//! Local adjustments end to end, on a real photograph.
//!
//! Two edits a photographer actually makes, both driven by the model finding
//! the subject rather than by anyone drawing a shape:
//!
//! - **The subject in colour, everything else monochrome.** One layer, the
//!   subject's mask inverted, saturation at −100.
//! - **The subject lifted out of its background.** Two layers over the same
//!   mask: the subject brightened, the background pulled down.
//!
//! ```sh
//! cargo run -p dr-gpu --example local --release \
//!   --features segment-readback -- photo.CR2 out
//! ```
//!
//! Writes `<prefix>-original.ppm`, `<prefix>-colour-pop.ppm`,
//! `<prefix>-subject-lift.ppm` and `<prefix>-mask.ppm`. PPM for the reason
//! every other example here uses it: no encoder dependency, and every viewer
//! reads it.
//!
//! # What this is really testing
//!
//! That the whole chain agrees with itself. The mask is rasterised in *source*
//! space at proxy resolution and sampled by the composed shader after the
//! framing map, so a fault anywhere in that handoff — a transposed axis, a
//! mask pinned to the viewport, a slice read from the wrong layer — shows up
//! here as an adjustment in the wrong place, and nowhere else.

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

/// Longest edge the mask and the model work at.
const PROXY: u32 = 1600;
/// Longest edge of the written frames.
const OUT: u32 = 1400;

fn main() {
    env_logger::init();

    let mut args = std::env::args().skip(1);
    let Some(path) = args.next() else {
        eprintln!("usage: local <photo.CR2|photo.RAF> [out-prefix]");
        std::process::exit(2);
    };
    let prefix = args.next().unwrap_or_else(|| "local".into());

    let ctx = pollster::block_on(GpuContext::new_headless()).expect("gpu context");
    println!("gpu        {}", ctx.adapter_name());

    // ---- the photograph ---------------------------------------------------
    let bytes = std::fs::read(&path).expect("read file");
    let raw = dr_decode::decode(&bytes).expect("decode");
    // The tag, because the model reads photographs and the sensor stores
    // scanlines. See `stand_up` below: this example exists to be the shipping
    // path with pictures attached, so it has to make the same turn the
    // develop session makes.
    let orientation = dr_decode::orientation(&bytes).unwrap_or_default();
    println!("source     {} × {}", raw.crop.width, raw.crop.height);
    println!("turns      {}", orientation.quarter_turns);
    let source = Demosaicer::new(&ctx)
        .expect("demosaicer")
        .run(&raw)
        .expect("demosaic");

    // ---- what the model sees ----------------------------------------------
    //
    // The *unedited* image, so the detection does not shift when the edit
    // does. Through `export_pixels`, which is ungated: an export is not the
    // display round-trip AC-8 forbids, and neither is this.
    let (sw, sh) = source.size();
    let scale = (PROXY as f32 / sw.max(sh) as f32).min(1.0);
    let (pw, ph) = (
        ((sw as f32 * scale) as u32).max(1),
        ((sh as f32 * scale) as u32).max(1),
    );

    let neutral = EditGraph::default_chain();
    let mut proxy_pass = AdjustPass::new(&ctx);
    proxy_pass
        .render(&source, &neutral.compose(), pw, ph)
        .expect("proxy render");
    let (rgba, pw, ph) = proxy_pass.export_pixels().expect("proxy readback");
    println!("proxy      {pw} × {ph}");

    let rgb: Vec<f32> = rgba
        .chunks_exact(4)
        .flat_map(|p| {
            [
                p[0] as f32 / 255.0,
                p[1] as f32 / 255.0,
                p[2] as f32 / 255.0,
            ]
        })
        .collect();

    // ---- find the subject -------------------------------------------------
    //
    // Stood up first. A model trained on upright photographs is very bad at
    // sideways ones, and the proxy above is in the sensor's own orientation
    // — see `stand_up`.
    let (upright, uw, uh) = stand_up(&rgb, pw as usize, ph as usize, orientation);

    let t = std::time::Instant::now();
    let mut model = SemanticModel::embedded().expect("model");
    let instances = model
        .detect(&upright, uw, uh, &SemanticOptions::default())
        .expect("detect");
    println!(
        "detect     {} found in {:.0} ms",
        instances.len(),
        t.elapsed().as_secs_f32() * 1000.0
    );
    for (i, inst) in instances.iter().enumerate() {
        println!("  [{i}] {:<14} {:.2}", inst.class_name, inst.score);
    }

    let Some((index, subject)) = pick_subject(&instances) else {
        eprintln!("\nNothing recognised in this frame — nothing to adjust locally.");
        eprintln!("The model knows COCO's 80 classes; a landscape with no person,");
        eprintln!("animal or vehicle in it has no subject for it to find.");
        std::process::exit(1);
    };
    println!(
        "subject    [{index}] {} at {:.2}",
        subject.class_name, subject.score
    );

