Hexbin Density

import { type ChartPoint, defineChart } from "@tanstack/charts";
import { motion } from "@tanstack/charts/motion";
import { hexbin } from "@tanstack/charts/spatial/hexbin";
import { tooltip } from "@tanstack/charts/tooltip";
import { Chart } from "@tanstack/react-charts/core";
import { useMemo } from "react";

import { scaleLinear, scaleThreshold } from "d3-scale";
import { Hexagon } from "lucide-react";

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

interface HexDatum {
    weight: number;
    mpg: number;
}

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

function generateDemoData(): HexDatum[] {
    const results: HexDatum[] = [];
    for (let i = 0; i < 250; i++) {
        const weight = 1800 + Math.random() * 3200;
        const baseMpg = 45 - (weight - 1800) * 0.008;
        const mpg = Math.max(8, baseMpg + (Math.random() - 0.5) * 12);
        results.push({ weight, mpg });
    }
    return results;
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const datum = points[0].datum as { x: number; y: number; count: number };
    if (!datum) return { title: "", rows: [] };
    return {
        title: `Bin Center: ${datum.x?.toFixed(0)} lb, ${datum.y?.toFixed(1)} mpg`,
        rows: [{ label: "Data Point Count", value: `${datum.count} items`, color: "var(--chart-1)" }],
    };
}

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

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        hexbin(data, {
                            x: "weight",
                            y: "mpg",
                            binWidth: 24,
                            color: "count",
                            r: 11,
                            stroke: "var(--background)",
                            strokeWidth: 0.75,
                        }),
                    ],
                    scales: {
                        x: {
                            scale: scaleLinear().domain([1500, 5200]),
                            grid: true,
                            axis: { label: "Vehicle Weight (lb)" },
                        },
                        y: {
                            scale: scaleLinear().domain([5, 50]),
                            grid: true,
                            axis: { label: "Fuel Economy (mpg)" },
                        },
                    },
                    color: {
                        scale: scaleThreshold<number, string>,
                        domain: [3, 8, 15],
                        range: ["var(--chart-5)", "var(--chart-3)", "var(--chart-2)", "var(--chart-1)"],
                    },
                    margin: { top: 24, right: 24, bottom: 32, left: 45 },
                    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>Hexagonal Point Density Binned Plot</CardTitle>
                <CardDescription>
                    Spatial hexbin clustering mapping vehicle weight vs fuel efficiency density
                </CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[250px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={250}
                        ariaLabel="Hexagonal Point Density Binned Plot Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    High density concentration around 2,500 lbs & 30 mpg{" "}
                    <Hexagon className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    Hexagonal tessellation avoids visual scatter plot overlap in dense bivariate distributions
                </div>
            </CardFooter>
        </Card>
    );
}

export default HexbinDensity;