"""The rate-limit bucket must be the caller, not the proxy in front of them.

`get_remote_address` reads request.client.host. In staging and production the
backend has no published ports and its only caller is the Next proxy, so that
host is the Next container — one bucket for every browser user on the site.
Measured before this fix: 70 concurrent requests, 60 served and 10 refused.
"""

from starlette.datastructures import Headers

from backend.app import client_key


class _Req:
    """Enough of a Request for the key function: headers and a client host."""

    def __init__(self, headers: dict, host: str = "10.0.0.9"):
        self.headers = Headers(headers)
        self.client = type("C", (), {"host": host})()
        self.scope = {"type": "http", "client": (host, 0),
                      "headers": [(k.lower().encode(), v.encode())
                                  for k, v in headers.items()]}


def test_cloudflare_header_wins():
    # Cloudflare sets CF-Connecting-IP and overwrites any client-supplied
    # value, so it is trustworthy in a way a parsed XFF chain is not.
    assert client_key(_Req({"cf-connecting-ip": "203.0.113.7"})) == "203.0.113.7"


def test_forwarded_for_is_the_fallback_and_takes_the_first_entry():
    # Left-most is the original client; everything after it is proxies.
    assert client_key(
        _Req({"x-forwarded-for": "203.0.113.7, 10.0.0.2"})) == "203.0.113.7"


def test_remote_address_is_the_last_resort():
    assert client_key(_Req({}, host="10.0.0.9")) == "10.0.0.9"


def test_cloudflare_header_beats_forwarded_for():
    key = client_key(_Req({"cf-connecting-ip": "203.0.113.7",
                           "x-forwarded-for": "198.51.100.1"}))
    assert key == "203.0.113.7"


def test_two_callers_get_two_buckets():
    # The whole point: one user exhausting their limit must not refuse another.
    a = client_key(_Req({"cf-connecting-ip": "203.0.113.7"}))
    b = client_key(_Req({"cf-connecting-ip": "203.0.113.8"}))
    assert a != b


def test_whitespace_is_stripped():
    # "a, b" split on comma leaves a leading space on every entry but the
    # first; an unstripped key silently creates a second bucket per client.
    assert client_key(_Req({"x-forwarded-for": " 203.0.113.7 ,10.0.0.2"})) \
        == "203.0.113.7"