//! PDF → Document (hayro-interpret device that builds a VectorCraft node tree).

use std::collections::HashMap;
use std::sync::{Arc, Mutex};

use hayro_interpret::font::Glyph;
use hayro_interpret::hayro_cmap::BfString;
use hayro_interpret::pattern::{Pattern, TilingPattern};
use hayro_interpret::{
    CacheKey, ClipPath, Context, Device, GlyphDrawMode, Image, ImageData, InterpreterCache, InterpreterSettings, InterpreterWarning, LumaData,
    MaskType, PathDrawMode, SoftMask, StrokeProps, interpret_page,
};
use hayro_syntax::object::Name;
use kurbo::{Affine, BezPath, Rect, Shape};
use vectorcraft_color::{BlendMode, Color, Paint, Swatch};
use vectorcraft_doc::{
    Appearance, AppearanceItem, Artboard, ColorMode, Dash, Document, FillLayer, ImageBlob, ImageObject, Knockout, LayerColor, LineCap, LineJoin,
    Node, NodeId, NodeKind, OpacityMask, PatternDef, StrokeLayer,
};
use vectorcraft_geom::{FillRule, PathData};

use crate::import_color::{Colors, Native};
use crate::import_mask::{MaskSpec, contains, is_rectangle, luminance, mask_spec};
use crate::import_scan::{Ocgs, Scan, all_on, hides_forms, scan_page};
use crate::import_shading::{clipped, extend_clip, fold_stop_opacity, mesh_shading, shading_gradient};
use crate::import_text::{Families, Look, Placement, TextLine};
use crate::{CropTo, ImportOptions, ImportReport, PdfError, TextAs};

/// The name of the paths text imports as.
const TEXT_OUTLINES: &str = "<Text Outlines>";
/// The deepest soft masks, patterns and type 3 glyphs are read within each other.
const MAX_NESTED: u32 = 8;
/// A tiling pattern read this many times with the same art is taken to always draw it.
const PATTERN_REUSE: u32 = 16;

/// Import a PDF (or PDF-compatible `.ai`) with default options.
pub fn import(bytes: &[u8]) -> Result<Document, PdfError> {
    import_with_report(bytes, &ImportOptions::default()).map(|r| r.document)
}

/// A layer of the imported document, in paint order.
enum Slot {
    /// A page's art outside optional content groups.
    Page(Box<Node>),
    /// An optional content group (index into [`Ocgs::list`]).
    Group(usize),
}

/// Import a PDF, returning the document plus warnings about content that was approximated or skipped.
pub fn import_with_report(bytes: &[u8], opts: &ImportOptions) -> Result<ImportReport, PdfError> {
    let original = crate::pages::open(bytes, opts.password.as_deref())?;
    let picked = crate::pages::picked(opts, original.pages().len())?;
    let mut ocgs = Ocgs::read(&original);
    let route = opts.layers && !ocgs.list.is_empty();
    // Content that is off imports as hidden layers: an update of the file turns every group on
    // (unless a form is hidden by its own group: its art couldn't be told apart).
    let hide = route && ocgs.any_off();
    let turned_on = (hide && !picked.iter().filter_map(|&n| original.pages().get(n)).any(|p| hides_forms(p, &mut ocgs)))
        .then(|| all_on(bytes, &original))
        .flatten()
        .and_then(|b| crate::pages::open(&b, opts.password.as_deref()).ok())
        .filter(|p| Ocgs::read(p).list.is_empty());
    let mut notes = vec![];
    if hide && turned_on.is_none() {
        notes.push("the art of hidden layers couldn't be read and was left out".to_string());
    }
    let all_on = turned_on.is_some();
    let pdf = turned_on.unwrap_or(original);
    let pages = pdf.pages();

    let sink: Arc<Mutex<Vec<String>>> = Arc::default();
    let sink2 = sink.clone();
    let settings = InterpreterSettings {
        warning_sink: Arc::new(move |w| {
            let msg = match w {
                InterpreterWarning::UnsupportedFont => "a font could not be read; its text was skipped",
                InterpreterWarning::ImageDecodeFailure => "an image could not be decoded and was skipped",
            };
            if let Ok(mut v) = sink2.lock()
                && !v.iter().any(|x| x == msg)
            {
                v.push(msg.to_string());
            }
        }),
        render_annotations: false,
        ..Default::default()
    };

