//! TRACES: FR-DEV-3j | FR-DEV-2
//! The view transform, end to end on a device.
//!
//! `dr-pipeline` checks the curve on the CPU and that the composer emits it in
//! the right place. Neither would notice a shader that disagreed with the CPU
//! reference, or a clamp somewhere upstream that made two highlights the same
//! number before the curve ever saw them — which is exactly what the retired
//! base curve did, and why D19 exists. So this renders real pixels.

use dr_decode::{CfaPattern, CropRect, RawImage};
use dr_gpu::{AdjustPass, Demosaicer, GpuContext};
use dr_pipeline::view::Sigmoid;
use dr_pipeline::EditGraph;

const SIZE: u32 = 16;

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

/// A flat RGGB frame at `level` out of 65535, with an identity matrix and a
/// neutral balance, so the only things that move a pixel are the edit and the
/// view transform.
fn flat_raw(level: u16) -> RawImage {
    RawImage {
        width: SIZE,
        height: SIZE,
        data: vec![level; (SIZE * SIZE) as usize],
        cfa_pattern: CfaPattern::Rggb,
        black_level: [0; 4],
        white_level: u16::MAX,
        wb_coeffs: [1.0, 1.0, 1.0, 1.0],
        color_matrix: Some([1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0]),
        samples_per_pixel: 1,
        profile: None,
        profile_tables: None,
        baseline_exposure: 0.0,
        make: String::new(),
        model: String::new(),
        crop: CropRect {
            x: 0,
            y: 0,
            width: SIZE,
            height: SIZE,
        },
    }
}

/// The default chain with D19's sigmoid chosen: Camera Raw's tone is the
/// default since D21, and these tests are about the sigmoid.
fn sigmoid_chain() -> EditGraph {
    let mut g = EditGraph::default_chain();
    g.set_param(
        dr_pipeline::ops::view_transform::ID,
        dr_pipeline::ops::view_transform::CURVE,
        dr_pipeline::ops::view_transform::SIGMOID,
    );
    g
}

#[test]
fn camera_raw_tone_is_the_default_and_agrees_with_the_acr3_curve() {
    // TRACES: FR-DEV-3j
    // D21: a raw with no profile renders a grey through Camera Raw's default
    // curve, which the profile buffer's placeholder carries.
    let Some(ctx) = ctx() else {
        eprintln!("skipping: no GPU adapter");
        return;
    };
    let graph = EditGraph::default_chain();
    for level in [500u16, 4_000, 8_520, 20_000, 40_000] {
        let scene = f32::from(level) / f32::from(u16::MAX);
        let display = dr_types::tone::evaluate(&dr_types::tone::ACR3_DEFAULT, scene);
        let expected = (dr_types::Transfer::Srgb.encode(display) * 255.0).round() as i32;
        let got = i32::from(rendered(&ctx, level, &graph));
        assert!(
            (got - expected).abs() <= 2,
            "raw {level} rendered as {got}, the ACR3 curve says {expected}"
        );
    }
}

/// Render `graph` over a flat frame and return the centre pixel's red.
///
/// The centre rather than a corner: a demosaic has to invent its edges.
fn rendered(ctx: &GpuContext, level: u16, graph: &EditGraph) -> u8 {
    let source = Demosaicer::new(ctx)
        .expect("demosaicer")
        .run(&flat_raw(level))
        .expect("demosaic");
    let shader = graph.compose();
    let mut adjust = AdjustPass::new(ctx);
    adjust.render(&source, &shader, SIZE, SIZE).expect("render");
    let (pixels, _, _) = adjust.export_pixels().expect("readback");
    let centre = ((SIZE / 2) * SIZE + SIZE / 2) * 4;
    pixels[centre as usize]
}

#[test]
fn the_shader_agrees_with_the_cpu_reference() {
    // TRACES: FR-DEV-3j
    let Some(ctx) = ctx() else {
        eprintln!("skipping: no GPU adapter");
        return;
    };
    let curve = Sigmoid::default_curve();
    let graph = sigmoid_chain();
    for level in [0u16, 500, 4_000, 8_520, 32_768, 60_000, u16::MAX] {
        let scene = f32::from(level) / f32::from(u16::MAX);
        let display = curve.channel(scene).min(1.0);
        let expected = (dr_types::Transfer::Srgb.encode(display) * 255.0).round() as i32;
        let got = i32::from(rendered(&ctx, level, &graph));
        // Two 8-bit steps, for the `Rgba16Float` intermediate and the
        // rounding either side of the encode.
        assert!(
            (got - expected).abs() <= 2,
            "raw {level} rendered as {got}, expected about {expected}"
        );
    }
}

