//! Chart layout: title, legend, axes and every chart kind, drawn into [`Prim`]s.

use std::collections::HashSet;
use std::f32::consts::{PI, TAU};

use gridcraft_model::{Chart, ChartKind, LegendPos, LineDash, Theme, TrendlineKind};

use crate::axis::{Fmt, Scale, clean, fixed_scale, nice_scale};
use crate::resolve::{MAX_POINTS, MAX_SERIES, MAX_TRENDLINES, series_color};
use crate::trend::{auto_name, fit_trendline, moving_average};
use crate::{ChartData, HAlign, Measure, Prim, Rgba, SeriesData, VAlign};

pub(crate) const TEXT: Rgba = [0x59, 0x59, 0x59, 0xFF];
const DARK_TEXT: Rgba = [0x26, 0x26, 0x26, 0xFF];
const GRID: Rgba = [0xD9, 0xD9, 0xD9, 0xFF];
const AXIS: Rgba = [0xBF, 0xBF, 0xBF, 0xFF];
const WHITE: Rgba = [0xFF, 0xFF, 0xFF, 0xFF];
const STOCK: Rgba = [0x40, 0x40, 0x40, 0xFF];
pub(crate) const UP: Rgba = [0x3E, 0x9B, 0x5F, 0xFF];
pub(crate) const DOWN: Rgba = [0xD6, 0x4F, 0x45, 0xFF];

const TITLE_SIZE: f32 = 14.0;
const LABEL_SIZE: f32 = 9.0;
const AXIS_TITLE_SIZE: f32 = 10.0;
/// Most categories drawn by category-axis charts.
const MAX_CATS: usize = 20_000;
/// Lines with more points than this are decimated (min/max per pixel column).
const MAX_LINE_PTS: usize = 2000;
/// Most markers per series (after de-duplicating by pixel).
const MAX_MARKERS: usize = 5000;
/// Data labels are skipped when a series has more points than this.
const MAX_LABELS: usize = 200;

#[derive(Clone, Copy, Debug)]
struct Bx {
    x: f32,
    y: f32,
    w: f32,
    h: f32,
}

impl Bx {
    fn right(&self) -> f32 {
        self.x + self.w
    }
    fn bottom(&self) -> f32 {
        self.y + self.h
    }
    fn ok(&self) -> bool {
        self.w.is_finite() && self.h.is_finite() && self.w > 4.0 && self.h > 4.0
    }
    fn cx(&self) -> f32 {
        self.x + self.w / 2.0
    }
    fn cy(&self) -> f32 {
        self.y + self.h / 2.0
    }
}

struct Ctx<'a> {
    out: Vec<Prim>,
    m: &'a dyn Measure,
}

impl Ctx<'_> {
    fn tw(&self, s: &str, size: f32) -> f32 {
        let w = self.m.text_width(s, size, false);
        if w.is_finite() { w.max(0.0) } else { 0.0 }
    }
    fn fit(&self, s: &str, size: f32, maxw: f32) -> String {
        if self.tw(s, size) <= maxw {
            return s.to_string();
        }
        let chars: Vec<char> = s.chars().collect();
        let mut n = chars.len().min(400);
        while n > 0 {
            n -= 1;
            let t: String = chars.iter().take(n).collect::<String>() + "…";
            if self.tw(&t, size) <= maxw {
                return if n == 0 { String::new() } else { t };
            }
        }
        String::new()
    }
    #[allow(clippy::too_many_arguments)]
    fn text(&mut self, x: f32, y: f32, s: &str, size: f32, color: Rgba, align: HAlign, valign: VAlign) {
        if s.is_empty() {
            return;
        }
        self.out.push(Prim::Text { x, y, text: s.to_string(), size, color, bold: false, align, valign, rotation: 0.0 });
    }
    fn rect(&mut self, x: f32, y: f32, w: f32, h: f32, fill: Rgba, stroke: Option<(Rgba, f32)>) {
        self.out.push(Prim::Rect { x, y, w, h, fill: Some(fill), stroke, radius: 0.0 });
    }
    fn line(&mut self, pts: Vec<[f32; 2]>, color: Rgba, width: f32) {
        if pts.len() >= 2 {
            self.out.push(Prim::Line { pts, color, width, dash: false });
        }
    }
    fn hline(&mut self, x0: f32, x1: f32, y: f32, color: Rgba, width: f32) {
        self.line(vec![[x0, y], [x1, y]], color, width);
    }
    fn vline(&mut self, x: f32, y0: f32, y1: f32, color: Rgba, width: f32) {
        self.line(vec![[x, y0], [x, y1]], color, width);
    }
}

/// Text colour readable on `fill`.
fn on(fill: Rgba) -> Rgba {
    let l = 0.299 * fill[0] as f32 + 0.587 * fill[1] as f32 + 0.114 * fill[2] as f32;
    if l < 150.0 { WHITE } else { DARK_TEXT }
}

/// How a legend entry's swatch is drawn.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Swatch {
    Box,
    Line,
    LineMarker,
    Marker,
}

/// The kind a series is drawn as (per-series kinds only apply to combo charts).
fn plot_kind(chart: &Chart, s: &SeriesData) -> ChartKind {
    if chart.kind == ChartKind::Combo { if s.kind == ChartKind::Combo { ChartKind::Line } else { s.kind } } else { chart.kind }
}

/// Colour of point `j` for charts that colour by point (pie, doughnut, treemap, sunburst).
fn point_color(data: &ChartData, j: usize) -> Rgba {
    match (j, data.series.first()) {
        (0, Some(s)) => s.color,
        _ => series_color(&Theme::default(), j),
    }
}

fn first_len(data: &ChartData) -> usize {
    data.series.first().map(|s| s.values.len()).unwrap_or(0)
}

fn cat_label(data: &ChartData, j: usize) -> String {
    data.categories.get(j).cloned().unwrap_or_else(|| (j + 1).to_string())
}

/// Legend entries (text, colour, swatch) `render` draws for this chart; empty when hidden.
pub fn legend_entries(chart: &Chart, data: &ChartData) -> Vec<(String, Rgba, Swatch)> {
    if chart.legend == LegendPos::None {
        return vec![];
    }
    match chart.kind {
        ChartKind::Pie | ChartKind::Doughnut | ChartKind::Treemap | ChartKind::Sunburst => {
            let n = first_len(data).min(MAX_CATS);
            (0..n).map(|j| (cat_label(data, j), point_color(data, j), Swatch::Box)).collect()
        }
        ChartKind::Histogram | ChartKind::Funnel | ChartKind::Stock => vec![],
        ChartKind::Waterfall => {
            if data.series.is_empty() {
                return vec![];
            }
            let total = data.series.first().map(|s| s.color).unwrap_or(TEXT);
            vec![("Increase".into(), UP, Swatch::Box), ("Decrease".into(), DOWN, Swatch::Box), ("Total".into(), total, Swatch::Box)]
        }
        _ => {
            let series = data.series.iter().take(MAX_SERIES);
            let mut out: Vec<(String, Rgba, Swatch)> = series
                .clone()
                .map(|s| {
                    let sw = match plot_kind(chart, s) {
                        ChartKind::Line | ChartKind::LineStacked | ChartKind::Radar | ChartKind::ScatterLines => Swatch::Line,
                        ChartKind::LineMarkers => Swatch::LineMarker,
                        ChartKind::Scatter | ChartKind::Bubble => Swatch::Marker,
                        _ => Swatch::Box,
                    };
                    (s.name.clone(), s.color, sw)
                })
                .collect();
            // Trendlines follow the series, named "Linear (Sales)" unless given a name.
            for s in series.filter(|s| supports_trendline(plot_kind(chart, s))) {
                for t in s.trendlines.iter().take(MAX_TRENDLINES) {
                    out.push((t.spec.name.clone().unwrap_or_else(|| auto_name(t.spec.kind, &s.name)), t.color, Swatch::Line));
                }
            }
            out
        }
    }
}

fn sanitize_vals(v: &[Option<f64>]) -> Vec<Option<f64>> {
    v.iter().take(MAX_POINTS).map(|x| x.filter(|n| n.is_finite()).map(clean)).collect()
}

fn sanitize(d: &ChartData) -> ChartData {
    ChartData {
        categories: d.categories.iter().take(MAX_POINTS).cloned().collect(),
        series: d
            .series
            .iter()
            .take(MAX_SERIES)
            .map(|s| SeriesData {
                name: s.name.clone(),
                values: sanitize_vals(&s.values),
                x: s.x.as_deref().map(sanitize_vals),
                sizes: s.sizes.as_deref().map(sanitize_vals),
                color: s.color,
                kind: s.kind,
                secondary: s.secondary,
                smooth: s.smooth,
                trendlines: s.trendlines.iter().take(MAX_TRENDLINES).cloned().collect(),
                number_format: s.number_format.clone(),
            })
            .collect(),
    }
}

fn chart_title(chart: &Chart, data: &ChartData) -> Option<String> {
    match &chart.title {
        Some(t) => Some(t.trim().to_string()).filter(|t| !t.is_empty()),
        None if data.series.len() == 1 => data.series.first().map(|s| s.name.clone()).filter(|t| !t.is_empty()),
        None => None,
    }
}