    let mut doc = Document::new(1.0, 1.0);
    doc.title = "Imported PDF".into();
    doc.artboards.clear();
    doc.layers.clear();
    let taken: Vec<String> = doc.swatches_iter().map(|s| s.name.clone()).chain(doc.swatch_groups.iter().map(|g| g.name.clone())).collect();
    let mut b = Builder::new(doc.peek_next_id(), Colors::new(&pdf, taken.clone()), opts.text_as, route);
    b.taken = taken;
    b.warnings = notes;
    let cache = InterpreterCache::new();
    let mut x = 0.0;
    // Every page only a placeholder (text) over private data: the file's art isn't in its PDF part.
    let mut placeholder = true;
    let mut slots: Vec<Slot> = vec![];
    let mut group_art: HashMap<usize, Vec<Arc<Node>>> = HashMap::new();
    for (i, &number) in picked.iter().enumerate() {
        let Some(page) = pages.get(number) else { continue };
        // The chosen box sits at (x, 0); the page draws round it.
        let (init, frame) = crate::pages::frame(page, opts.crop);
        let mut ab = Rect::new(x, 0.0, x + frame.width(), frame.height());
        let xf = Affine::translate((x - frame.x0, -frame.y0)) * init;
        let mut ctx = Context::new(xf, ab, &cache, pdf.xref(), settings.clone());
        b.page = ab;
        let scan = scan_page(page, &mut ocgs, all_on, &mut b.fonts);
        b.begin_page(scan);
        interpret_page(page, &mut ctx, &mut b);
        let mut parts = b.end_page();
        // A file with several artboards writes, on each page, the art of its neighbours that
        // reaches into the page's box: art lying wholly outside this page is theirs (each page
        // draws it shifted by its own artboard spacing), so keep it only where it belongs.
        if picked.len() > 1 {
            for (_, art) in &mut parts {
                art.retain(|n| n.visual_bounds().is_none_or(|r| r.x0 <= ab.x1 && r.x1 >= ab.x0 && r.y0 <= ab.y1 && r.y1 >= ab.y0));
            }
            parts.retain(|(_, art)| !art.is_empty());
        }
        let children: Vec<Arc<Node>> = parts.iter().flat_map(|(_, v)| v.iter().cloned()).collect();
        placeholder &= crate::pages::has_private_data(page) && only_text(&children);
        let mut right = ab.x1;
        if opts.crop == CropTo::Bounding
            && let Some(art) = vectorcraft_doc::live::nodes_bounds(&children)
        {
            right = right.max(art.x1);
            ab = art;
        }
        x = right + opts.artboard_gap;
        doc.artboards.push(Artboard {
            id: i as u32 + 1,
            name: format!("Artboard {}", i + 1),
            rect: ab,
            show_center_mark: false,
            show_cross_hairs: false,
        });
        let page_layer = |b: &mut Builder<'_>, art: Vec<Arc<Node>>| {
            let mut layer = Node::layer(b.id(), &format!("Page {}", number + 1), LayerColor::Preset((i % 27) as u8));
            if let NodeKind::Layer { children: c, .. } = &mut layer.kind {
                *c = art;
            }
            Slot::Page(Box::new(layer))
        };
        if parts.is_empty() {
            slots.push(page_layer(&mut b, vec![]));
        }
        for (key, art) in parts {
            match key {
                None => slots.push(page_layer(&mut b, art)),
                Some(g) => {
                    let into = group_art.entry(g).or_insert_with(|| {
                        slots.push(Slot::Group(g));
                        vec![]
                    });
                    into.extend(art);
                }
            }
        }
    }
    if placeholder {
        return Err(PdfError::PlaceholderOnly);
    }
    for (n, slot) in slots.into_iter().enumerate() {
        let layer = match slot {
            Slot::Page(l) => *l,
            Slot::Group(g) => {
                let Some(ocg) = ocgs.list.get(g) else { continue };
                let mut l = Node::layer(b.id(), &ocg.name, LayerColor::Preset((n % 27) as u8));
                (l.visible, l.locked) = (ocg.on, ocg.locked);
                if let NodeKind::Layer { children, printable, .. } = &mut l.kind {
                    *children = group_art.remove(&g).unwrap_or_default();
                    *printable = ocg.print;
                }
                l
            }
        };
        doc.layers.push(Arc::new(layer));
    }
    for (k, blob) in b.images.drain() {
        doc.images.insert(k, blob);
    }
    // A file painted mostly in CMYK opens as a CMYK document (with CMYK default swatches).
    if b.colors.cmyk_document() {
        doc.color_mode = ColorMode::Cmyk;
        (doc.swatches, doc.swatch_groups) = vectorcraft_color::default_swatches(ColorMode::Cmyk.model());
    }
    doc.swatches.extend(b.colors.swatches());
    // Tiling patterns are pattern swatches.
    for p in b.patterns.drain(..) {
        doc.swatches.push(Swatch {
            name: p.name.clone(),
            paint: Paint::Pattern { pattern: p.name.clone(), xf: Affine::IDENTITY },
            global: false,
            spot: false,
        });
        doc.patterns.push(p);
    }
    if b.colors.mixed {
        b.warn("colours mixing several inks (DeviceN) were imported as RGB");
    }
    if !b.missing_fonts.is_empty() {
        let list = b.missing_fonts.join(", ");
        b.warn(&format!("fonts that aren't available show in the fallback font until they are: {list}"));
    }
    doc.fix_next_id();
    doc.reserve_ids(b.next);

    let mut warnings = b.warnings;
    if let Ok(v) = sink.lock() {
        for w in v.iter() {
            if !warnings.contains(w) {
                warnings.push(w.clone());
            }
        }
    }
    Ok(ImportReport { document: doc, warnings, native: crate::editing::editing_in(&pdf) })
}

/// Is this art text and nothing else (in groups and clips), with some text?
fn only_text(nodes: &[Arc<Node>]) -> bool {
    fn walk(nodes: &[Arc<Node>], text: &mut bool) -> bool {
        nodes.iter().all(|n| match &n.kind {
            NodeKind::Path { clipping: true, .. } => true,
            NodeKind::Path { .. } if n.name.as_deref() == Some(TEXT_OUTLINES) => {
                *text = true;
                true
            }
            NodeKind::Text(_) => {
                *text = true;
                true
            }
            NodeKind::Group { children, .. } => walk(children, text),
            _ => false,
        })
    }
    let mut text = false;
    walk(nodes, &mut text) && text
}

/// Decoded RGBA pixels, width, height and hayro's scale factors.
type Decoded = (Vec<u8>, u32, u32, (f32, f32));

enum FrameKind {
    Root,
    /// A clip group whose clip path node is stored here.
    Clip(Box<Node>),
    /// A clip that was redundant (covers the page); children go straight to the parent.
    Skip,
    Group {
        opacity: f32,
        blend: BlendMode,
        mask: Option<Arc<MaskSpec>>,
        isolate: bool,
        knockout: bool,
    },
}

struct Frame {
    kind: FrameKind,
    children: Vec<Arc<Node>>,
    /// The first optional content group entered inside (where the frame's art goes).
    group: Option<usize>,
}

impl Frame {
    fn new(kind: FrameKind) -> Self {
        Self { kind, children: vec![], group: None }
    }
}

/// Glyphs drawn consecutively with the same paint, merged into one path.
struct GlyphRun {
    path: BezPath,
    paint: Paint,
    opacity: f32,
    stroke: Option<StrokeProps>,
    scale: f64,
}

/// How often a tiling pattern was read, and the art (as its paints) each reading drew with the
/// swatch made for it.
type PatternReadings = (u32, Vec<(Vec<Paint>, String)>);

