use super::*;
use deckcraft_model::chart::ChartType;
use deckcraft_model::style::ColorRef;
use deckcraft_model::text::TextBody;
use deckcraft_model::{Chart, Geom, Presentation, Shape, ShapeId, ShapeKind, ShapeStyle, Table, Xfrm};

fn deck_with(shapes: Vec<Shape>) -> Presentation {
    let mut p = Presentation::default();
    let s = std::sync::Arc::make_mut(&mut p.slides[0]);
    s.shapes = shapes;
    p
}

#[test]
fn blank_slide_renders_white_background() {
    let p = Presentation::default();
    let img = render_slide(&p, 0, &RenderOpts { scale: 0.25, ..Default::default() });
    assert_eq!((img.width, img.height), (240, 135));
    assert_eq!(img.pixel(5, 5), [255, 255, 255, 255]);
}

#[test]
fn shape_fill_uses_theme_accent() {
    let sh = Shape {
        id: ShapeId(500),
        xfrm: Some(Xfrm::new(100.0, 100.0, 200.0, 100.0)),
        style: Some(ShapeStyle::accent(deckcraft_color::SchemeSlot::Accent1)),
        ..Default::default()
    };
    let p = deck_with(vec![sh]);
    let img = render_slide(&p, 0, &RenderOpts { scale: 1.0, ..Default::default() });
    let accent = p.masters[0].theme.colors.get(deckcraft_color::SchemeSlot::Accent1);
    let px = img.pixel(200, 150);
    assert!((px[0] as i32 - accent.r as i32).abs() <= 2 && (px[2] as i32 - accent.b as i32).abs() <= 2, "{px:?} vs {accent:?}");
    assert_eq!(img.pixel(50, 50), [255, 255, 255, 255]);
}

#[test]
fn text_draws_ink() {
    let mut sh = Shape { id: ShapeId(501), xfrm: Some(Xfrm::new(0.0, 0.0, 960.0, 540.0)), text_box: true, ..Default::default() };
    let mut t = TextBody::from_text("HELLO WORLD");
    t.paragraphs[0].runs[0].props.size = Some(120.0);
    sh.text = Some(t);
    let p = deck_with(vec![sh]);
    let img = render_slide(&p, 0, &RenderOpts { scale: 0.5, ..Default::default() });
    let dark = img.pixels.as_chunks::<4>().0.iter().filter(|px| px[0] < 128).count();
    assert!(dark > 500, "dark pixels {dark}");
}

#[test]
fn every_preset_renders_without_panic() {
    let shapes: Vec<Shape> = deckcraft_geom::preset::CATALOG
        .iter()
        .enumerate()
        .map(|(i, pr)| Shape {
            id: ShapeId(1000 + i as u32),
            xfrm: Some(Xfrm::new((i % 16) as f64 * 60.0, (i / 16) as f64 * 55.0, 50.0, 45.0)),
            geom: Geom::preset(pr.name),
            style: Some(ShapeStyle::accent(deckcraft_color::SchemeSlot::Accent2)),
            ..Default::default()
        })
        .collect();
    let p = deck_with(shapes);
    let img = render_slide(&p, 0, &RenderOpts { scale: 1.0, edit: true, ..Default::default() });
    assert_eq!(img.width, 960);
}

#[test]
fn effects_tables_charts_render() {
    let mut sh = Shape {
        id: ShapeId(600),
        xfrm: Some(Xfrm::new(50.0, 50.0, 200.0, 100.0)),
        style: Some(ShapeStyle::accent(deckcraft_color::SchemeSlot::Accent1)),
        ..Default::default()
    };
    sh.effects = Some(deckcraft_model::Effects {
        outer_shadow: Some(deckcraft_model::style::Shadow {
            color: ColorRef::rgb(deckcraft_color::Rgba::BLACK),
            blur: 8.0,
            dist: 6.0,
            dir: 45.0,
            inner: false,
            sx: 1.0,
            sy: 1.0,
            kx: 0.0,
            ky: 0.0,
            align: String::new(),
            rotate_with_shape: false,
        }),
        glow: Some(deckcraft_model::style::Glow { color: ColorRef::rgb(deckcraft_color::Rgba::rgb(255, 200, 0)), radius: 6.0 }),
        soft_edge: Some(4.0),
        ..Default::default()
    });
    let mut t = Table::new(3, 3, 300.0, 30.0);
    t.cell_mut(0, 0).unwrap().text = TextBody::from_text("Head");
    let tbl = Shape { id: ShapeId(601), xfrm: Some(Xfrm::new(300.0, 50.0, 300.0, 90.0)), kind: ShapeKind::Table(t), ..Default::default() };
    let mut charts = vec![];
    for (i, k) in [
        ChartType::Column,
        ChartType::Bar,
        ChartType::Line,
        ChartType::Pie,
        ChartType::Doughnut,
        ChartType::Area,
        ChartType::Scatter,
        ChartType::StackedColumn,
    ]
    .iter()
    .enumerate()
    {
        charts.push(Shape {
            id: ShapeId(700 + i as u32),
            xfrm: Some(Xfrm::new(i as f64 * 110.0, 300.0, 100.0, 100.0)),
            kind: ShapeKind::Chart(Box::new(Chart::sample(*k))),
            ..Default::default()
        });
    }
    let mut all = vec![sh, tbl];
    all.extend(charts);
    let p = deck_with(all);
    let img = render_slide(&p, 0, &RenderOpts { scale: 1.0, ..Default::default() });
    // Shadow darkens below-right of the shape.
    let px = img.pixel(258, 156);
    assert!(px[0] < 250, "{px:?}");
}

