from __future__ import unicode_literals

import os
import sys
from warnings import warn

from django import VERSION
from django.conf import global_settings as defaults
from django.template.base import add_to_builtins

from wenlincms.utils.timezone import get_best_local_timezone


class SitesAllowedHosts(object):
    """
    This is a fallback for Django 1.5's ALLOWED_HOSTS setting
    which is required when DEBUG is False. It looks up the
    ``Site`` model and uses any domains added to it, the
    first time the setting is accessed.
    """
    def __iter__(self):
        if getattr(self, "_hosts", None) is None:
            from django.contrib.sites.models import Site
            self._hosts = [s.domain.split(":")[0] for s in Site.objects.all()]
        return iter(self._hosts)


def set_dynamic_settings(s):
    """
    Called at the end of the project's settings module, and is passed
    its globals dict for updating with some final tweaks for settings
    that generally aren't specified, but can be given some better
    defaults based on other settings that have been specified. Broken
    out into its own function so that the code need not be replicated
    in the settings modules of other project-based apps that leverage
    wenlincms's settings module.
    """

    # Moves an existing list setting value to a different position.
    move = lambda n, k, i: s[n].insert(i, s[n].pop(s[n].index(k)))
    # Add a value to the end of a list setting if not in the list.
    append = lambda n, k: s[n].append(k) if k not in s[n] else None
    # Add a value to the start of a list setting if not in the list.
    prepend = lambda n, k: s[n].insert(0, k) if k not in s[n] else None
    # Remove a value from a list setting if in the list.
    remove = lambda n, k: s[n].remove(k) if k in s[n] else None

    s["TEMPLATE_DEBUG"] = s.get("TEMPLATE_DEBUG", s.get("DEBUG", False))
    add_to_builtins("wenlincms.template.loader_tags")

    if not s.get("ALLOWED_HOSTS", []):
        warn("You haven't defined the ALLOWED_HOSTS settings, which "
             "Django 1.5 requires. Will fall back to the domains "
             "configured as sites.")
        s["ALLOWED_HOSTS"] = SitesAllowedHosts()

    if s.get("TIME_ZONE", None) is None:
        tz = get_best_local_timezone()
        s["TIME_ZONE"] = tz
        warn("TIME_ZONE setting is not set, using closest match: %s" % tz)

    # Define some settings based on management command being run.
    management_command = sys.argv[1] if len(sys.argv) > 1 else ""
    # Some kind of testing is running via test or testserver.
    s["TESTING"] = management_command in ("test", "testserver")
    # Some kind of development server is running via runserver,
    # runserver_plus or harvest (lettuce)
    s["DEV_SERVER"] = management_command.startswith(("runserver", "harvest"))

    # Change tuple settings to lists for easier manipulation.
    s.setdefault("AUTHENTICATION_BACKENDS", defaults.AUTHENTICATION_BACKENDS)
    s.setdefault("STATICFILES_FINDERS", defaults.STATICFILES_FINDERS)
    tuple_list_settings = ["AUTHENTICATION_BACKENDS", "INSTALLED_APPS",
                           "MIDDLEWARE_CLASSES", "STATICFILES_FINDERS",
                           "LANGUAGES", "TEMPLATE_CONTEXT_PROCESSORS"]
    for setting in tuple_list_settings[:]:
        if not isinstance(s.get(setting, []), list):
            s[setting] = list(s[setting])
        else:
            # Setting is already a list, so we'll exclude it from
            # the list of settings we'll revert back to tuples.
            tuple_list_settings.remove(setting)

    # From wenlincms 3.1.2 and onward we added the context processor
    # for handling the page variable in templates - here we help
    # upgrading by adding it if missing, with a warning. This helper
    # can go away eventually.
    cp = "wenlincms.pages.context_processors.page"
    if ("wenlincms.pages" in s["INSTALLED_APPS"] and
            cp not in s["TEMPLATE_CONTEXT_PROCESSORS"]):
        warn("%s is required in the TEMPLATE_CONTEXT_PROCESSORS setting. "
             "Adding it now, but you should update settings.py to "
             "explicitly include it." % cp)
        append("TEMPLATE_CONTEXT_PROCESSORS", cp)

    # Set up cookie messaging if none defined.
    storage = "django.contrib.messages.storage.cookie.CookieStorage"
    s.setdefault("MESSAGE_STORAGE", storage)

    if s["TESTING"]:
        # Following bits are work-arounds for some assumptions that
        # Django 1.5's tests make.

