//! Every path that produces pixels must apply the masks.
//!
//! The display, the export and the thumbnail run the same generated shader,
//! and that shader always emits a block per active mask layer. Bind the empty
//! placeholder instead of the real array and every one of those blocks
//! multiplies by zero: the local adjustments are simply absent, with no error
//! and no warning.
//!
//! That is what happened — exports and thumbnails both took the unmasked
//! path — and it is invisible from inside either one. The only way to see it
//! is to render the same edit twice and compare, which is what this does.

use dr_gpu::{AdjustPass, DemosaicedImage, GpuContext, MaskPass, SubjectMasks};
use dr_pipeline::descriptor::ParamId;
use dr_pipeline::mask::{MaskLayer, MaskSource, MaskStack};
use dr_pipeline::operation::compose_full;
use dr_pipeline::spot::SpotSet;
use dr_pipeline::{ops, Framing};
use dr_segment::Shaped;
use dr_types::ColourSpace;

const PROXY: u32 = 24;

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

fn grey(ctx: &GpuContext, size: u32) -> DemosaicedImage {
    let data: Vec<u8> = (0..size * size)
        .flat_map(|_| [128, 128, 128, 255])
        .collect();
    DemosaicedImage::from_rgba8(ctx, &data, size, size).expect("upload")
}

/// Coverage over the left half, as a detection would produce.
fn left_half() -> Vec<u8> {
    (0..PROXY * PROXY)
        .map(|i| if i % PROXY < PROXY / 2 { 255 } else { 0 })
        .collect()
}

fn brightening_stack() -> MaskStack {
    let mut stack = MaskStack::new();
    let mut layer = MaskLayer::new(
        "m1",
        MaskSource::Subject {
            signature: 1,
            index: 0,
            class: "person".into(),
            score: 0.9,
        },
    );
    layer.set_param("exposure", ParamId("exposure"), 2.0);
    layer.feather = 0.0;
    stack.push(layer);
    stack
}

/// Render `stack` at `out` pixels, exactly as the session's shared helper
/// does: fields, array, then a masked render.
fn render_at(ctx: &GpuContext, stack: &MaskStack, out: u32) -> Vec<u8> {
    let source = grey(ctx, 64);

    let coverage = left_half();
    let fields: Vec<Vec<f32>> = stack
        .active()
        .map(|_| {
            Shaped::build(
                &coverage,
                PROXY as usize,
                PROXY as usize,
                128,
                dr_segment::Morphology::None,
                0.0,
            )
            .distance
        })
        .collect();
    let refs: Vec<&[f32]> = fields.iter().map(|f| f.as_slice()).collect();
    let subjects = SubjectMasks::upload(ctx, &refs, PROXY, PROXY).expect("upload");

    let mut masks = MaskPass::new(ctx).expect("mask pass");
    let array = masks
        .render(stack, None, Some(&subjects), PROXY, PROXY)
        .expect("rasterise");

    let shader = compose_full(
        &ops::chain(),
        &Framing::new(),
        ColourSpace::Srgb,
        stack,
        &SpotSet::new(),
        &[],
    );
    let mut adjust = AdjustPass::new(ctx);
    adjust
        .render_masked(&source, &shader, out, out, Some(array))
        .expect("render");
    adjust.export_pixels().expect("readback").0
}

/// The same edit rendered *without* the array bound — what export and
/// thumbnail were doing.
fn render_unmasked(ctx: &GpuContext, stack: &MaskStack, out: u32) -> Vec<u8> {
    let source = grey(ctx, 64);
    let shader = compose_full(
        &ops::chain(),
        &Framing::new(),
        ColourSpace::Srgb,
        stack,
        &SpotSet::new(),
        &[],
    );
    let mut adjust = AdjustPass::new(ctx);
    adjust.render(&source, &shader, out, out).expect("render");
    adjust.export_pixels().expect("readback").0
}

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

/// The fault itself, stated as a test: the two paths must not agree.
///
/// If binding the array made no difference, the masks would not be reaching
/// the shader at all — which is precisely the bug this file exists for.
#[test]
fn binding_the_masks_changes_the_result() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    let stack = brightening_stack();
    const OUT: u32 = 64;

    let masked = render_at(&ctx, &stack, OUT);
    let unmasked = render_unmasked(&ctx, &stack, OUT);

    let left_masked = luma(&masked, OUT, 8, 32);
    let left_unmasked = luma(&unmasked, OUT, 8, 32);

    assert!(
        left_masked > left_unmasked + 40,
        "with the array bound the masked half must brighten: {left_masked} \
         against {left_unmasked}"
    );
    assert!(
        (120..=136).contains(&left_unmasked),
        "and without it the layer contributes nothing at all, silently: \
         {left_unmasked}"
    );
}

/// A thumbnail is the same edit at a small size, so it must carry the same
/// local adjustments. This is the reported bug.
#[test]
fn a_thumbnail_sized_render_still_carries_its_masks() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    let stack = brightening_stack();

    for out in [16u32, 32, 64, 128] {
        let pixels = render_at(&ctx, &stack, out);
        let inside = luma(&pixels, out, out / 8, out / 2);
        let outside = luma(&pixels, out, out - out / 8 - 1, out / 2);

        assert!(
            inside > outside + 40,
            "at {out}px the masked half should be brighter: {inside} against \
             {outside}"
        );
    }
}