/// Lays out and draws a chart into a `w`×`h` box at the origin. Empty for a degenerate box.
pub fn render(chart: &Chart, data: &ChartData, w: f32, h: f32, m: &dyn Measure) -> Vec<Prim> {
    if !(w.is_finite() && h.is_finite()) || w < 1.0 || h < 1.0 || w > 1e7 || h > 1e7 {
        return vec![];
    }
    let data = sanitize(data);
    let mut ctx = Ctx { out: Vec::new(), m };
    ctx.out.push(Prim::Rect { x: 0.0, y: 0.0, w, h, fill: Some(WHITE), stroke: Some((GRID, 1.0)), radius: 0.0 });
    let pad = (w.min(h) * 0.04).clamp(2.0, 10.0);
    let mut area = Bx { x: pad, y: pad, w: w - 2.0 * pad, h: h - 2.0 * pad };
    if let Some(t) = chart_title(chart, &data) {
        let size = TITLE_SIZE.min(h * 0.12).max(4.0);
        let t = ctx.fit(&t, size, area.w);
        ctx.text(w / 2.0, area.y, &t, size, TEXT, HAlign::Center, VAlign::Top);
        let used = size * 1.3 + 4.0;
        area.y += used;
        area.h -= used;
    }
    let entries = legend_entries(chart, &data);
    if !entries.is_empty() && area.ok() {
        area = draw_legend(&mut ctx, &entries, chart.legend, area);
    }
    if area.ok() && !data.series.is_empty() {
        draw_kind(&mut ctx, chart, &data, area);
    }
    finalize(ctx.out, w, h)
}

fn draw_kind(ctx: &mut Ctx, chart: &Chart, data: &ChartData, area: Bx) {
    use ChartKind::*;
    match chart.kind {
        Pie => pie(ctx, chart, data, area, 0.0, false),
        Doughnut => pie(ctx, chart, data, area, 0.5, false),
        Sunburst => pie(ctx, chart, data, area, 0.2, true),
        Treemap => treemap(ctx, chart, data, area),
        Funnel => funnel(ctx, data, area),
        Radar => radar(ctx, chart, data, area),
        _ => {
            let area = axis_titles(ctx, chart, area);
            if !area.ok() {
                return;
            }
            match chart.kind {
                BarClustered | BarStacked | BarStacked100 => cartesian(ctx, chart, data, area, true),
                Scatter | ScatterLines | Bubble => scatter(ctx, chart, data, area),
                Histogram => histogram(ctx, chart, data, area),
                Waterfall => waterfall(ctx, chart, data, area),
                BoxWhisker => box_whisker(ctx, data, area),
                Stock => stock(ctx, data, area),
                _ => cartesian(ctx, chart, data, area, false),
            }
        }
    }
}

fn axis_titles(ctx: &mut Ctx, chart: &Chart, mut area: Bx) -> Bx {
    let lh = AXIS_TITLE_SIZE * 1.4 + 2.0;
    if let Some(t) = chart.x_title.as_deref().map(str::trim).filter(|t| !t.is_empty()) {
        let t = ctx.fit(t, AXIS_TITLE_SIZE, area.w);
        ctx.text(area.cx(), area.bottom(), &t, AXIS_TITLE_SIZE, TEXT, HAlign::Center, VAlign::Bottom);
        area.h -= lh;
    }
    if let Some(t) = chart.y_title.as_deref().map(str::trim).filter(|t| !t.is_empty()) {
        let t = ctx.fit(t, AXIS_TITLE_SIZE, area.h);
        if !t.is_empty() {
            ctx.out.push(Prim::Text {
                x: area.x,
                y: area.cy(),
                text: t,
                size: AXIS_TITLE_SIZE,
                color: TEXT,
                bold: false,
                align: HAlign::Center,
                valign: VAlign::Top,
                rotation: -PI / 2.0,
            });
        }
        area.x += lh;
        area.w -= lh;
    }
    area
}

// ---------------------------------------------------------------- legend

fn swatch_w(sw: Swatch, s: f32) -> f32 {
    if sw == Swatch::Box { s } else { s * 2.0 }
}

fn draw_swatch(ctx: &mut Ctx, sw: Swatch, x: f32, yc: f32, s: f32, color: Rgba) {
    match sw {
        Swatch::Box => ctx.rect(x, yc - s / 2.0, s, s, color, None),
        Swatch::Line => ctx.hline(x, x + 2.0 * s, yc, color, 2.0),
        Swatch::LineMarker => {
            ctx.hline(x, x + 2.0 * s, yc, color, 2.0);
            ctx.out.push(Prim::Circle { cx: x + s, cy: yc, r: s * 0.35, fill: Some(color), stroke: None });
        }
        Swatch::Marker => ctx.out.push(Prim::Circle { cx: x + s, cy: yc, r: s * 0.4, fill: Some(color), stroke: None }),
    }
}

fn draw_legend(ctx: &mut Ctx, entries: &[(String, Rgba, Swatch)], pos: LegendPos, area: Bx) -> Bx {
    let size = LABEL_SIZE;
    let row_h = size * 1.6;
    let s = size * 0.8;
    let gap = 4.0;
    let spacing = size * 1.3;
    let item_w = |ctx: &Ctx, e: &(String, Rgba, Swatch)| swatch_w(e.2, s) + gap + ctx.tw(&e.0, size);
    match pos {
        LegendPos::None => area,
        LegendPos::Top | LegendPos::Bottom => {
            let max_rows = ((area.h * 0.3 / row_h).floor() as usize).max(1);
            let mut rows: Vec<Vec<(usize, f32)>> = vec![vec![]];
            let mut cur = 0.0f32;
            for (i, e) in entries.iter().enumerate() {
                let iw = item_w(ctx, e).min(area.w);
                let need = if cur > 0.0 { spacing + iw } else { iw };
                if cur > 0.0 && cur + need > area.w {
                    if rows.len() >= max_rows {
                        break;
                    }
                    rows.push(vec![]);
                    cur = 0.0;
                }
                cur += if cur > 0.0 { spacing + iw } else { iw };
                if let Some(r) = rows.last_mut() {
                    r.push((i, iw));
                }
            }
            let lh = rows.len() as f32 * row_h;
            let y0 = if pos == LegendPos::Bottom { area.bottom() - lh } else { area.y };
            for (ri, row) in rows.iter().enumerate() {
                let total: f32 = row.iter().map(|(_, w)| w).sum::<f32>() + spacing * row.len().saturating_sub(1) as f32;
                let mut x = area.x + (area.w - total).max(0.0) / 2.0;
                let yc = y0 + ri as f32 * row_h + row_h / 2.0;
                for &(i, iw) in row {
                    if let Some(e) = entries.get(i) {
                        draw_swatch(ctx, e.2, x, yc, s, e.1);
                        let sx = swatch_w(e.2, s) + gap;
                        let t = ctx.fit(&e.0, size, (iw - sx).max(0.0) + 0.5);
                        ctx.text(x + sx, yc, &t, size, TEXT, HAlign::Left, VAlign::Middle);
                    }
                    x += iw + spacing;
                }
            }
            let used = lh + 4.0;
            if pos == LegendPos::Bottom { Bx { h: area.h - used, ..area } } else { Bx { y: area.y + used, h: area.h - used, ..area } }
        }
        LegendPos::Left | LegendPos::Right => {
            let colw = entries.iter().map(|e| item_w(ctx, e)).fold(0.0f32, f32::max).min(area.w * 0.35);
            let max_rows = ((area.h / row_h).floor() as usize).max(1);
            let n = entries.len().min(max_rows);
            let lh = n as f32 * row_h;
            let y0 = area.y + (area.h - lh).max(0.0) / 2.0;
            let x0 = if pos == LegendPos::Right { area.right() - colw } else { area.x };
            for (i, e) in entries.iter().take(n).enumerate() {
                let yc = y0 + i as f32 * row_h + row_h / 2.0;
                draw_swatch(ctx, e.2, x0, yc, s, e.1);
                let sx = swatch_w(e.2, s) + gap;
                let t = ctx.fit(&e.0, size, (colw - sx).max(0.0) + 0.5);
                ctx.text(x0 + sx, yc, &t, size, TEXT, HAlign::Left, VAlign::Middle);
            }
            let used = colw + 8.0;
            if pos == LegendPos::Right { Bx { w: area.w - used, ..area } } else { Bx { x: area.x + used, w: area.w - used, ..area } }
        }
    }
}

// ---------------------------------------------------------------- axes frame

enum CatAxis<'a> {
    Labels(&'a [String]),
    Numeric(Scale, &'a Fmt),
}

struct ValAxis<'a> {
    scale: Scale,
    fmt: &'a Fmt,
}

impl ValAxis<'_> {
    fn labels(&self) -> Vec<(f64, String)> {
        self.scale.ticks().into_iter().map(|v| (v, self.fmt.format(v, Some(self.scale.step)))).collect()
    }
}

