//! Renderer-level phase translation experiment, not application code.
use iced::advanced::{Renderer as _, graphics::geometry::Renderer as _, renderer::Headless};
use iced::{
    Color, Point, Rectangle, Renderer, Size, Vector,
    widget::canvas::{Cache, Frame, Geometry, Path},
};
use std::{cell::Cell, hint::black_box, time::Instant};
const BG: Color = Color::from_rgb8(246, 248, 251);
const DOT: Color = Color::from_rgb(0.86, 0.89, 0.91);
fn dots(f: &mut Frame, size: Size, step: f32, phase: Vector) {
    for x in 0..(size.width / step) as i32 + 1 {
        for y in 0..(size.height / step) as i32 + 1 {
            f.fill(
                &Path::circle(
                    Point::new(phase.x + x as f32 * step, phase.y + y as f32 * step),
                    0.65,
                ),
                DOT,
            );
        }
    }
}
fn old(r: &Renderer, size: Size, step: f32, phase: Vector) -> Geometry {
    let mut f = Frame::new(r, size);
    f.fill_rectangle(Point::ORIGIN, size, BG);
    dots(&mut f, size, step, phase);
    f.into_geometry()
}
fn phase(r: &Renderer, cache: &Cache, size: Size, step: f32, builds: &Cell<usize>) -> Geometry {
    cache.draw_with_bounds(
        r,
        Rectangle {
            x: -step,
            y: -step,
            width: size.width + 3. * step,
            height: size.height + 3. * step,
        },
        |f| {
            builds.set(builds.get() + 1);
            f.fill_rectangle(
                Point::new(-step, -step),
                Size::new(size.width + 3. * step, size.height + 3. * step),
                BG,
            );
            dots(f, size, step, Vector::ZERO);
        },
    )
}
fn submit(r: &mut Renderer, size: Size, g: Geometry, pan: Vector) {
    r.with_layer(Rectangle::with_size(size), |r| {
        r.with_translation(pan, |r| r.draw_geometry(g))
    });
}
fn shot(r: &mut Renderer, size: Size, scale: f32) -> Vec<u8> {
    Headless::screenshot(
        r,
        Size::new(
            (size.width * scale).ceil() as u32,
            (size.height * scale).ceil() as u32,
        ),
        scale,
        BG,
    )
}
fn main() {
    let rt = tokio::runtime::Builder::new_current_thread()
        .enable_all()
        .build()
        .unwrap();
    let mut r = rt
        .block_on(<Renderer as Headless>::new(
            iced::Font::DEFAULT,
            16.into(),
            None,
        ))
        .unwrap();
    println!(
        "renderer={}; phase-cache prototype; NOT native FPS",
        r.name()
    );
    for (size, zoom) in [
        (Size::new(1900., 660.), 1.),
        (Size::new(1900., 660.), 0.5),
        (Size::new(1440., 900.), 1.),
        (Size::new(1440., 900.), 0.5),
        (Size::new(301.5, 211.25), 0.73),
    ] {
        if size.width != 301.5 {
            continue;
        }
        let step = (24f32 * zoom).max(14.);
        let cache = Cache::new();
        let builds = Cell::new(0);
        println!(
            "size={}x{} zoom={zoom} step={step}",
            size.width, size.height
        );
        for scale in [1., 1.25, 2.] {
            for pan in [
                Vector::ZERO,
                Vector::new(-13.25, 9.75),
                Vector::new(6.125, -8.5),
                Vector::new(step - 0.125, step - 0.25),
                Vector::new(-0.125, 0.125),
            ] {
                let offset = Vector::new(pan.x.rem_euclid(step), pan.y.rem_euclid(step));
                r.reset(Rectangle::with_size(size));
                let g = old(&r, size, step, offset);
                r.draw_geometry(g);
                let expected = shot(&mut r, size, scale);
                r.reset(Rectangle::with_size(size));
                let g = phase(&r, &cache, size, step, &builds);
                submit(&mut r, size, g, offset);
                let actual = shot(&mut r, size, scale);
                assert_eq!(expected.len(), actual.len());
                for (index, (a, b)) in expected
                    .chunks_exact(4)
                    .zip(actual.chunks_exact(4))
                    .enumerate()
                    .filter(|(_, (a, b))| a != b)
                    .take(20)
                {
                    println!(
                        "difference_xy={},{} expected={a:?} actual={b:?}",
                        index % (size.width * scale).ceil() as usize,
                        index / (size.width * scale).ceil() as usize
                    );
                }
                let changed = expected
                    .chunks_exact(4)
                    .zip(actual.chunks_exact(4))
                    .filter(|(a, b)| a != b)
                    .count();
                let max = expected
                    .iter()
                    .zip(&actual)
                    .map(|(a, b)| a.abs_diff(*b))
                    .max()
                    .unwrap_or(0);
                println!(
                    "scale={scale} pan={},{} changed_pixels={changed} max_channel_delta={max}",
                    pan.x, pan.y
                );
            }
        }
        assert_eq!(builds.get(), 1);
        for cached in [false, true] {
            let mut ms = Vec::new();
            for i in 0..23 {
                r.reset(Rectangle::with_size(size));
                let offset = Vector::new((i as f32 * 0.25).rem_euclid(step), 9.75);
                let now = Instant::now();
                let g = if cached {
                    phase(&r, &cache, size, step, &builds)
                } else {
                    old(&r, size, step, offset)
                };
                if cached {
                    submit(&mut r, size, g, offset)
                } else {
                    r.draw_geometry(g)
                };
                let elapsed = black_box(now.elapsed().as_secs_f64() * 1000.);
                if i >= 3 {
                    ms.push(elapsed);
                }
            }
            ms.sort_by(f64::total_cmp);
            println!(
                "cached={cached} construct_and_submit changing_pan n=20 p50_ms={:.4} p95_ms={:.4} max_ms={:.4}",
                ms[10], ms[19], ms[19]
            );
        }
        println!("cache_builds={}", builds.get());
        assert_eq!(builds.get(), 1);
        // Includes backend prepare/upload and readback; still not native presentation.
        if size.width == 1900. && zoom == 1. || size.width == 1440. && zoom == 0.5 {
            for cached in [false, true] {
                let mut ms = Vec::new();
                for i in 0..10 {
                    r.reset(Rectangle::with_size(size));
                    let offset = Vector::new((i as f32 * 0.25).rem_euclid(step), 9.75);
                    let now = Instant::now();
                    let g = if cached {
                        phase(&r, &cache, size, step, &builds)
                    } else {
                        old(&r, size, step, offset)
                    };
                    if cached {
                        submit(&mut r, size, g, offset);
                    } else {
                        r.draw_geometry(g);
                    }
                    let pixels = black_box(shot(&mut r, size, 1.));
                    let elapsed = now.elapsed().as_secs_f64() * 1000.;
                    drop(pixels);
                    if i >= 2 {
                        ms.push(elapsed);
                    }
                }
                ms.sort_by(f64::total_cmp);
                println!(
                    "cached={cached} construct_submit_screenshot changing_pan n=8 p50_ms={:.4} min_ms={:.4} max_ms={:.4}",
                    ms[4], ms[0], ms[7]
                );
            }
        }
    }
}