import functools
from importlib import import_module
from inspect import ismethod
import logging
import threading
from typing import Any, Callable, List, Optional, cast, get_type_hints
import warnings

from django.apps import AppConfig, apps
from django.conf import Settings, settings
from django.core import management
try:
    from django.core.handlers.asgi import ASGIRequest
except ImportError:
    ASGIRequest = None
from django.http import HttpRequest
from django.template.engine import Engine
from django.urls import URLPattern, URLResolver, get_resolver
from django.utils.module_loading import import_string
from django.views.decorators.csrf import csrf_exempt

from injector import (
    Binder,
    Injector,
    Module,
    Provider,
    ScopeDecorator,
    ThreadLocalScope,
    inject,
    singleton,
)


__version__ = '0.2.3'
__all__ = ['RequestScope', 'request']
default_app_config = 'django_injector.DjangoInjectorConfig'
logger = logging.getLogger(__name__)


class DjangoInjectorConfig(AppConfig):

    name = 'django_injector'

    def ready(self) -> None:
        self.django_module = DjangoModule()
        self.injector = Injector([self.django_module])

        for mod_str in getattr(settings, 'INJECTOR_MODULES', []):
            module = import_string(mod_str)
            if isinstance(module, type) and issubclass(module, Module):
                module = module()
            self.injector.binder.install(module)

        resolver = get_resolver()
        process_resolver(resolver, self.injector)

        engine = Engine.get_default()
        engine.template_context_processors = tuple(process_list(
            engine.template_context_processors,
            self.injector
        ))

        patch_command_loader(self.injector)


def inject_request_middleware(get_response: Callable) -> Callable:
    app = apps.get_app_config('django_injector')

    def middleware(request: HttpRequest) -> Any:
        app.django_module.set_request(request)
        return get_response(request)

    return middleware


inject_request_middleware.async_callable = True  # type: ignore


def DjangoInjectorMiddleware(get_response: Callable) -> Callable:
    warnings.warn(
        'django_injector.DjangoInjectorMiddleware is deprecated. Please update your settings '
        'to use djangoo_injector.inject_request_middleware instead',
        DeprecationWarning,
    )
    return inject_request_middleware(get_response)


def wrap_function(fun: Callable, injector: Injector) -> Callable:
    @functools.wraps(fun)
    def wrapper(*args: Any, **kwargs: Any) -> Any:
        return injector.call_with_injection(callable=fun, args=args, kwargs=kwargs)
    return wrapper


def wrap_drf_view_set(fun: Callable, injector: Injector) -> Callable:
    cls = cast(Any, fun).cls
    actions = cast(Any, fun).actions
    initkwargs = cast(Any, fun).initkwargs

    # Code copied from DRFs ViewSet.as_view
    def view(request: HttpRequest, *args: Any, **kwargs: Any) -> Any:
        self = injector.create_object(cls, additional_kwargs=initkwargs)

        if 'get' in actions and 'head' not in actions:
            actions['head'] = actions['get']

        # We also store the mapping of request methods to actions,
        # so that we can later set the action attribute.
        # eg. `self.action = 'list'` on an incoming GET request.
        self.action_map = actions

        # Bind methods to actions
        # This is the bit that's different to a standard view
        for method, action in actions.items():
            handler = getattr(self, action)
            setattr(self, method, handler)

        self.request = request
        self.args = args
        self.kwargs = kwargs

        injector.call_with_injection(
            callable=self.setup,
            args=(request,) + args,
            kwargs=kwargs,
        )

        # And continue as usual
        return self.dispatch(request, *args, **kwargs)

    cast(Any, view).actions = actions
    cast(Any, view).cls = cls
    cast(Any, view).initkwargs = initkwargs

    # Django Rest Framework views are exempt from CSRF checks through the CSRF
    # middlware. Selective auth backends (session based authentication in particular)
    # may selectively enforce csrf protection.
    return csrf_exempt(view)


def wrap_class_based_view(fun: Callable, injector: Injector) -> Callable:
    cls = cast(Any, fun).view_class

    try:
        initkwargs = cast(Any, fun).view_initkwargs
    except AttributeError:
        return fun