/// Draws gridlines, axis labels and the category axis line; returns the plot rectangle.
fn frame(ctx: &mut Ctx, area: Bx, cat: CatAxis, y: &ValAxis, y2: Option<&ValAxis>, horizontal: bool, grid: bool) -> Bx {
    let ls = LABEL_SIZE;
    let lh = ls * 1.4;
    let ylabels = y.labels();
    let maxw = |ctx: &Ctx, l: &[(f64, String)]| l.iter().map(|(_, t)| ctx.tw(t, ls)).fold(0.0f32, f32::max);
    if !horizontal {
        let left = (maxw(ctx, &ylabels) + 6.0).min(area.w * 0.4);
        let y2labels = y2.map(|a| a.labels());
        let right = match (&y2labels, &cat) {
            (Some(l), _) => (maxw(ctx, l) + 6.0).min(area.w * 0.3),
            (None, CatAxis::Numeric(s, f)) => (ctx.tw(&f.format(s.max, Some(s.step)), ls) / 2.0).min(area.w * 0.2),
            _ => 4.0,
        };
        let plot = Bx { x: area.x + left, y: area.y + lh * 0.5, w: area.w - left - right, h: area.h - lh * 1.5 - 4.0 };
        if !plot.ok() {
            return plot;
        }
        for (v, t) in &ylabels {
            let yy = plot.bottom() - y.scale.frac(*v) * plot.h;
            if grid {
                ctx.hline(plot.x, plot.right(), yy, GRID, 0.75);
            }
            ctx.text(plot.x - 4.0, yy, t, ls, TEXT, HAlign::Right, VAlign::Middle);
        }
        if let (Some(a), Some(l)) = (y2, &y2labels) {
            for (v, t) in l {
                let yy = plot.bottom() - a.scale.frac(*v) * plot.h;
                ctx.text(plot.right() + 4.0, yy, t, ls, TEXT, HAlign::Left, VAlign::Middle);
            }
        }
        let zero = if y.scale.min <= 0.0 && y.scale.max >= 0.0 { 0.0 } else { y.scale.min };
        let y0 = plot.bottom() - y.scale.frac(zero) * plot.h;
        ctx.hline(plot.x, plot.right(), y0, AXIS, 0.75);
        match cat {
            CatAxis::Labels(l) => {
                let n = l.len().max(1);
                let cw = plot.w / n as f32;
                let lw = l.iter().take(2000).map(|t| ctx.tw(t, ls)).fold(0.0f32, f32::max);
                let k = (((lw + 6.0) / cw.max(1e-3)).ceil() as usize).clamp(1, n);
                for (j, t) in l.iter().enumerate().step_by(k) {
                    let t = ctx.fit(t, ls, cw * k as f32 - 2.0);
                    ctx.text(plot.x + (j as f32 + 0.5) * cw, plot.bottom() + 3.0, &t, ls, TEXT, HAlign::Center, VAlign::Top);
                }
            }
            CatAxis::Numeric(s, f) => {
                let ticks = s.ticks();
                let labels: Vec<String> = ticks.iter().map(|v| f.format(*v, Some(s.step))).collect();
                let lw = labels.iter().map(|t| ctx.tw(t, ls)).fold(0.0f32, f32::max);
                let slot = plot.w / ticks.len().max(1) as f32;
                let k = (((lw + 6.0) / slot.max(1e-3)).ceil() as usize).max(1);
                for (v, t) in ticks.iter().zip(&labels).step_by(k) {
                    let xx = plot.x + s.frac(*v) * plot.w;
                    ctx.text(xx, plot.bottom() + 3.0, t, ls, TEXT, HAlign::Center, VAlign::Top);
                }
                if s.min <= 0.0 && s.max >= 0.0 {
                    let xx = plot.x + s.frac(0.0) * plot.w;
                    ctx.vline(xx, plot.y, plot.bottom(), AXIS, 0.75);
                }
            }
        }
        plot
    } else {
        let labels: Vec<String> = match cat {
            CatAxis::Labels(l) => l.to_vec(),
            CatAxis::Numeric(..) => vec![],
        };
        let lw = (labels.iter().take(2000).map(|t| ctx.tw(t, ls)).fold(0.0f32, f32::max) + 6.0).min(area.w * 0.35);
        let right = ylabels.last().map(|(_, t)| ctx.tw(t, ls) / 2.0).unwrap_or(0.0).min(area.w * 0.2) + 2.0;
        let plot = Bx { x: area.x + lw, y: area.y + 2.0, w: area.w - lw - right, h: area.h - lh - 6.0 };
        if !plot.ok() {
            return plot;
        }
        let vw = maxw(ctx, &ylabels);
        let slot = plot.w / ylabels.len().max(1) as f32;
        let k = (((vw + 6.0) / slot.max(1e-3)).ceil() as usize).max(1);
        for (i, (v, t)) in ylabels.iter().enumerate() {
            let xx = plot.x + y.scale.frac(*v) * plot.w;
            if grid {
                ctx.vline(xx, plot.y, plot.bottom(), GRID, 0.75);
            }
            if i % k == 0 {
                ctx.text(xx, plot.bottom() + 3.0, t, ls, TEXT, HAlign::Center, VAlign::Top);
            }
        }
        let zero = if y.scale.min <= 0.0 && y.scale.max >= 0.0 { 0.0 } else { y.scale.min };
        let x0 = plot.x + y.scale.frac(zero) * plot.w;
        ctx.vline(x0, plot.y, plot.bottom(), AXIS, 0.75);
        let n = labels.len().max(1);
        let ch = plot.h / n as f32;
        let k = ((lh / ch.max(1e-3)).ceil() as usize).clamp(1, n);
        for (j, t) in labels.iter().enumerate().step_by(k) {
            let t = ctx.fit(t, ls, lw - 6.0);
            ctx.text(plot.x - 4.0, plot.bottom() - (j as f32 + 0.5) * ch, &t, ls, TEXT, HAlign::Right, VAlign::Middle);
        }
        plot
    }
}

// ---------------------------------------------------------------- helpers

/// Reduces a long polyline to first/min/max/last per pixel column.
fn decimate(pts: Vec<[f32; 2]>, max: usize) -> Vec<[f32; 2]> {
    if pts.len() <= max {
        return pts;
    }
    let mut out = Vec::with_capacity(max * 2);
    let mut i = 0;
    while let Some(p) = pts.get(i) {
        let col = p[0].floor();
        let (start, mut mn, mut mx) = (i, i, i);
        let mut k = i + 1;
        while let Some(q) = pts.get(k) {
            if q[0].floor() != col {
                break;
            }
            if pts.get(mn).is_some_and(|m| q[1] < m[1]) {
                mn = k;
            }
            if pts.get(mx).is_some_and(|m| q[1] > m[1]) {
                mx = k;
            }
            k += 1;
        }
        let mut idx = [start, mn, mx, k - 1];
        idx.sort_unstable();
        let mut last = usize::MAX;
        for ix in idx {
            if ix != last
                && let Some(q) = pts.get(ix)
            {
                out.push(*q);
                last = ix;
            }
        }
        i = k;
    }
    if out.len() > max * 4 {
        let step = out.len() / (max * 2) + 1;
        let last = out.last().copied();
        let mut s: Vec<[f32; 2]> = out.into_iter().step_by(step).collect();
        if let Some(l) = last
            && s.last() != Some(&l)
        {
            s.push(l);
        }
        return s;
    }
    out
}

/// Draws a polyline split at gaps (`None`), decimated when long. With `smooth` (the plot box),
/// each run is interpolated with a Catmull-Rom spline so the line curves through the data points.
fn draw_runs(ctx: &mut Ctx, pts: &[Option<[f32; 2]>], color: Rgba, width: f32, smooth: Option<Bx>) {
    let mut run: Vec<[f32; 2]> = Vec::new();
    for p in pts.iter().chain(std::iter::once(&None)) {
        match p {
            Some(p) => run.push(*p),
            None => {
                if run.len() >= 2 {
                    let r = decimate(std::mem::take(&mut run), MAX_LINE_PTS);
                    let r = match smooth {
                        Some(plot) => smooth_run(r, plot),
                        None => r,
                    };
                    ctx.line(r, color, width);
                } else {
                    run.clear();
                }
            }
        }
    }
}

/// Catmull-Rom spline through `pts`: every segment gets the same number of sub-segments (up to
/// 100), chosen so the whole curve stays within `MAX_LINE_PTS * 2` points. Endpoints are
/// duplicated so the curve passes through the first and last points, and the curve is clamped
/// to the `plot` box (a spline overshoots its data near sharp turns).
fn smooth_run(pts: Vec<[f32; 2]>, plot: Bx) -> Vec<[f32; 2]> {
    let n = pts.len();
    if n < 3 {
        return pts;
    }
    let cap = MAX_LINE_PTS * 2;
    let steps = (cap / n).clamp(1, 100);
    let mut out: Vec<[f32; 2]> = Vec::with_capacity(n.saturating_mul(steps).min(cap) + 1);
    let at = |i: isize| -> [f32; 2] {
        let j = i.clamp(0, n as isize - 1) as usize;
        pts.get(j).copied().unwrap_or([0.0, 0.0])
    };
    let (x0, x1) = (plot.x.min(plot.right()), plot.x.max(plot.right()));
    let (y0, y1) = (plot.y.min(plot.bottom()), plot.y.max(plot.bottom()));
    let clip = |p: [f32; 2]| [p[0].clamp(x0, x1), p[1].clamp(y0, y1)];
    for i in 0..n.saturating_sub(1) {
        let (p0, p1, p2, p3) = (at(i as isize - 1), at(i as isize), at(i as isize + 1), at(i as isize + 2));
        for s in 0..steps {
            let t = s as f32 / steps as f32;
            out.push(clip(catmull(p0, p1, p2, p3, t)));
        }
    }
    out.push(clip(at(n as isize - 1)));
    out
}

/// One Catmull-Rom point between `p1` and `p2` (uniform parameterisation), tangent-scaled by 0.5.
fn catmull(p0: [f32; 2], p1: [f32; 2], p2: [f32; 2], p3: [f32; 2], t: f32) -> [f32; 2] {
    let t2 = t * t;
    let t3 = t2 * t;
    let mut o = [0.0f32; 2];
    for k in 0..2 {
        let (a0, a1, a2, a3) = (p0[k], p1[k], p2[k], p3[k]);
        o[k] = 0.5 * ((2.0 * a1) + (-a0 + a2) * t + (2.0 * a0 - 5.0 * a1 + 4.0 * a2 - a3) * t2 + (-a0 + 3.0 * a1 - 3.0 * a2 + a3) * t3);
    }
    o
}

fn draw_markers(ctx: &mut Ctx, pts: impl Iterator<Item = [f32; 2]>, r: f32, color: Rgba) {
    let mut seen = HashSet::new();
    for p in pts {
        if seen.len() >= MAX_MARKERS {
            break;
        }
        if seen.insert(((p[0] * 0.5) as i32, (p[1] * 0.5) as i32)) {
            ctx.out.push(Prim::Circle { cx: p[0], cy: p[1], r, fill: Some(color), stroke: Some((WHITE, 0.75)) });
        }
    }
}

fn value_range(it: impl Iterator<Item = f64>) -> Option<(f64, f64)> {
    it.fold(None, |acc, v| match acc {
        None => Some((v, v)),
        Some((a, b)) => Some((a.min(v), b.max(v))),
    })
}

// ---------------------------------------------------------------- trendlines

/// Samples along a regression trendline.
const TREND_STEPS: usize = 200;

/// Whether series drawn as `k` show trendlines (Excel offers them on 2-D unstacked column,
/// bar, line, area, scatter and bubble charts).
pub fn supports_trendline(k: ChartKind) -> bool {
    use ChartKind::*;
    matches!(k, ColumnClustered | BarClustered | Line | LineMarkers | Area | Scatter | ScatterLines | Bubble)
}

/// A forecast distance as drawn: finite, non-negative and bounded.
fn forecast(v: f64) -> f64 {
    if v.is_finite() && v > 0.0 { v.min(1e9) } else { 0.0 }
}

/// Longest forward forecast among `s`'s regression trendlines.
fn max_forward(s: &SeriesData) -> f64 {
    s.trendlines.iter().filter(|t| !matches!(t.spec.kind, TrendlineKind::MovingAverage(_))).map(|t| forecast(t.spec.forward)).fold(0.0, f64::max)
}

/// Longest backward forecast among `s`'s regression trendlines.
fn max_backward(s: &SeriesData) -> f64 {
    s.trendlines.iter().filter(|t| !matches!(t.spec.kind, TrendlineKind::MovingAverage(_))).map(|t| forecast(t.spec.backward)).fold(0.0, f64::max)
}