    // Laid back down, then quantised exactly as the develop session does, so
    // this example exercises the shipping path rather than a shortcut around
    // it. The mask has to end up in *source* space: the composed shader
    // samples the mask array after the framing map.
    let alpha: Vec<u8> = lay_down(&subject.mask, uw, uh, orientation)
        .iter()
        .map(|&v| (v.clamp(0.0, 1.0) * 255.0).round() as u8)
        .collect();

    let (ow, oh) = fit(sw, sh, OUT);
    let mut masks = MaskPass::new(&ctx).expect("mask pass");
    let mut adjust = AdjustPass::new(&ctx);

    // ---- the original, for comparison -------------------------------------
    adjust
        .render(&source, &neutral.compose(), ow, oh)
        .expect("render");
    write(&format!("{prefix}-original.ppm"), &adjust);

    // ---- 1. the subject in colour, the rest monochrome --------------------
    //
    // One layer, inverted. Inverting rather than making a second mask for the
    // background is the whole point of having one: there is exactly one
    // boundary, so there is exactly one thing to get right.
    let mut pop = MaskStack::new();
    let mut drain = subject_layer("m1", index, subject);
    drain.invert = true;
    drain.set_param("saturation", ParamId("saturation"), -100.0);
    // A touch of feather, or the colour stops dead on the model's outline and
    // the eye goes straight to the edge instead of to the subject.
    drain.feather = 0.02;
    pop.push(drain);

    render_stack(
        &ctx,
        &source,
        &mut masks,
        &mut adjust,
        &pop,
        &alpha,
        pw,
        ph,
        ow,
        oh,
    );
    write(&format!("{prefix}-colour-pop.ppm"), &adjust);

    // ---- 2. lift the subject out of its background ------------------------
    let mut lift = MaskStack::new();

    let mut brighter = subject_layer("m1", index, subject);
    brighter.set_param("exposure", ParamId("exposure"), 0.45);
    brighter.feather = 0.015;
    lift.push(brighter);

    let mut darker = subject_layer("m2", index, subject);
    darker.invert = true;
    darker.set_param("exposure", ParamId("exposure"), -0.55);
    darker.set_param("saturation", ParamId("saturation"), -25.0);
    darker.feather = 0.03;
    lift.push(darker);

    render_stack(
        &ctx,
        &source,
        &mut masks,
        &mut adjust,
        &lift,
        &alpha,
        pw,
        ph,
        ow,
        oh,
    );
    write(&format!("{prefix}-subject-lift.ppm"), &adjust);

    // ---- 3. the same edit, grown and shrunk -------------------------------
    //
    // The model's outline is approximately right and slightly soft, so the
    // everyday correction is to move it: grow to catch a halo the detector
    // stopped short of, shrink to pull off one it caught. Both are a threshold
    // of the distance field, which is why they cost a uniform.
    for (name, morphology, radius) in [
        ("grown", Morphology::Dilate, 0.012),
        ("shrunk", Morphology::Erode, 0.012),
    ] {
        let mut stack = MaskStack::new();
        let mut layer = subject_layer("m1", index, subject);
        layer.invert = true;
        layer.set_param("saturation", ParamId("saturation"), -100.0);
        layer.feather = 0.004;
        layer.morphology = morphology;
        layer.morph_radius = radius;
        stack.push(layer);

        render_stack(
            &ctx,
            &source,
            &mut masks,
            &mut adjust,
            &stack,
            &alpha,
            pw,
            ph,
            ow,
            oh,
        );
        write(&format!("{prefix}-{name}.ppm"), &adjust);
    }

    // ---- the mask itself, to check the outline ----------------------------
    write_mask(&format!("{prefix}-mask.ppm"), &alpha, pw, ph);

    println!("\nwrote      {prefix}-original.ppm");
    println!("           {prefix}-colour-pop.ppm");
    println!("           {prefix}-subject-lift.ppm");
    println!("           {prefix}-grown.ppm, {prefix}-shrunk.ppm");
    println!("           {prefix}-mask.ppm");
}

/// A layer masked to one detected object.
fn subject_layer(id: &str, index: usize, subject: &dr_segment::Instance) -> MaskLayer {
    let mut layer = MaskLayer::new(
        id,
        MaskSource::Subject {
            // One segmentation in this process, so any signature agrees with
            // itself; the session computes a real one.
            signature: 0,
            index: index as u32,
            class: subject.class_name.to_string(),
            score: subject.score,
        },
    );
    layer.name = subject.class_name.to_string();
    layer
}