#[test]
fn placeholder_prompts_only_in_edit_view() {
    let p = Presentation::default();
    let edit = render_slide(&p, 0, &RenderOpts { scale: 0.5, edit: true, ..Default::default() });
    let show = render_slide(&p, 0, &RenderOpts { scale: 0.5, ..Default::default() });
    let ink = |i: &Image| i.pixels.as_chunks::<4>().0.iter().filter(|px| px[0] < 200).count();
    assert!(ink(&edit) > 100);
    assert_eq!(ink(&show), 0);
}

#[test]
fn png_encodes() {
    let p = Presentation::default();
    let img = render_slide(&p, 0, &RenderOpts { scale: 0.1, ..Default::default() });
    let png = img.to_png();
    assert!(png.starts_with(&[0x89, b'P', b'N', b'G']));
    assert!(!img.to_jpeg(80).is_empty());
}

#[test]
fn crop_dest_math() {
    let r = crop_dest(Rect::new(0.0, 0.0, 100.0, 100.0), [0.5, 0.0, 0.0, 0.0]);
    assert!((r.x0 + 100.0).abs() < 1e-9 && (r.width() - 200.0).abs() < 1e-9);
    let r = crop_dest(Rect::new(0.0, 0.0, 100.0, 100.0), [f64::NAN, 2.0, -50.0, 0.0]);
    assert!(r.x0.is_finite() && r.y1.is_finite());
}

#[test]
fn custom_path_parse() {
    let p = parse_path("M 0 0 L 10 0 C 1 2 3 4 5 6 Q 1 1 2 2 Z garbage L x y");
    assert!(p.elements().len() >= 5);
    assert!(parse_path("").elements().is_empty());
}

#[test]
fn table_rows_of_zero_height_grow_to_fit_text() {
    // pandoc and python-pptx write `<a:tr h="0">`: the stored row height is only a minimum.
    let mut t = Table::new(3, 2, 300.0, 0.0);
    for (r, row) in [["Col A", "Col B"], ["1", "alpha"], ["2", "beta"]].iter().enumerate() {
        for (c, text) in row.iter().enumerate() {
            t.cell_mut(r, c).unwrap().text = TextBody::from_text(text);
        }
    }
    let tbl = Shape { id: ShapeId(610), xfrm: Some(Xfrm::new(100.0, 100.0, 300.0, 0.0)), kind: ShapeKind::Table(t.clone()), ..Default::default() };
    let p = deck_with(vec![tbl]);
    let ctx = deckcraft_model::resolve::Ctx::for_slide(&p, &p.slides[0]).unwrap();
    let hs = crate::table::row_heights(&ctx, &t, &deckcraft_text::NoFields);
    assert_eq!(hs.len(), 3);
    assert!(hs.iter().all(|h| *h > 10.0), "{hs:?}");
    let tops: Vec<f64> = crate::table::cell_rects(&t, &hs).iter().filter(|(_, c, _)| *c == 0).map(|(_, _, r)| r.y0).collect();
    assert!(tops.len() == 3 && tops.windows(2).all(|w| w[1] > w[0] + 10.0), "{tops:?}");
    // A taller stored height is kept.
    let mut tall = t;
    tall.rows[1].height = 200.0;
    assert_eq!(crate::table::row_heights(&ctx, &tall, &deckcraft_text::NoFields)[1], 200.0);
    // The PDF text layer gets every cell's text, rows one below the other.
    let placed = place_slide(&p, 0);
    let top = |s: &str| {
        let pt = placed.texts.iter().find(|pt| pt.body.text() == s).unwrap_or_else(|| panic!("no placed text {s:?}"));
        (pt.transform * kurbo::Point::new(0.0, pt.layout.lines[0].top)).y
    };
    assert!(top("Col A") < top("1") && top("1") < top("2"));
    assert!((top("alpha") - top("1")).abs() < 1.0 && (top("beta") - top("2")).abs() < 1.0);
    assert!(top("Col B") >= 100.0);
}

#[test]
fn blend_ends_match_the_slides_and_mixes_backdrops() {
    let sh = Shape {
        id: ShapeId(500),
        xfrm: Some(Xfrm::new(100.0, 100.0, 200.0, 100.0)),
        style: Some(ShapeStyle::accent(deckcraft_color::SchemeSlot::Accent1)),
        ..Default::default()
    };
    let mut p = deck_with(vec![sh.clone()]);
    let mut dark = (*p.slides[0]).clone();
    dark.background =
        Some(deckcraft_model::Background::Fill { fill: deckcraft_model::Fill::solid(ColorRef::rgb(deckcraft_color::Rgba::rgb(0, 0, 0))) });
    p.slides.push(std::sync::Arc::new(dark));
    let o = RenderOpts { scale: 0.5, ..Default::default() };
    let shapes = vec![(sh, false)];
    // At the ends the frame is the slide itself; the shape stays opaque throughout.
    assert_eq!(render_blend(&p, 0, 1, 1.0, &shapes, &[], &[], &o).pixels, render_slide(&p, 1, &o).pixels);
    let mid = render_blend(&p, 0, 1, 0.5, &shapes, &[], &[], &o);
    let px = mid.pixel(5, 5);
    assert!((px[0] as i32 - 128).abs() <= 3, "{px:?}");
    assert_eq!(mid.pixel(100, 75), render_slide(&p, 1, &o).pixel(100, 75));
    // Hostile input: bad indices and NaN never panic.
    assert_eq!(render_blend(&p, 0, 9, 0.5, &shapes, &[], &[], &o).width, 0);
    let _ = render_blend(&p, 0, 1, f64::NAN, &shapes, &[], &[], &o);
}

