//! The retained renderer: every partial render must match a full render of the same view.

use std::sync::{Arc, Once};

use figcraft_color::{Color, Paint};
use figcraft_doc::{Document, Effect, EffectKind, Node, NodeId, NodeKind, Shadow, TextAutoResize, TextData};
use figcraft_geom::Affine;

use crate::{Options, Pixmap, Retained, View, Work, render_view, retained::snap};

/// System fonts load once, before any render here, so text has glyphs and fonts never change
/// mid-test (a font change makes the next render full).
fn fonts() {
    static ONCE: Once = Once::new();
    ONCE.call_once(figcraft_text::scan_system_fonts);
}

struct Scene {
    doc: Arc<Document>,
    page: NodeId,
    rect: NodeId,
    text: NodeId,
    frame: NodeId,
    child: NodeId,
}

fn solid(n: &mut Node, hex: &str) {
    n.fills = vec![Paint::solid(Color::from_hex(hex).unwrap())];
}

/// Shapes, a clipping frame with children, a group with a drop shadow and fixed-width text; with
/// `cut_sensitive`, also layers whose look depends on where a render cuts them (inner shadow and
/// noise, a background blur). A full render cuts those at the view's edge, so tests compare them
/// only in views that contain them whole.
fn scene(cut_sensitive: bool) -> Scene {
    fonts();
    let mut d = Document::new("retained");
    let page = d.first_page().unwrap();
    let rect = d.create(page, NodeKind::Rectangle, "R", 20.0, 20.0, 80.0, 50.0).unwrap();
    solid(d.get_mut(rect).unwrap(), "E03030");
    let ell = d.create(page, NodeKind::Ellipse { start: 0.0, sweep: std::f64::consts::TAU, inner: 0.0 }, "E", 140.0, 30.0, 60.0, 60.0).unwrap();
    solid(d.get_mut(ell).unwrap(), "3070E0");
    let frame = d.create(page, NodeKind::Frame, "F", 40.0, 120.0, 200.0, 120.0).unwrap();
    let child = d.create(frame, NodeKind::Rectangle, "C", 150.0, 20.0, 90.0, 40.0).unwrap();
    solid(d.get_mut(child).unwrap(), "20A060");
    let group = d.create(page, NodeKind::Group, "G", 280.0, 40.0, 60.0, 60.0).unwrap();
    let g1 = d.create(group, NodeKind::Rectangle, "G1", 0.0, 0.0, 60.0, 60.0).unwrap();
    solid(d.get_mut(g1).unwrap(), "F0B020");
    d.get_mut(group)
        .unwrap()
        .effects
        .push(Effect { kind: EffectKind::DropShadow(Shadow { offset: (12.0, 16.0), radius: 6.0, ..Shadow::default() }), visible: true });
    let mut td = TextData::new("A line of text that overflows its box");
    td.auto_resize = TextAutoResize::None;
    td.style.font_size = 14.0;
    let text = d.create(page, NodeKind::Text(td), "T", 20.0, 270.0, 60.0, 20.0).unwrap();
    if cut_sensitive {
        let inner = d.create(page, NodeKind::Rectangle, "Inner", 180.0, 150.0, 70.0, 50.0).unwrap();
        solid(d.get_mut(inner).unwrap(), "FFFFFF");
        d.get_mut(inner).unwrap().effects.push(Effect::inner_shadow());
        d.get_mut(inner).unwrap().effects.push(Effect {
            kind: EffectKind::Noise(figcraft_doc::Noise { size: 1.0, density: 0.3, color: Color::BLACK, ..Default::default() }),
            visible: true,
        });
        let glass = d.create(page, NodeKind::Rectangle, "Glass", 120.0, 280.0, 120.0, 40.0).unwrap();
        d.get_mut(glass).unwrap().fills = vec![Paint::solid(Color::new(1.0, 1.0, 1.0, 0.3))];
        d.get_mut(glass).unwrap().effects.push(Effect { kind: EffectKind::BackgroundBlur(figcraft_doc::Blur::uniform(8.0)), visible: true });
    }
    Scene { doc: Arc::new(d), page, rect, text, frame, child }
}

fn view(x: f64, y: f64, scale: f64) -> View {
    View { origin: (x, y), scale, width: 300, height: 220 }
}

fn edit(doc: &Arc<Document>, f: impl FnOnce(&mut Document)) -> Arc<Document> {
    let mut d = (**doc).clone();
    f(&mut d);
    Arc::new(d)
}