        # contrib.auth tests fail without its own auth backend installed.
        append("AUTHENTICATION_BACKENDS",
               "django.contrib.auth.backends.ModelBackend")

        # Tests in contrib.redirects simply don't work with a
        # catch-all urlpattern such as wenlincms's pages app.
        remove("INSTALLED_APPS", "django.contrib.redirects")
        remove("MIDDLEWARE_CLASSES",
            "django.contrib.redirects.middleware.RedirectFallbackMiddleware")

    else:
        # Setup for optional apps.
        optional = list(s.get("OPTIONAL_APPS", []))
        s["USE_SOUTH"] = s.get("USE_SOUTH") and VERSION < (1, 7)
        if s.get("USE_SOUTH"):
            optional.append("south")
        elif not s.get("USE_SOUTH", True) and "south" in s["INSTALLED_APPS"]:
            s["INSTALLED_APPS"].remove("south")
        for app in optional:
            if app not in s["INSTALLED_APPS"]:
                try:
                    __import__(app)
                except ImportError:
                    pass
                else:
                    s["INSTALLED_APPS"].append(app)
    if "debug_toolbar" in s["INSTALLED_APPS"]:
        debug_mw = "debug_toolbar.middleware.DebugToolbarMiddleware"
        append("MIDDLEWARE_CLASSES", debug_mw)

    # If compressor installed, ensure it's configured and make
    # wenlincms's settings available to its offline context,
    # since jQuery is configured via a setting.
    if "compressor" in s["INSTALLED_APPS"]:
        append("STATICFILES_FINDERS", "compressor.finders.CompressorFinder")
        s.setdefault("COMPRESS_OFFLINE_CONTEXT", {
            "MEDIA_URL": s.get("MEDIA_URL", ""),
            "STATIC_URL": s.get("STATIC_URL", ""),
        })

        def wenlincms_settings():
            from wenlincms.conf import settings
            return settings
        s["COMPRESS_OFFLINE_CONTEXT"]["settings"] = wenlincms_settings

    # Ensure the wenlincms auth backend is enabled if
    # wlapps.accounts is being used.
    if "wlapps.accounts" in s["INSTALLED_APPS"]:
        auth_backend = "wenlincms.core.auth_backends.wenlincmsBackend"
        s.setdefault("AUTHENTICATION_BACKENDS", [])
        prepend("AUTHENTICATION_BACKENDS", auth_backend)

    # Ensure WlAdmin is after wenlincms in app order so that
    # admin templates are loaded in the correct order.
    wladmin_name = s.get("PACKAGE_NAME_ADMIN")
    if s["TESTING"]:
        # Optional apps aren't installed when testing, but we need
        # wladmin to perform some admin tests for certain HTML.
        try:
            __import__(wladmin_name)
        except ImportError:
            pass
        else:
            append("INSTALLED_APPS", wladmin_name)
    try:
        move("INSTALLED_APPS", wladmin_name, len(s["INSTALLED_APPS"]))
    except ValueError:
        s["WLADMIN_INSTALLED"] = False
    else:
        s["WLADMIN_INSTALLED"] = True

    # Ensure admin is at the bottom of the app order so that admin
    # templates are loaded in the correct order, and that staticfiles
    # is also at the end so its runserver can be overridden.
    apps = ["django.contrib.admin"]
    if VERSION >= (1, 7):
        apps += ["django.contrib.staticfiles"]
    for app in apps:
        try:
            move("INSTALLED_APPS", app, len(s["INSTALLED_APPS"]))
        except ValueError:
            pass

    # Ensure we have a test runner (removed in Django 1.6)
    s.setdefault("TEST_RUNNER", "django.test.simple.DjangoTestSuiteRunner")

    # Add missing apps if existing apps depend on them.
    if "wenlincms.generic" in s["INSTALLED_APPS"]:
        s.setdefault("COMMENTS_APP", "wenlincms.generic")
        append("INSTALLED_APPS", "django.contrib.comments")

    # Ensure wenlincms.boot is first.
    try:
        move("INSTALLED_APPS", "wenlincms.boot", 0)
    except ValueError:
        pass

    # Remove caching middleware if no backend defined.
    if not (s.get("CACHE_BACKEND") or s.get("CACHES")):
        s["MIDDLEWARE_CLASSES"] = [mw for mw in s["MIDDLEWARE_CLASSES"] if not
                                   (mw.endswith("UpdateCacheMiddleware") or
                                    mw.endswith("FetchFromCacheMiddleware"))]

    # If only LANGUAGE_CODE has been defined, ensure the other required
    # settings for translations are configured.
    if (s.get("LANGUAGE_CODE") and len(s.get("LANGUAGES", [])) == 1 and
            s["LANGUAGE_CODE"] != s["LANGUAGES"][0][0]):
        s["USE_I18N"] = True
        s["LANGUAGES"] = [(s["LANGUAGE_CODE"], "")]

    # Revert tuple settings back to tuples.
    for setting in tuple_list_settings:
        s[setting] = tuple(s[setting])

    # Some settings tweaks for different DB engines.
    for (key, db) in s["DATABASES"].items():
        shortname = db["ENGINE"].split(".")[-1]
        if shortname == "sqlite3" and os.sep not in db["NAME"]:
            # If the Sqlite DB name doesn't contain a path, assume
            # it's in the project directory and add the path to it.
            db_path = os.path.join(s.get("PROJECT_ROOT", ""), db["NAME"])
            s["DATABASES"][key]["NAME"] = db_path
        elif shortname == "mysql":
            # Required MySQL collation for tests.
            s["DATABASES"][key]["TEST_COLLATION"] = "utf8_general_ci"