/// Liang–Barsky: the part of segment `a`–`b` inside the unit square, with whether the start and
/// end were cut.
#[allow(clippy::type_complexity)]
fn clip_segment(a: (f64, f64), b: (f64, f64)) -> Option<((f64, f64), (f64, f64), bool, bool)> {
    let (dx, dy) = (b.0 - a.0, b.1 - a.1);
    let (mut t0, mut t1) = (0.0f64, 1.0f64);
    for (p, q) in [(-dx, a.0), (dx, 1.0 - a.0), (-dy, a.1), (dy, 1.0 - a.1)] {
        if p == 0.0 {
            if q < 0.0 {
                return None;
            }
        } else {
            let r = q / p;
            if p < 0.0 {
                if r > t1 {
                    return None;
                }
                t0 = t0.max(r);
            } else {
                if r < t0 {
                    return None;
                }
                t1 = t1.min(r);
            }
        }
    }
    Some(((a.0 + t0 * dx, a.1 + t0 * dy), (a.0 + t1 * dx, a.1 + t1 * dy), t0 > 0.0, t1 < 1.0))
}

/// Clips a sampled polyline in plot fractions (`None` = gap) to the plot box (the unit
/// square), returning the visible runs.
fn clip_unit(pts: &[Option<(f64, f64)>]) -> Vec<Vec<(f64, f64)>> {
    const LIM: f64 = 1e9;
    let ok = |p: &(f64, f64)| p.0.is_finite() && p.1.is_finite();
    let cl = |p: (f64, f64)| (p.0.clamp(-LIM, LIM), p.1.clamp(-LIM, LIM));
    let mut runs: Vec<Vec<(f64, f64)>> = Vec::new();
    let mut run: Vec<(f64, f64)> = Vec::new();
    for w in pts.windows(2) {
        let seg = match w {
            [Some(a), Some(b)] if ok(a) && ok(b) => clip_segment(cl(*a), cl(*b)),
            _ => None,
        };
        match seg {
            Some((p, q, cut_start, cut_end)) => {
                if cut_start || run.is_empty() {
                    if run.len() >= 2 {
                        runs.push(std::mem::take(&mut run));
                    }
                    run.clear();
                    run.push(p);
                }
                run.push(q);
                if cut_end {
                    runs.push(std::mem::take(&mut run));
                }
            }
            None => {
                if run.len() >= 2 {
                    runs.push(std::mem::take(&mut run));
                }
                run.clear();
            }
        }
    }
    if run.len() >= 2 {
        runs.push(run);
    }
    runs
}

/// Draws `s`'s trendlines fitted to its plotted points `pts` (data x, y). `frac` maps data to
/// fractions of the plot box (0..1 inside, along the x and y axes), `px` fractions to pixels.
/// Equation and R² label lines are appended to `labels`. Degenerate fits draw nothing.
fn draw_trendlines(
    ctx: &mut Ctx,
    s: &SeriesData,
    pts: &[(f64, f64)],
    frac: &dyn Fn(f64, f64) -> (f64, f64),
    px: &dyn Fn((f64, f64)) -> [f32; 2],
    labels: &mut Vec<String>,
) {
    let Some((xlo, xhi)) = value_range(pts.iter().map(|p| p.0)) else { return };
    for t in s.trendlines.iter().take(MAX_TRENDLINES) {
        let spec = &t.spec;
        let samples: Vec<Option<(f64, f64)>> = match spec.kind {
            TrendlineKind::MovingAverage(p) => moving_average(pts, p).into_iter().map(|(x, y)| Some(frac(x, y))).collect(),
            _ => {
                let Some(fit) = fit_trendline(spec, pts) else { continue };
                let (lo, hi) = (xlo - forecast(spec.backward), xhi + forecast(spec.forward));
                if spec.display_equation {
                    labels.push(fit.equation());
                }
                if spec.display_r_squared {
                    labels.push(fit.r_squared());
                }
                (0..=TREND_STEPS)
                    .map(|i| {
                        let x = lo + (hi - lo) * i as f64 / TREND_STEPS as f64;
                        fit.eval(x).map(|y| frac(x, y))
                    })
                    .collect()
            }
        };
        let width = spec.width.filter(|w| w.is_finite()).unwrap_or(1.5).clamp(0.25, 12.0);
        let dash = spec.dash != Some(LineDash::Solid);
        for run in clip_unit(&samples) {
            let line = decimate(run.into_iter().map(px).collect(), MAX_LINE_PTS);
            if line.len() >= 2 {
                ctx.out.push(Prim::Line { pts: line, color: t.color, width, dash });
            }
        }
    }
}

/// Trendline equation / R² labels, stacked in the plot's top-right corner.
fn draw_trend_labels(ctx: &mut Ctx, plot: Bx, labels: &[String]) {
    let lh = LABEL_SIZE * 1.3;
    for (i, t) in labels.iter().enumerate() {
        let y = plot.y + 4.0 + i as f32 * lh;
        if y + lh > plot.bottom() {
            break;
        }
        let t = ctx.fit(t, LABEL_SIZE, plot.w - 8.0);
        ctx.text(plot.right() - 4.0, y, &t, LABEL_SIZE, TEXT, HAlign::Right, VAlign::Top);
    }
}

// ---------------------------------------------------------------- cartesian (column/bar/line/area/combo)

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum Fam {
    Col,
    ColStack,
    Col100,
    Line,
    LineStack,
    Area,
    AreaStack,
}

fn family(k: ChartKind) -> Fam {
    use ChartKind::*;
    match k {
        ColumnStacked | BarStacked => Fam::ColStack,
        ColumnStacked100 | BarStacked100 => Fam::Col100,
        Line | LineMarkers | Scatter | ScatterLines | Radar | Stock => Fam::Line,
        LineStacked => Fam::LineStack,
        Area => Fam::Area,
        AreaStacked => Fam::AreaStack,
        _ => Fam::Col,
    }
}

fn is_col(f: Fam) -> bool {
    matches!(f, Fam::Col | Fam::ColStack | Fam::Col100)
}
fn is_line(f: Fam) -> bool {
    matches!(f, Fam::Line | Fam::LineStack)
}

fn cartesian(ctx: &mut Ctx, chart: &Chart, data: &ChartData, area: Bx, horizontal: bool) {
    let ncat = data.categories.len().max(data.series.iter().map(|s| s.values.len()).max().unwrap_or(0)).min(MAX_CATS);
    if ncat == 0 {
        return;
    }
    let kinds: Vec<ChartKind> = data.series.iter().map(|s| if horizontal { chart.kind } else { plot_kind(chart, s) }).collect();
    let fams: Vec<Fam> = kinds.iter().map(|k| family(*k)).collect();
    let any_primary = data.series.iter().any(|s| !s.secondary);
    let sec: Vec<bool> = data.series.iter().map(|s| s.secondary && any_primary && !horizontal).collect();

    // Totals for 100% stacking, per axis.
    let mut totals = [vec![0.0f64; ncat], vec![0.0f64; ncat]];
    for (i, s) in data.series.iter().enumerate() {
        if fams.get(i) == Some(&Fam::Col100) {
            let a = sec.get(i).copied().unwrap_or(false) as usize;
            for (j, v) in s.values.iter().take(ncat).enumerate() {
                if let (Some(v), Some(t)) = (v, totals.get_mut(a).and_then(|t| t.get_mut(j))) {
                    *t += v.abs();
                }
            }
        }
    }
    // Stack accumulators keyed by (axis, family): positive and negative running sums.
    let mut stacks: Vec<((bool, Fam), Vec<f64>, Vec<f64>)> = Vec::new();
    let mut spans: Vec<Vec<Option<(f64, f64)>>> = Vec::with_capacity(data.series.len());
    for (i, s) in data.series.iter().enumerate() {
        let fam = fams.get(i).copied().unwrap_or(Fam::Col);
        let a = sec.get(i).copied().unwrap_or(false);
        let stacked = matches!(fam, Fam::ColStack | Fam::Col100 | Fam::LineStack | Fam::AreaStack);
        let key = (a, fam);
        let si = if stacked {
            match stacks.iter().position(|(k, _, _)| *k == key) {
                Some(p) => Some(p),
                None => {
                    stacks.push((key, vec![0.0; ncat], vec![0.0; ncat]));
                    Some(stacks.len() - 1)
                }
            }
        } else {
            None
        };
        let mut row = Vec::with_capacity(ncat);
        for j in 0..ncat {
            let v = s.values.get(j).copied().flatten();
            let span = match (si.and_then(|p| stacks.get_mut(p)), fam) {
                (Some((_, pos, neg)), Fam::ColStack | Fam::Col100) => v.and_then(|v| {
                    let v = if fam == Fam::Col100 {
                        let t = totals.get(a as usize).and_then(|t| t.get(j)).copied().unwrap_or(0.0);
                        if t > 0.0 { v / t } else { 0.0 }
                    } else {
                        v
                    };
                    let acc = if v >= 0.0 { pos.get_mut(j) } else { neg.get_mut(j) }?;
                    let base = *acc;
                    *acc += v;
                    Some((base, *acc))
                }),
                (Some((_, pos, _)), _) => {
                    let v = v.unwrap_or(0.0);
                    pos.get_mut(j).map(|acc| {
                        let base = *acc;
                        *acc = clean(*acc + v);
                        (base, *acc)
                    })
                }
                (None, _) => v.map(|v| (0.0, v)),
            };
            row.push(span);
        }
        spans.push(row);
    }

