Refactor code structure for improved readability and maintainability

hcie-filter/tests/filters_verify.rs

@@ -0,0 +1,277 @@
+use hcie_filter::apply_filter;
+
+/// Value-verification tests for hcie-filter.
+///
+/// Upgrades existing "does not panic" smoke tests to actual
+/// correctness assertions with known input → known output checks.
+
+// ---------------------------------------------------------------------------
+// Helper: create a small test layer with known pixel data
+// ---------------------------------------------------------------------------
+fn make_gradient_layer() -> hcie_protocol::Layer {
+    let mut layer = hcie_protocol::Layer::new_blank("gradient", 4, 4);
+    for y in 0..4 {
+        for x in 0..4 {
+            layer.set_pixel(x, y, [x as u8 * 64, y as u8 * 64, 128, 255]);
+        }
+    }
+    layer
+}
+
+fn make_solid_layer(r: u8, g: u8, b: u8, a: u8) -> hcie_protocol::Layer {
+    let mut layer = hcie_protocol::Layer::new_blank("solid", 4, 4);
+    for y in 0..4 {
+        for x in 0..4 {
+            layer.set_pixel(x, y, [r, g, b, a]);
+        }
+    }
+    layer
+}
+
+fn make_1x1_layer(r: u8, g: u8, b: u8, a: u8) -> hcie_protocol::Layer {
+    let mut layer = hcie_protocol::Layer::new_blank("tiny", 1, 1);
+    layer.set_pixel(0, 0, [r, g, b, a]);
+    layer
+}
+
+// ---------------------------------------------------------------------------
+// Invert filter — exact value verification
+// ---------------------------------------------------------------------------
+
+#[test]
+fn invert_white_becomes_black() {
+    let mut layer = make_solid_layer(255, 255, 255, 255);
+    apply_filter(&mut layer, "invert", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[0], 0, "invert of white R should be 0");
+    assert_eq!(pixel[1], 0, "invert of white G should be 0");
+    assert_eq!(pixel[2], 0, "invert of white B should be 0");
+    // Alpha typically unchanged
+    assert_eq!(pixel[3], 255, "invert should leave alpha unchanged");
+}
+
+#[test]
+fn invert_black_becomes_white() {
+    let mut layer = make_solid_layer(0, 0, 0, 255);
+    apply_filter(&mut layer, "invert", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[0], 255);
+    assert_eq!(pixel[1], 255);
+    assert_eq!(pixel[2], 255);
+}
+
+#[test]
+fn invert_red_becomes_cyan() {
+    let mut layer = make_solid_layer(255, 0, 0, 255);
+    apply_filter(&mut layer, "invert", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[0], 0,   "invert red: R should be 0");
+    assert_eq!(pixel[1], 255, "invert red: G should be 255");
+    assert_eq!(pixel[2], 255, "invert red: B should be 255");
+}
+
+#[test]
+fn invert_preserves_transparency() {
+    let mut layer = make_solid_layer(100, 150, 200, 0);
+    apply_filter(&mut layer, "invert", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[3], 0, "invert should preserve zero alpha");
+}
+
+#[test]
+fn invert_invert_is_identity() {
+    let original = make_gradient_layer();
+    let mut layer = make_gradient_layer();
+    apply_filter(&mut layer, "invert", &serde_json::json!({}));
+    apply_filter(&mut layer, "invert", &serde_json::json!({}));
+    for y in 0..4 {
+        for x in 0..4 {
+            assert_eq!(
+                layer.get_pixel(x, y),
+                original.get_pixel(x, y),
+                "double invert should restore original at ({},{})", x, y
+            );
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Grayscale filter — value verification
+// ---------------------------------------------------------------------------
+
+#[test]
+fn grayscale_makes_rgb_equal() {
+    let mut layer = make_gradient_layer();
+    apply_filter(&mut layer, "grayscale", &serde_json::json!({}));
+    for y in 0..4 {
+        for x in 0..4 {
+            let p = layer.get_pixel(x, y);
+            let diff_rg = (p[0] as i16 - p[1] as i16).abs();
+            let diff_rb = (p[0] as i16 - p[2] as i16).abs();
+            let diff_gb = (p[1] as i16 - p[2] as i16).abs();
+            // Allow small tolerance for integer rounding
+            assert!(
+                diff_rg <= 3 && diff_rb <= 3 && diff_gb <= 3,
+                "grayscale should produce R≈G≈B at ({},{}): got {:?}",
+                x, y, p
+            );
+        }
+    }
+}
+
+#[test]
+fn grayscale_identity_on_gray_input() {
+    let mut layer = make_solid_layer(128, 128, 128, 255);
+    apply_filter(&mut layer, "grayscale", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[0], 128);
+    assert_eq!(pixel[1], 128);
+    assert_eq!(pixel[2], 128);
+}
+
+#[test]
+fn grayscale_preserves_alpha() {
+    let mut layer = make_solid_layer(100, 150, 200, 128);
+    apply_filter(&mut layer, "grayscale", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[3], 128, "grayscale should preserve alpha");
+}
+
+// ---------------------------------------------------------------------------
+// Brightness/Contrast filter
+// ---------------------------------------------------------------------------
+
+#[test]