/// Builder state a nested interpretation (soft mask, pattern cell) starts afresh and gives back.
struct Saved {
    stack: Vec<Frame>,
    root_groups: Vec<Option<usize>>,
    blend: BlendMode,
    mask: Option<Arc<MaskSpec>>,
    page: Rect,
    pending: bool,
}

struct Builder<'p> {
    colors: Colors<'p>,
    next: u64,
    stack: Vec<Frame>,
    /// The optional content group of each child of the root frame.
    root_groups: Vec<Option<usize>>,
    blend: BlendMode,
    page: Rect,
    glyphs: Option<GlyphRun>,
    text: Option<TextLine>,
    text_as: TextAs,
    images: HashMap<String, ImageBlob>,
    image_keys: HashMap<u128, (String, u32, u32)>,
    warnings: Vec<String>,
    /// Fonts by cache key → base font name (from [`scan_page`]).
    fonts: HashMap<u128, String>,
    font_names: HashMap<u128, (String, String)>,
    families: Option<Families>,
    missing_fonts: Vec<String>,
    /// The soft mask of the graphics state, the art drawn through it so far, and the masks read.
    mask: Option<Arc<MaskSpec>>,
    masked: Vec<Arc<Node>>,
    masks: HashMap<u128, Arc<MaskSpec>>,
    /// Pattern swatches made, and per (pattern, stroke) the art signatures read and their names.
    patterns: Vec<PatternDef>,
    pattern_keys: HashMap<(u128, bool), PatternReadings>,
    /// Swatch names in use.
    taken: Vec<String>,
    /// The page as walked by [`scan_page`], and how far the interpreter is through it.
    scan: Scan,
    tag_at: usize,
    group_at: usize,
    aligned: bool,
    /// Whether optional content groups become layers.
    route: bool,
    /// The marked-content sequences open: the group each marks.
    marked: Vec<Option<usize>>,
    /// A transparency group was just pushed: a form's (whose flags come next) or an image's.
    pending: bool,
    nested: u32,
}

fn blend(b: hayro_interpret::BlendMode) -> BlendMode {
    use hayro_interpret::BlendMode as H;
    match b {
        H::Normal => BlendMode::Normal,
        H::Multiply => BlendMode::Multiply,
        H::Screen => BlendMode::Screen,
        H::Overlay => BlendMode::Overlay,
        H::Darken => BlendMode::Darken,
        H::Lighten => BlendMode::Lighten,
        H::ColorDodge => BlendMode::ColorDodge,
        H::ColorBurn => BlendMode::ColorBurn,
        H::HardLight => BlendMode::HardLight,
        H::SoftLight => BlendMode::SoftLight,
        H::Difference => BlendMode::Difference,
        H::Exclusion => BlendMode::Exclusion,
        H::Hue => BlendMode::Hue,
        H::Saturation => BlendMode::Saturation,
        H::Color => BlendMode::Color,
        H::Luminosity => BlendMode::Luminosity,
    }
}

fn fill_rule(r: hayro_interpret::FillRule) -> FillRule {
    match r {
        hayro_interpret::FillRule::NonZero => FillRule::NonZero,
        hayro_interpret::FillRule::EvenOdd => FillRule::EvenOdd,
    }
}

fn mean_scale(a: Affine) -> f64 {
    a.determinant().abs().sqrt()
}

fn stroke_layer(paint: Paint, opacity: f32, p: &StrokeProps, scale: f64) -> StrokeLayer {
    let mut st = StrokeLayer::new(paint, p.line_width as f64 * scale);
    st.opacity = opacity;
    st.cap = match p.line_cap {
        kurbo::Cap::Butt => LineCap::Butt,
        kurbo::Cap::Round => LineCap::Round,
        kurbo::Cap::Square => LineCap::Square,
    };
    st.join = match p.line_join {
        kurbo::Join::Miter => LineJoin::Miter,
        kurbo::Join::Round => LineJoin::Round,
        kurbo::Join::Bevel => LineJoin::Bevel,
    };
    st.miter_limit = p.miter_limit as f64;
    let dash = Dash { pattern: p.dash_array.iter().map(|v| *v as f64 * scale).collect(), offset: p.dash_offset as f64 * scale, align_corners: false };
    // An invalid dash array (a negative value, or all zeros) strokes solid.
    st.dash = dash.is_dashed().then_some(dash);
    st
}

pub(crate) fn round3(v: f32) -> f32 {
    (v * 1000.0).round() / 1000.0
}

/// The paints of `nodes`' leaves, in order: what tells two readings of a pattern cell apart.
fn paints(nodes: &[Arc<Node>]) -> Vec<Paint> {
    let mut out = vec![];
    for n in nodes {
        n.walk(&mut |c| out.extend(c.appearance.items.iter().map(|i| i.paint().clone())));
    }
    out
}

/// Visual bounds of `nodes`; `None` when one has none.
fn bounds(nodes: &[Arc<Node>]) -> Option<Rect> {
    nodes.iter().try_fold(None, |acc, n| n.visual_bounds().map(|b| Some(acc.map_or(b, |a: Rect| a.union(b)))))?
}

impl<'p> Builder<'p> {
    fn new(next: u64, colors: Colors<'p>, text_as: TextAs, route: bool) -> Self {
        Self {
            colors,
            next,
            stack: vec![],
            root_groups: vec![],
            blend: BlendMode::Normal,
            page: Rect::ZERO,
            glyphs: None,
            text: None,
            text_as,
            images: HashMap::new(),
            image_keys: HashMap::new(),
            warnings: vec![],
            fonts: HashMap::new(),
            font_names: HashMap::new(),
            families: None,
            missing_fonts: vec![],
            mask: None,
            masked: vec![],
            masks: HashMap::new(),
            patterns: vec![],
            pattern_keys: HashMap::new(),
            taken: vec![],
            scan: Scan::default(),
            tag_at: 0,
            group_at: 0,
            aligned: true,
            route,
            marked: vec![],
            pending: false,
            nested: 0,
        }
    }

    fn id(&mut self) -> NodeId {
        let id = NodeId(self.next);
        self.next += 1;
        id
    }

    /// A deep copy of `node` with fresh ids.
    fn reid(&mut self, node: &Node) -> Node {
        let mut n = node.clone();
        n.id = self.id();
        if let Some(ch) = n.children_mut() {
            let old = std::mem::take(ch);
            *ch = old.iter().map(|c| Arc::new(self.reid(c))).collect();
        }
        n
    }