fn text_shape(id: u32, text: &str, x: f64, y: f64) -> Shape {
    let mut t = TextBody::from_text(text);
    for p in &mut t.paragraphs {
        for r in &mut p.runs {
            r.props.size = Some(40.0);
        }
    }
    Shape { id: ShapeId(id), xfrm: Some(Xfrm::new(x, y, 600.0, 120.0)), text_box: true, text: Some(t), ..Default::default() }
}

#[test]
fn morph_text_tokens_are_words_or_characters() {
    let p = Presentation::default();
    let rctx = Ctx::for_slide(&p, &p.slides[0]).unwrap();
    let s = text_shape(1, "Hello big  world\nHello", 0.0, 0.0);
    let l = deckcraft_text::layout(
        &rctx,
        &s,
        s.text.as_ref().unwrap(),
        &Opts { rect: Rect::new(0.0, 0.0, 600.0, 120.0), fields: &deckcraft_text::NoFields, prompt_color: None, no_shrink: false },
    );
    assert_eq!(morph_text::token_keys(&l, false), ["Hello", "big", "world", "Hello"]);
    assert_eq!(morph_text::token_keys(&l, true).concat(), "Hellobigworld".to_string() + "Hello");
    assert_eq!(morph_text::token_keys(&l, true).len(), 18);
}

#[test]
fn morph_text_ends_match_the_slides() {
    let from = Xfrm::new(100.0, 60.0, 600.0, 120.0);
    let to = Xfrm::new(200.0, 300.0, 600.0, 120.0);
    let mut p = deck_with(vec![text_shape(1, "Hello wide world", from.x, from.y)]);
    let mut b = (*p.slides[0]).clone();
    b.shapes = vec![text_shape(1, "world says Hello", to.x, to.y)];
    p.slides.push(std::sync::Arc::new(b));
    let o = RenderOpts { scale: 0.5, ..Default::default() };
    let frame = |t: f64| {
        let x = Xfrm::new(from.x + (to.x - from.x) * t, from.y + (to.y - from.y) * t, 600.0, 120.0);
        let mut sb = text_shape(10, "world says Hello", 0.0, 0.0);
        let mut sa = text_shape(11, "Hello wide world", 0.0, 0.0);
        sb.xfrm = Some(x);
        sa.xfrm = Some(x);
        let tm = TextMorph { old: ShapeId(11), new: ShapeId(10), from, to, chars: false, t };
        render_blend(&p, 0, 1, t, &[(sb, false), (sa, true)], &[tm], &[], &o)
    };
    // Warm up: faces load lazily (a background scan runs), so the first render may still fall back.
    let _ = (render_slide(&p, 0, &o), render_slide(&p, 1, &o), frame(0.5));
    let close = |a: &Image, b: &Image| a.pixels.iter().zip(&b.pixels).filter(|(x, y)| x.abs_diff(**y) > 8).count();
    let d0 = close(&frame(0.0), &render_slide(&p, 0, &o));
    assert!(d0 < 40, "start differs {d0}");
    let d1 = close(&frame(1.0), &render_slide(&p, 1, &o));
    assert!(d1 < 40, "end differs {d1}");
    // Halfway the shared words are on their way: ink between the two texts' rows.
    let mid = frame(0.5);
    let ink = (95..140).flat_map(|y| (0..480).map(move |x| (x, y))).filter(|&(x, y)| mid.pixel(x, y)[0] < 128).count();
    assert!(ink > 50, "ink {ink}");
}

/// A text box holding one run of `kind` (a field type, or plain text for `None`) saved as `saved`.
fn field_shape(kind: Option<&str>, saved: &str) -> Shape {
    let mut sh = text_shape(1, saved, 40.0, 40.0);
    if let (Some(k), Some(run)) = (kind, sh.text.as_mut().and_then(|t| t.paragraphs[0].runs.first_mut())) {
        run.kind = deckcraft_model::text::RunKind::Field { field: k.into() };
    }
    sh
}

