//! Local adjustments, end to end on a device.
//!
//! The unit tests either side of this one check halves: `dr-pipeline` asserts
//! the generated WGSL says the right thing, and `dr-gpu`'s mask tests assert
//! an array of the right shape comes out. Neither would notice if the two
//! agreed with each other and both were wrong — a mask sampled with x and y
//! swapped satisfies both.
//!
//! So this renders a real frame and reads the pixels back: the masked region
//! must change, the rest must not, and the boundary must fall where the label
//! field says it does.

use dr_gpu::{AdjustPass, DemosaicedImage, GpuContext, LabelField, MaskPass};
use dr_pipeline::descriptor::ParamId;
use dr_pipeline::mask::{MaskLayer, MaskSource, MaskStack};
use dr_pipeline::operation::compose_full;
use dr_pipeline::{ops, EditGraph, Framing};
use dr_types::ColourSpace;

const SIZE: u32 = 32;

fn ctx() -> Option<GpuContext> {
    pollster::block_on(GpuContext::new_headless()).ok()
}

/// A flat mid-grey JPEG-path image, so any change is the adjustment's.
fn grey(ctx: &GpuContext) -> DemosaicedImage {
    let data: Vec<u8> = (0..SIZE * SIZE).flat_map(|_| [128, 128, 128, 255]).collect();
    DemosaicedImage::from_rgba8(ctx, &data, SIZE, SIZE).expect("upload")
}

/// Two regions: 0 is the left half, 1 the right.
fn split_field(ctx: &GpuContext) -> LabelField {
    let labels: Vec<u32> = (0..SIZE * SIZE)
        .map(|i| u32::from(i % SIZE >= SIZE / 2))
        .collect();
    LabelField::upload(ctx, &labels, SIZE, SIZE, 2).expect("label upload")
}

/// A layer brightening whatever it covers, by a lot, so it cannot be missed.
fn brighten(source: MaskSource) -> MaskLayer {
    let mut layer = MaskLayer::new("m1", source);
    layer.set_param("exposure", ParamId("exposure"), 2.0);
    layer
}

fn luma_at(pixels: &[u8], x: u32, y: u32) -> u8 {
    pixels[((y * SIZE + x) * 4) as usize]
}

/// Render `stack` over flat grey and hand back the RGBA8 result.
fn render(ctx: &GpuContext, stack: &MaskStack, field: Option<&LabelField>) -> Vec<u8> {
    let source = grey(ctx);
    let shader = compose_full(
        &ops::chain(),
        &Framing::new(),
        ColourSpace::Srgb,
        stack,
    );

    let mut masks = MaskPass::new(ctx).expect("mask pass");
    let array = masks.render(stack, field, None, SIZE, SIZE).expect("rasterise");

    let mut adjust = AdjustPass::new(ctx);
    adjust
        .render_masked(&source, &shader, SIZE, SIZE, Some(array))
        .expect("render");
    adjust.export_pixels().expect("readback").0
}

#[test]
fn a_region_mask_changes_only_the_regions_it_names() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    let field = split_field(&ctx);

    let mut stack = MaskStack::new();
    stack.push(brighten(MaskSource::Regions {
        signature: 1,
        level: 2,
        ids: vec![0],
    }));

    let pixels = render(&ctx, &stack, Some(&field));

    // Sampled well inside each half, clear of the feathered boundary.
    let inside = luma_at(&pixels, 4, SIZE / 2);
    let outside = luma_at(&pixels, SIZE - 5, SIZE / 2);

    assert!(
        inside > outside + 40,
        "the masked half should be much brighter: {inside} vs {outside}"
    );
    assert!(
        (120..=136).contains(&outside),
        "the unmasked half must be untouched mid-grey, got {outside}"
    );
}

/// The failure a swapped axis or an inverted comparison would produce, and
/// which the "inside is brighter" assertion alone would not catch.
#[test]
fn inverting_a_region_mask_swaps_which_half_moves() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    let field = split_field(&ctx);

    let mut layer = brighten(MaskSource::Regions {
        signature: 1,
        level: 2,
        ids: vec![0],
    });
    layer.invert = true;

    let mut stack = MaskStack::new();
    stack.push(layer);

    let pixels = render(&ctx, &stack, Some(&field));
    let left = luma_at(&pixels, 4, SIZE / 2);
    let right = luma_at(&pixels, SIZE - 5, SIZE / 2);

    assert!(
        right > left + 40,
        "inverted, the *other* half should brighten: left {left}, right {right}"
    );
}

