"""The paged readers' loop protections, exercised rather than assumed.

GRB and official vector both refuse a repeated page URL and bound the page
count, and GRB deduplicates on feature identity. None of that had a test, so
none of it was known to work — the same category as the redirect handler that
turned out to be dead code while looking like protection.

A provider that answers every page with a "next" link pointing back at itself
is not hypothetical: it is what a misconfigured cursor or a caching proxy in
front of an OGC endpoint produces.
"""

from __future__ import annotations

import pytest
from shapely.geometry import Polygon

from app.core.config import Settings
from app.core.errors import AppError
from app.services.grb_acquisition_service import GrbAcquisitionService
from tests.test_sprint239_bounded_grb_acquisition import JsonResponse, polygon_feature

COLLECTION_ITEMS = "https://geo.api.vlaanderen.be/GRB/ogc/features/v1/collections/GBG/items"
SCOPE = Polygon([(5.15, 51.18), (5.17, 51.18), (5.17, 51.20), (5.15, 51.20), (5.15, 51.18)])


def _building(feature_id: str) -> dict:
    return polygon_feature(
        feature_id,
        [(5.155, 51.185), (5.175, 51.185), (5.175, 51.195), (5.155, 51.195), (5.155, 51.185)],
    )


def _fetch(opener):
    return GrbAcquisitionService._fetch_features(
        GrbAcquisitionService._product("buildings"),
        SCOPE,
        SCOPE.bounds,
        "bounded_selection",
        Settings(_env_file=None),
        opener,
    )


def test_a_next_link_pointing_at_itself_is_refused() -> None:
    requests: list[str] = []

    def opener(request, timeout):  # noqa: ARG001
        requests.append(request.full_url)
        return JsonResponse(
            {
                "type": "FeatureCollection",
                "features": [_building("GBG.1")],
                "links": [{"rel": "next", "href": f"{COLLECTION_ITEMS}?cursor=stuck"}],
            }
        )

    with pytest.raises(AppError) as exc_info:
        _fetch(opener)

    assert exc_info.value.code == "GRB_PROVIDER_PAGINATION_LOOP"
    # Refused on the second sighting, not after exhausting the page budget.
    assert len(requests) == 2


def test_an_endless_chain_of_fresh_pages_stops_at_the_page_limit() -> None:
    """Distinct URLs defeat the loop check, so the page budget is the backstop."""

    settings = Settings(_env_file=None)
    requests: list[str] = []

    def opener(request, timeout):  # noqa: ARG001
        requests.append(request.full_url)
        cursor = len(requests)
        return JsonResponse(
            {
                "type": "FeatureCollection",
                "features": [_building(f"GBG.{cursor}")],
                "links": [{"rel": "next", "href": f"{COLLECTION_ITEMS}?cursor=p{cursor}"}],
            }
        )

    with pytest.raises(AppError) as exc_info:
        _fetch(opener)

    assert exc_info.value.code == "GRB_SELECTION_TOO_LARGE"
    assert exc_info.value.status_code == 422
    assert len(requests) == settings.grb_max_pages


def test_a_repeated_feature_across_pages_is_counted_once() -> None:
    """Two pages, distinct URLs, overlapping content.

    Unlike a repeated URL this is not necessarily provider misbehaviour — a
    cursor over a changing table can hand back a record twice — so the reader
    keeps it once rather than failing the acquisition.
    """

    def opener(request, timeout):  # noqa: ARG001
        if "cursor=next" in request.full_url:
            return JsonResponse(
                {
                    "type": "FeatureCollection",
                    "features": [_building("GBG.1"), _building("GBG.2")],
                    "links": [],
                }
            )
        return JsonResponse(
            {
                "type": "FeatureCollection",
                "features": [_building("GBG.1")],
                "links": [{"rel": "next", "href": f"{COLLECTION_ITEMS}?cursor=next"}],
            }
        )

    features, transfer = _fetch(opener)

    assert {feature["id"] for feature in features} == {"GBG:GBG.1", "GBG:GBG.2"}
    assert transfer["candidate_feature_count"] == 3
    assert transfer["feature_count"] == 2