/// Render through `r` and check the image against a full render of the same (snapped) view.
fn check(r: &mut Retained, doc: &Arc<Document>, page: NodeId, v: &View) -> Work {
    let (shown, pix, work) = r.render(doc, page, v, &Options::default()).unwrap();
    let pix = pix.clone();
    let key = |v: &View| (v.origin, v.scale, v.width, v.height);
    if let Some((snapped, _)) = snap(v) {
        assert_eq!(key(&shown), key(&snapped), "the snapped view is what's shown");
    }
    let full = render_view(doc, page, &shown, &Options::default()).unwrap();
    assert_same(&pix, &full, &format!("{work:?}"));
    work
}

/// Equal up to anti-aliasing: a part rendered on its own sees its paths translated by a whole
/// number of pixels, and float rounding can move an edge sample (a fraction of one pixel's
/// coverage along a curve). Stale or missing areas differ by whole colours, over many pixels.
pub(crate) fn assert_same(a: &Pixmap, b: &Pixmap, what: &str) {
    assert_eq!((a.width(), a.height()), (b.width(), b.height()));
    let (mut slight, mut big, mut first) = (0usize, 0usize, None);
    for (i, (x, y)) in a.data().iter().zip(b.data()).enumerate() {
        let d = x.abs_diff(*y);
        slight += usize::from(d > 2);
        big += usize::from(d > 96);
        if d > 2 && first.is_none() {
            first = Some(((i / 4) as u32 % a.width(), (i / 4) as u32 / a.width(), d));
        }
    }
    assert!(slight <= 200 && big == 0, "{what}: partial render differs from a full one ({slight} channels over 2, {big} over 96, first {first:?})");
}

fn partial(w: Work) -> bool {
    matches!(w, Work::Partial { .. })
}

#[test]
fn unchanged_view_is_reused() {
    let s = scene(false);
    let mut r = Retained::default();
    assert_eq!(check(&mut r, &s.doc, s.page, &view(0.0, 0.0, 1.0)), Work::Full);
    assert_eq!(check(&mut r, &s.doc, s.page, &view(0.0, 0.0, 1.0)), Work::Reused);
    // A sub-pixel move of the view stays on the same pixel grid.
    assert_eq!(check(&mut r, &s.doc, s.page, &view(0.3, 0.2, 1.0)), Work::Reused);
}

#[test]
fn pans_render_only_the_uncovered_strips() {
    let s = scene(false);
    let mut r = Retained::default();
    check(&mut r, &s.doc, s.page, &view(0.0, 0.0, 1.0));
    for (x, y) in [(37.0, 0.0), (37.0, 23.0), (-12.5, 41.0), (40.0, 80.0), (10.0, 30.0), (0.0, 0.0)] {
        eprintln!("pan to {x} {y}");
        let w = check(&mut r, &s.doc, s.page, &view(x, y, 1.0));
        assert!(partial(w), "pan to ({x}, {y}): {w:?}");
    }
    // At another zoom too (the grid is that zoom's).
    check(&mut r, &s.doc, s.page, &view(10.0, 10.0, 1.7));
    assert!(partial(check(&mut r, &s.doc, s.page, &view(25.0, -8.0, 1.7))));
    // A jump further than the view renders it whole.
    assert_eq!(check(&mut r, &s.doc, s.page, &view(2000.0, 0.0, 1.7)), Work::Full);
}