    # Code copied from Django's django.views.generic.base.View
    # to enable injection into class based view constructors.
    def view(request: Any, *args: Any, **kwargs: Any) -> Any:
        self = injector.create_object(cls, additional_kwargs=initkwargs)
        injector.call_with_injection(
            callable=self.setup,
            args=(request,) + args,
            kwargs=kwargs,
        )
        if not hasattr(self, 'request'):
            raise AttributeError(
                "%s instance has no 'request' attribute. Did you override "
                "setup() and forget to call super()?" % cls.__name__
            )
        return self.dispatch(request, *args, **kwargs)

    cast(Any, view).view_class = cls
    cast(Any, view).view_initkwargs = initkwargs

    if hasattr(fun, 'cls'):
        # Django Rest Framework APIView's as_view returns a callable with a cls attribute
        # instead of view_class. If the original callable has a cls attribute, assume it's
        # DRF. In addition, DRF views are csrf exempt by default, the SessionAuthentication
        # auth backend will selectively apply CSRF protection.
        cast(Any, view).cls = cls
        view = csrf_exempt(view)

    return view


def instance_method_wrapper(im: Callable) -> Callable:
    @functools.wraps(im)
    def wrapper(*args: Any, **kwargs: Any) -> Any:
        return im(*args, **kwargs)
    return wrapper


def wrap_fun(fun: Callable, injector: Injector) -> Callable:

    if ismethod(fun):
        fun = instance_method_wrapper(fun)

    # This blockes needs to come before the block that checks for __call__
    # to prevent infinite recursion.
    if hasattr(fun, '__bindings__'):
        return wrap_function(fun, injector)

    if hasattr(fun, '__call__') and not isinstance(fun, type):
        try:
            type_hints = get_type_hints(fun)
        except (AttributeError, TypeError):
            # Some callables are not supported by get_type_hints:
            # https://github.com/alecthomas/flask_injector/blob/master/flask_injector/__init__.py#L75
            wrap_it = False
        else:
            type_hints.pop('return', None)
            wrap_it = type_hints != {}
        if wrap_it:
            return wrap_fun(inject(fun), injector)

    if hasattr(fun, 'view_class'):
        return wrap_class_based_view(fun, injector)
    elif hasattr(fun, 'cls'):
        # Django Rest Framework ViewSet's as_view returns a callable that
        # does NOT have a view_class attribute. Instead it has a cls attribute.
        return wrap_drf_view_set(fun, injector)

    return fun


def process_resolver(resolver: URLResolver, injector: Injector) -> None:
    if resolver.callback:
        resolver.callback = wrap_fun(resolver.callback, injector)

    for pattern in resolver.url_patterns:
        if isinstance(pattern, URLPattern) and pattern.callback:
            pattern.callback = wrap_fun(pattern.callback, injector)
        elif isinstance(pattern, URLResolver):
            process_resolver(pattern, injector)

    if resolver._populated:
        resolver._populate()


def patch_command_loader(injector: Injector) -> None:
    ''' Patches the management command loader to allow injection into management commands. '''
    # Original at:
    # https://github.com/django/django/blob/master/django/core/management/__init__.py#L33

    def load_command_class(app_name: str, name: str) -> None:
        module = import_module('%s.management.commands.%s' % (app_name, name))
        return injector.create_object(cast(Any, module).Command)

    management.load_command_class = load_command_class


def process_list(lst: List, injector: Injector) -> List:
    return [wrap_fun(f, injector) for f in lst]


class RequestScope(ThreadLocalScope):
    """A scope whose object lifetime is tied to a request."""

    def get(self, key: Any, provider: Provider) -> Any:
        app = apps.get_app_config('django_injector')
        request = app.django_module.get_request()

        if request is None:
            raise RuntimeError(
                'RequestScope.get was called without binding to a request. '
                'In order for RequestScope to work make sure '
                'django_injector.inject_request_middleware is in your MIDDLEWARES settings '
                'and make sure you are not running on an ASGI container like daphne. '
                'ASGI containers are not supported currently.'
            )
        return super().get(key, provider)


request = ScopeDecorator(RequestScope)


class DjangoModule(Module):

    def __init__(self, request_scope_class: type = RequestScope) -> None:
        self.request_scope_class = request_scope_class
        self._local = threading.local()

    def set_request(self, request: HttpRequest) -> None:
        if ASGIRequest and isinstance(request, ASGIRequest):
            if settings.DEBUG:
                logger.warning(
                    'Calling DjangoModule.set_request with a ASGIRequest will lead to '
                    'bad results because the asgi handler does not spawn a thread per '
                    'request. Ignoring call to set_request'
                )
            self._local.request = None
            return
        self._local.request = request

    def get_request(self) -> Optional[HttpRequest]:
        try:
            return self._local.request
        except AttributeError:
            return None

    def configure(self, binder: Binder) -> None:
        binder.bind(Settings, to=settings, scope=singleton)
        binder.bind(HttpRequest, to=lambda: self.get_request())