#[test]
fn date_fields_show_the_date_in_their_format() {
    use deckcraft_text::datetime::DateTime;
    let fri = DateTime::new(2026, 10, 9, 20, 5, 7);
    let at = |p: &Presentation, now: DateTime| render_slide(p, 0, &RenderOpts { scale: 0.5, now: Some(now), ..Default::default() });
    let mut p = deck_with(vec![field_shape(Some("datetime1"), "1/1/2000")]);
    let _ = at(&p, fri); // faces load lazily
    // The field shows the date (it changes with the clock), not its saved text.
    let a = at(&p, fri);
    assert!(diff_px(&a, &at(&p, DateTime::new(2027, 3, 4, 0, 0, 0))) > 0);
    let shown = deck_with(vec![field_shape(None, "10/9/2026")]);
    assert_eq!(diff_px(&a, &at(&shown, fri)), 0, "datetime1 is M/D/YYYY");
    // Another slide's fixed date (a deck-wide Header & Footer text) doesn't replace it.
    p.header_footer.date_text = "Fixed on another slide".into();
    assert_eq!(diff_px(&a, &at(&p, fri)), 0);
    // Every type has its format; the run's language orders numeric dates.
    let f = Renderer::fields(&p, 0, &RenderOpts { now: Some(fri), ..Default::default() });
    assert_eq!(f.field_in("datetime4", Some("en-US")).as_deref(), Some("October 9, 2026"));
    assert_eq!(f.field_in("datetimeFigureOut", Some("en-GB")).as_deref(), Some("09/10/2026"));
    assert_eq!(f.field("datetime13").as_deref(), Some("8:05:07 PM"));
    assert_eq!(f.field("slidenum").as_deref(), Some("1"));
    // A date the app can't compute (no clock, unknown type, other-language names) keeps the saved text.
    assert_eq!(SlideFields { now: None, ..f }.field("datetime1"), None);
    let unknown = deck_with(vec![field_shape(Some("datetime99"), "Saved text")]);
    let plain = deck_with(vec![field_shape(None, "Saved text")]);
    assert_eq!(diff_px(&at(&unknown, fri), &at(&plain, fri)), 0);
    // An explicit override still wins.
    let o = RenderOpts { date_text: Some("Today".into()), now: Some(fri), ..Default::default() };
    assert_eq!(Renderer::fields(&p, 0, &o).field("datetime2").as_deref(), Some("Today"));
}

/// Channel values that differ noticeably between two images of the same size.
fn diff_px(a: &Image, b: &Image) -> usize {
    a.pixels.iter().zip(&b.pixels).filter(|(x, y)| x.abs_diff(**y) > 64).count()
}

/// Two 8×8 frames, red then blue, 100 ms each.
fn two_frame_gif() -> Vec<u8> {
    use image::{Delay, Frame, Rgba, RgbaImage};
    let frame = |c: [u8; 4]| Frame::from_parts(RgbaImage::from_pixel(8, 8, Rgba(c)), 0, 0, Delay::from_numer_denom_ms(100, 1));
    let mut out = Vec::new();
    image::codecs::gif::GifEncoder::new(&mut out).encode_frames([frame([255, 0, 0, 255]), frame([0, 0, 255, 255])]).expect("gif");
    out
}

#[test]
fn animated_gif_shows_the_frame_for_its_time() {
    let mut p = Presentation::default();
    let media = p.add_media("a.gif", "image/gif", two_frame_gif());
    let fill = deckcraft_model::style::PictureFill { media, ..Default::default() };
    let sh = Shape { id: ShapeId(600), xfrm: Some(Xfrm::new(0.0, 0.0, 960.0, 540.0)), kind: ShapeKind::Picture { fill }, ..Default::default() };
    std::sync::Arc::make_mut(&mut p.slides[0]).shapes = vec![sh];
    let at = |t: Option<f64>| {
        let times: Vec<(ShapeId, f64)> = t.map(|t| vec![(ShapeId(600), t)]).unwrap_or_default();
        render_slide(&p, 0, &RenderOpts { scale: 0.1, gif_times: &times, ..Default::default() }).pixel(48, 27)
    };
    let red = |px: [u8; 4]| px[0] > 200 && px[2] < 60;
    let blue = |px: [u8; 4]| px[2] > 200 && px[0] < 60;
    assert!(red(at(None)), "no time: the first frame, as exports draw it");
    assert!(red(at(Some(0.05))));
    assert!(blue(at(Some(0.15))));
    assert!(red(at(Some(0.25))), "it loops");
    let bytes = p.media(media).map(|m| m.data.clone()).expect("media");
    let adj = Default::default();
    assert_eq!(gif_frame(&bytes, &adj, 0.15).map(|f| f.0), Some(1));
    assert_eq!(gif_frame(&bytes, &adj, f64::NAN).map(|f| f.0), Some(0));
    assert!(gif_frame(&std::sync::Arc::new(b"\x89PNG".to_vec()), &adj, 0.0).is_none());
}