    /// `m` with fresh ids for its art: a mask read once can mask several objects.
    fn fresh_mask(&mut self, mut m: OpacityMask) -> OpacityMask {
        m.art = Arc::new(self.reid(&m.art));
        m
    }

    fn warn(&mut self, w: &str) {
        if !self.warnings.iter().any(|x| x == w) {
            self.warnings.push(w.to_string());
        }
    }

    fn begin_page(&mut self, scan: Scan) {
        self.stack = vec![Frame::new(FrameKind::Root)];
        self.root_groups.clear();
        self.blend = BlendMode::Normal;
        self.glyphs = None;
        self.text = None;
        self.mask = None;
        self.masked.clear();
        self.marked.clear();
        self.pending = false;
        (self.scan, self.tag_at, self.group_at, self.aligned) = (scan, 0, 0, true);
    }

    /// The page's art, split by optional content group (in the order they first paint).
    fn end_page(&mut self) -> Vec<(Option<usize>, Vec<Arc<Node>>)> {
        let children = self.close_frames();
        let groups = std::mem::take(&mut self.root_groups);
        let mut parts: Vec<(Option<usize>, Vec<Arc<Node>>)> = vec![];
        for (n, g) in children.into_iter().zip(groups.into_iter().chain(std::iter::repeat(None))) {
            match parts.iter_mut().find(|(k, _)| *k == g) {
                Some((_, v)) => v.push(n),
                None => parts.push((g, vec![n])),
            }
        }
        parts
    }

    /// Finish the open runs and frames → the root frame's children.
    fn close_frames(&mut self) -> Vec<Arc<Node>> {
        self.flush();
        while self.stack.len() > 1 {
            self.pop_frame();
        }
        self.stack.pop().map(|f| f.children).unwrap_or_default()
    }

    /// The group art drawn now belongs to (the innermost marked as one).
    fn current_group(&self) -> Option<usize> {
        self.marked.iter().rev().find_map(|g| *g)
    }

    /// Add `n` to the open frame; `group`: the optional content group it was drawn in, if it
    /// knows one (else the current one).
    fn emit(&mut self, n: Arc<Node>, group: Option<usize>) {
        let root = self.stack.len() == 1;
        let current = self.current_group();
        let Some(f) = self.stack.last_mut() else { return };
        f.children.push(n);
        if root {
            self.root_groups.push(group.or(current));
        } else if f.group.is_none() {
            f.group = group;
        }
    }

    fn push_node(&mut self, mut n: Node) {
        if self.blend != BlendMode::Normal && !n.is_container() {
            n.blend = self.blend;
        }
        if self.mask.is_some() {
            self.masked.push(Arc::new(n));
        } else {
            self.emit(Arc::new(n), None);
        }
    }

    /// Finish the open glyph runs and the art drawn through the current soft mask.
    fn flush(&mut self) {
        self.flush_glyphs();
        self.flush_text();
        self.flush_masked();
    }

    /// The art drawn through the graphics state's soft mask so far, as one masked object.
    fn flush_masked(&mut self) {
        if self.masked.is_empty() {
            return;
        }
        let art = std::mem::take(&mut self.masked);
        let Some(spec) = self.mask.clone() else {
            art.into_iter().for_each(|n| self.emit(n, None));
            return;
        };
        match spec.as_ref() {
            // Each object is drawn through the mask on its own.
            MaskSpec::Opacity(a) => {
                for mut n in art {
                    Arc::make_mut(&mut n).opacity *= a;
                    self.emit(n, None);
                }
            }
            MaskSpec::Mask(m) => {
                let m = self.fresh_mask(m.clone());
                let node = match <[Arc<Node>; 1]>::try_from(art) {
                    Ok([one]) if one.mask.is_none() => {
                        fold_stop_opacity(&one, &m).unwrap_or_else(|| Node { mask: Some(Box::new(m)), ..Arc::unwrap_or_clone(one) })
                    }
                    Ok([one]) => {
                        let mut g = Node::group(self.id(), vec![one]);
                        g.mask = Some(Box::new(m));
                        g
                    }
                    Err(all) => {
                        let mut g = Node::group(self.id(), all);
                        g.mask = Some(Box::new(m));
                        g
                    }
                };
                self.emit(Arc::new(node), None);
            }
        }
    }

    /// A clip path node.
    fn clip_node(&mut self, path: &BezPath, rule: FillRule) -> Node {
        let mut clip = Node::new(self.id(), NodeKind::Path { path: PathData::from_bezpath(path), rule, live: None, clipping: true, guide: false });
        clip.name = Some("<Clipping Path>".into());
        clip
    }

    fn pop_frame(&mut self) {
        if self.stack.len() <= 1 {
            return;
        }
        let Some(f) = self.stack.pop() else { return };
        let group = f.group;
        let node = match f.kind {
            FrameKind::Root => None,
            FrameKind::Skip => {
                f.children.into_iter().for_each(|c| self.emit(c, group));
                None
            }
            FrameKind::Clip(clip) => {
                let noop = clip.path_data().map(|p| p.to_bezpath()).filter(is_rectangle).map(|p| p.bounding_box().inflate(0.01, 0.01));
                if f.children.is_empty() {
                    None
                } else if noop.is_some_and(|r| bounds(&f.children).is_some_and(|b| contains(r, b))) {
                    // A rectangle around all of its art (a form's box) clips nothing.
                    f.children.into_iter().for_each(|c| self.emit(c, group));
                    None
                } else {
                    let mut ch = vec![Arc::new(*clip)];
                    ch.extend(f.children);
                    Some(Node::new(self.id(), NodeKind::Group { children: ch, clip: true }))
                }
            }
            FrameKind::Group { opacity, blend, mask, isolate, knockout } => {
                let children = f.children;
                // A constant alpha mask is opacity (of a group that isn't isolated).
                let (opacity, mask) = match mask.as_deref() {
                    Some(MaskSpec::Opacity(a)) => (opacity * a, None),
                    Some(MaskSpec::Mask(m)) => (opacity, Some(m.clone())),
                    None => (opacity, None),
                };
                // Isolation only shows with blending inside; knockout with several objects.
                let isolate = isolate && Node::children_blend(&children, &mut |c| c.blends_through());
                let knockout = knockout && children.len() > 1;
                let plain = opacity >= 0.999 && blend == BlendMode::Normal && mask.is_none() && !isolate && !knockout;
                if children.is_empty() {
                    None
                } else if plain {
                    children.into_iter().for_each(|c| self.emit(c, group));
                    None
                } else if let [only] = children.as_slice()
                    && !only.is_container()
                    && !isolate
                    && !knockout
                    && (mask.is_none() || only.mask.is_none())
                {
                    // A single object in a group: fold opacity, blend and mask into the object.
                    let mut only = (**only).clone();
                    only.opacity *= opacity;
                    if blend != BlendMode::Normal {
                        only.blend = blend;
                    }
                    if let Some(m) = mask {
                        let m = self.fresh_mask(m);
                        only = fold_stop_opacity(&only, &m).unwrap_or(Node { mask: Some(Box::new(m)), ..only });
                    }
                    Some(only)
                } else {
                    let mut g = Node::group(self.id(), children);
                    (g.opacity, g.blend, g.isolate) = (opacity, blend, isolate);
                    if knockout {
                        g.knockout = Knockout::On;
                    }
                    g.mask = mask.map(|m| Box::new(self.fresh_mask(m)));
                    Some(g)
                }
            }
        };
        if let Some(n) = node {
            self.emit(Arc::new(n), group);
        }
    }