+fn brightness_zero_is_identity() {
+    let original = make_gradient_layer();
+    let mut layer = make_gradient_layer();
+    // PS-style brightness/contrast: 0 brightness, 0 contrast should be identity
+    apply_filter(&mut layer, "brightness_contrast", &serde_json::json!({
+        "brightness": 0.0,
+        "contrast": 0.0
+    }));
+    for y in 0..4 {
+        for x in 0..4 {
+            let o = original.get_pixel(x, y);
+            let p = layer.get_pixel(x, y);
+            // Allow ±1 for rounding
+            assert!(
+                (o[0] as i16 - p[0] as i16).abs() <= 1 &&
+                (o[1] as i16 - p[1] as i16).abs() <= 1 &&
+                (o[2] as i16 - p[2] as i16).abs() <= 1,
+                "identity params should preserve pixel at ({},{}): orig={:?}, got={:?}",
+                x, y, o, p
+            );
+        }
+    }
+}
+
+#[test]
+fn brightness_changes_pixels() {
+    let mut layer = make_solid_layer(64, 64, 64, 255);
+    let before = layer.get_pixel(0, 0);
+    // PS-style brightness uses 0-100 scale
+    apply_filter(&mut layer, "brightness_contrast", &serde_json::json!({
+        "brightness": 50.0,
+        "contrast": 0.0
+    }));
+    let after = layer.get_pixel(0, 0);
+    assert!(
+        after[0] != before[0] || after[1] != before[1] || after[2] != before[2],
+        "brightness=50 should change at least one channel"
+    );
+}
+
+#[test]
+fn brightness_negative_changes_pixels() {
+    let mut layer = make_solid_layer(128, 128, 128, 255);
+    let before = layer.get_pixel(0, 0);
+    // PS-style brightness uses 0-100 scale
+    apply_filter(&mut layer, "brightness_contrast", &serde_json::json!({
+        "brightness": -50.0,
+        "contrast": 0.0
+    }));
+    let after = layer.get_pixel(0, 0);
+    assert!(
+        after[0] != before[0] || after[1] != before[1] || after[2] != before[2],
+        "brightness=-50 should change at least one channel"
+    );
+}
+
+// ---------------------------------------------------------------------------
+// Edge cases: 1×1 images (minimal boundary)
+// ---------------------------------------------------------------------------
+
+#[test]
+fn invert_works_on_1x1() {
+    let mut layer = make_1x1_layer(128, 64, 32, 255);
+    apply_filter(&mut layer, "invert", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[0], 127); // 255 - 128
+    assert_eq!(pixel[1], 191); // 255 - 64
+    assert_eq!(pixel[2], 223); // 255 - 32
+}
+
+#[test]
+fn grayscale_works_on_1x1() {
+    let mut layer = make_1x1_layer(100, 50, 200, 255);
+    apply_filter(&mut layer, "grayscale", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    // Grayscale: R, G, B should be approximately equal
+    let diff = (pixel[0] as i16 - pixel[1] as i16).abs()
+        .max((pixel[0] as i16 - pixel[2] as i16).abs())
+        .max((pixel[1] as i16 - pixel[2] as i16).abs());
+    assert!(diff <= 3, "grayscale on 1x1 should make R≈G≈B: {:?}", pixel);
+}
+
+// ---------------------------------------------------------------------------
+// Unknown / missing parameters do not crash
+// ---------------------------------------------------------------------------
+
+#[test]
+fn invert_with_empty_params_works() {
+    let mut layer = make_solid_layer(100, 100, 100, 255);
+    apply_filter(&mut layer, "invert", &serde_json::json!({}));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[0], 155);
+}
+
+#[test]
+fn invert_with_extra_params_does_not_crash() {
+    let mut layer = make_solid_layer(0, 0, 0, 255);
+    apply_filter(&mut layer, "invert", &serde_json::json!({
+        "unknown_param": 42,
+        "another_one": "hello"
+    }));
+    let pixel = layer.get_pixel(0, 0);
+    assert_eq!(pixel[0], 255, "invert with extra params should still work");
+}
+
+// ---------------------------------------------------------------------------
+// Filters preserve layer dimensions
+// ---------------------------------------------------------------------------
+
+#[test]
+fn filter_preserves_dimensions() {
+    for filter_name in &["invert", "grayscale", "brightness_contrast", "box_blur"] {
+        let mut layer = make_gradient_layer();
+        apply_filter(&mut layer, filter_name, &serde_json::json!({}));
+        assert_eq!(layer.width, 4, "{} should preserve width", filter_name);
+        assert_eq!(layer.height, 4, "{} should preserve height", filter_name);
+        assert_eq!(layer.pixels.len(), 4 * 4 * 4, "{} should preserve pixel count", filter_name);
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Multiple filters in sequence do not crash
+// ---------------------------------------------------------------------------
+
+#[test]
+fn sequence_of_filters_does_not_crash() {
+    let mut layer = make_gradient_layer();
+    for &filter in &["invert", "grayscale", "brightness_contrast", "sharpen", "box_blur"] {
+        apply_filter(&mut layer, filter, &serde_json::json!({}));
+    }
+    // If we got here without panic, the test passes
+    assert_eq!(layer.width, 4);
+}