"""A selection smaller than a raster cell must not silently read as zero.

``geometry_mask`` selects a cell when its *centre* falls inside the geometry.
A rectangle smaller than one cell, or one that lands between four centres,
therefore selects nothing at all — and the analysis returned zeros, which on
screen is indistinguishable from "we looked and there is nothing here". On a
100 m population raster a 40 m rectangle over a city block reported no
inhabitants.

Selection now falls back to every touched cell and says that it did, so the
value is readable as "at least one whole cell", not as an empty area.
"""

from __future__ import annotations

import pytest

np = pytest.importorskip("numpy")
rasterio = pytest.importorskip("rasterio")

from rasterio.transform import from_origin
from shapely.geometry import box

from app.services.raster_cell_selection import select_cells


# 100 m cells, origin at the top-left corner of a 3x3 grid.
TRANSFORM = from_origin(200_000, 210_000, 100.0, 100.0)
SHAPE = (3, 3)


def test_a_normal_selection_uses_cell_centres() -> None:
    selection = select_cells(box(200_000, 209_700, 200_300, 210_000), out_shape=SHAPE, transform=TRANSFORM)

    assert selection.mask.sum() == 9
    assert selection.mode == "cell_centre"
    assert selection.expanded_to_touched_cells is False
    assert selection.warning is None


def test_a_rectangle_smaller_than_one_cell_still_returns_that_cell() -> None:
    selection = select_cells(box(200_010, 209_960, 200_050, 209_990), out_shape=SHAPE, transform=TRANSFORM)

    assert selection.mask.sum() == 1
    assert selection.mode == "all_touched"
    assert selection.expanded_to_touched_cells is True
    assert "cel" in selection.warning


def test_a_rectangle_between_four_cell_centres_returns_all_four() -> None:
    selection = select_cells(box(200_080, 209_880, 200_120, 209_920), out_shape=SHAPE, transform=TRANSFORM)

    assert selection.mask.sum() == 4
    assert selection.expanded_to_touched_cells is True


def test_a_selection_entirely_off_the_raster_selects_nothing() -> None:
    """Falling back must not invent coverage where the geometry does not reach."""

    selection = select_cells(box(300_000, 300_000, 300_100, 300_100), out_shape=SHAPE, transform=TRANSFORM)

    assert selection.mask.sum() == 0
    assert selection.expanded_to_touched_cells is False
    assert selection.mode == "cell_centre"


def test_the_warning_states_how_much_larger_the_analysed_area_is() -> None:
    selection = select_cells(
        box(200_010, 209_960, 200_050, 209_990),
        out_shape=SHAPE,
        transform=TRANSFORM,
        cell_area_m2=100.0 * 100.0,
    )

    # One 100x100 m cell was analysed for a 40x30 m request.
    assert "1 rastercel" in selection.warning
    assert "1.0 ha" in selection.warning


def test_the_mask_shape_always_matches_the_raster_window() -> None:
    selection = select_cells(box(200_010, 209_960, 200_050, 209_990), out_shape=SHAPE, transform=TRANSFORM)

    assert selection.mask.shape == SHAPE
    assert selection.mask.dtype == np.bool_