    // Axis scales.
    let mut axes: Vec<(Scale, Fmt)> = Vec::new();
    for axis in [false, true] {
        let members: Vec<usize> = (0..data.series.len()).filter(|i| sec.get(*i).copied().unwrap_or(false) == axis).collect();
        if members.is_empty() {
            continue;
        }
        let force_zero = members.iter().any(|i| fams.get(*i).is_some_and(|f| !is_line(*f)));
        let all100 = members.iter().all(|i| fams.get(*i) == Some(&Fam::Col100));
        let range = value_range(members.iter().flat_map(|i| {
            let line = fams.get(*i).is_some_and(|f| is_line(*f));
            spans.get(*i).into_iter().flatten().flatten().flat_map(move |(b, t)| if line { vec![*t] } else { vec![*b, *t] })
        }));
        let (lo, hi) = range.unwrap_or((0.0, 0.0));
        let (scale, fmt) = if all100 {
            (fixed_scale(if lo < -1e-9 { -1.0 } else { 0.0 }, if hi > 1e-9 || lo >= -1e-9 { 1.0 } else { 0.0 }, 0.2), Fmt::new("0%"))
        } else {
            let code = members.first().and_then(|i| data.series.get(*i)).map(|s| s.number_format.as_str()).unwrap_or("General");
            (nice_scale(lo, hi, force_zero), Fmt::new(code))
        };
        axes.push((scale, fmt));
        if !axis && sec.iter().all(|s| !s) {
            break;
        }
    }
    let Some((s1, f1)) = axes.first() else { return };
    let y1 = ValAxis { scale: *s1, fmt: f1 };
    let y2 = axes.get(1).map(|(s, f)| ValAxis { scale: *s, fmt: f });
    // A forward forecast on a category axis adds empty category slots after the data.
    let fwd = data
        .series
        .iter()
        .enumerate()
        .filter(|(i, _)| kinds.get(*i).is_some_and(|k| supports_trendline(*k)))
        .map(|(_, s)| max_forward(s))
        .fold(0.0, f64::max);
    let ncat_slots = ncat.saturating_add(fwd.ceil() as usize).min(MAX_CATS.max(ncat));
    let labels: Vec<String> = (0..ncat_slots).map(|j| if j < ncat { cat_label(data, j) } else { String::new() }).collect();
    let plot = frame(ctx, area, CatAxis::Labels(&labels), &y1, y2.as_ref(), horizontal, chart.gridlines);
    if !plot.ok() {
        return;
    }
    let scale_of = |i: usize| -> Scale { if sec.get(i).copied().unwrap_or(false) { y2.as_ref().map(|a| a.scale).unwrap_or(*s1) } else { *s1 } };
    let cat_len = if horizontal { plot.h } else { plot.w };
    let cw = cat_len / ncat_slots as f32;
    let center = |j: usize| if horizontal { plot.bottom() - (j as f32 + 0.5) * cw } else { plot.x + (j as f32 + 0.5) * cw };
    let vpos = |v: f64, sc: &Scale| if horizontal { plot.x + sc.frac(v) * plot.w } else { plot.bottom() - sc.frac(v) * plot.h };

    // Column slots: each clustered series gets one, each stack group shares one.
    let mut slot_keys: Vec<(bool, Fam, usize)> = Vec::new();
    let mut slot_of = vec![0usize; data.series.len()];
    for (i, f) in fams.iter().enumerate() {
        if !is_col(*f) {
            continue;
        }
        let a = sec.get(i).copied().unwrap_or(false);
        let key = if *f == Fam::Col { (a, *f, i) } else { (a, *f, usize::MAX) };
        let k = match slot_keys.iter().position(|k| *k == key) {
            Some(p) => p,
            None => {
                slot_keys.push(key);
                slot_keys.len() - 1
            }
        };
        if let Some(s) = slot_of.get_mut(i) {
            *s = k;
        }
    }
    let nslots = slot_keys.len().max(1) as f32;
    let bw = cw / (nslots + 1.5);
    let labels_on = chart.data_labels && ncat <= MAX_LABELS;

    // Areas first, then columns, then lines on top.
    for pass in 0..3 {
        for (i, s) in data.series.iter().enumerate() {
            let fam = fams.get(i).copied().unwrap_or(Fam::Col);
            let want = match pass {
                0 => matches!(fam, Fam::Area | Fam::AreaStack),
                1 => is_col(fam),
                _ => is_line(fam),
            };
            if !want {
                continue;
            }
            let sc = scale_of(i);
            let fmt = Fmt::new(&s.number_format);
            let row = match spans.get(i) {
                Some(r) => r,
                None => continue,
            };
            match pass {
                0 => {
                    let mut top = Vec::with_capacity(ncat * 2);
                    let mut base = Vec::with_capacity(ncat);
                    for (j, sp) in row.iter().enumerate() {
                        let (b, t) = sp.unwrap_or((0.0, 0.0));
                        let c = center(j);
                        top.push([c, vpos(t, &sc)]);
                        base.push([c, vpos(b, &sc)]);
                    }
                    if top.len() == 1 {
                        // A single point: give it some width.
                        if let (Some(t), Some(b)) = (top.first().copied(), base.first().copied()) {
                            top = vec![[t[0] - cw * 0.3, t[1]], [t[0] + cw * 0.3, t[1]]];
                            base = vec![[b[0] - cw * 0.3, b[1]], [b[0] + cw * 0.3, b[1]]];
                        }
                    }
                    let top = decimate(top, MAX_LINE_PTS * 2);
                    let base = decimate(base, MAX_LINE_PTS * 2);
                    let mut poly = top;
                    poly.extend(base.into_iter().rev());
                    if poly.len() >= 3 {
                        ctx.out.push(Prim::Polygon { pts: poly, fill: s.color, stroke: None });
                    }
                }
                1 => {
                    let k = slot_of.get(i).copied().unwrap_or(0) as f32;
                    for (j, sp) in row.iter().enumerate() {
                        let Some((b, t)) = sp else { continue };
                        let (pb, pt) = (vpos(*b, &sc), vpos(*t, &sc));
                        let c = center(j);
                        let lo = pb.min(pt);
                        let len = (pb - pt).abs();
                        if horizontal {
                            let y = c + nslots * bw / 2.0 - (k + 1.0) * bw;
                            ctx.rect(lo, y, len, bw, s.color, None);
                        } else {
                            let x = c - nslots * bw / 2.0 + k * bw;
                            ctx.rect(x, lo, bw, len, s.color, None);
                        }
                        if labels_on && let Some(v) = s.values.get(j).copied().flatten() {
                            let t = fmt.format(v, None);
                            let stacked = fam != Fam::Col;
                            let mid = (pb + pt) / 2.0;
                            if horizontal {
                                let y = c + nslots * bw / 2.0 - (k + 0.5) * bw;
                                if stacked {
                                    ctx.text(mid, y, &t, LABEL_SIZE, on(s.color), HAlign::Center, VAlign::Middle);
                                } else if v >= 0.0 {
                                    ctx.text(pb.max(pt) + 3.0, y, &t, LABEL_SIZE, TEXT, HAlign::Left, VAlign::Middle);
                                } else {
                                    ctx.text(lo - 3.0, y, &t, LABEL_SIZE, TEXT, HAlign::Right, VAlign::Middle);
                                }
                            } else {
                                let x = c - nslots * bw / 2.0 + (k + 0.5) * bw;
                                if stacked {
                                    ctx.text(x, mid, &t, LABEL_SIZE, on(s.color), HAlign::Center, VAlign::Middle);
                                } else if v >= 0.0 {
                                    ctx.text(x, lo - 2.0, &t, LABEL_SIZE, TEXT, HAlign::Center, VAlign::Bottom);
                                } else {
                                    ctx.text(x, lo + len + 2.0, &t, LABEL_SIZE, TEXT, HAlign::Center, VAlign::Top);
                                }
                            }
                        }
                    }
                }
                _ => {
                    let pts: Vec<Option<[f32; 2]>> = row.iter().enumerate().map(|(j, sp)| sp.map(|(_, t)| [center(j), vpos(t, &sc)])).collect();
                    draw_runs(ctx, &pts, s.color, 2.25, s.smooth.then_some(plot));
                    let k = kinds.get(i).copied().unwrap_or(ChartKind::Line);
                    if k == ChartKind::LineMarkers && cw >= 3.0 {
                        draw_markers(ctx, pts.iter().flatten().copied(), 3.5, s.color);
                    }
                    if labels_on {
                        for (j, p) in pts.iter().enumerate() {
                            if let (Some(p), Some(v)) = (p, s.values.get(j).copied().flatten()) {
                                ctx.text(p[0], p[1] - 5.0, &fmt.format(v, None), LABEL_SIZE, TEXT, HAlign::Center, VAlign::Bottom);
                            }
                        }
                    }
                }
            }
        }
    }
    // Trendlines on top: x is the category number 1..n.
    let mut trend_labels = Vec::new();
    for (i, s) in data.series.iter().enumerate() {
        if s.trendlines.is_empty() || !kinds.get(i).is_some_and(|k| supports_trendline(*k)) {
            continue;
        }
        let sc = scale_of(i);
        let pts: Vec<(f64, f64)> = s.values.iter().take(ncat).enumerate().filter_map(|(j, v)| v.map(|v| ((j + 1) as f64, v))).collect();
        let frac = |x: f64, y: f64| ((x - 0.5) / ncat_slots as f64, (y - sc.min) / (sc.max - sc.min));
        let px = |(fx, fy): (f64, f64)| {
            if horizontal {
                [plot.x + fy as f32 * plot.w, plot.bottom() - fx as f32 * plot.h]
            } else {
                [plot.x + fx as f32 * plot.w, plot.bottom() - fy as f32 * plot.h]
            }
        };
        draw_trendlines(ctx, s, &pts, &frac, &px, &mut trend_labels);
    }
    draw_trend_labels(ctx, plot, &trend_labels);
}

// ---------------------------------------------------------------- scatter & bubble