    fn flush_glyphs(&mut self) {
        let Some(run) = self.glyphs.take() else { return };
        if run.path.elements().is_empty() {
            return;
        }
        let mut ap = Appearance::default();
        match &run.stroke {
            None => {
                let mut f = FillLayer::new(run.paint);
                f.opacity = run.opacity;
                ap.items.push(AppearanceItem::Fill(f));
            }
            Some(p) => ap.items.push(AppearanceItem::Stroke(stroke_layer(run.paint, run.opacity, p, run.scale))),
        }
        let id = self.id();
        let mut n = Node::path(id, PathData::from_bezpath(&run.path), ap);
        n.name = Some(TEXT_OUTLINES.into());
        self.push_node(n);
    }

    fn flush_text(&mut self) {
        let Some((t, opacity)) = self.text.take().and_then(TextLine::finish) else { return };
        let mut n = Node::new(self.id(), NodeKind::Text(Box::new(t)));
        n.opacity = opacity;
        self.push_node(n);
    }

    /// Convert a hayro paint to a VectorCraft paint and opacity (`stroke`: for a stroke).
    fn paint(&mut self, p: &hayro_interpret::Paint<'_>, stroke: bool) -> (Paint, f32) {
        match p {
            hayro_interpret::Paint::Color(c) => {
                let [r, g, b, a] = c.to_rgba().components();
                let paint = self.colors.solid(c).map_or_else(|| Paint::solid(Color::rgb(round3(r), round3(g), round3(b))), Native::paint);
                (paint, a)
            }
            hayro_interpret::Paint::Pattern(pat) => match pat.as_ref() {
                Pattern::Shading(sp) => match shading_gradient(sp, &mut self.colors) {
                    Some((g, _)) => (Paint::Gradient(Box::new(g)), sp.opacity),
                    None => {
                        self.warn("function-based shadings (and very large meshes) are imported as a flat colour");
                        (Paint::solid(Color::rgb(0.5, 0.5, 0.5)), sp.opacity)
                    }
                },
                Pattern::Tiling(t) => match self.tiling(t, stroke) {
                    Some(paint) => (paint, 1.0),
                    None => {
                        self.warn("tiling patterns nested too deeply are imported as a flat grey");
                        (Paint::solid(Color::rgb(0.5, 0.5, 0.5)), 1.0)
                    }
                },
            },
        }
    }

    /// Read a soft mask, pattern cell or type 3 glyph (`read`) on its own: its art, in the
    /// coordinates `page` has. `None` when nested too deeply.
    fn nested(&mut self, page: Rect, read: impl FnOnce(&mut Self)) -> Option<Vec<Arc<Node>>> {
        if self.nested >= MAX_NESTED {
            return None;
        }
        self.flush();
        let saved = Saved {
            stack: std::mem::replace(&mut self.stack, vec![Frame::new(FrameKind::Root)]),
            root_groups: std::mem::take(&mut self.root_groups),
            blend: std::mem::replace(&mut self.blend, BlendMode::Normal),
            mask: self.mask.take(),
            page: std::mem::replace(&mut self.page, page),
            pending: std::mem::take(&mut self.pending),
        };
        self.nested += 1;
        read(self);
        let art = self.close_frames();
        self.nested -= 1;
        (self.stack, self.root_groups, self.blend, self.mask, self.page, self.pending) =
            (saved.stack, saved.root_groups, saved.blend, saved.mask, saved.page, saved.pending);
        Some(art)
    }

    /// What soft mask `m` does (read once per mask and placement).
    fn soft_mask(&mut self, m: &SoftMask<'_>) -> Arc<MaskSpec> {
        let key = m.cache_key();
        if let Some(s) = self.masks.get(&key) {
            return s.clone();
        }
        let page = self.page;
        let spec = match self.nested(page, |b| m.interpret(b)) {
            Some(art) => {
                let [r, g, b, _] = m.background_color().to_rgba().components();
                let backdrop = luminance(&Color::rgb(r, g, b));
                let inverted = m.transfer_function().is_some_and(|tf| tf.apply(0.0) > tf.apply(1.0));
                let id = self.id();
                mask_spec(art, m.mask_type() == MaskType::Alpha, backdrop, inverted, page, |all| Node::group(id, all))
            }
            None => {
                self.warn("soft masks nested too deeply were left out (content drawn unmasked)");
                MaskSpec::Opacity(1.0)
            }
        };
        let spec = Arc::new(spec);
        self.masks.insert(key, spec.clone());
        spec
    }