#[test]
fn morph_path_ends_match_the_slides() {
    let from = Xfrm::new(100.0, 100.0, 200.0, 200.0);
    let to = Xfrm::new(500.0, 150.0, 300.0, 150.0);
    let form = |id: u32, g: &str, x: Xfrm| Shape {
        id: ShapeId(id),
        xfrm: Some(x),
        geom: Geom::preset(g),
        style: Some(ShapeStyle::accent(deckcraft_color::SchemeSlot::Accent1)),
        ..Default::default()
    };
    let mut p = deck_with(vec![form(1, "ellipse", from)]);
    let mut b = (*p.slides[0]).clone();
    b.shapes = vec![form(1, "star5", to)];
    p.slides.push(std::sync::Arc::new(b));
    let o = RenderOpts { scale: 0.5, ..Default::default() };
    let frame = |t: f64| {
        let lerp = |a: f64, b: f64| a + (b - a) * t;
        let x = Xfrm::new(lerp(from.x, to.x), lerp(from.y, to.y), lerp(from.w, to.w), lerp(from.h, to.h));
        let pm = PathMorph { id: ShapeId(10), from: Geom::preset("ellipse"), from_box: from, to_box: to, t };
        render_blend(&p, 0, 1, t, &[(form(10, "star5", x), false)], &[], &[pm], &o)
    };
    // The morph splits the outlines into more curves, which flatten slightly differently: edge pixels
    // may differ a little, a different shape differs a lot.
    let differ = |a: &Image, b: &Image| a.pixels.iter().zip(&b.pixels).filter(|(x, y)| x.abs_diff(**y) > 60).count();
    // At the start the star is still the circle, at the end the star.
    let d0 = differ(&frame(0.0), &render_slide(&p, 0, &o));
    assert!(d0 < 40, "start differs {d0}");
    let d1 = differ(&frame(1.0), &render_slide(&p, 1, &o));
    assert!(d1 < 40, "end differs {d1}");
    // Without the morph the start would show the star.
    let star = render_blend(&p, 0, 1, 0.0, &[(form(10, "star5", from), false)], &[], &[], &o);
    assert!(differ(&star, &render_slide(&p, 0, &o)) > 400);
    // Halfway the shape is filled around the middle of its box.
    let mid = frame(0.5);
    let c = (from.center().to_vec2() + to.center().to_vec2()) * 0.5 * 0.5;
    assert_ne!(mid.pixel(c.x as u32, c.y as u32), [255, 255, 255, 255]);
}

#[test]
fn morph_path_fades_a_fill_only_one_side_has() {
    let bx = Xfrm::new(100.0, 100.0, 200.0, 200.0);
    let form = |id: u32, g: &str| Shape {
        id: ShapeId(id),
        xfrm: Some(bx),
        geom: Geom::preset(g),
        style: Some(ShapeStyle::accent(deckcraft_color::SchemeSlot::Accent1)),
        ..Default::default()
    };
    let mut p = deck_with(vec![form(1, "rect")]);
    let mut b = (*p.slides[0]).clone();
    b.shapes = vec![form(1, "line")];
    p.slides.push(std::sync::Arc::new(b));
    let o = RenderOpts { scale: 0.5, ..Default::default() };
    let at = |t: f64| {
        let pm = PathMorph { id: ShapeId(10), from: Geom::preset("rect"), from_box: bx, to_box: bx, t };
        // A point near the line but not on it: inside the shape all the way.
        render_blend(&p, 0, 1, t, &[(form(10, "line"), false)], &[], &[pm], &o).pixel(110, 90)
    };
    let (full, half, none) = (at(0.0), at(0.5), at(1.0));
    assert_eq!(none, [255, 255, 255, 255]);
    assert!(full[0] < 128, "{full:?}");
    // Halfway the fill is half there: between the full colour and the white slide.
    assert!(half[0] > full[0] + 40 && half[0] < 215, "{half:?} vs {full:?}");
}

#[test]
fn text_transform_unmirrors_flips() {
    // Asymmetric text rect in a 100×50 box: flips move the rect, never mirror the text.
    let tr = Rect::new(10.0, 0.0, 40.0, 50.0);
    let at = |x: Xfrm, p: Point| text_transform(x.affine(), tr, 0.0) * p;
    let near = |a: Point, b: Point| (a - b).hypot() < 1e-9;
    let base = Xfrm::new(0.0, 0.0, 100.0, 50.0);
    // flipH: the rect moves to 60..90 and the text still runs left to right.
    let h = Xfrm { flip_h: true, ..base };
    assert!(near(at(h, Point::new(10.0, 0.0)), Point::new(60.0, 0.0)));
    assert!(near(at(h, Point::new(40.0, 50.0)), Point::new(90.0, 50.0)));
    // flipV: the text is turned 180° in its (vertically mirrored) rect.
    let v = Xfrm { flip_v: true, ..base };
    assert!(near(at(v, Point::new(10.0, 0.0)), Point::new(40.0, 50.0)));
    assert!(near(at(v, Point::new(40.0, 50.0)), Point::new(10.0, 0.0)));
    // Both flips: the same as a 180° turn.
    let hv = Xfrm { flip_h: true, flip_v: true, ..base };
    let turned = Xfrm { rot: 180.0, ..base };
    for p in [Point::new(10.0, 0.0), Point::new(40.0, 50.0), Point::new(25.0, 10.0)] {
        assert!(near(at(hv, p), at(turned, p)));
    }
    // Unflipped and hostile input: plain transform, nothing NaN from the helper itself.
    assert_eq!(text_transform(base.affine(), tr, 0.0), base.affine());
    let _ = text_transform(h.affine(), Rect::new(f64::NAN, 0.0, f64::INFINITY, 1.0), f64::NAN);
}

/// Slide with text box `x` holding left-aligned, asymmetric text.
fn flipped_text(x: Xfrm, group: Option<Xfrm>) -> Image {
    let mut s = text_shape(1, "Fly 42 RJ", 0.0, 0.0);
    s.xfrm = Some(x);
    let s = match group {
        Some(g) => Shape {
            id: ShapeId(2),
            xfrm: Some(g),
            kind: ShapeKind::Group { children: vec![s], child: Xfrm::new(0.0, 0.0, 600.0, 120.0) },
            ..Default::default()
        },
        None => s,
    };
    render_slide(&deck_with(vec![s]), 0, &RenderOpts { scale: 0.5, ..Default::default() })
}

fn differing(a: &Image, b: &Image) -> usize {
    a.pixels.iter().zip(&b.pixels).filter(|(x, y)| x.abs_diff(**y) > 64).count()
}

