//! Charts: title, plot area with axes and gridlines, series marks, legend.

use deckcraft_color::{ColorTransform, Rgba, SchemeSlot};
use deckcraft_model::Shape;
use deckcraft_model::chart::{Chart, ChartType, nice_scale};
use deckcraft_model::resolve::Ctx;
use deckcraft_model::style::{ColorRef, Fill};
use deckcraft_model::text::{Align, Anchor, Bullet, TextBody};
use kurbo::{Affine, BezPath, Point, Rect, Shape as _};
use vello_cpu::RenderContext;

use crate::color;

const SLOTS: [SchemeSlot; 6] =
    [SchemeSlot::Accent1, SchemeSlot::Accent2, SchemeSlot::Accent3, SchemeSlot::Accent4, SchemeSlot::Accent5, SchemeSlot::Accent6];

/// Colour of series/point `i`: accents, then darker and lighter rounds.
pub fn series_color(ctx: &Ctx, c: &Chart, i: usize) -> Rgba {
    let slot = SLOTS.get(i % 6).copied().unwrap_or(SchemeSlot::Accent1);
    let base = ctx.color(&ColorRef::scheme(slot), None);
    let mono = c.palette.starts_with("monochrome");
    let base = if mono { ctx.color(&ColorRef::scheme(SchemeSlot::Accent1), None) } else { base };
    let round = if mono { i } else { i / 6 };
    match round {
        0 => base,
        1 => deckcraft_color::apply(base, &[ColorTransform::Shade(60000)]),
        2 => deckcraft_color::apply(base, &[ColorTransform::Tint(60000)]),
        n => deckcraft_color::apply(base, &[ColorTransform::LumMod(100000 - (n as i32 % 5) * 12000)]),
    }
}

fn series_fill(ctx: &Ctx, c: &Chart, i: usize, s: Option<&deckcraft_model::chart::Series>) -> Rgba {
    match s.and_then(|s| s.fill.as_ref()) {
        Some(Fill::Solid { color: cc }) => ctx.color(cc, None),
        _ => series_color(ctx, c, i),
    }
}

fn label(ctx: &mut RenderContext, rctx: &Ctx, m: Affine, text: &str, r: Rect, size: f64, align: Align, anchor: Anchor, col: Rgba, bold: bool) {
    let mut body = TextBody::from_text(text);
    body.body.inset_l = Some(0.0);
    body.body.inset_r = Some(0.0);
    body.body.inset_t = Some(0.0);
    body.body.inset_b = Some(0.0);
    body.body.anchor = Some(anchor);
    body.body.wrap = Some(false);
    for p in &mut body.paragraphs {
        p.props.align = Some(align);
        p.props.bullet = Some(Bullet::None);
        p.props.margin_left = Some(0.0);
        p.props.indent = Some(0.0);
        for run in &mut p.runs {
            run.props.size = Some(size);
            run.props.bold = Some(bold);
            run.props.fill = Some(Fill::solid(ColorRef::rgb(col)));
        }
    }
    let tmp = Shape { text: Some(body.clone()), ..Default::default() };
    crate::draw_text(ctx, rctx, &tmp, &body, r, m, &deckcraft_text::NoFields, None);
}

fn fmt_num(v: f64) -> String {
    if (v - v.round()).abs() < 1e-9 { format!("{}", v.round() as i64) } else { format!("{v:.1}") }
}

