session_data.locale = a
                    return

    async def render_page(self, request, skip_parse_url=False):
        """Main method to handle the workflow of a LiberviaPage"""
        # template_data are the variables passed to template
        if not hasattr(request, "template_data"):
            # if template_data doesn't exist, it's the beginning of the request workflow
            # so we fill essential data
            session_data = self.host.get_session_data(request, session_iface.IWebSession)
            profile = session_data.profile
            request.template_data = {
                "profile": profile,
                # it's important to not add CSRF token and session uuid if service profile
                # is used because the page may be cached, and the token then leaked
                "csrf_token": "" if profile is None else session_data.csrf_token,
                "session_uuid": "public" if profile is None else session_data.uuid,
                "breadcrumbs": []
            }

            # XXX: here is the code which need to be executed once
            #      at the beginning of the request hanling
            if request.postpath and not request.postpath[-1]:
                # we don't differenciate URLs finishing with '/' or not
                del request.postpath[-1]

            # i18n
            key_lang = C.KEY_LANG.encode()
            if key_lang in request.args:
                try:
                    locale = request.args.pop(key_lang)[0].decode()
                except IndexError:
                    log.warning("empty lang received")
                else:
                    if "/" in locale:
                        # "/" is refused because locale may sometime be used to access
                        # path, if localised documents are available for instance
                        log.warning(_('illegal char found in locale ("/"), hack '
                                      'attempt? locale={locale}').format(locale=locale))
                        locale = None
                    session_data.locale = locale

            # if locale is not specified, we try to find one requested by browser
            if session_data.locale is None:
                self.set_best_locale(request)

            # theme
            key_theme = C.KEY_THEME.encode()
            if key_theme in request.args:
                theme = request.args.pop(key_theme)[0].decode()
                if key_theme != session_data.theme:
                    if theme not in self.site_themes:
                        log.warning(_(
                            "Theme {theme!r} doesn't exist for {vhost}"
                            .format(theme=theme, vhost=self.vhost_root)))
                    else:
                        session_data.theme = theme
        try:

            try:
                self._check_access(request)

                if self.redirect is not None:
                    self.page_redirect(self.redirect, request, skip_parse_url=False)

                if self.parse_url is not None and not skip_parse_url:
                    if self.url_cache:
                        profile = self.get_profile(request)
                        try:
                            cache_url = self.cached_urls[profile][request.uri]
                        except KeyError:
                            # no cache for this URI yet
                            #  we do normal URL parsing, and then the cache
                            await as_deferred(self.parse_url, self, request)
                            self._cache_url(request, profile)
                        else:
                            log.debug(f"using URI cache for {self}")
                            cache_url.use(request)
                    else:
                        await as_deferred(self.parse_url, self, request)

                if self.add_breadcrumb is None:
                    label = (
                        self.label
                        or self.name
                        or self.url[self.url.rfind('/')+1:]
                    )
                    breadcrumb = {
                        "url": self.url,
                        "label": label.title(),
                    }
                    request.template_data["breadcrumbs"].append(breadcrumb)
                else:
                    await as_deferred(
                        self.add_breadcrumb,
                        self,
                        request,
                        request.template_data["breadcrumbs"]
                    )

                self._subpages_handler(request)

                if request.method not in (C.HTTP_METHOD_GET, C.HTTP_METHOD_POST):
                    # only HTTP GET and POST are handled so far
                    self.page_error(request, C.HTTP_BAD_REQUEST)

                if request.method == C.HTTP_METHOD_POST:
                    if self.on_data_post == 'continue':
                        pass
                    elif self.on_data_post is None:
                        # if we don't have on_data_post, the page was not expecting POST
                        # so we return an error
                        self.page_error(request, C.HTTP_BAD_REQUEST)
                    else:
                        await self._on_data_post(request)
                    # by default, POST follow normal behaviour after on_data_post is called
                    # this can be changed by a redirection or other method call in on_data_post

                if self.dynamic:
                    self._prepare_dynamic(request)

                if self.prepare_render:
                    await as_deferred(self.prepare_render, self, request)

                if self.template:
                    rendered = self._render_template(request)
                elif self.render_method:
                    rendered = await as_deferred(self.render_method, self, request)
                else:
                    raise exceptions.InternalError(
                        "No method set to render page, please set a template or use a "
                        "render method"
                    )

                self.write_data(rendered, request)

            except failure.Failure as f:
                # we have to unpack the Failure to catch the right Exception
                raise f.value

        except exceptions.CancelError:
            pass
        except BridgeException as e:
            if e.condition == 'not-allowed':
                log.warning("not allowed exception catched")
                self.page_error(request, C.HTTP_FORBIDDEN)
            elif e.condition == 'item-not-found' or e.classname == 'NotFound':
                self.page_error(request, C.HTTP_NOT_FOUND)
            elif e.condition == 'remote-server-not-found':
                self.page_error(request, C.HTTP_NOT_FOUND)
            elif e.condition == 'forbidden':
                if self.get_profile(request) is None:
                    log.debug("access forbidden, we're redirecting to log-in page")
                    self.http_redirect(request, self.get_page_redirect_url(request))
                else:
                    self.page_error(request, C.HTTP_FORBIDDEN)
            else:
                log.error(
                    _("Uncatched bridge exception for HTTP request on {url}: {e}\n"
                      "page name: {name}\npath: {path}\nURL: {full_url}\n{tb}")
                    .format(
                        url=self.url,
                        e=e,
                        name=self.name or "",
                        path=self.root_dir,
                        full_url=request.URLPath(),
                        tb=traceback.format_exc(),
                    )
                )
                try:
                    self.page_error(request, C.HTTP_INTERNAL_ERROR)
                except exceptions.CancelError:
                    pass
        except Exception as e:
            log.error(
                _("Uncatched error for HTTP request on {url}: {e}\npage name: "
                  "{name}\npath: {path}\nURL: {full_url}\n{tb}")
                .format(
                    url=self.url,
                    e=e,
                    name=self.name or "",
                    path=self.root_dir,
                    full_url=request.URLPath(),
                    tb=traceback.format_exc(),
                )
            )
            try:
                self.page_error(request, C.HTTP_INTERNAL_ERROR)
            except exceptions.CancelError:
                pass

    def render_GET(self, request):
        defer.ensureDeferred(self.render_page(request))
        return server.NOT_DONE_YET

    def render_POST(self, request):
        defer.ensureDeferred(self.render_page(request))
        return server.NOT_DONE_YET