
import os
import sys

from django.conf import global_settings as defaults
from django.template.loader import add_to_builtins


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
    Mezzanine'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("mezzanine.template.loader_tags")

    if not s.get("ALLOWED_HOSTS", []):
        from warnings import warn
        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()

    # 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")
    for setting in tuple_list_settings:
        s[setting] = list(s[setting])

    if s["DEV_SERVER"]:
        s["STATICFILES_DIRS"] = list(s.get("STATICFILES_DIRS", []))
        s["STATICFILES_DIRS"].append(s.pop("STATIC_ROOT"))

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

    if s["TESTING"]:
        # Enable accounts when testing so the URLs exist.
        append("INSTALLED_APPS", "mezzanine.accounts")

        # 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 Mezzanine'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", []))
        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"
        prepend("MIDDLEWARE_CLASSES", debug_mw)
    # If compressor installed, ensure it's configured and make
    # Mezzanine'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 mezzanine_settings():
            from mezzanine.conf import settings
            return settings
        s["COMPRESS_OFFLINE_CONTEXT"]["settings"] = mezzanine_settings

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

    # Ensure Grappelli is after Mezzanine in app order so that
    # admin templates are loaded in the correct order.
    grappelli_name = s.get("PACKAGE_NAME_GRAPPELLI")
    try:
        move("INSTALLED_APPS", grappelli_name, len(s["INSTALLED_APPS"]))
    except ValueError:
        s["GRAPPELLI_INSTALLED"] = False
    else:
        s["GRAPPELLI_INSTALLED"] = True
        s.setdefault("GRAPPELLI_ADMIN_HEADLINE", "Mezzanine")
        s.setdefault("GRAPPELLI_ADMIN_TITLE", "Mezzanine")

    # Ensure admin is last in the app order so that admin templates
    # are loaded in the correct order.
    move("INSTALLED_APPS", "django.contrib.admin", len(s["INSTALLED_APPS"]))

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

    # Ensure mezzanine.boot is first.
    try:
        move("INSTALLED_APPS", "mezzanine.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"))]

    # 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"
