Slopegraph Chart

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

import { scaleBand, scaleLinear } from "d3-scale";
import { TrendingUp } from "lucide-react";

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

interface SlopeDatum {
    Metro: string;
    year: string;
    inequality: number;
}

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

function generateDemoData(): SlopeDatum[] {
    const metros = ["New York", "San Francisco", "Chicago", "Boston", "Houston"];
    const results: SlopeDatum[] = [];

    metros.forEach((m, idx) => {
        const v1980 = 4.0 + idx * 0.4;
        const v2015 = v1980 + 2.5 + (idx % 2 === 0 ? 1.2 : -0.5);
        results.push({ Metro: m, year: "1980", inequality: v1980 });
        results.push({ Metro: m, year: "2015", inequality: v2015 });
    });
    return results;
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const d = points[0].datum as SlopeDatum;
    if (!d) return { title: "", rows: [] };
    return {
        title: `${d.Metro} (${d.year})`,
        rows: [
            {
                label: "Wage Ratio",
                value: d.inequality.toFixed(1),
                color: points[0].color || "var(--chart-1)",
            },
        ],
    };
}

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

    const labels = useMemo(() => {
        return data.filter((d) => d.year === "2015");
    }, [data]);

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        lineY(data, {
                            id: "metro-lines",
                            x: "year",
                            y: "inequality",
                            color: "Metro",
                            key: (d: SlopeDatum) => `${d.Metro}:${d.year}`,
                            strokeWidth: 2,
                        }),
                        dot(data, {
                            id: "metro-points",
                            x: "year",
                            y: "inequality",
                            color: "Metro",
                            key: (d: SlopeDatum) => `${d.Metro}:${d.year}`,
                            r: 3.5,
                        }),
                        text(labels, {
                            id: "endpoint-labels",
                            x: "year",
                            y: "inequality",
                            text: "Metro",
                            color: "Metro",
                            dx: 6,
                            anchor: "start",
                            fontSize: 11,
                            fontWeight: 600,
                        }),
                    ],
                    scales: {
                        x: {
                            scale: () => scaleBand<string>().domain(["1980", "2015"]).padding(0.2),
                            axis: {
                                line: false,
                                ticks: { size: 0, padding: 10 },
                            },
                        },
                        y: {
                            scale: scaleLinear().domain([3, 10]),
                            grid: true,
                            axis: {
                                line: false,
                                label: "90/10 Wage Inequality Ratio",
                                ticks: { size: 0 },
                            },
                        },
                    },
                    color: {
                        domain: ["New York", "San Francisco", "Chicago", "Boston", "Houston"],
                        range: [
                            "var(--chart-1)",
                            "var(--chart-2)",
                            "var(--chart-3)",
                            "var(--chart-4)",
                            "var(--chart-5)",
                        ],
                    },
                    margin: { top: 24, right: 85, bottom: 32, left: 45 },
                    theme: {
                        foreground: "var(--muted-foreground)",
                        grid: "var(--border)",
                        background: "transparent",
                    },
                },
                {
                    focus: "group-x",
                    tooltip: {
                        use: tooltip,
                        className:
                            "font-sans shadow-none rounded-md bg-popover text-popover-foreground border p-2 text-xs",
                        anchor: "group-center",
                        placement: "auto",
                        content: (points) => shadcnTooltipContent(points),
                    },
                },
            ),
        [data, labels],
    );

    return (
        <Card className="w-full max-w-xl">
            <CardHeader>
                <CardTitle>Metro Inequality Slopegraph</CardTitle>
                <CardDescription>
                    Two-period slopegraph tracking metro wage inequality changes from 1980 to 2015
                </CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[250px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={250}
                        ariaLabel="Metro Inequality Slopegraph Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    All observed metropolitan areas show steep upward ratio trajectories{" "}
                    <TrendingUp className="h-4 w-4 text-amber-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    Slope inclination directly visualizes relative rate of increase across periods
                </div>
            </CardFooter>
        </Card>
    );
}

export default SlopegraphChart;