#[test]
fn flipped_shapes_draw_readable_text() {
    let base = Xfrm::new(180.0, 200.0, 600.0, 120.0);
    let plain = flipped_text(base, None);
    // Warm up: faces load lazily, so the first render may still fall back.
    let plain = if differing(&plain, &flipped_text(base, None)) > 0 { flipped_text(base, None) } else { plain };
    let turned = flipped_text(Xfrm { rot: 180.0, ..base }, None);
    assert!(differing(&plain, &turned) > 200, "the comparisons below must mean something");
    // flipH: text as unflipped (the text box is symmetric). flipV and both: turned 180°.
    let d = differing(&plain, &flipped_text(Xfrm { flip_h: true, ..base }, None));
    assert!(d < 40, "flipH mirrored the text: {d}");
    let d = differing(&turned, &flipped_text(Xfrm { flip_v: true, ..base }, None));
    assert!(d < 40, "flipV mirrored the text: {d}");
    let d = differing(&turned, &flipped_text(Xfrm { flip_h: true, flip_v: true, ..base }, None));
    assert!(d < 40, "flipH+flipV: {d}");
    // Rotation then flipH: still the rotated text, not its mirror image.
    let rot = Xfrm { rot: 30.0, ..base };
    let d = differing(&flipped_text(rot, None), &flipped_text(Xfrm { flip_h: true, ..rot }, None));
    assert!(d < 40, "rotated flipH: {d}");
    // Groups: a flipped group's text isn't mirrored; a flipped child in a flipped group neither.
    let child = Xfrm::new(0.0, 0.0, 600.0, 120.0);
    let d = differing(&plain, &flipped_text(child, Some(Xfrm { flip_h: true, ..base })));
    assert!(d < 40, "group flipH: {d}");
    let d = differing(&plain, &flipped_text(Xfrm { flip_h: true, ..child }, Some(Xfrm { flip_h: true, ..base })));
    assert!(d < 40, "flipH child in flipH group: {d}");
    let d = differing(&turned, &flipped_text(child, Some(Xfrm { flip_v: true, ..base })));
    assert!(d < 40, "group flipV: {d}");
}

/// A text box with one run of `props` (40 pt).
fn run_deck(props: deckcraft_model::RunProps) -> Presentation {
    let mut sh = text_shape(1, "Linked text", 40.0, 40.0);
    if let Some(run) = sh.text.as_mut().and_then(|t| t.paragraphs[0].runs.first_mut()) {
        run.props = deckcraft_model::RunProps { size: Some(40.0), ..props };
    }
    deck_with(vec![sh])
}

#[test]
fn hyperlinks_draw_in_the_hyperlink_colour_underlined() {
    use deckcraft_model::RunProps;
    use deckcraft_model::text::{Action, Hyperlink};
    let o = RenderOpts { scale: 0.5, ..Default::default() };
    let px = |p: &Presentation| render_slide(p, 0, &o);
    let diff = |a: &Image, b: &Image| a.pixels.iter().zip(&b.pixels).filter(|(x, y)| x.abs_diff(**y) > 64).count();
    let link = Some(Hyperlink { action: Action::Url { url: "https://example.org".into() }, tooltip: String::new(), highlight_click: false });
    let hlink = Some(Fill::solid(ColorRef::scheme(deckcraft_color::SchemeSlot::Hlink)));
    let red = Some(Fill::solid(ColorRef::rgb(Rgba::rgb(200, 0, 0))));
    let _ = px(&run_deck(RunProps::default())); // faces load lazily
    let linked = px(&run_deck(RunProps { link: link.clone(), ..Default::default() }));
    assert!(diff(&linked, &px(&run_deck(RunProps::default()))) > 100, "a link doesn't look like plain text");
    // Exactly the theme's hyperlink colour, single underline.
    let styled = px(&run_deck(RunProps { fill: hlink, underline: Some("sng".into()), ..Default::default() }));
    assert_eq!(diff(&linked, &styled), 0);
    // A colour on the run itself wins; u="none" drops the underline.
    let own = px(&run_deck(RunProps { link: link.clone(), fill: red.clone(), underline: Some("none".into()), ..Default::default() }));
    assert_eq!(diff(&own, &px(&run_deck(RunProps { fill: red.clone(), ..Default::default() }))), 0);
    let own = px(&run_deck(RunProps { link, fill: red.clone(), ..Default::default() }));
    assert_eq!(diff(&own, &px(&run_deck(RunProps { fill: red, underline: Some("sng".into()), ..Default::default() }))), 0);
}

#[test]
fn a_linear_gradient_ramps_like_powerpoint() {
    // Black to white, left to right: PowerPoint draws 105 a quarter of the way and 186 half way
    // (linear-light mix, S-shaped), not 64 and 128.
    use deckcraft_model::style::{Fill, Gradient, GradientShape, GradientStop};
    let stop = |pos, c| GradientStop { pos, color: ColorRef::rgb(c) };
    let sh = Shape {
        id: ShapeId(700),
        xfrm: Some(Xfrm::new(0.0, 0.0, 800.0, 100.0)),
        fill: Some(Fill::Gradient(Gradient {
            stops: vec![stop(0.0, deckcraft_color::Rgba::rgb(0, 0, 0)), stop(1.0, deckcraft_color::Rgba::rgb(255, 255, 255))],
            shape: GradientShape::Linear { angle: 0.0, scaled: false },
            rotate_with_shape: true,
        })),
        line: Some(deckcraft_model::style::Line { fill: Some(Fill::None), ..Default::default() }),
        ..Default::default()
    };
    let p = deck_with(vec![sh]);
    let img = render_slide(&p, 0, &RenderOpts { scale: 1.0, ..Default::default() });
    for (x, want) in [(200, 105), (400, 186), (600, 238)] {
        let got = img.pixel(x, 50)[0] as i32;
        assert!((got - want).abs() <= 4, "x {x}: {got} vs {want}");
    }
}