/// The most promising thing to adjust.
///
/// Prefers a person, then falls back to the strongest detection of anything.
/// Not because people are special to the pipeline, but because they are what a
/// local adjustment is usually *for*, and an example that picks the parked car
/// behind the subject demonstrates the mechanism while missing the point.
fn pick_subject(instances: &[dr_segment::Instance]) -> Option<(usize, &dr_segment::Instance)> {
    instances
        .iter()
        .enumerate()
        .find(|(_, i)| &*i.class_name == "person")
        .or_else(|| instances.iter().enumerate().next())
}

#[allow(clippy::too_many_arguments)]
fn render_stack(
    ctx: &GpuContext,
    source: &DemosaicedImage,
    masks: &mut MaskPass,
    adjust: &mut AdjustPass,
    stack: &MaskStack,
    coverage: &[u8],
    pw: u32,
    ph: u32,
    ow: u32,
    oh: u32,
) {
    // One signed distance field per active layer, in that order — the order
    // the rasteriser indexes them by. Built here rather than once up front
    // because a compound morphology rebuilds the field, so it belongs to the
    // layer that shaped it rather than to the object.
    let fields: Vec<Vec<f32>> = stack
        .active()
        .map(|layer| {
            Shaped::build(
                coverage,
                pw as usize,
                ph as usize,
                128,
                match layer.morphology {
                    Morphology::None => dr_segment::Morphology::None,
                    Morphology::Dilate => dr_segment::Morphology::Dilate,
                    Morphology::Erode => dr_segment::Morphology::Erode,
                    Morphology::Close => dr_segment::Morphology::Close,
                    Morphology::Open => dr_segment::Morphology::Open,
                },
                layer.morph_radius * pw.min(ph) as f32,
            )
            .distance
        })
        .collect();
    let refs: Vec<&[f32]> = fields.iter().map(|f| f.as_slice()).collect();
    let subjects = SubjectMasks::upload(ctx, &refs, pw, ph).expect("upload fields");

    // Rasterised at *proxy* size in source space, then sampled by the shader
    // after the framing map — which is what makes one mask correct at every
    // output size, zoom and crop.
    let array = masks
        .render(stack, None, Some(&subjects), pw, ph)
        .expect("rasterise masks");

    let shader = compose_full(
        &ops::chain(),
        &Framing::new(),
        ColourSpace::Srgb,
        stack,
        &SpotSet::new(),
    );
    adjust
        .render_masked(source, &shader, ow, oh, Some(array))
        .expect("render");
}

/// Turn the proxy the way the photographer is looking at it, so the model
/// reads a photograph rather than a scanline order — and turn the mask it
/// answers with back again, because the composed shader samples masks in
/// source space, after the framing map.
///
/// Both are `dr_types::Orientation`, which is the one place the permutation
/// is written: the grid's thumbnails, the develop session's segmentation and
/// this example all go through it, so "upright" means one thing across the
/// application. A local copy here would be a fourth opinion, and this example
/// exists to be the shipping path rather than an imitation of it.
fn stand_up(
    rgb: &[f32],
    width: usize,
    height: usize,
    o: dr_types::Orientation,
) -> (Vec<f32>, usize, usize) {
    let (out, w, h) = o.into_shown(rgb, width as u32, height as u32, 3);
    (out, w as usize, h as usize)
}

fn lay_down(mask: &[f32], dw: usize, dh: usize, o: dr_types::Orientation) -> Vec<f32> {
    o.into_stored(mask, dw as u32, dh as u32, 1).0
}

fn fit(w: u32, h: u32, longest: u32) -> (u32, u32) {
    let s = (longest as f32 / w.max(h) as f32).min(1.0);
    (
        ((w as f32 * s) as u32).max(1),
        ((h as f32 * s) as u32).max(1),
    )
}

fn write(path: &str, adjust: &AdjustPass) {
    let (rgba, w, h) = adjust.export_pixels().expect("readback");
    let rgb: Vec<u8> = rgba
        .chunks_exact(4)
        .flat_map(|p| [p[0], p[1], p[2]])
        .collect();
    write_ppm(path, &rgb, w, h);
}

fn write_mask(path: &str, alpha: &[u8], w: u32, h: u32) {
    let rgb: Vec<u8> = alpha.iter().flat_map(|&a| [a, a, a]).collect();
    write_ppm(path, &rgb, w, h);
}

fn write_ppm(path: &str, rgb: &[u8], w: u32, h: u32) {
    use std::io::Write as _;
    let mut f = std::io::BufWriter::new(std::fs::File::create(path).expect("create"));
    write!(f, "P6\n{w} {h}\n255\n").expect("header");
    f.write_all(rgb).expect("body");
}