#[test]
fn opacity_scales_the_effect() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    let field = split_field(&ctx);
    let source = MaskSource::Regions {
        signature: 1,
        level: 2,
        ids: vec![0],
    };

    let mut full = MaskStack::new();
    full.push(brighten(source.clone()));

    let mut half = MaskStack::new();
    let mut layer = brighten(source);
    layer.opacity = 0.5;
    half.push(layer);

    let at_full = luma_at(&render(&ctx, &full, Some(&field)), 4, SIZE / 2);
    let at_half = luma_at(&render(&ctx, &half, Some(&field)), 4, SIZE / 2);
    let untouched = 128;

    assert!(
        at_half > untouched && at_half < at_full,
        "half opacity should land between neutral and full: {untouched} < {at_half} < {at_full}"
    );
}

#[test]
fn a_linear_gradient_ramps_across_the_frame() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };

    let mut stack = MaskStack::new();
    stack.push(brighten(MaskSource::Linear {
        centre: (0.5, 0.5),
        angle: 0.0,
        width: 1.0,
    }));

    let pixels = render(&ctx, &stack, None);
    let left = luma_at(&pixels, 1, SIZE / 2);
    let middle = luma_at(&pixels, SIZE / 2, SIZE / 2);
    let right = luma_at(&pixels, SIZE - 2, SIZE / 2);

    assert!(
        left < middle && middle < right,
        "a horizontal ramp should increase left to right: {left}, {middle}, {right}"
    );
}

#[test]
fn a_radial_mask_is_strongest_at_its_centre() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };

    let mut stack = MaskStack::new();
    stack.push(brighten(MaskSource::Radial {
        centre: (0.5, 0.5),
        radii: (0.3, 0.3),
        angle: 0.0,
        feather: 0.5,
    }));

    let pixels = render(&ctx, &stack, None);
    let centre = luma_at(&pixels, SIZE / 2, SIZE / 2);
    let corner = luma_at(&pixels, 1, 1);

    assert!(
        centre > corner + 40,
        "the centre should carry the effect: {centre} vs corner {corner}"
    );
    assert!(
        (120..=136).contains(&corner),
        "outside the radius must be untouched, got {corner}"
    );
}

/// Two layers must not read each other's slice.
#[test]
fn stacked_layers_use_their_own_masks() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    let field = split_field(&ctx);

    let mut stack = MaskStack::new();
    // Left half up.
    stack.push(brighten(MaskSource::Regions {
        signature: 1,
        level: 2,
        ids: vec![0],
    }));
    // Right half down.
    let mut darken = MaskLayer::new("m2", MaskSource::Regions {
        signature: 1,
        level: 2,
        ids: vec![1],
    });
    darken.set_param("exposure", ParamId("exposure"), -2.0);
    stack.push(darken);

    let pixels = render(&ctx, &stack, Some(&field));
    let left = luma_at(&pixels, 4, SIZE / 2);
    let right = luma_at(&pixels, SIZE - 5, SIZE / 2);

    assert!(left > 150, "left should have brightened, got {left}");
    assert!(right < 100, "right should have darkened, got {right}");
}

/// A neutral edit must render identically whether or not masks are bound —
/// otherwise merely *having* the feature would alter every unedited image.
#[test]
fn an_empty_stack_renders_exactly_as_the_unmasked_path() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };

    let plain = {
        let source = grey(&ctx);
        let mut adjust = AdjustPass::new(&ctx);
        let shader = EditGraph::default_chain().compose();
        adjust.render(&source, &shader, SIZE, SIZE).expect("render");
        adjust.export_pixels().expect("readback").0
    };

    let masked = render(&ctx, &MaskStack::new(), None);
    assert_eq!(plain, masked, "an empty mask stack must be a no-op");
}