Pie Chart with Radial Callout Leader Lines

import { type ChartPoint, defineChart } from "@tanstack/charts";
import { motion } from "@tanstack/charts/motion";
import { pie, polar, radialArc, radialRule, radialText } from "@tanstack/charts/polar";
import { tooltip } from "@tanstack/charts/tooltip";
import { Chart } from "@tanstack/react-charts/core";
import { useMemo } from "react";

import { scaleLinear } from "d3-scale";
import { PieChart as PieIcon } from "lucide-react";

import { Card, CardContent, CardDescription, CardFooter, CardHeader, CardTitle } from "@/components/ui/card";

interface CategoricalShare {
    category: string;
    value: number;
}

const motionRenderer = motion({
    initial: "always",
    transition: { type: "spring", stiffness: 170, damping: 18, mass: 1 },
});

const tau = Math.PI * 2;
const categories = ["Direct", "Organic Search", "Social Media", "Referral Traffic"];
const colors = ["var(--chart-1)", "var(--chart-2)", "var(--chart-3)", "var(--chart-4)"];

function generateDemoData(): CategoricalShare[] {
    return [
        { category: "Direct", value: 35 },
        { category: "Organic Search", value: 40 },
        { category: "Social Media", value: 15 },
        { category: "Referral Traffic", value: 10 },
    ];
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const d = points[0].datum as CategoricalShare;
    if (!d) return { title: "", rows: [] };
    return {
        title: d.category,
        rows: [{ label: "Share Percentage", value: `${d.value}%`, color: "var(--chart-1)" }],
    };
}

export function LabeledPie() {
    const data = useMemo(() => generateDemoData(), []);

    const definition = useMemo(() => {
        const arcs = pie(data, { value: "value" });

        return defineChart(
            {
                renderer: motionRenderer,
                scales: {
                    x: null,
                    y: null,
                },
                marks: [
                    polar({
                        radiusRatio: 0.5,
                        scales: {
                            angle: { scale: scaleLinear().domain([0, tau]) },
                            radius: { scale: scaleLinear().domain([0, 1]) },
                        },
                        marks: [
                            radialArc(arcs, {
                                id: "pie-slices",
                                key: "category",
                                color: "category",
                            }),
                            radialRule(arcs, {
                                id: "pie-leaders",
                                angle: "angle",
                                radius1: 1,
                                radius2: 1,
                                radius2Offset: 16,
                                key: "category",
                                stroke: "var(--muted-foreground)",
                                strokeWidth: 1,
                            }),
                            radialText(arcs, {
                                id: "pie-labels",
                                angle: "angle",
                                radius: 1,
                                radiusOffset: 18,
                                text: "category",
                                key: "category",
                                color: "category",
                                fontSize: 11,
                                fontWeight: 600,
                                anchor: "outside",
                            }),
                        ],
                    }),
                ],
                color: { domain: categories, range: colors },
                margin: { top: 30, right: 40, bottom: 30, left: 40 },
                theme: {
                    foreground: "var(--muted-foreground)",
                    grid: "var(--border)",
                    background: "transparent",
                },
            },
            {
                keyboard: true,
                tooltip: {
                    use: tooltip,
                    className: "font-sans shadow-none rounded-md bg-popover text-popover-foreground border p-2 text-xs",
                    anchor: "pointer",
                    placement: "auto",
                    content: (points) => shadcnTooltipContent(points),
                },
            },
        );
    }, [data]);

    return (
        <Card className="w-full max-w-xl">
            <CardHeader>
                <CardTitle>Pie Chart with Radial Callout Leader Labels</CardTitle>
                <CardDescription>
                    Categorical breakdown pie chart with pointer leader lines and radial texts
                </CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[270px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={270}
                        ariaLabel="Pie Chart with Radial Callout Leader Labels Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    Leader callouts ensure clear label visibility for tight sectors{" "}
                    <PieIcon className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    `radialRule` and `radialText` project external leader labels around polar pie geometry
                </div>
            </CardFooter>
        </Card>
    );
}

export default LabeledPie;