/// One mask array, every output size. The array is rasterised in source space
/// and sampled through the framing map, so a thumbnail and a full-size export
/// must reach the same *proportion* of the frame — not merely both be
/// non-empty.
#[test]
fn the_mask_covers_the_same_fraction_at_every_size() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    let stack = brightening_stack();

    let fraction = |out: u32| {
        let pixels = render_at(&ctx, &stack, out);
        let lit = (0..out * out)
            .filter(|i| pixels[(*i as usize) * 4] > 150)
            .count();
        lit as f32 / (out * out) as f32
    };

    let small = fraction(32);
    let large = fraction(128);
    assert!(
        (small - large).abs() < 0.05,
        "the same edit should mask the same share of the frame at any size: \
         {small:.3} at 32px against {large:.3} at 128px"
    );
    assert!(
        (0.4..0.6).contains(&small),
        "and that share is the left half: {small:.3}"
    );
}

// ---------------------------------------------------------------------------
// Gradient geometry
//
// The mask is rasterised over the source frame, whose two axes are not the
// same length. A gradient measured in raw 0..1 fractions therefore means a
// different distance horizontally than vertically — so a circle comes out an
// ellipse and an angle is not the angle asked for. Neither shows in the stored
// numbers, and both are what a photographer is looking straight at while
// dragging a handle.
// ---------------------------------------------------------------------------

/// A flat grey frame at an arbitrary shape, brightened wherever `stack` covers.
fn render_gradient(ctx: &GpuContext, stack: &MaskStack, w: u32, h: u32) -> Vec<u8> {
    let data: Vec<u8> = (0..w * h).flat_map(|_| [128u8, 128, 128, 255]).collect();
    let source = DemosaicedImage::from_rgba8(ctx, &data, w, h).expect("upload");

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

    let shader = compose_full(
        &ops::chain(),
        &Framing::new(),
        ColourSpace::Srgb,
        stack,
        &SpotSet::new(),
        &[],
    );
    let mut adjust = AdjustPass::new(ctx);
    adjust
        .render_masked(&source, &shader, w, h, Some(array))
        .expect("render");
    adjust.export_pixels().expect("readback").0
}

fn brightened(pixels: &[u8], w: u32, x: u32, y: u32) -> bool {
    pixels[((y * w + x) * 4) as usize] > 160
}

fn gradient(source: MaskSource) -> MaskStack {
    let mut stack = MaskStack::new();
    let mut layer = MaskLayer::new("g1", source);
    layer.set_param("exposure", ParamId("exposure"), 2.0);
    stack.push(layer);
    stack
}

/// A radial with equal radii must be round on the screen, not on the numbers.
#[test]
fn a_radial_with_equal_radii_is_a_circle_on_a_wide_frame() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    // 3:2. On a square frame this test cannot fail, which is why it is not one.
    const W: u32 = 96;
    const H: u32 = 64;

    // 0.3 of the frame's height. In pixels that is 19 either way — the x axis
    // spans 0..1.5 in the same units, so the fraction is smaller and the
    // distance is the same.
    let pixels = render_gradient(
        &ctx,
        &gradient(MaskSource::Radial {
            centre: (0.5, 0.5),
            radii: (0.3, 0.3),
            angle: 0.0,
            // Hard, so "covered" is a question with an answer rather than a
            // ramp to pick a threshold out of.
            feather: 0.0,
        }),
        W,
        H,
    );

    let (cx, cy) = (W / 2, H / 2);
    assert!(brightened(&pixels, W, cx, cy), "the centre must be covered");

    for (dx, dy, what) in [(15u32, 0u32, "right"), (0, 15, "down")] {
        assert!(
            brightened(&pixels, W, cx + dx, cy + dy),
            "15px {what} of centre is inside a 19px radius"
        );
    }
    for (dx, dy, what) in [(24u32, 0u32, "right"), (0, 24, "down")] {
        assert!(
            !brightened(&pixels, W, cx + dx, cy + dy),
            "24px {what} of centre is outside it — before the aspect \
             correction the horizontal reach was 28px and this passed only \
             downwards"
        );
    }
}

/// And a ramp at 45° must be at 45° where the photographer sees it.
#[test]
fn a_diagonal_ramp_runs_at_the_angle_it_was_given() {
    let Some(ctx) = ctx() else {
        eprintln!("no adapter; skipping");
        return;
    };
    const W: u32 = 96;
    const H: u32 = 64;

    let pixels = render_gradient(
        &ctx,
        &gradient(MaskSource::Linear {
            centre: (0.5, 0.5),
            angle: std::f32::consts::FRAC_PI_4,
            width: 0.0,
        }),
        W,
        H,
    );

    // Coverage increases along (cos 45°, sin 45°), so the half-way line runs
    // from lower-left to upper-right through the centre: equal steps right and
    // down stay on the covered side, and the two sides of it disagree.
    let (cx, cy) = (W / 2, H / 2);
    assert!(
        brightened(&pixels, W, cx + 16, cy + 16),
        "down and to the right of the line is inside"
    );
    assert!(
        !brightened(&pixels, W, cx - 16, cy - 16),
        "up and to the left of it is outside"
    );
    // The diagonal itself, sampled a few pixels either side. Without the
    // aspect correction the line comes out at 34 degrees and both of these
    // land on the same side of it.
    assert!(
        brightened(&pixels, W, cx + 18, cy - 14),
        "just below the 45 degree line is inside"
    );
    assert!(
        !brightened(&pixels, W, cx + 14, cy - 18),
        "just above it is not"
    );
}