"""An extended building is a change, not a deletion plus a new building.

With only added/removed/unchanged, a footprint that grew by an annexe drops
below the IoU threshold and is reported twice: once as removed and once as
added. That hides exactly the category a change-detection product exists to
show, and inflates both counts.
"""

from __future__ import annotations

import pytest
from shapely.geometry import box

from app.services.change_detection_service import ChangeDetectionService


def _feature(feature_id: str, geometry):
    return {"feature_id": feature_id, "properties": {}, "geometry": geometry}


def _classify(source, target, *, iou_threshold=0.8, modified_threshold=0.3):
    return ChangeDetectionService._classify_features(
        source,
        target,
        iou_threshold=iou_threshold,
        modified_threshold=modified_threshold,
    )


def test_an_extended_footprint_is_reported_as_modified() -> None:
    source = [_feature("b1", box(0, 0, 10, 10))]
    target = [_feature("b1-new", box(0, 0, 10, 14))]  # IoU 100/140 = 0.71

    result = _classify(source, target)

    assert [item["change_type"] for item in result] == ["modified"]
    assert result[0]["source_feature_id"] == "b1"
    assert result[0]["target_feature_id"] == "b1-new"
    assert result[0]["iou"] == pytest.approx(100 / 140)


def test_a_nearly_identical_footprint_is_unchanged() -> None:
    source = [_feature("b1", box(0, 0, 10, 10))]
    target = [_feature("b1", box(0, 0, 10, 10.2))]

    result = _classify(source, target)

    assert [item["change_type"] for item in result] == ["unchanged"]


def test_a_genuinely_new_building_stays_added() -> None:
    source = [_feature("b1", box(0, 0, 10, 10))]
    target = [_feature("b1", box(0, 0, 10, 10)), _feature("b2", box(50, 50, 60, 60))]

    result = _classify(source, target)

    assert sorted(item["change_type"] for item in result) == ["added", "unchanged"]


def test_a_demolished_building_stays_removed() -> None:
    source = [_feature("b1", box(0, 0, 10, 10)), _feature("b2", box(50, 50, 60, 60))]
    target = [_feature("b1", box(0, 0, 10, 10))]

    result = _classify(source, target)

    assert sorted(item["change_type"] for item in result) == ["removed", "unchanged"]


def test_barely_overlapping_footprints_are_not_called_modified() -> None:
    """Below the modified floor the two are separate objects, not one changed."""

    source = [_feature("b1", box(0, 0, 10, 10))]
    target = [_feature("b2", box(9, 9, 19, 19))]  # IoU ~0.005

    result = _classify(source, target)

    assert sorted(item["change_type"] for item in result) == ["added", "removed"]


def test_each_target_is_claimed_at_most_once() -> None:
    source = [_feature("a", box(0, 0, 10, 10)), _feature("b", box(0, 0, 10, 12))]
    target = [_feature("t", box(0, 0, 10, 10))]

    result = _classify(source, target)

    claimed = [item for item in result if item["target_feature_id"] == "t"]
    assert len(claimed) == 1


def test_classification_is_independent_of_input_order() -> None:
    source = [_feature("a", box(0, 0, 10, 10)), _feature("b", box(30, 30, 40, 40))]
    target = [_feature("a2", box(0, 0, 10, 14)), _feature("c", box(70, 70, 80, 80))]

    forward = _classify(source, target)
    reverse = _classify(list(reversed(source)), list(reversed(target)))

    def signature(items):
        return sorted(
            (item["change_type"], item["source_feature_id"], item["target_feature_id"]) for item in items
        )

    assert signature(forward) == signature(reverse)


def test_large_populations_do_not_use_a_full_cross_product() -> None:
    """A spatial index keeps a city-sized comparison tractable."""

    source = [_feature(f"s{i}", box(i * 10, 0, i * 10 + 8, 8)) for i in range(400)]
    target = [_feature(f"t{i}", box(i * 10, 0, i * 10 + 8, 8)) for i in range(400)]

    result = _classify(source, target)

    assert all(item["change_type"] == "unchanged" for item in result)
    assert len(result) == 400