fn scatter(ctx: &mut Ctx, chart: &Chart, data: &ChartData, area: Bx) {
    let pts_of = |s: &SeriesData| -> Vec<Option<(f64, f64)>> {
        s.values
            .iter()
            .enumerate()
            .map(|(j, v)| {
                let x = match &s.x {
                    Some(xs) => xs.get(j).copied().flatten(),
                    None => Some((j + 1) as f64),
                };
                match (x, v) {
                    (Some(x), Some(y)) => Some((x, *y)),
                    _ => None,
                }
            })
            .collect()
    };
    let all: Vec<Vec<Option<(f64, f64)>>> = data.series.iter().map(pts_of).collect();
    let Some((mut xlo, mut xhi)) = value_range(all.iter().flatten().flatten().map(|p| p.0)) else { return };
    // Forecasts extend the x axis to the trendline's ends.
    for (s, pts) in data.series.iter().zip(&all) {
        if let Some((lo, hi)) = value_range(pts.iter().flatten().map(|p| p.0)).filter(|_| !s.trendlines.is_empty()) {
            xlo = xlo.min(lo - max_backward(s));
            xhi = xhi.max(hi + max_forward(s));
        }
    }
    let Some((ylo, yhi)) = value_range(all.iter().flatten().flatten().map(|p| p.1)) else { return };
    let xs = nice_scale(xlo, xhi, false);
    let ys = nice_scale(ylo, yhi, false);
    let fx = Fmt::new("General");
    let fy = Fmt::new(data.series.first().map(|s| s.number_format.as_str()).unwrap_or("General"));
    let plot = frame(ctx, area, CatAxis::Numeric(xs, &fx), &ValAxis { scale: ys, fmt: &fy }, None, false, chart.gridlines);
    if !plot.ok() {
        return;
    }
    let map = |(x, y): (f64, f64)| [plot.x + xs.frac(x) * plot.w, plot.bottom() - ys.frac(y) * plot.h];
    let bubble = chart.kind == ChartKind::Bubble;
    let rmax = plot.w.min(plot.h) * 0.12;
    for (s, pts) in data.series.iter().zip(&all) {
        let px: Vec<Option<[f32; 2]>> = pts.iter().map(|p| p.map(map)).collect();
        if bubble {
            let sizes = s.sizes.as_deref().unwrap_or(&[]);
            let smax = sizes.iter().flatten().fold(0.0f64, |a, b| a.max(*b));
            let mut bubbles: Vec<([f32; 2], f64)> = px
                .iter()
                .enumerate()
                .filter_map(|(j, p)| {
                    let sz = if sizes.is_empty() { Some(1.0) } else { sizes.get(j).copied().flatten() };
                    match (p, sz) {
                        (Some(p), Some(sz)) if sz > 0.0 => Some((*p, sz)),
                        _ => None,
                    }
                })
                .take(MAX_MARKERS)
                .collect();
            bubbles.sort_by(|a, b| b.1.total_cmp(&a.1));
            let smax = if sizes.is_empty() { 1.0 } else { smax };
            let fill = [s.color[0], s.color[1], s.color[2], 0xC0];
            for (p, sz) in bubbles {
                let r = ((sz / smax).sqrt() as f32 * rmax).max(1.0);
                ctx.out.push(Prim::Circle { cx: p[0], cy: p[1], r, fill: Some(fill), stroke: Some((WHITE, 0.75)) });
            }
        } else {
            let lines = chart.kind == ChartKind::ScatterLines || s.kind == ChartKind::ScatterLines;
            if lines {
                draw_runs(ctx, &px, s.color, 2.0, s.smooth.then_some(plot));
            }
            if !lines || px.len() <= 500 {
                draw_markers(ctx, px.iter().flatten().copied(), 3.5, s.color);
            }
        }
        if chart.data_labels && pts.len() <= MAX_LABELS {
            for (p, raw) in px.iter().zip(pts) {
                if let (Some(p), Some((_, y))) = (p, raw) {
                    ctx.text(p[0], p[1] - 6.0, &fy.format(*y, None), LABEL_SIZE, TEXT, HAlign::Center, VAlign::Bottom);
                }
            }
        }
    }
    let mut trend_labels = Vec::new();
    for (s, pts) in data.series.iter().zip(&all) {
        if s.trendlines.is_empty() {
            continue;
        }
        let pts: Vec<(f64, f64)> = pts.iter().flatten().copied().collect();
        let frac = |x: f64, y: f64| ((x - xs.min) / (xs.max - xs.min), (y - ys.min) / (ys.max - ys.min));
        let px = |(fx, fy): (f64, f64)| [plot.x + fx as f32 * plot.w, plot.bottom() - fy as f32 * plot.h];
        draw_trendlines(ctx, s, &pts, &frac, &px, &mut trend_labels);
    }
    draw_trend_labels(ctx, plot, &trend_labels);
}

// ---------------------------------------------------------------- histogram

fn histogram(ctx: &mut Ctx, chart: &Chart, data: &ChartData, area: Bx) {
    let Some(s) = data.series.first() else { return };
    let vals: Vec<f64> = s.values.iter().flatten().copied().collect();
    let Some((lo, hi)) = value_range(vals.iter().copied()) else { return };
    let n = vals.len();
    let span = hi - lo;
    let mut bins = ((n as f64).sqrt().ceil() as usize).clamp(1, 100);
    if !(span.is_finite() && span > 0.0) {
        bins = 1;
    }
    let width = if bins == 1 && span.partial_cmp(&0.0) != Some(std::cmp::Ordering::Greater) { 1.0 } else { span / bins as f64 };
    let mut counts = vec![0usize; bins];
    for v in &vals {
        let b = if width > 0.0 { ((v - lo) / width).floor() } else { 0.0 };
        let b = if b.is_finite() && b > 0.0 { (b as usize).min(bins - 1) } else { 0 };
        if let Some(c) = counts.get_mut(b) {
            *c += 1;
        }
    }
    let f = Fmt::new(&s.number_format);
    let labels: Vec<String> = (0..bins)
        .map(|b| {
            let a = lo + b as f64 * width;
            let e = if b + 1 == bins { hi.max(a) } else { a + width };
            let open = if b == 0 { '[' } else { '(' };
            format!("{open}{}, {}]", f.format(a, Some(width / 10.0)), f.format(e, Some(width / 10.0)))
        })
        .collect();
    let maxc = counts.iter().copied().max().unwrap_or(0) as f64;
    let ys = nice_scale(0.0, maxc, true);
    let fc = Fmt::new("General");
    let plot = frame(ctx, area, CatAxis::Labels(&labels), &ValAxis { scale: ys, fmt: &fc }, None, false, chart.gridlines);
    if !plot.ok() {
        return;
    }
    let cw = plot.w / bins as f32;
    for (b, c) in counts.iter().enumerate() {
        let top = plot.bottom() - ys.frac(*c as f64) * plot.h;
        let x = plot.x + b as f32 * cw;
        ctx.rect(x, top, cw, plot.bottom() - top, s.color, Some((WHITE, 0.75)));
        if chart.data_labels {
            ctx.text(x + cw / 2.0, top - 2.0, &c.to_string(), LABEL_SIZE, TEXT, HAlign::Center, VAlign::Bottom);
        }
    }
}

// ---------------------------------------------------------------- waterfall

fn waterfall(ctx: &mut Ctx, chart: &Chart, data: &ChartData, area: Bx) {
    let Some(s) = data.series.first() else { return };
    let mut ncat = data.categories.len().max(s.values.len()).min(MAX_CATS);
    if ncat == 0 {
        return;
    }
    let mut labels: Vec<String> = (0..ncat).map(|j| cat_label(data, j)).collect();
    let mut vals: Vec<f64> = (0..ncat).map(|j| s.values.get(j).copied().flatten().unwrap_or(0.0)).collect();
    let mut is_total = vec![false; ncat];
    let last_total = labels.last().is_some_and(|l| l.to_lowercase().contains("total"));
    if let Some(t) = is_total.last_mut() {
        *t = last_total;
    }
    if !last_total {
        labels.push("Total".into());
        vals.push(0.0);
        is_total.push(true);
        ncat += 1;
    }
    let mut bars = Vec::with_capacity(ncat);
    let mut cum = 0.0f64;
    for (j, v) in vals.iter().enumerate() {
        if is_total.get(j).copied().unwrap_or(false) {
            let total = if last_total && j + 1 == ncat && *v != 0.0 { *v } else { cum };
            bars.push((0.0, total, 0u8));
            cum = total;
        } else {
            let top = clean(cum + v);
            bars.push((cum, top, if *v >= 0.0 { 1 } else { 2 }));
            cum = top;
        }
    }
    let (lo, hi) = value_range(bars.iter().flat_map(|(b, t, _)| [*b, *t])).unwrap_or((0.0, 0.0));
    let ys = nice_scale(lo, hi, true);
    let f = Fmt::new(&s.number_format);
    let plot = frame(ctx, area, CatAxis::Labels(&labels), &ValAxis { scale: ys, fmt: &f }, None, false, chart.gridlines);
    if !plot.ok() {
        return;
    }
    let cw = plot.w / ncat as f32;
    let bw = cw / 1.5;
    let vy = |v: f64| plot.bottom() - ys.frac(v) * plot.h;
    for (j, (b, t, kind)) in bars.iter().enumerate() {
        let color = match kind {
            1 => UP,
            2 => DOWN,
            _ => s.color,
        };
        let x = plot.x + (j as f32 + 0.5) * cw - bw / 2.0;
        let (yb, yt) = (vy(*b), vy(*t));
        ctx.rect(x, yb.min(yt), bw, (yb - yt).abs().max(0.5), color, None);
        if j + 1 < bars.len() && ncat <= 500 {
            ctx.out.push(Prim::Line { pts: vec![[x + bw, yt], [x + cw, yt]], color: AXIS, width: 0.75, dash: true });
        }
        if chart.data_labels && ncat <= MAX_LABELS {
            let v = if *kind == 0 { *t } else { t - b };
            ctx.text(x + bw / 2.0, yb.min(yt) - 2.0, &f.format(v, None), LABEL_SIZE, TEXT, HAlign::Center, VAlign::Bottom);
        }
    }
}

// ---------------------------------------------------------------- funnel

fn funnel(ctx: &mut Ctx, data: &ChartData, area: Bx) {
    let Some(s) = data.series.first() else { return };
    let n = data.categories.len().max(s.values.len()).min(MAX_CATS);
    if n == 0 {
        return;
    }
    let vals: Vec<f64> = (0..n).map(|j| s.values.get(j).copied().flatten().unwrap_or(0.0).abs()).collect();
    let max = vals.iter().copied().fold(0.0f64, f64::max);
    if max.is_nan() || max <= 0.0 {
        return;
    }
    let labels: Vec<String> = (0..n).map(|j| cat_label(data, j)).collect();
    let lw = (labels.iter().take(2000).map(|t| ctx.tw(t, LABEL_SIZE)).fold(0.0f32, f32::max) + 8.0).min(area.w * 0.35);
    let plot = Bx { x: area.x + lw, w: area.w - lw, ..area };
    if !plot.ok() {
        return;
    }
    let slot = plot.h / n as f32;
    let bh = slot * 0.85;
    let f = Fmt::new(&s.number_format);
    let show = slot >= LABEL_SIZE * 0.9;
    for (j, v) in vals.iter().enumerate() {
        let bw = (*v / max) as f32 * plot.w;
        let x = plot.x + (plot.w - bw) / 2.0;
        let y = plot.y + j as f32 * slot + (slot - bh) / 2.0;
        if bw > 0.0 {
            ctx.rect(x, y, bw, bh, s.color, None);
        }
        if show {
            let yc = y + bh / 2.0;
            let t = f.format(s.values.get(j).copied().flatten().unwrap_or(0.0), None);
            let color = if ctx.tw(&t, LABEL_SIZE) + 4.0 <= bw { on(s.color) } else { TEXT };
            ctx.text(plot.cx(), yc, &t, LABEL_SIZE, color, HAlign::Center, VAlign::Middle);
            let l = ctx.fit(labels.get(j).map(String::as_str).unwrap_or(""), LABEL_SIZE, lw - 8.0);
            ctx.text(plot.x - 6.0, yc, &l, LABEL_SIZE, TEXT, HAlign::Right, VAlign::Middle);
        }
    }
}