#[test]
fn a_gradient_with_a_stop_off_the_end_stays_linear() {
    // Stops at 20 % and 100 %: PowerPoint blends linearly in sRGB (96 at 50 %, 175 at 75 %).
    use deckcraft_model::style::{Fill, Gradient, GradientShape, GradientStop};
    let stop = |pos, c| GradientStop { pos, color: ColorRef::rgb(c) };
    let sh = Shape {
        id: ShapeId(701),
        xfrm: Some(Xfrm::new(0.0, 0.0, 800.0, 100.0)),
        fill: Some(Fill::Gradient(Gradient {
            stops: vec![stop(0.2, deckcraft_color::Rgba::rgb(0, 0, 0)), stop(1.0, deckcraft_color::Rgba::rgb(255, 255, 255))],
            shape: GradientShape::Linear { angle: 0.0, scaled: false },
            rotate_with_shape: true,
        })),
        line: Some(deckcraft_model::style::Line { fill: Some(Fill::None), ..Default::default() }),
        ..Default::default()
    };
    let p = deck_with(vec![sh]);
    let img = render_slide(&p, 0, &RenderOpts { scale: 1.0, ..Default::default() });
    for (x, want) in [(400, 96), (600, 175)] {
        let got = img.pixel(x, 50)[0] as i32;
        assert!((got - want).abs() <= 4, "x {x}: {got} vs {want}");
    }
}

#[test]
fn a_shape_filled_with_the_background_shows_the_slide_background() {
    // `useBgFill`: PowerPoint paints the slide's background into the shape, laid out on the
    // slide. A white panel covers a black-to-grey background; a shape on it with the background
    // fill is a window onto that background.
    use deckcraft_model::style::{Fill, Gradient, GradientShape, GradientStop};
    let none = || Some(deckcraft_model::style::Line { fill: Some(Fill::None), ..Default::default() });
    let panel = Shape {
        id: ShapeId(710),
        xfrm: Some(Xfrm::new(0.0, 0.0, 960.0, 540.0)),
        fill: Some(Fill::solid(ColorRef::rgb(deckcraft_color::Rgba::rgb(255, 255, 255)))),
        line: none(),
        ..Default::default()
    };
    let window = Shape {
        id: ShapeId(711),
        xfrm: Some(Xfrm::new(100.0, 100.0, 760.0, 340.0)),
        fill: Some(Fill::Background),
        line: none(),
        ..Default::default()
    };
    let mut p = deck_with(vec![panel, window]);
    let stop = |pos, v| GradientStop { pos, color: ColorRef::rgb(deckcraft_color::Rgba::rgb(v, v, v)) };
    std::sync::Arc::make_mut(&mut p.slides[0]).background = Some(deckcraft_model::Background::Fill {
        fill: Fill::Gradient(Gradient {
            stops: vec![stop(0.0, 0), stop(0.5, 0), stop(1.0, 200)],
            shape: GradientShape::Linear { angle: 0.0, scaled: false },
            rotate_with_shape: true,
        }),
    });
    let img = render_slide(&p, 0, &RenderOpts { scale: 1.0, ..Default::default() });
    assert_eq!(img.pixel(50, 50)[0], 255, "the panel stays white outside the window");
    assert!(img.pixel(300, 270)[0] < 8, "the window shows the background's black half: {:?}", img.pixel(300, 270));
    // Laid out on the slide: three quarters across the slide is half way from black to grey.
    let v = img.pixel(720, 270)[0] as i32;
    assert!((v - 100).abs() <= 6, "{v}");
}

#[test]
fn a_background_is_laid_over_white() {
    // A background picture stretched into the bottom-right quarter (fillRect l=50% t=50%), and a
    // half-transparent colour: PowerPoint shows white around and under them, not transparency.
    use deckcraft_model::style::{Fill, PictureFill, PictureMode};
    let mut png = std::io::Cursor::new(Vec::new());
    image::DynamicImage::ImageRgb8(image::RgbImage::from_pixel(4, 4, image::Rgb([0, 0, 200]))).write_to(&mut png, image::ImageFormat::Png).unwrap();
    let mut p = deck_with(vec![]);
    let media = p.add_media("bg.png", "image/png", png.into_inner());
    let pf = PictureFill { media, mode: PictureMode::Stretch { fill_rect: [0.5, 0.5, 0.0, 0.0] }, ..Default::default() };
    std::sync::Arc::make_mut(&mut p.slides[0]).background = Some(deckcraft_model::Background::Fill { fill: Fill::Picture(pf) });
    let img = render_slide(&p, 0, &RenderOpts { scale: 0.5, ..Default::default() });
    assert_eq!(img.pixel(20, 20), [255, 255, 255, 255], "white where the picture doesn't reach");
    let q = img.pixel(400, 230);
    assert!(q[2] > 190 && q[0] < 10 && q[3] == 255, "{q:?}");
    let see_through = ColorRef::rgb(deckcraft_color::Rgba { r: 0, g: 0, b: 0, a: 128 });
    std::sync::Arc::make_mut(&mut p.slides[0]).background = Some(deckcraft_model::Background::Fill { fill: Fill::solid(see_through) });
    let img = render_slide(&p, 0, &RenderOpts { scale: 0.5, ..Default::default() });
    let g = img.pixel(20, 20);
    assert!(g[3] == 255 && (g[0] as i32 - 127).abs() <= 3, "half-transparent black over white is grey: {g:?}");
}