    /// Tiling pattern `t` as a pattern swatch's paint (the swatch made the first time).
    fn tiling(&mut self, t: &TilingPattern<'_>, stroke: bool) -> Option<Paint> {
        let key = (t.cache_key(), stroke);
        let tile = Rect::from_origin_size(t.bbox.origin(), (t.x_step.abs().max(1e-3) as f64, t.y_step.abs().max(1e-3) as f64));
        let xf = t.matrix * Affine::translate(tile.origin().to_vec2());
        // An uncoloured pattern draws in the current colour: read it again unless it always
        // drew the same.
        if let Some((n, seen)) = self.pattern_keys.get(&key)
            && *n >= PATTERN_REUSE
            && let [(_, name)] = seen.as_slice()
        {
            return Some(Paint::Pattern { pattern: name.clone(), xf });
        }
        let art = self.nested(Rect::ZERO, |b| {
            // A cell whose content can't be decoded is empty.
            let _ = t.interpret(b, Affine::IDENTITY, stroke);
        })?;
        let sig = paints(&art);
        let entry = self.pattern_keys.entry(key).or_default();
        entry.0 += 1;
        let name = match entry.1.iter().find(|(s, _)| *s == sig) {
            Some((_, name)) => name.clone(),
            None => {
                let name = (self.patterns.len() + 1..).map(|i| format!("Pattern {i}")).find(|n| !self.taken.contains(n)).unwrap_or_default();
                self.taken.push(name.clone());
                let mut def = PatternDef::new(&name, art);
                def.tile = tile;
                self.patterns.push(def);
                if let Some(e) = self.pattern_keys.get_mut(&key) {
                    e.1.push((sig, name.clone()));
                }
                name
            }
        };
        Some(Paint::Pattern { pattern: name, xf })
    }

    fn add_image(&mut self, key: u128, make: impl FnOnce() -> Option<(ImageBlob, u32, u32)>, xf: Affine) {
        let (k, w, h) = if let Some(v) = self.image_keys.get(&key).cloned() {
            v
        } else {
            let Some((blob, w, h)) = make() else {
                self.warn("an image could not be decoded and was skipped");
                return;
            };
            // Content keys: placing this page into another document merges its images safely.
            let k = blob.content_key();
            self.images.insert(k.clone(), blob);
            self.image_keys.insert(key, (k.clone(), w, h));
            (k, w, h)
        };
        let id = self.id();
        self.push_node(Node::new(id, NodeKind::Image(ImageObject { key: k, width: w, height: h, xf, link: None, placement: Default::default() })));
    }

    /// Mesh shadings filling `region` (document space): gradient meshes, clipped to the region
    /// when they reach past it.
    fn draw_meshes(&mut self, meshes: Vec<vectorcraft_doc::live::GradientMesh>, region: &BezPath, opacity: f32) {
        let nodes: Vec<Arc<Node>> = meshes.into_iter().map(|m| Arc::new(Node::new(self.id(), NodeKind::Mesh(m)))).collect();
        let Some(art) = bounds(&nodes) else { return };
        let mut content = match <[Arc<Node>; 1]>::try_from(nodes) {
            Ok([one]) => Arc::unwrap_or_clone(one),
            Err(all) => Node::group(self.id(), all),
        };
        content.opacity *= opacity;
        if !contains(region.bounding_box().inflate(0.5, 0.5), art) {
            let clip = self.clip_node(region, FillRule::NonZero);
            content = clipped(clip, content, self.id());
        }
        self.push_node(content);
    }

    /// The family and style of font `key` (drawing glyph `o`).
    fn font_name(&mut self, key: u128, o: &hayro_interpret::font::OutlineGlyph) -> (String, String) {
        if let Some(n) = self.font_names.get(&key) {
            return n.clone();
        }
        let data = o.font_data();
        let name = self.fonts.get(&key).cloned().or_else(|| data.as_ref().and_then(|d| d.postscript_name.clone()));
        let (weight, italic) = data.as_ref().map_or((None, false), |d| (d.weight, d.is_italic));
        let families = self.families.get_or_insert_with(Families::available);
        let n = match name {
            Some(name) => {
                let (family, style, found) = families.resolve(&name, weight, italic);
                if !found && !family.is_empty() && !self.missing_fonts.contains(&family) {
                    self.missing_fonts.push(family.clone());
                }
                (family, style)
            }
            None => {
                let d = vectorcraft_doc::CharStyle::default();
                (d.font_family, d.font_style)
            }
        };
        self.font_names.insert(key, n.clone());
        n
    }

    /// Glyph `o` as type: added to the line being gathered (or starting one). `false`: it keeps
    /// its outline (no Unicode text, mirrored, or not type mode).
    fn type_glyph(
        &mut self,
        o: &hayro_interpret::font::OutlineGlyph,
        m: Affine,
        scale: f64,
        paint: &hayro_interpret::Paint<'_>,
        stroke: Option<&StrokeProps>,
    ) -> bool {
        if self.text_as != TextAs::Text || self.nested > 0 {
            return false;
        }
        let text = match o.as_unicode() {
            Some(BfString::Char(c)) => c.to_string(),
            Some(BfString::String(s)) => s,
            None => return false,
        };
        let Some(at) = Placement::of(m) else { return false };
        if text.is_empty() || text.chars().any(|c| c.is_control()) {
            return false;
        }
        self.flush_glyphs();
        let font = o.font_cache_key();
        let (paint, opacity) = self.paint(paint, stroke.is_some());
        let stroke = stroke.map(|p| (paint.clone(), p.line_width as f64 * scale));
        // A stroke over the glyph just filled (fill and stroke rendering).
        if let (Some(s), Some(line)) = (&stroke, &mut self.text)
            && line.stroke_last(font, at, s.clone())
        {
            return true;
        }
        let (family, style) = self.font_name(font, o);
        let look = Look { font, family, style, size: at.size, h_scale: at.h_scale, fill: stroke.is_none().then_some(paint), stroke };
        let advance = o.advance_width().filter(|w| w.is_finite()).map_or(at.size * 0.5, |w| w as f64 / 1000.0 * at.size * at.h_scale / 100.0);
        if !self.text.as_mut().is_some_and(|l| l.push(&look, at, opacity, advance, &text)) {
            self.flush_text();
            let mut line = TextLine::new(at, opacity);
            line.push(&look, at, opacity, advance, &text);
            self.text = Some(line);
        }
        true
    }
}