pub fn draw(ctx: &mut RenderContext, rctx: &Ctx, c: &Chart, m: Affine, w: f64, h: f64) {
    let text_col = c.text_color.as_ref().map(|t| rctx.color(t, None)).unwrap_or(Rgba::rgb(0x59, 0x59, 0x59));
    let grid_col = Rgba::rgb(0xD9, 0xD9, 0xD9);
    if let Some(f) = &c.chart_fill {
        crate::paint::fill_path(
            ctx,
            rctx,
            f,
            None,
            &Rect::new(0.0, 0.0, w, h).to_path(0.1),
            Rect::new(0.0, 0.0, w, h),
            m,
            deckcraft_geom::preset::FillMode::Norm,
            1.0,
            rctx.pres,
        );
    }
    let base = (h.min(w) / 22.0).clamp(7.0, 18.0);
    let mut area = Rect::new(w * 0.04, h * 0.04, w * 0.96, h * 0.96);
    if let Some(t) = &c.title {
        label(ctx, rctx, m, t, Rect::new(0.0, area.y0, w, area.y0 + base * 1.8), base * 1.4, Align::Center, Anchor::Top, text_col, false);
        area.y0 += base * 2.4;
    }
    let pie = matches!(c.kind, ChartType::Pie | ChartType::Doughnut);
    // Legend at the bottom.
    let legend_items: Vec<(String, Rgba)> = if pie {
        c.categories.iter().enumerate().map(|(i, n)| (n.clone(), series_color(rctx, c, i))).collect()
    } else {
        c.series.iter().enumerate().map(|(i, s)| (s.name.clone(), series_fill(rctx, c, i, Some(s)))).collect()
    };
    if c.legend.is_some() && !legend_items.is_empty() {
        let ly = area.y1 - base * 1.4;
        let item_w = (legend_items.iter().map(|(n, _)| n.chars().count() as f64 * base * 0.55 + base * 1.6).sum::<f64>()).min(w * 0.9);
        let mut x = (w - item_w) / 2.0;
        for (name, col) in &legend_items {
            ctx.set_transform(m);
            ctx.set_paint(color(*col, 1.0));
            ctx.fill_rect(&Rect::new(x, ly + base * 0.3, x + base * 0.7, ly + base));
            let tw = name.chars().count() as f64 * base * 0.55 + base;
            label(ctx, rctx, m, name, Rect::new(x + base, ly, x + base + tw, ly + base * 1.3), base, Align::Left, Anchor::Middle, text_col, false);
            x += tw + base * 0.6;
        }
        area.y1 = ly - base * 0.5;
    }
    if pie {
        let Some(s) = c.series.first() else { return };
        let vals: Vec<f64> = s.values.iter().map(|v| v.unwrap_or(0.0).max(0.0)).collect();
        let total: f64 = vals.iter().sum();
        if total <= 0.0 {
            return;
        }
        let r = (area.width().min(area.height()) / 2.0) * 0.95;
        let cen = area.center();
        let mut a0 = -std::f64::consts::FRAC_PI_2;
        for (i, v) in vals.iter().enumerate() {
            let sweep = v / total * std::f64::consts::TAU;
            let mut p = BezPath::new();
            p.move_to(cen);
            let arc = kurbo::Arc::new(cen, (r, r), a0, sweep, 0.0);
            p.line_to(Point::new(cen.x + r * a0.cos(), cen.y + r * a0.sin()));
            p.extend(arc.append_iter(0.1));
            p.close_path();
            ctx.set_transform(m);
            let col = s
                .point_fills
                .iter()
                .find(|(k, _)| *k == i)
                .and_then(|(_, f)| if let Fill::Solid { color: cc } = f { Some(rctx.color(cc, None)) } else { None })
                .unwrap_or_else(|| series_color(rctx, c, i));
            ctx.set_paint(color(col, 1.0));
            ctx.fill_path(&p);
            ctx.set_paint(color(Rgba::WHITE, 1.0));
            ctx.set_stroke(kurbo::Stroke::new(1.0));
            ctx.stroke_path(&p);
            if c.data_labels {
                let mid = a0 + sweep / 2.0;
                let lp = Point::new(cen.x + r * 0.65 * mid.cos(), cen.y + r * 0.65 * mid.sin());
                label(
                    ctx,
                    rctx,
                    m,
                    &fmt_num(*v),
                    Rect::new(lp.x - 30.0, lp.y - 10.0, lp.x + 30.0, lp.y + 10.0),
                    base,
                    Align::Center,
                    Anchor::Middle,
                    Rgba::WHITE,
                    false,
                );
            }
            a0 += sweep;
        }
        if c.kind == ChartType::Doughnut {
            ctx.set_transform(m);
            ctx.set_paint(color(Rgba::WHITE, 1.0));
            ctx.fill_path(&kurbo::Circle::new(cen, r * c.hole_size.clamp(0.1, 0.9)).to_path(0.1));
        }
        return;
    }
    let (lo, hi) = c.value_range();
    let (min, max, step) = nice_scale(lo.min(0.0), hi);
    let horiz = c.kind.horizontal();