#[test]
fn colour_glyphs_paint_their_layers() {
    // A COLRv0 test font (crates/render/tests/fixtures): U+E000 is a red square with a blue
    // square in its middle, U+E001 a square in the text colour.
    deckcraft_fonts::FontDb::global().add_font(include_bytes!("../tests/fixtures/colr-squares.ttf").to_vec());
    let mut sh = Shape { id: ShapeId(720), xfrm: Some(Xfrm::new(0.0, 0.0, 400.0, 200.0)), text_box: true, ..Default::default() };
    let mut t = TextBody::from_text("\u{E000} \u{E001}");
    let props = &mut t.paragraphs[0].runs[0].props;
    props.size = Some(72.0);
    props.font = Some("DeckCraft Colr Squares".into());
    props.fill = Some(deckcraft_model::style::Fill::solid(ColorRef::rgb(deckcraft_color::Rgba::rgb(0, 160, 0))));
    sh.text = Some(t);
    let p = deck_with(vec![sh]);
    let img = render_slide(&p, 0, &RenderOpts { scale: 1.0, ..Default::default() });
    let count = |f: &dyn Fn(&[u8; 4]) -> bool| img.pixels.as_chunks::<4>().0.iter().filter(|px| f(px)).count();
    let red = count(&|p| p[0] > 230 && p[1] < 30 && p[2] < 30);
    let blue = count(&|p| p[0] < 30 && p[1] < 30 && p[2] > 230);
    let green = count(&|p| p[0] < 30 && p[1] > 140 && p[1] < 180 && p[2] < 30);
    // 72 pt squares: the blue one is 40 % of the side (16 % of the area).
    assert!(red > 2500 && blue > 500, "red {red} blue {blue}");
    let share = blue as f64 / (red + blue) as f64;
    assert!((share - 0.16).abs() < 0.03, "blue share {share}");
    // The text-colour glyph is as big as the other square.
    assert!((green as f64 / (red + blue) as f64 - 1.0).abs() < 0.1, "green {green} vs {}", red + blue);
}

#[test]
fn a_text_gradient_starts_over_on_every_line() {
    // PowerPoint fills each line of gradient text with the whole gradient, spanning that line
    // (black at the top of every line to white at its bottom), not the text box.
    use deckcraft_model::style::{Fill, Gradient, GradientShape, GradientStop};
    let stop = |pos, v| GradientStop { pos, color: ColorRef::rgb(deckcraft_color::Rgba::rgb(v, v, v)) };
    let mut sh = Shape { id: ShapeId(730), xfrm: Some(Xfrm::new(0.0, 0.0, 600.0, 500.0)), text_box: true, ..Default::default() };
    let mut t = TextBody::from_text("HHHH\nHHHH");
    for p in &mut t.paragraphs {
        let props = &mut p.runs[0].props;
        props.size = Some(80.0);
        props.fill = Some(Fill::Gradient(Gradient {
            stops: vec![stop(0.0, 0), stop(1.0, 255)],
            shape: GradientShape::Linear { angle: 90.0, scaled: false },
            rotate_with_shape: true,
        }));
    }
    sh.text = Some(t);
    let p = deck_with(vec![sh]);
    let img = render_slide(&p, 0, &RenderOpts { scale: 1.0, ..Default::default() });
    // Ink rows (any pixel not white), grouped into the two lines.
    let ink = |y: u32| (0..600).any(|x| img.pixel(x, y)[0] < 250);
    let mut bands: Vec<(u32, u32)> = vec![];
    for y in 0..500 {
        if ink(y) {
            match bands.last_mut() {
                Some(b) if b.1 + 1 == y => b.1 = y,
                _ => bands.push((y, y)),
            }
        }
    }
    assert_eq!(bands.len(), 2, "{bands:?}");
    // The darkest ink in the first rows of each line.
    let top = |b: (u32, u32)| (b.0..b.0 + 6).flat_map(|y| (0..600).map(move |x| (x, y))).map(|(x, y)| img.pixel(x, y)[0]).min().unwrap();
    let (a, b) = (top(bands[0]), top(bands[1]));
    assert!(a < 140 && (a as i32 - b as i32).abs() < 25, "line tops {a} and {b}: the second line starts dark again");
    // ...and each line ends light.
    let bottom = |b: (u32, u32)| (b.1 - 5..=b.1).flat_map(|y| (0..600).map(move |x| (x, y))).map(|(x, y)| img.pixel(x, y)[0]).min().unwrap();
    for band in bands {
        assert!(bottom(band) > 150, "line {band:?} ends at {}", bottom(band));
    }
}