fn rgba_png(rgba: Vec<u8>, w: u32, h: u32) -> Option<Vec<u8>> {
    let img = image::RgbaImage::from_raw(w, h, rgba)?;
    let mut out = Vec::new();
    img.write_to(&mut std::io::Cursor::new(&mut out), image::ImageFormat::Png).ok()?;
    Some(out)
}

fn resize_alpha(a: &LumaData, w: u32, h: u32) -> Vec<u8> {
    if a.width == w && a.height == h {
        return a.data.clone();
    }
    match image::GrayImage::from_raw(a.width, a.height, a.data.clone()) {
        Some(g) => image::imageops::resize(&g, w, h, image::imageops::FilterType::Triangle).into_raw(),
        None => vec![255; (w * h) as usize],
    }
}

impl<'a> Device<'a> for Builder<'_> {
    fn set_soft_mask(&mut self, mask: Option<SoftMask<'a>>) {
        let spec = mask.map(|m| self.soft_mask(&m));
        let same = match (&spec, &self.mask) {
            (Some(a), Some(b)) => Arc::ptr_eq(a, b),
            (None, None) => true,
            _ => false,
        };
        if !same {
            self.flush();
            self.mask = spec;
        }
    }

    fn set_blend_mode(&mut self, blend_mode: hayro_interpret::BlendMode) {
        let b = blend(blend_mode);
        if b != self.blend {
            self.flush_glyphs();
            self.flush_text();
            self.blend = b;
        }
    }

    fn draw_path(&mut self, path: &BezPath, transform: Affine, paint: &hayro_interpret::Paint<'a>, draw_mode: &PathDrawMode) {
        self.flush_glyphs();
        self.flush_text();
        self.pending = false;
        let mut bp = path.clone();
        bp.apply_affine(transform);
        if bp.elements().is_empty() {
            return;
        }
        let shading = match paint {
            hayro_interpret::Paint::Pattern(p) => match p.as_ref() {
                Pattern::Shading(sp) => Some(sp),
                Pattern::Tiling(_) => None,
            },
            hayro_interpret::Paint::Color(_) => None,
        };
        // Patch and triangle meshes are gradient meshes.
        if let (PathDrawMode::Fill(_), Some(sp)) = (draw_mode, shading)
            && let Some(meshes) = mesh_shading(sp, &mut self.colors)
        {
            self.draw_meshes(meshes, &bp, sp.opacity);
            return;
        }
        let pd = PathData::from_bezpath(&bp);
        let stroke = matches!(draw_mode, PathDrawMode::Stroke(_));
        let (paint, opacity) = self.paint(paint, stroke);
        // A gradient that doesn't extend past its ends paints only between them.
        let width = match draw_mode {
            PathDrawMode::Stroke(p) => p.line_width as f64 * mean_scale(transform),
            PathDrawMode::Fill(_) => 0.0,
        };
        let band = shading.and_then(|sp| extend_clip(sp, bp.bounding_box().inflate(width, width)));
        let wrap = |b: &mut Self, n: Node| match &band {
            Some(band) => {
                let clip = b.clip_node(band, FillRule::EvenOdd);
                let id = b.id();
                clipped(clip, n, id)
            }
            None => n,
        };
        match draw_mode {
            PathDrawMode::Fill(rule) => {
                let mut f = FillLayer::new(paint);
                f.opacity = opacity;
                let mut n = Node::path(self.id(), pd, Appearance { items: vec![AppearanceItem::Fill(f)], ..Default::default() });
                if let NodeKind::Path { rule: r, .. } = &mut n.kind {
                    *r = fill_rule(*rule);
                }
                let n = wrap(self, n);
                self.push_node(n);
            }
            PathDrawMode::Stroke(props) => {
                let st = stroke_layer(paint, opacity, props, mean_scale(transform));
                // Fill-then-stroke of the same path (the `B` operator) becomes one object.
                let blend = self.blend;
                let last = match self.mask {
                    Some(_) => self.masked.last_mut(),
                    None => self.stack.last_mut().and_then(|f| f.children.last_mut()),
                };
                if band.is_none()
                    && let Some(last) = last
                    && last.blend == blend
                    && last.path_data() == Some(&pd)
                    && last.appearance.stroke().is_none()
                {
                    Arc::make_mut(last).appearance.items.push(AppearanceItem::Stroke(st));
                    return;
                }
                let n = Node::path(self.id(), pd, Appearance { items: vec![AppearanceItem::Stroke(st)], ..Default::default() });
                let n = wrap(self, n);
                self.push_node(n);
            }
        }
    }

    fn push_clip_path(&mut self, clip_path: &ClipPath) {
        self.flush();
        // A form's box right after its transparency group: the group's isolate and knockout
        // flags are the next ones read from the file.
        if std::mem::take(&mut self.pending) {
            let flags = self.scan.groups.get(self.group_at).copied();
            self.group_at += 1;
            if let Some((i, k)) = flags
                && let Some(Frame { kind: FrameKind::Group { isolate, knockout, .. }, .. }) = self.stack.last_mut()
            {
                (*isolate, *knockout) = (i, k);
            }
        }
        let bb = clip_path.path.bounding_box();
        // Clips that contain the whole page do nothing visible; don't create groups for them.
        let redundant = clip_path.path.elements().len() <= 6
            && bb.x0 <= self.page.x0 + 0.01
            && bb.y0 <= self.page.y0 + 0.01
            && bb.x1 >= self.page.x1 - 0.01
            && bb.y1 >= self.page.y1 - 0.01
            && self.page.area() > 0.0;
        let kind = if redundant { FrameKind::Skip } else { FrameKind::Clip(Box::new(self.clip_node(&clip_path.path, fill_rule(clip_path.fill)))) };
        self.stack.push(Frame::new(kind));
    }

    fn push_transparency_group(&mut self, opacity: f32, mask: Option<SoftMask<'a>>, blend_mode: hayro_interpret::BlendMode) {
        self.flush();
        let mask = mask.map(|m| self.soft_mask(&m));
        self.stack.push(Frame::new(FrameKind::Group { opacity, blend: blend(blend_mode), mask, isolate: false, knockout: false }));
        self.pending = self.nested == 0;
        // Blend mode applies to the group as a whole, not to its children.
        self.blend = BlendMode::Normal;
    }