// ---------------------------------------------------------------- pie, doughnut, sunburst

fn pie(ctx: &mut Ctx, chart: &Chart, data: &ChartData, area: Bx, inner: f32, names: bool) {
    let Some(s) = data.series.first() else { return };
    let vals: Vec<f64> = s.values.iter().take(MAX_CATS).map(|v| v.map(f64::abs).unwrap_or(0.0)).collect();
    let total: f64 = vals.iter().sum();
    if !(total.is_finite() && total > 0.0) {
        return;
    }
    let (cx, cy) = (area.cx(), area.cy());
    let r = area.w.min(area.h) / 2.0 * 0.92;
    if r < 2.0 {
        return;
    }
    let ri = r * inner;
    let f = Fmt::new(&s.number_format);
    let mut a = 0.0f32;
    let mut labels = Vec::new();
    for (j, v) in vals.iter().enumerate() {
        let sweep = (*v / total) as f32 * TAU;
        if sweep > 1e-4 {
            let fill = point_color(data, j);
            ctx.out.push(Prim::Wedge { cx, cy, r_outer: r, r_inner: ri, a0: a, a1: (a + sweep).min(TAU), fill, stroke: Some((WHITE, 1.5)) });
            if (chart.data_labels || names) && vals.len() <= MAX_LABELS {
                let t = if names { cat_label(data, j) } else { f.format(s.values.get(j).copied().flatten().unwrap_or(0.0), None) };
                let mid = a + sweep / 2.0;
                let rr = if ri > 0.0 { (r + ri) / 2.0 } else { r * 0.65 };
                let room = sweep * rr;
                if ctx.tw(&t, LABEL_SIZE) <= room.max(r - ri) && room >= LABEL_SIZE {
                    labels.push((cx + rr * mid.sin(), cy - rr * mid.cos(), t, on(fill)));
                }
            }
        }
        a += sweep;
    }
    for (x, y, t, c) in labels {
        ctx.text(x, y, &t, LABEL_SIZE, c, HAlign::Center, VAlign::Middle);
    }
}

// ---------------------------------------------------------------- treemap

fn worst(row: &[f64], side: f64) -> f64 {
    let s: f64 = row.iter().sum();
    if s <= 0.0 || side <= 0.0 {
        return f64::INFINITY;
    }
    let (mn, mx) = row.iter().fold((f64::INFINITY, 0.0f64), |(a, b), v| (a.min(*v), b.max(*v)));
    let s2 = s * s;
    let w2 = side * side;
    (w2 * mx / s2).max(s2 / (w2 * mn))
}

/// Squarified treemap layout of (index, area) items, sorted descending, into `r`.
fn squarify(items: &[(usize, f64)], r: Bx) -> Vec<(usize, Bx)> {
    let total: f64 = items.iter().map(|i| i.1).sum();
    let area = (r.w as f64) * (r.h as f64);
    if !(total > 0.0 && area > 0.0) {
        return vec![];
    }
    let scale = area / total;
    let mut out = Vec::with_capacity(items.len());
    let mut rem = r;
    let mut row: Vec<(usize, f64)> = Vec::new();
    let mut i = 0;
    let layout = |row: &[(usize, f64)], rem: &mut Bx, out: &mut Vec<(usize, Bx)>| {
        let s: f64 = row.iter().map(|x| x.1).sum();
        if s <= 0.0 {
            return;
        }
        if rem.w >= rem.h {
            let cw = (s / rem.h.max(1e-6) as f64) as f32;
            let mut y = rem.y;
            for (j, a) in row {
                let h = (*a / cw.max(1e-6) as f64) as f32;
                out.push((*j, Bx { x: rem.x, y, w: cw, h }));
                y += h;
            }
            rem.x += cw;
            rem.w = (rem.w - cw).max(0.0);
        } else {
            let rh = (s / rem.w.max(1e-6) as f64) as f32;
            let mut x = rem.x;
            for (j, a) in row {
                let w = (*a / rh.max(1e-6) as f64) as f32;
                out.push((*j, Bx { x, y: rem.y, w, h: rh }));
                x += w;
            }
            rem.y += rh;
            rem.h = (rem.h - rh).max(0.0);
        }
    };
    while let Some(&(j, v)) = items.get(i) {
        let a = v * scale;
        let side = rem.w.min(rem.h) as f64;
        let cur: Vec<f64> = row.iter().map(|x| x.1).collect();
        let mut with = cur.clone();
        with.push(a);
        if row.is_empty() || worst(&with, side) <= worst(&cur, side) {
            row.push((j, a));
            i += 1;
        } else {
            layout(&row, &mut rem, &mut out);
            row.clear();
        }
    }
    if !row.is_empty() {
        layout(&row, &mut rem, &mut out);
    }
    out
}

fn treemap(ctx: &mut Ctx, chart: &Chart, data: &ChartData, area: Bx) {
    let Some(s) = data.series.first() else { return };
    let mut items: Vec<(usize, f64)> =
        s.values.iter().take(MAX_MARKERS).enumerate().filter_map(|(j, v)| v.filter(|v| *v > 0.0).map(|v| (j, v))).collect();
    items.sort_by(|a, b| b.1.total_cmp(&a.1));
    let f = Fmt::new(&s.number_format);
    for (j, b) in squarify(&items, area) {
        let fill = point_color(data, j);
        ctx.rect(b.x, b.y, b.w, b.h, fill, Some((WHITE, 1.5)));
        if b.w > 24.0 && b.h > LABEL_SIZE * 1.6 {
            let name = ctx.fit(&cat_label(data, j), LABEL_SIZE, b.w - 8.0);
            ctx.text(b.x + 4.0, b.y + 4.0, &name, LABEL_SIZE, on(fill), HAlign::Left, VAlign::Top);
            if chart.data_labels && b.h > LABEL_SIZE * 3.2 {
                let v = items.iter().find(|x| x.0 == j).map(|x| x.1).unwrap_or(0.0);
                let t = ctx.fit(&f.format(v, None), LABEL_SIZE, b.w - 8.0);
                ctx.text(b.x + 4.0, b.y + 4.0 + LABEL_SIZE * 1.4, &t, LABEL_SIZE, on(fill), HAlign::Left, VAlign::Top);
            }
        }
    }
}

// ---------------------------------------------------------------- radar

fn radar(ctx: &mut Ctx, chart: &Chart, data: &ChartData, area: Bx) {
    let ncat = data.categories.len().max(data.series.iter().map(|s| s.values.len()).max().unwrap_or(0)).min(1000);
    if ncat == 0 {
        return;
    }
    let labels: Vec<String> = (0..ncat).map(|j| cat_label(data, j)).collect();
    let lw = labels.iter().map(|t| ctx.tw(t, LABEL_SIZE)).fold(0.0f32, f32::max).min(area.w * 0.2);
    let r = ((area.w - 2.0 * (lw + 8.0)).min(area.h - 2.0 * (LABEL_SIZE * 1.4 + 6.0)) / 2.0).max(0.0);
    if r < 5.0 {
        return;
    }
    let (cx, cy) = (area.cx(), area.cy());
    let (lo, hi) = value_range(data.series.iter().flat_map(|s| s.values.iter().flatten().copied())).unwrap_or((0.0, 0.0));
    let sc = nice_scale(lo, hi, true);
    let f = Fmt::new(data.series.first().map(|s| s.number_format.as_str()).unwrap_or("General"));
    let ang = |j: usize| j as f32 / ncat as f32 * TAU;
    let pt = |a: f32, rr: f32| [cx + rr * a.sin(), cy - rr * a.cos()];
    let ticks = sc.ticks();
    let spacing = r / ticks.len().saturating_sub(1).max(1) as f32;
    let every = ((LABEL_SIZE * 1.3 / spacing.max(1e-3)).ceil() as usize).max(1);
    for (ti, t) in ticks.into_iter().enumerate() {
        let rr = sc.frac(t) * r;
        if rr > 0.5 && chart.gridlines {
            let mut ring: Vec<[f32; 2]> = (0..ncat).map(|j| pt(ang(j), rr)).collect();
            if ncat < 3 {
                ring = (0..=48).map(|k| pt(k as f32 / 48.0 * TAU, rr)).collect();
            } else if let Some(p) = ring.first().copied() {
                ring.push(p);
            }
            ctx.line(ring, GRID, 0.75);
        }
        if ti % every == 0 {
            ctx.text(cx - 3.0, cy - rr, &f.format(t, Some(sc.step)), LABEL_SIZE * 0.9, TEXT, HAlign::Right, VAlign::Middle);
        }
    }
    let step = ncat.div_ceil(72).max(1);
    for j in (0..ncat).step_by(step) {
        let a = ang(j);
        ctx.line(vec![[cx, cy], pt(a, r)], GRID, 0.75);
        let p = pt(a, r + 6.0);
        let (sa, ca) = (a.sin(), a.cos());
        let align = if sa > 0.1 {
            HAlign::Left
        } else if sa < -0.1 {
            HAlign::Right
        } else {
            HAlign::Center
        };
        let valign = if ca > 0.1 {
            VAlign::Bottom
        } else if ca < -0.1 {
            VAlign::Top
        } else {
            VAlign::Middle
        };
        let t = ctx.fit(labels.get(j).map(String::as_str).unwrap_or(""), LABEL_SIZE, lw.max(20.0));
        ctx.text(p[0], p[1], &t, LABEL_SIZE, TEXT, align, valign);
    }
    for s in &data.series {
        let mut pts: Vec<[f32; 2]> = (0..ncat).map(|j| pt(ang(j), sc.frac(s.values.get(j).copied().flatten().unwrap_or(sc.min)) * r)).collect();
        if let Some(p) = pts.first().copied() {
            pts.push(p);
        }
        ctx.line(pts, s.color, 2.0);
    }
}

