<|file_name|>betaserialization.py<|end_file_name|><｜fim▁begin｜>"""
extend TiddlyWiki serialization to optionally use beta or
externalized releases and add the UniversalBackstage.

activated via "twrelease=beta" URL parameter or ServerSettings,
see build_config_var
"""


import logging

from tiddlyweb.util import read_utf8_file

from tiddlywebwiki.serialization import Serialization as WikiSerialization

from tiddlywebplugins.tiddlyspace.web import (determine_host,
        determine_space, determine_space_recipe)

LOGGER = logging.getLogger(__name__)


def build_config_var(beta=False, external=False):
    """
    Create the configuration key which will be used to locate
    the base tiddlywiki file.
    """
    base = 'base_tiddlywiki'
    if external:
        base += '_external'
    if beta:
                <|fim_middle|>

    return base


class Serialization(WikiSerialization):
    """
    Subclass of the standard TiddlyWiki serialization to allow
    choosing beta or externalized versions of the base empty.html
    in which the tiddlers will be servered.

    Also, if the TiddlyWiki is not being downloaded, add
    the UniversalBackstage by injecting a script tag.
    """

    def list_tiddlers(self, tiddlers):
        """
        Override tiddlers.link so the location in noscript is to
        /tiddlers.
        """
        http_host, _ = determine_host(self.environ)
        space_name = determine_space(self.environ, http_host)
        if space_name:
            recipe_name = determine_space_recipe(self.environ, space_name)
            if '/recipes/%s' % recipe_name in tiddlers.link:
                tiddlers.link = '/tiddlers'
        return WikiSerialization.list_tiddlers(self, tiddlers)

    def _get_wiki(self):
        beta = external = False

        release = self.environ.get('tiddlyweb.query', {}).get(
                'twrelease', [False])[0]
        externalize = self.environ.get('tiddlyweb.query', {}).get(
                'external', [False])[0]
        download = self.environ.get('tiddlyweb.query', {}).get(
                'download', [False])[0]

        if release == 'beta':
            beta = True
        if externalize:
            external = True

        # If somebody is downloading, don't allow them to
        # externalize.
        if download:
            external = False

        wiki = None
        if beta or external:
            config_var = build_config_var(beta, external)
            LOGGER.debug('looking for %s', config_var)
            base_wiki_file = self.environ.get('tiddlyweb.config',
                    {}).get(config_var, '')
            if base_wiki_file:
                LOGGER.debug('using %s as base_tiddlywiki', base_wiki_file)
                wiki = read_utf8_file(base_wiki_file)
        if not wiki:
            wiki = WikiSerialization._get_wiki(self)
        tag = "<!--POST-SCRIPT-START-->"
        if not download:
            wiki = wiki.replace(tag, '<script type="text/javascript" '
                'src="/bags/common/tiddlers/backstage.js"></script> %s' % tag)
        return wiki
<｜fim▁end｜>
        base += '_beta'