    fn draw_glyph(
        &mut self,
        glyph: &Glyph<'a>,
        transform: Affine,
        glyph_transform: Affine,
        paint: &hayro_interpret::Paint<'a>,
        draw_mode: &GlyphDrawMode,
    ) {
        self.pending = false;
        let stroke = match draw_mode {
            GlyphDrawMode::Invisible => return,
            GlyphDrawMode::Fill => None,
            GlyphDrawMode::Stroke(p) => Some(p.clone()),
        };
        match glyph {
            Glyph::Outline(o) => {
                let scale = mean_scale(transform);
                if self.type_glyph(o, transform * glyph_transform, scale, paint, stroke.as_ref()) {
                    return;
                }
                self.flush_text();
                let mut bp = o.outline();
                bp.apply_affine(transform * glyph_transform);
                let (paint, opacity) = self.paint(paint, stroke.is_some());
                let same = self.glyphs.as_ref().is_some_and(|r| {
                    r.paint == paint
                        && r.opacity == opacity
                        && r.stroke.as_ref().map(|s| s.line_width) == stroke.as_ref().map(|s| s.line_width)
                        && (r.scale - scale).abs() < 1e-9
                });
                if !same {
                    self.flush_glyphs();
                    self.glyphs = Some(GlyphRun { path: BezPath::new(), paint, opacity, stroke, scale });
                }
                if let Some(r) = &mut self.glyphs {
                    r.path.extend(bp.iter());
                }
                self.warn("text was converted to outlines");
            }
            Glyph::Type3(t3) => {
                if self.nested >= MAX_NESTED {
                    return;
                }
                self.flush();
                self.nested += 1;
                t3.interpret(self, transform, glyph_transform, paint);
                self.nested -= 1;
            }
        }
    }

    fn draw_image(&mut self, image: Image<'a, '_>, transform: Affine) {
        self.flush_glyphs();
        self.flush_text();
        self.pending = false;
        match image {
            Image::Raster(r) => {
                let key = hayro_interpret::CacheKey::cache_key(&r);
                // JPEG passthrough for plain DeviceRGB/DeviceGray DCT images.
                let st = r.stream();
                let dict = st.dict();
                let filters = st.filters();
                let cs_ok = dict.get::<Name<'_>>(b"ColorSpace").is_some_and(|n| matches!(n.as_ref(), b"DeviceRGB" | b"DeviceGray"));
                let jpeg = filters.len() == 1
                    && matches!(filters[0], hayro_syntax::Filter::DctDecode)
                    && cs_ok
                    && !dict.contains_key(b"SMask")
                    && !dict.contains_key(b"Mask")
                    && !dict.contains_key(b"Decode");
                if jpeg {
                    let (w, h) = (r.width(), r.height());
                    let bytes = st.raw_data().to_vec();
                    self.add_image(key, || Some((ImageBlob::new("image/jpeg", bytes), w, h)), transform);
                    return;
                }
                let mut decoded: Option<Decoded> = None;
                r.with_rgba(
                    |img, alpha| {
                        let (w, h, sf) = (img.width(), img.height(), img.scale_factors());
                        let a = alpha.map(|a| resize_alpha(&a, w, h)).unwrap_or_else(|| vec![255; (w * h) as usize]);
                        let rgba: Vec<u8> = match img {
                            ImageData::Rgb(d) => d.data.as_chunks::<3>().0.iter().zip(a).flat_map(|(c, a)| [c[0], c[1], c[2], a]).collect(),
                            ImageData::Luma(d) => d.data.iter().zip(a).flat_map(|(g, a)| [*g, *g, *g, a]).collect(),
                        };
                        decoded = Some((rgba, w, h, sf));
                    },
                    None,
                );
                let Some((rgba, w, h, sf)) = decoded else {
                    self.warn("an image could not be decoded and was skipped");
                    return;
                };
                let xf = transform * Affine::scale_non_uniform(sf.0 as f64, sf.1 as f64);
                self.add_image(key, || rgba_png(rgba, w, h).map(|png| (ImageBlob::new("image/png", png), w, h)), xf);
            }
            Image::Stencil(s) => {
                let key = hayro_interpret::CacheKey::cache_key(&s);
                let mut decoded: Option<Decoded> = None;
                s.with_stencil(
                    |luma, paint| {
                        let rgb = match paint {
                            hayro_interpret::Paint::Color(c) => c.to_rgba().to_rgba8(),
                            _ => [0, 0, 0, 255],
                        };
                        let rgba = luma.data.iter().flat_map(|a| [rgb[0], rgb[1], rgb[2], *a]).collect();
                        decoded = Some((rgba, luma.width, luma.height, luma.scale_factors));
                    },
                    None,
                );
                let Some((rgba, w, h, sf)) = decoded else { return };
                let xf = transform * Affine::scale_non_uniform(sf.0 as f64, sf.1 as f64);
                self.add_image(key ^ 0x5_7e9c, || rgba_png(rgba, w, h).map(|png| (ImageBlob::new("image/png", png), w, h)), xf);
            }
        }
    }

    fn pop_clip_path(&mut self) {
        self.flush();
        self.pending = false;
        self.pop_frame();
    }

    fn pop_transparency_group(&mut self) {
        self.flush();
        self.pending = false;
        self.pop_frame();
    }

    fn begin_marked_content(&mut self, tag: &[u8], _mcid: Option<i32>) {
        if self.nested > 0 {
            return;
        }
        self.flush();
        let at = self.tag_at;
        self.tag_at += 1;
        let group = match self.scan.tags.get(at) {
            Some((t, g)) if self.aligned && t.as_slice() == tag => *g,
            _ => {
                if self.route && self.aligned {
                    self.aligned = false;
                    self.warn("some art couldn't be told apart by layer and went to its page's layer");
                }
                None
            }
        }
        .filter(|_| self.route);
        if let Some(g) = group
            && self.stack.len() > 1
            && let Some(f) = self.stack.last_mut()
        {
            f.group.get_or_insert(g);
        }
        self.marked.push(group);
    }

    fn end_marked_content(&mut self) {
        if self.nested > 0 {
            return;
        }
        self.flush();
        self.marked.pop();
    }
}