// ---------------------------------------------------------------- box & whisker

fn quantile(sorted: &[f64], q: f64) -> f64 {
    let n = sorted.len();
    if n == 0 {
        return 0.0;
    }
    let pos = q * (n - 1) as f64;
    let i = pos.floor() as usize;
    let frac = pos - i as f64;
    let a = sorted.get(i).copied().unwrap_or(0.0);
    let b = sorted.get(i + 1).copied().unwrap_or(a);
    a + (b - a) * frac
}

fn box_whisker(ctx: &mut Ctx, data: &ChartData, area: Bx) {
    let labels: Vec<String> = data.series.iter().map(|s| s.name.clone()).collect();
    let Some((lo, hi)) = value_range(data.series.iter().flat_map(|s| s.values.iter().flatten().copied())) else { return };
    let ys = nice_scale(lo, hi, false);
    let f = Fmt::new(data.series.first().map(|s| s.number_format.as_str()).unwrap_or("General"));
    let plot = frame(ctx, area, CatAxis::Labels(&labels), &ValAxis { scale: ys, fmt: &f }, None, false, true);
    if !plot.ok() {
        return;
    }
    let n = data.series.len().max(1);
    let cw = plot.w / n as f32;
    let bw = (cw * 0.4).min(80.0);
    let vy = |v: f64| plot.bottom() - ys.frac(v) * plot.h;
    for (i, s) in data.series.iter().enumerate() {
        let mut v: Vec<f64> = s.values.iter().flatten().copied().collect();
        if v.is_empty() {
            continue;
        }
        v.sort_by(f64::total_cmp);
        let (q1, med, q3) = (quantile(&v, 0.25), quantile(&v, 0.5), quantile(&v, 0.75));
        let iqr = q3 - q1;
        let (flo, fhi) = (q1 - 1.5 * iqr, q3 + 1.5 * iqr);
        let wlo = v.iter().copied().find(|x| *x >= flo).unwrap_or(q1);
        let whi = v.iter().rev().copied().find(|x| *x <= fhi).unwrap_or(q3);
        let mean = v.iter().sum::<f64>() / v.len() as f64;
        let c = plot.x + (i as f32 + 0.5) * cw;
        ctx.vline(c, vy(whi), vy(q3), s.color, 1.25);
        ctx.vline(c, vy(q1), vy(wlo), s.color, 1.25);
        ctx.hline(c - bw / 4.0, c + bw / 4.0, vy(whi), s.color, 1.25);
        ctx.hline(c - bw / 4.0, c + bw / 4.0, vy(wlo), s.color, 1.25);
        let (yt, yb) = (vy(q3), vy(q1));
        ctx.rect(c - bw / 2.0, yt, bw, (yb - yt).max(0.5), s.color, None);
        ctx.hline(c - bw / 2.0, c + bw / 2.0, vy(med), WHITE, 1.5);
        let (mx, my, d) = (c, vy(mean), 3.0);
        ctx.line(vec![[mx - d, my - d], [mx + d, my + d]], WHITE, 1.25);
        ctx.line(vec![[mx - d, my + d], [mx + d, my - d]], WHITE, 1.25);
        for o in v.iter().filter(|x| **x < flo || **x > fhi).take(MAX_MARKERS) {
            ctx.out.push(Prim::Circle { cx: c, cy: vy(*o), r: 2.5, fill: None, stroke: Some((s.color, 1.0)) });
        }
    }
}

// ---------------------------------------------------------------- stock

fn stock(ctx: &mut Ctx, data: &ChartData, area: Bx) {
    let ncat = data.categories.len().max(data.series.iter().map(|s| s.values.len()).max().unwrap_or(0)).min(MAX_CATS);
    if ncat == 0 {
        return;
    }
    let labels: Vec<String> = (0..ncat).map(|j| cat_label(data, j)).collect();
    let Some((lo, hi)) = value_range(data.series.iter().flat_map(|s| s.values.iter().flatten().copied())) else { return };
    let ys = nice_scale(lo, hi, false);
    let f = Fmt::new(data.series.first().map(|s| s.number_format.as_str()).unwrap_or("General"));
    let plot = frame(ctx, area, CatAxis::Labels(&labels), &ValAxis { scale: ys, fmt: &f }, None, false, true);
    if !plot.ok() {
        return;
    }
    let ser = |k: usize| data.series.get(k);
    let (open, high, low, close) = match data.series.len() {
        0 => return,
        1 => (None, None, None, ser(0)),
        2 => (None, ser(0), ser(1), None),
        3 => (None, ser(0), ser(1), ser(2)),
        _ => (ser(0), ser(1), ser(2), ser(3)),
    };
    let get = |s: Option<&SeriesData>, j: usize| s.and_then(|s| s.values.get(j).copied().flatten());
    let cw = plot.w / ncat as f32;
    let tick = (cw * 0.25).max(1.0);
    let vy = |v: f64| plot.bottom() - ys.frac(v) * plot.h;
    for j in 0..ncat {
        let c = plot.x + (j as f32 + 0.5) * cw;
        if let (Some(h), Some(l)) = (get(high, j), get(low, j)) {
            ctx.vline(c, vy(h), vy(l), STOCK, 1.25);
        }
        match (get(open, j), get(close, j)) {
            (Some(o), Some(cl)) => {
                let (yo, yc) = (vy(o), vy(cl));
                let bw = (cw * 0.5).max(1.0);
                let fill = if cl >= o { WHITE } else { STOCK };
                ctx.rect(c - bw / 2.0, yo.min(yc), bw, (yo - yc).abs().max(0.75), fill, Some((STOCK, 1.0)));
            }
            (None, Some(cl)) => {
                if high.is_some() {
                    ctx.hline(c, c + tick, vy(cl), STOCK, 1.25);
                } else {
                    ctx.out.push(Prim::Circle { cx: c, cy: vy(cl), r: 2.5, fill: Some(STOCK), stroke: None });
                }
            }
            _ => {}
        }
    }
}

// ---------------------------------------------------------------- final safety pass

fn fin(v: f32) -> bool {
    v.is_finite()
}

fn clamp_stroke(s: Option<(Rgba, f32)>) -> Option<(Rgba, f32)> {
    s.filter(|(_, w)| fin(*w) && *w > 0.0).map(|(c, w)| (c, w.min(50.0)))
}

/// Drops non-finite primitives and clamps every coordinate into the `w`×`h` box.
pub(crate) fn finalize(prims: Vec<Prim>, w: f32, h: f32) -> Vec<Prim> {
    let cx = |v: f32| v.clamp(0.0, w);
    let cy = |v: f32| v.clamp(0.0, h);
    let pts_ok = |pts: &[[f32; 2]]| pts.iter().all(|p| fin(p[0]) && fin(p[1]));
    prims
        .into_iter()
        .filter_map(|p| match p {
            Prim::Rect { x, y, w: rw, h: rh, fill, stroke, radius } => {
                if !(fin(x) && fin(y) && fin(rw) && fin(rh)) {
                    return None;
                }
                let (x0, x1) = (cx(x.min(x + rw)), cx(x.max(x + rw)));
                let (y0, y1) = (cy(y.min(y + rh)), cy(y.max(y + rh)));
                if x1 - x0 <= 0.0 || y1 - y0 <= 0.0 {
                    return None;
                }
                let radius = if fin(radius) { radius.clamp(0.0, (x1 - x0).min(y1 - y0) / 2.0) } else { 0.0 };
                Some(Prim::Rect { x: x0, y: y0, w: x1 - x0, h: y1 - y0, fill, stroke: clamp_stroke(stroke), radius })
            }
            Prim::Line { pts, color, width, dash } => {
                if !pts_ok(&pts) || pts.len() < 2 || !fin(width) {
                    return None;
                }
                let pts = pts.into_iter().map(|p| [cx(p[0]), cy(p[1])]).collect();
                Some(Prim::Line { pts, color, width: width.clamp(0.1, 50.0), dash })
            }
            Prim::Polygon { pts, fill, stroke } => {
                if !pts_ok(&pts) || pts.len() < 3 {
                    return None;
                }
                let pts = pts.into_iter().map(|p| [cx(p[0]), cy(p[1])]).collect();
                Some(Prim::Polygon { pts, fill, stroke: clamp_stroke(stroke) })
            }
            Prim::Wedge { cx: x, cy: y, r_outer, r_inner, a0, a1, fill, stroke } => {
                if ![x, y, r_outer, r_inner, a0, a1].iter().all(|v| fin(*v)) {
                    return None;
                }
                let (x, y) = (cx(x), cy(y));
                let maxr = x.min(w - x).min(y).min(h - y);
                let ro = r_outer.min(maxr);
                if ro <= 0.0 {
                    return None;
                }
                Some(Prim::Wedge { cx: x, cy: y, r_outer: ro, r_inner: r_inner.clamp(0.0, ro), a0, a1, fill, stroke: clamp_stroke(stroke) })
            }
            Prim::Circle { cx: x, cy: y, r, fill, stroke } => {
                if !(fin(x) && fin(y) && fin(r)) {
                    return None;
                }
                let (x, y) = (cx(x), cy(y));
                let r = r.min(x.min(w - x).min(y).min(h - y));
                if r <= 0.0 {
                    return None;
                }
                Some(Prim::Circle { cx: x, cy: y, r, fill, stroke: clamp_stroke(stroke) })
            }
            Prim::Text { x, y, text, size, color, bold, align, valign, rotation } => {
                if !(fin(x) && fin(y) && fin(size) && fin(rotation)) || text.is_empty() {
                    return None;
                }
                Some(Prim::Text { x: cx(x), y: cy(y), text, size: size.clamp(1.0, 200.0), color, bold, align, valign, rotation })
            }
        })
        .collect()
}

#[cfg(test)]
mod smooth_tests {
    use super::*;

    #[test]
    fn long_runs_are_smoothed_uniformly_within_the_cap() {
        let plot = Bx { x: 0.0, y: 0.0, w: 3000.0, h: 100.0 };
        let pts: Vec<[f32; 2]> = (0..1500).map(|i| [i as f32 * 2.0, if i % 2 == 0 { 20.0 } else { 80.0 }]).collect();
        let out = smooth_run(pts, plot);
        assert!(out.len() <= MAX_LINE_PTS * 2 + 1, "{}", out.len());
        // Two sub-segments per segment all the way to the end, not 100 each and then a straight tail.
        assert_eq!(out.len(), 1499 * 2 + 1);
        assert_eq!(out.last().copied(), Some([2998.0, 80.0]));
    }

    #[test]
    fn spline_overshoot_is_clamped_to_the_plot() {
        let plot = Bx { x: 0.0, y: 10.0, w: 300.0, h: 100.0 };
        // A step right at the plot edges: Catmull-Rom overshoots past both.
        let pts = vec![[0.0, 110.0], [100.0, 110.0], [110.0, 10.0], [200.0, 10.0], [300.0, 10.0]];
        let out = smooth_run(pts, plot);
        assert!(out.len() > 5);
        assert!(out.iter().all(|p| (0.0..=300.0).contains(&p[0]) && (10.0..=110.0).contains(&p[1])));
    }
}