    // Axis label gutter.
    let gutter = base * 3.0;
    let plot = if horiz {
        Rect::new(area.x0 + gutter * 1.5, area.y0, area.x1, area.y1 - base * 1.6)
    } else {
        Rect::new(area.x0 + gutter, area.y0, area.x1, area.y1 - base * 1.8)
    };
    if let Some(f) = &c.plot_fill {
        crate::paint::fill_path(ctx, rctx, f, None, &plot.to_path(0.1), plot, m, deckcraft_geom::preset::FillMode::Norm, 1.0, rctx.pres);
    }
    let span = (max - min).max(1e-9);
    let to_v = |v: f64| if horiz { plot.x0 + (v - min) / span * plot.width() } else { plot.y1 - (v - min) / span * plot.height() };
    // Gridlines and value labels.
    let n_steps = ((span / step).round() as i64).clamp(1, 50);
    for k in 0..=n_steps {
        let v = min + k as f64 * step;
        let pos = to_v(v);
        let mut g = BezPath::new();
        if horiz {
            g.move_to((pos, plot.y0));
            g.line_to((pos, plot.y1));
            label(
                ctx,
                rctx,
                m,
                &fmt_num(v),
                Rect::new(pos - 30.0, plot.y1 + 2.0, pos + 30.0, plot.y1 + base * 1.5),
                base,
                Align::Center,
                Anchor::Top,
                text_col,
                false,
            );
        } else {
            g.move_to((plot.x0, pos));
            g.line_to((plot.x1, pos));
            label(
                ctx,
                rctx,
                m,
                &fmt_num(v),
                Rect::new(area.x0, pos - base, plot.x0 - base * 0.4, pos + base),
                base,
                Align::Right,
                Anchor::Middle,
                text_col,
                false,
            );
        }
        if c.gridlines {
            ctx.set_transform(m);
            ctx.set_paint(color(grid_col, 1.0));
            ctx.set_stroke(kurbo::Stroke::new(0.75));
            ctx.stroke_path(&g);
        }
    }
    let ncat = c.categories.len().max(c.series.iter().map(|s| s.values.len()).max().unwrap_or(0)).max(1);
    let band = if horiz { plot.height() / ncat as f64 } else { plot.width() / ncat as f64 };
    // Category labels.
    for (i, name) in c.categories.iter().enumerate() {
        let mid = if horiz { plot.y0 + band * (i as f64 + 0.5) } else { plot.x0 + band * (i as f64 + 0.5) };
        if horiz {
            label(
                ctx,
                rctx,
                m,
                name,
                Rect::new(area.x0, mid - base, plot.x0 - base * 0.4, mid + base),
                base,
                Align::Right,
                Anchor::Middle,
                text_col,
                false,
            );
        } else {
            label(
                ctx,
                rctx,
                m,
                name,
                Rect::new(mid - band / 2.0, plot.y1 + 3.0, mid + band / 2.0, plot.y1 + base * 1.6),
                base,
                Align::Center,
                Anchor::Top,
                text_col,
                false,
            );
        }
    }
    let ns = c.series.len().max(1);
    let zero = to_v(0.0f64.clamp(min, max));
    if c.kind.is_bar_like() {
        let gap = c.gap_width.clamp(0.0, 5.0);
        let group = band / (1.0 + gap);
        let stacked = c.kind.stacked();
        let bar = if stacked { group } else { group / ns as f64 };
        for i in 0..ncat {
            let mut pos_acc = 0.0;
            let mut neg_acc = 0.0;
            let total: f64 = if c.kind.percent() {
                c.series.iter().map(|s| s.values.get(i).copied().flatten().unwrap_or(0.0).abs()).sum::<f64>().max(1e-9)
            } else {
                1.0
            };
            for (si, s) in c.series.iter().enumerate() {
                let v = s.values.get(i).copied().flatten().unwrap_or(0.0) / total;
                let start = band * i as f64 + (band - group) / 2.0 + if stacked { 0.0 } else { bar * si as f64 };
                let (a, b) = if stacked {
                    if v >= 0.0 {
                        let r = (pos_acc, pos_acc + v);
                        pos_acc += v;
                        r
                    } else {
                        let r = (neg_acc + v, neg_acc);
                        neg_acc += v;
                        r
                    }
                } else {
                    (0.0f64.min(v), 0.0f64.max(v))
                };
                let r = if horiz {
