from typing import TYPE_CHECKING, cast
from posthog import scopes

if TYPE_CHECKING:
    from django.http import HttpRequest, HttpResponse  # noqa: F401
    from typing import Callable, Dict, Any, Optional  # noqa: F401


class PosthogContextMiddleware:
    """Middleware to automatically track Django requests.

    This middleware wraps all calls with a posthog context. It attempts to extract the following from the request headers:
    - Session ID, (extracted from `X-POSTHOG-SESSION-ID`)
    - Distinct ID, (extracted from `X-POSTHOG-DISTINCT-ID`)
    - Request URL as $current_url
    - Request Method as $request_method

    The context will also auto-capture exceptions and send them to PostHog, unless you disable it by setting
    `POSTHOG_MW_CAPTURE_EXCEPTIONS` to `False` in your Django settings.

    The middleware behaviour is customisable through 3 additional functions:
    - `POSTHOG_MW_EXTRA_TAGS`, which is a Callable[[HttpRequest], Dict[str, Any]] expected to return a dictionary of additional tags to be added to the context.
    - `POSTHOG_MW_REQUEST_FILTER`, which is a Callable[[HttpRequest], bool] expected to return `False` if the request should not be tracked.
    - `POSTHOG_MW_TAG_MAP`, which is a Callable[[Dict[str, Any]], Dict[str, Any]], which you can use to modify the tags before they're added to the context.

    You can use the `POSTHOG_MW_TAG_MAP` function to remove any default tags you don't want to capture, or override them with your own values.

    Context tags are automatically included as properties on all events captured within a context, including exceptions.
    See the context documentation for more information. The extracted distinct ID and session ID, if found, are used to
    associate all events captured in the middleware context with the same distinct ID and session as currently active on the
    frontend. See the documentation for `set_context_session` and `identify_context` for more details.
    """

    def __init__(self, get_response):
        # type: (Callable[[HttpRequest], HttpResponse]) -> None
        self.get_response = get_response

        from django.conf import settings

        if hasattr(settings, "POSTHOG_MW_EXTRA_TAGS") and callable(
            settings.POSTHOG_MW_EXTRA_TAGS
        ):
            self.extra_tags = cast(
                "Optional[Callable[[HttpRequest], Dict[str, Any]]]",
                settings.POSTHOG_MW_EXTRA_TAGS,
            )
        else:
            self.extra_tags = None

        if hasattr(settings, "POSTHOG_MW_REQUEST_FILTER") and callable(
            settings.POSTHOG_MW_REQUEST_FILTER
        ):
            self.request_filter = cast(
                "Optional[Callable[[HttpRequest], bool]]",
                settings.POSTHOG_MW_REQUEST_FILTER,
            )
        else:
            self.request_filter = None

        if hasattr(settings, "POSTHOG_MW_TAG_MAP") and callable(
            settings.POSTHOG_MW_TAG_MAP
        ):
            self.tag_map = cast(
                "Optional[Callable[[Dict[str, Any]], Dict[str, Any]]]",
                settings.POSTHOG_MW_TAG_MAP,
            )
        else:
            self.tag_map = None

        if hasattr(settings, "POSTHOG_MW_CAPTURE_EXCEPTIONS") and isinstance(
            settings.POSTHOG_MW_CAPTURE_EXCEPTIONS, bool
        ):
            self.capture_exceptions = settings.POSTHOG_MW_CAPTURE_EXCEPTIONS
        else:
            self.capture_exceptions = True

    def extract_tags(self, request):
        # type: (HttpRequest) -> Dict[str, Any]
        tags = {}

        # Extract session ID from X-POSTHOG-SESSION-ID header
        session_id = request.headers.get("X-POSTHOG-SESSION-ID")
        if session_id:
            scopes.set_context_session(session_id)

        # Extract distinct ID from X-POSTHOG-DISTINCT-ID header
        distinct_id = request.headers.get("X-POSTHOG-DISTINCT-ID")
        if distinct_id:
            scopes.identify_context(distinct_id)

        # Extract current URL
        absolute_url = request.build_absolute_uri()
        if absolute_url:
            tags["$current_url"] = absolute_url

        # Extract request method
        if request.method:
            tags["$request_method"] = request.method

        # Apply extra tags if configured
        if self.extra_tags:
            extra = self.extra_tags(request)
            if extra:
                tags.update(extra)

        # Apply tag mapping if configured
        if self.tag_map:
            tags = self.tag_map(tags)

        return tags

    def __call__(self, request):
        # type: (HttpRequest) -> HttpResponse
        if self.request_filter and not self.request_filter(request):
            return self.get_response(request)

        with scopes.new_context(self.capture_exceptions):
            for k, v in self.extract_tags(request).items():
                scopes.tag(k, v)

            return self.get_response(request)