"""Tests for pixel-level change detection."""
import numpy as np
import pytest


def test_compute_zscore_raster():
    from app.analysis.change import compute_zscore_raster
    current = np.array([[0.5, 0.3], [0.7, 0.4]], dtype=np.float32)
    baseline_mean = np.array([[0.6, 0.6], [0.6, 0.6]], dtype=np.float32)
    baseline_std = np.array([[0.05, 0.05], [0.05, 0.05]], dtype=np.float32)
    z = compute_zscore_raster(current, baseline_mean, baseline_std, min_std=0.02)
    expected = np.array([[-2.0, -6.0], [2.0, -4.0]], dtype=np.float32)
    np.testing.assert_array_almost_equal(z, expected, decimal=1)


def test_compute_zscore_raster_clamps_std():
    from app.analysis.change import compute_zscore_raster
    current = np.array([[0.5]], dtype=np.float32)
    baseline_mean = np.array([[0.5]], dtype=np.float32)
    baseline_std = np.array([[0.001]], dtype=np.float32)
    z = compute_zscore_raster(current, baseline_mean, baseline_std, min_std=0.02)
    assert z[0, 0] == pytest.approx(0.0, abs=0.01)


def test_detect_hotspots():
    from app.analysis.change import detect_hotspots
    z = np.array([[-3.0, 0.5, 2.5], [1.0, -0.3, -2.1]], dtype=np.float32)
    mask, pct = detect_hotspots(z, threshold=2.0)
    assert mask[0, 0] == True
    assert mask[0, 1] == False
    assert mask[0, 2] == True
    assert mask[1, 2] == True
    assert pct == pytest.approx(50.0, abs=0.1)


def test_cluster_hotspots():
    from app.analysis.change import cluster_hotspots
    mask = np.array([
        [True, True, False, False, False],
        [True, True, False, False, False],
        [False, False, False, True, True],
        [False, False, False, True, True],
    ], dtype=bool)
    z = np.array([
        [-2.5, -2.3, 0.0, 0.0, 0.0],
        [-2.1, -2.0, 0.0, 0.0, 0.0],
        [0.0, 0.0, 0.0, 2.5, 2.3],
        [0.0, 0.0, 0.0, 2.1, 2.8],
    ], dtype=np.float32)
    clusters = cluster_hotspots(mask, z, pixel_area_ha=1.0, min_pixels=2)
    assert len(clusters) == 2
    assert clusters[0]["area_ha"] == 4.0
    assert clusters[1]["area_ha"] == 4.0


def test_cluster_hotspots_filters_small():
    from app.analysis.change import cluster_hotspots
    mask = np.array([[True, False, False], [False, False, True]], dtype=bool)
    z = np.full((2, 3), -2.5, dtype=np.float32)
    clusters = cluster_hotspots(mask, z, pixel_area_ha=1.0, min_pixels=2)
    assert len(clusters) == 0