                    Rect::new(to_v(a), plot.y0 + start, to_v(b), plot.y0 + start + bar)
                } else {
                    Rect::new(plot.x0 + start, to_v(b), plot.x0 + start + bar, to_v(a))
                };
                ctx.set_transform(m);
                ctx.set_paint(color(series_fill(rctx, c, si, Some(s)), 1.0));
                ctx.fill_rect(&r.abs());
                if c.data_labels {
                    let t = fmt_num(s.values.get(i).copied().flatten().unwrap_or(0.0));
                    let lr = if horiz {
                        Rect::new(r.x1 + 2.0, r.y0, r.x1 + 40.0, r.y1)
                    } else {
                        Rect::new(r.x0 - 10.0, r.y0 - base * 1.4, r.x1 + 10.0, r.y0)
                    };
                    label(
                        ctx,
                        rctx,
                        m,
                        &t,
                        lr,
                        base * 0.9,
                        if horiz { Align::Left } else { Align::Center },
                        if horiz { Anchor::Middle } else { Anchor::Bottom },
                        text_col,
                        false,
                    );
                }
            }
        }
    } else {
        // Lines, areas, scatter, radar (drawn as lines).
        let stacked = c.kind.stacked();
        let mut acc = vec![0.0; ncat];
        for (si, s) in c.series.iter().enumerate() {
            let col = series_fill(rctx, c, si, Some(s));
            let mut pts = vec![];
            for i in 0..ncat {
                let Some(v) = s.values.get(i).copied().flatten() else { continue };
                let v = if stacked {
                    let base_v = acc.get(i).copied().unwrap_or(0.0);
                    if let Some(a) = acc.get_mut(i) {
                        *a += v;
                    }
                    base_v + v
                } else {
                    v
                };
                let x = match c.kind {
                    ChartType::Scatter | ChartType::Bubble => {
                        let xs: Vec<f64> = s.x_values.iter().flatten().copied().collect();
                        let (xl, xh) = (xs.iter().copied().fold(f64::MAX, f64::min), xs.iter().copied().fold(f64::MIN, f64::max));
                        let xv = s.x_values.get(i).copied().flatten().unwrap_or(i as f64);
                        if xh > xl { plot.x0 + (xv - xl) / (xh - xl) * plot.width() } else { plot.x0 + band * (i as f64 + 0.5) }
                    }
                    _ => plot.x0 + band * (i as f64 + 0.5),
                };
                pts.push(Point::new(x, to_v(v)));
            }
            if pts.is_empty() {
                continue;
            }
            let mut p = BezPath::new();
            for (k, q) in pts.iter().enumerate() {
                if k == 0 {
                    p.move_to(*q);
                } else {
                    p.line_to(*q);
                }
            }
            ctx.set_transform(m);
            if matches!(c.kind, ChartType::Area | ChartType::StackedArea | ChartType::FilledRadar) {
                let mut a = p.clone();
                if let (Some(l), Some(f)) = (pts.last(), pts.first()) {
                    a.line_to((l.x, zero));
                    a.line_to((f.x, zero));
                    a.close_path();
                }
                ctx.set_paint(color(col, 0.85));
                ctx.fill_path(&a);
            } else if c.kind != ChartType::Scatter {
                ctx.set_paint(color(col, 1.0));
                ctx.set_stroke(kurbo::Stroke::new(2.25).with_join(kurbo::Join::Round).with_caps(kurbo::Cap::Round));
                ctx.stroke_path(&p);
            }
            if matches!(c.kind, ChartType::LineMarkers | ChartType::Scatter | ChartType::Bubble) {
                ctx.set_paint(color(col, 1.0));
                for q in &pts {
                    ctx.fill_path(&kurbo::Circle::new(*q, 3.5).to_path(0.1));
                }
            }
        }
    }
    // Axis line.
    let mut ax = BezPath::new();
    if horiz {
        ax.move_to((zero, plot.y0));
        ax.line_to((zero, plot.y1));
    } else {
        ax.move_to((plot.x0, zero));
        ax.line_to((plot.x1, zero));
    }
    ctx.set_transform(m);
    ctx.set_paint(color(Rgba::rgb(0xBF, 0xBF, 0xBF), 1.0));
    ctx.set_stroke(kurbo::Stroke::new(0.75));
    ctx.stroke_path(&ax);
}