#[test]
fn edits_render_only_what_changed() {
    let s = scene(false);
    let mut r = Retained::default();
    let v = view(0.0, 0.0, 1.0);
    check(&mut r, &s.doc, s.page, &v);
    let moved = edit(&s.doc, |d| d.get_mut(s.rect).unwrap().transform = Affine::translate((60.0, 40.0)));
    let w = check(&mut r, &moved, s.page, &v);
    let Work::Partial { pixels } = w else { panic!("move: {w:?}") };
    assert!(pixels < 300 * 220 / 4, "only around the layer: {pixels}");
    let recolored = edit(&moved, |d| solid(d.get_mut(s.child).unwrap(), "000000"));
    assert!(partial(check(&mut r, &recolored, s.page, &v)));
    // Out of the clipping frame and back.
    let out = edit(&recolored, |d| d.get_mut(s.child).unwrap().transform = Affine::translate((180.0, 90.0)));
    assert!(partial(check(&mut r, &out, s.page, &v)));
    let hidden = edit(&out, |d| d.get_mut(s.child).unwrap().visible = false);
    assert!(partial(check(&mut r, &hidden, s.page, &v)));
    let removed = edit(&hidden, |d| d.remove(s.child).unwrap());
    assert!(partial(check(&mut r, &removed, s.page, &v)));
    let added = edit(&removed, |d| {
        let k = d.create(s.frame, NodeKind::Ellipse { start: 0.0, sweep: std::f64::consts::TAU, inner: 0.0 }, "K", 10.0, 10.0, 30.0, 30.0).unwrap();
        solid(d.get_mut(k).unwrap(), "8040C0");
    });
    assert!(partial(check(&mut r, &added, s.page, &v)));
    // Undo: back to an older version of the document.
    assert!(partial(check(&mut r, &s.doc, s.page, &v)));
}

#[test]
fn edits_under_and_beside_effects_match() {
    let s = scene(true);
    let mut r = Retained::default();
    // Holds the inner shadow + noise layer (180, 150) and the background blur (120, 280) whole.
    let v = view(0.0, 100.0, 1.0);
    check(&mut r, &s.doc, s.page, &v);
    // Under the background blur, then across the inner shadow + noise layer.
    let under = edit(&s.doc, |d| d.get_mut(s.rect).unwrap().transform = Affine::translate((150.0, 260.0)));
    assert!(partial(check(&mut r, &under, s.page, &v)));
    // Panning the blur (over the red layer) in from the view's edge, where a full render cut its
    // backdrop off (so only the view after it compares).
    let mut fresh = Retained::default();
    assert_eq!(fresh.render(&under, s.page, &view(0.0, 75.0, 1.0), &Options::default()).map(|r| r.2), Some(Work::Full));
    assert!(partial(check(&mut fresh, &under, s.page, &v)));
    let across = edit(&under, |d| d.get_mut(s.rect).unwrap().transform = Affine::translate((200.0, 170.0)));
    assert!(partial(check(&mut r, &across, s.page, &v)));
    let beside = edit(&across, |d| d.get_mut(s.rect).unwrap().transform = Affine::translate((10.0, 110.0)));
    assert!(partial(check(&mut r, &beside, s.page, &v)));
    // A child of a group with a drop shadow: the shadow moves too.
    let g1 = s.doc.find_by_name("G1", None)[0];
    let v = View { origin: (260.0, 0.0), scale: 1.0, width: 300, height: 220 };
    check(&mut r, &beside, s.page, &v);
    let shadowed = edit(&beside, |d| d.get_mut(g1).unwrap().transform = Affine::translate((30.0, 20.0)));
    assert!(partial(check(&mut r, &shadowed, s.page, &v)));
    let shadowed2 = edit(&shadowed, |d| d.get_mut(g1).unwrap().transform = Affine::translate((10.0, 60.0)));
    assert!(partial(check(&mut r, &shadowed2, s.page, &v)));
}