#[test]
fn highlights_above_one_stay_distinct() {
    // TRACES: FR-DEV-2 | FR-DEV-3j
    // The failure D19 names first. Two stops of exposure put these two
    // frames at 1.0 and 1.5 of sensor saturation. The base curve was flat
    // past 1.0, so both rendered as the same white; the view transform's
    // shoulder still separates them.
    let Some(ctx) = ctx() else {
        eprintln!("skipping: no GPU adapter");
        return;
    };
    let mut graph = sigmoid_chain();
    graph.set_param(
        dr_pipeline::ops::exposure::ID,
        dr_pipeline::ops::exposure::EXPOSURE,
        2.0,
    );
    let lower = rendered(&ctx, u16::MAX / 4, &graph);
    let upper = rendered(&ctx, (u16::MAX / 8) * 3, &graph);
    assert!(
        upper > lower,
        "scene 1.0 rendered {lower} and scene 1.5 rendered {upper}"
    );
    assert!(upper < 255, "scene 1.5 is below the default white point");
}

#[test]
fn the_rendering_is_monotone_through_the_whole_range() {
    // TRACES: FR-DEV-3j
    // A dip anywhere puts a dark band across a smooth gradient — a sky, most
    // visibly.
    let Some(ctx) = ctx() else {
        eprintln!("skipping: no GPU adapter");
        return;
    };
    let graph = EditGraph::default_chain();
    let mut last = 0u8;
    for step in 0..=32u32 {
        let level = (step * u32::from(u16::MAX) / 32) as u16;
        let got = rendered(&ctx, level, &graph);
        assert!(got >= last, "raw {level} rendered {got}, below {last}");
        last = got;
    }
}

/// Render `graph` over a flat frame through `render_detailed`, the path every
/// frontend takes, and return the centre pixel's red.
fn rendered_detailed(ctx: &GpuContext, level: u16, graph: &EditGraph) -> (u8, AdjustPass) {
    let source = Demosaicer::new(ctx)
        .expect("demosaicer")
        .run(&flat_raw(level))
        .expect("demosaic");
    let shader = graph.compose_for(dr_types::ColourSpace::Srgb);
    let detail = graph.compose_detail(source.size(), (SIZE, SIZE));
    let key = graph.invalidation().through(dr_pipeline::Affects::Colour);
    let mut adjust = AdjustPass::new(ctx);
    adjust
        .render_detailed(&source, &shader, SIZE, SIZE, None, &detail, key)
        .expect("render");
    let (pixels, _, _) = adjust.export_pixels().expect("readback");
    let centre = ((SIZE / 2) * SIZE + SIZE / 2) * 4;
    (pixels[centre as usize], adjust)
}

#[test]
fn a_detail_stage_renders_through_the_view_pass_unchanged() {
    // TRACES: FR-DEV-3j | FR-DEV-2
    // With a detail stage the view transform is a dispatch of its own after
    // it (D19). Sharpening a flat field changes nothing, so the same frame
    // with and without it must render the same: the view pass read the detail
    // stage's result, applied the view transform once, and encoded once.
    let Some(ctx) = ctx() else {
        eprintln!("skipping: no GPU adapter");
        return;
    };
    let plain = rendered(&ctx, 8_520, &EditGraph::default_chain());

    let mut sharpened = EditGraph::default_chain();
    let id = dr_pipeline::ops::capture_sharpen::ID;
    sharpened.set_param(id, dr_pipeline::ops::capture_sharpen::AMOUNT, 100.0);
    sharpened.set_param(id, dr_pipeline::ops::capture_sharpen::RADIUS, 1.0);
    let (detailed, pass) = rendered_detailed(&ctx, 8_520, &sharpened);

    assert!(
        pass.detail_dispatches() > 0,
        "the premise: a detail stage ran"
    );
    assert_eq!(pass.view_dispatches(), 1);
    assert!(
        detailed.abs_diff(plain) <= 1,
        "with a detail stage {detailed}, without {plain}"
    );
}