//! Regression coverage for optimized Normal-blend adjustment compositing.
//!
//! **Purpose:** Verifies that bypassing the generic blend dispatcher preserves
//! exact RGB output for opaque and partially opaque adjustments.
//! **Logic & Workflow:** Builds a one-pixel base and Curves layer, composites
//! through the public tiled path, and compares deterministic channel values.
//! **Side Effects / Dependencies:** Allocates only one-pixel protocol layers.

use hcie_blend::Adjustment;
use hcie_composite::tiled::composite_tiled;
use hcie_protocol::Layer;
use hcie_tile::TiledLayer;

/// Builds a Curves adjustment whose lookup tables map selected input channels.
///
/// **Arguments:** `opacity` controls the layer-level adjustment mix.
/// **Returns:** A one-pixel adjustment layer. **Side Effects / Dependencies:** None.
fn curves_layer(opacity: f32) -> Layer {
    let mut lut_r: Vec<u8> = (0..=255).map(|value| value as u8).collect();
    let mut lut_g = lut_r.clone();
    let mut lut_b = lut_r.clone();
    lut_r[10] = 100;
    lut_g[20] = 110;
    lut_b[30] = 120;

    let mut layer = Layer::new_transparent("Curves", 1, 1);
    layer.adjustment = Some(Adjustment::Curves {
        lut_r,
        lut_g,
        lut_b,
    });
    layer.opacity = opacity;
    layer
}

/// Confirms a fully opaque Normal adjustment assigns the LUT result exactly.
#[test]
fn opaque_normal_adjustment_matches_lookup_result() {
    let base = Layer::from_rgba("Base", 1, 1, vec![10, 20, 30, 255]);
    let adjustment = curves_layer(1.0);
    let tiles = vec![
        Some(TiledLayer::from_dense(&base.pixels, 1, 1)),
        Some(TiledLayer::from_dense(&adjustment.pixels, 1, 1)),
    ];

    let output = composite_tiled(&[base, adjustment], &tiles, 1, 1);

    assert_eq!(output, vec![100, 110, 120, 255]);
}

/// Confirms partial opacity retains the previous rounded interpolation behavior.
#[test]
fn partial_normal_adjustment_preserves_rounded_interpolation() {
    let base = Layer::from_rgba("Base", 1, 1, vec![10, 20, 30, 255]);
    let adjustment = curves_layer(0.5);
    let tiles = vec![
        Some(TiledLayer::from_dense(&base.pixels, 1, 1)),
        Some(TiledLayer::from_dense(&adjustment.pixels, 1, 1)),
    ];

    let output = composite_tiled(&[base, adjustment], &tiles, 1, 1);

    assert_eq!(output, vec![55, 65, 75, 255]);
}