#[test]
fn text_and_mask_edits_match() {
    let s = scene(false);
    let mut r = Retained::default();
    let v = view(0.0, 120.0, 1.5);
    check(&mut r, &s.doc, s.page, &v);
    // Longer text overflows further than its box.
    let longer = edit(&s.doc, |d| {
        if let NodeKind::Text(t) = &mut d.get_mut(s.text).unwrap().kind {
            t.characters = "Overflowing text, much longer than before, runs on and on".into();
        }
    });
    assert!(partial(check(&mut r, &longer, s.page, &v)));
    // Pans whose new strips hold only the overflowing part of the text.
    for x in [30.0, 60.0, 90.0] {
        assert!(partial(check(&mut r, &longer, s.page, &View { origin: (x, 120.0), ..v.clone() })));
    }
    check(&mut r, &longer, s.page, &v);
    // A mask clips the layers above it, wherever they are.
    let masked = edit(&longer, |d| {
        let m = d.create(s.frame, NodeKind::Rectangle, "M", 0.0, 0.0, 60.0, 60.0).unwrap();
        d.reorder(m, 0).unwrap();
        d.get_mut(m).unwrap().is_mask = true;
    });
    check(&mut r, &masked, s.page, &v);
    let unmasked = edit(&masked, |d| {
        let m = d.find_by_name("M", None)[0];
        d.get_mut(m).unwrap().is_mask = false;
    });
    check(&mut r, &unmasked, s.page, &v);
}

#[test]
fn zoom_page_and_options_render_full() {
    let s = scene(false);
    let mut r = Retained::default();
    let v = view(0.0, 0.0, 1.0);
    check(&mut r, &s.doc, s.page, &v);
    assert_eq!(check(&mut r, &s.doc, s.page, &view(0.0, 0.0, 1.25)), Work::Full);
    // Page background: the whole page changes.
    let bg = edit(&s.doc, |d| {
        if let NodeKind::Page { background, .. } = &mut d.get_mut(s.page).unwrap().kind {
            *background = Color::BLACK;
        }
    });
    assert_eq!(check(&mut r, &bg, s.page, &view(0.0, 0.0, 1.25)), Work::Full);
    // Another page.
    let two = edit(&bg, |d| {
        d.add_page("Two");
    });
    let p2 = two.pages[1];
    check(&mut r, &two, s.page, &view(0.0, 0.0, 1.25));
    assert_eq!(check(&mut r, &two, p2, &view(0.0, 0.0, 1.25)), Work::Full);
    // Outline mode.
    let (_, _, w) = r.render(&two, p2, &view(0.0, 0.0, 1.25), &Options { outline_mode: true, ..Default::default() }).unwrap();
    assert_eq!(w, Work::Full);
}

#[test]
fn junk_views_never_panic() {
    let s = scene(false);
    let mut r = Retained::default();
    for v in [view(f64::NAN, 0.0, 1.0), view(0.0, 0.0, f64::INFINITY), view(1e300, -1e300, 1.0), view(0.0, 0.0, 0.0), view(0.0, 0.0, 1.0)] {
        let _ = r.render(&s.doc, s.page, &v, &Options::default());
    }
    let tiny = View { origin: (0.0, 0.0), scale: 1.0, width: 0, height: 0 };
    assert!(r.render(&s.doc, s.page, &tiny, &Options::default()).is_some());
}

#[test]
fn overflowing_text_is_drawn_while_its_box_is_out_of_view() {
    fonts();
    let mut d = Document::new("overflow");
    let page = d.first_page().unwrap();
    // An auto-width box whose stored width is stale (a file saved where fonts measured narrower):
    // one line, far wider than the box.
    let mut td = TextData::new("Overflowing far to the right of a one pixel box");
    td.auto_resize = TextAutoResize::WidthAndHeight;
    td.style.font_size = 16.0;
    let t = d.create(page, NodeKind::Text(td), "T", 100.0, 10.0, 1.0, 20.0).unwrap();
    let Some((layout, _)) = figcraft_text::layout_node(d.node(t).unwrap()) else { return };
    if layout.glyphs.is_empty() || layout.width < 120.0 {
        return; // no fonts on this machine
    }
    // The box (x 100..101) is left of the view; the glyphs run on into it.
    let v = View { origin: (150.0, 0.0), scale: 1.0, width: 100, height: 40 };
    let pix = render_view(&d, page, &v, &Options { background: Some(Color::WHITE), ..Default::default() }).unwrap();
    let dark = pix.data().as_chunks::<4>().0.iter().filter(|c| c[0] < 128).count();
    assert!(dark > 20, "glyphs drawn: {dark}");
}