import logging
import urllib
from contextlib import suppress

import orjson
from circuitbreaker import CircuitBreakerError, circuit
from django.conf import settings
from django.http import HttpRequest, HttpResponse
from django.utils.translation import gettext as _
from django.views.decorators.csrf import csrf_exempt
from requests.exceptions import ProxyError, RequestException, Timeout
from sentry_sdk.integrations.logging import ignore_logger

from zerver.lib.exceptions import JsonableError
from zerver.lib.outgoing_http import OutgoingSession
from zerver.lib.validator import check_url, to_wild_value

# In order to not overload Sentry if it's having a bad day, we tell
# Sentry to ignore exceptions that we have when talking to Sentry.
logger = logging.getLogger(__name__)
ignore_logger(logger.name)


class SentryTunnelSession(OutgoingSession):
    def __init__(self) -> None:
        super().__init__(role="sentry_tunnel", timeout=1)


@csrf_exempt
def sentry_tunnel(
    request: HttpRequest,
) -> HttpResponse:
    try:
        envelope_header_line, envelope_items = request.body.split(b"\n", 1)
        envelope_header = to_wild_value("envelope_header", envelope_header_line.decode("utf-8"))
        dsn = urllib.parse.urlparse(envelope_header["dsn"].tame(check_url))
    except Exception:
        raise JsonableError(_("Invalid request format"))

    if dsn.geturl() != settings.SENTRY_FRONTEND_DSN:
        raise JsonableError(_("Invalid DSN"))

    assert dsn.hostname
    project_id = dsn.path.strip("/")
    url = dsn._replace(netloc=dsn.hostname, path=f"/api/{project_id}/envelope/").geturl()

    # Adjust the payload to explicitly contain the IP address of the
    # user we see.  If left blank, Sentry will assume the IP it
    # received the request from, which is Zulip's, which can make
    # debugging more complicated.
    updated_body = request.body
    # If we fail to update the body for any reason, leave it as-is; it
    # is better to misreport the IP than to drop the report entirely.
    with suppress(Exception):
        # This parses the Sentry ingestion format, known as an
        # Envelope.  See https://develop.sentry.dev/sdk/envelopes/ for
        # spec.
        parts = [envelope_header_line, b"\n"]
        while envelope_items != b"":
            item_header_line, rest = envelope_items.split(b"\n", 1)
            parts.append(item_header_line)
            parts.append(b"\n")
            item_header = orjson.loads(item_header_line.decode("utf-8"))
            length = item_header.get("length")
            if length is None:
                item_body, envelope_items = [*rest.split(b"\n", 1), b""][:2]
            else:
                item_body, envelope_items = rest[0:length], rest[length:]
            if item_header.get("type") in ("transaction", "event"):
                # Event schema:
                # https://develop.sentry.dev/sdk/event-payloads/#core-interfaces
                # https://develop.sentry.dev/sdk/event-payloads/user/
                #
                # Transaction schema:
                # https://develop.sentry.dev/sdk/event-payloads/transaction/#anatomy
                # Note that "Transactions are Events enriched with Span data."
                payload_data = orjson.loads(item_body)
                if "user" in payload_data:
                    payload_data["user"]["ip_address"] = request.META.get("REMOTE_ADDR")
                    item_body = orjson.dumps(payload_data)
            parts.append(item_body)
            if length is None:
                parts.append(b"\n")
        updated_body = b"".join(parts)

    try:
        sentry_request(url, updated_body)
    except CircuitBreakerError:
        logger.warning("Dropped a client exception due to circuit-breaking")
    except RequestException as e:
        # This logger has been configured, above, to not report to Sentry
        logger.exception(e)
    return HttpResponse(status=200)


# Circuit-break and temporarily stop trying to report to
# Sentry if it keeps timing out.  We include ProxyError in
# here because we are likely making our requests through
# Smokescreen as a CONNECT proxy, so failures from Smokescreen
# failing to connect at the TCP level will report as
# ProxyErrors.
@circuit(
    failure_threshold=2,
    recovery_timeout=30,
    name="Sentry tunnel",
    expected_exception=(ProxyError, Timeout),
)
def sentry_request(url: str, data: bytes) -> None:
    SentryTunnelSession().post(
        url=url,
        data=data,
        headers={"Content-Type": "application/x-sentry-envelope"},
    ).raise_for_status()