Pie Chart Legend

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

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

function generateDemoData() {
    return [
        { browser: "chrome", visitors: 275 },
        { browser: "safari", visitors: 200 },
        { browser: "firefox", visitors: 187 },
        { browser: "edge", visitors: 173 },
        { browser: "other", visitors: 90 },
    ];
}

const browserNames = ["chrome", "safari", "firefox", "edge", "other"] as const;
const chartColors = ["var(--chart-1)", "var(--chart-2)", "var(--chart-3)", "var(--chart-4)", "var(--chart-5)"];

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

function titleCase(value: string) {
    return value.charAt(0).toUpperCase() + value.slice(1);
}

function browserMetric(datum: unknown) {
    if (!datum || typeof datum !== "object") return undefined;
    const browser = Reflect.get(datum, "browser");
    const visitors = Reflect.get(datum, "visitors");
    return typeof browser === "string" && typeof visitors === "number" && Number.isFinite(visitors)
        ? { browser, visitors }
        : undefined;
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    const point = points.find((candidate) => browserMetric(candidate.datum));
    const metric = point && browserMetric(point.datum);
    return metric
        ? {
              title: titleCase(metric.browser),
              rows: [
                  {
                      label: "Visitors",
                      value: metric.visitors.toLocaleString("en-US"),
                      color: point.color,
                  },
              ],
          }
        : { rows: [] };
}

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

    const definition = useMemo(() => {
        const arcs = pie(data, {
            value: "visitors",
            startAngle: Math.PI / 2,
            endAngle: (-Math.PI * 3) / 2,
        });

        const separator = 1;
        const marks = [
            radialArc(arcs, {
                id: "browser-slices",
                key: "browser",
                innerRadius: undefined,
                color: "browser",
                stroke: "var(--background)",
                strokeWidth: separator,
            }),
        ];

        return defineChart(
            {
                renderer: motionRenderer,
                motion: {
                    transition: { type: "spring", stiffness: 170, damping: 18, mass: 1 },
                },
                scales: {
                    x: null,
                    y: null,
                },
                marks: [
                    polar({
                        radiusRatio: 0.78,
                        scales: {
                            angle: null,
                            radius: null,
                        },
                        marks,
                    }),
                ],
                color: { domain: browserNames, range: chartColors },
                margin: 0,
            },
            {
                focus: focusGroupAngle,
                tooltip: {
                    use: tooltip,
                    motion: { type: "spring", stiffness: 170, damping: 18 },
                    className: "font-sans shadow-none rounded-md bg-popover text-popover-foreground border p-2 text-xs",
                    anchor: "group-center",
                    placement: "auto",
                    sort: "color-domain",
                    content: (points) => shadcnTooltipContent(points),
                },
            },
        );
    }, [data]);

    return (
        <Card className="flex w-full max-w-md flex-col">
            <CardHeader className="items-center pb-0">
                <CardTitle>Global User Demographics</CardTitle>
                <CardDescription>Active user base distribution by geographic region</CardDescription>
            </CardHeader>
            <CardContent className="flex-1 pb-0">
                <div className="mx-auto flex aspect-square max-h-[250px] w-full items-center justify-center">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        initialWidth={250}
                        height={250}
                        ariaLabel="Global User Demographics Chart"
                    />
                </div>
                <div className="text-muted-foreground flex flex-wrap items-center justify-center gap-4 pt-4 pb-2 text-sm">
                    {data.map((item, index) => (
                        <div key={item.browser} className="flex items-center gap-1.5">
                            <span className="h-2 w-2 rounded-full" style={{ backgroundColor: chartColors[index] }} />
                            <span>{titleCase(item.browser)}</span>
                        </div>
                    ))}
                </div>
            </CardContent>
        </Card>
    );
}

export default PieLegend;