ECharts Axis Pointer

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

import { scaleLinear, scaleUtc } from "d3-scale";
import { Crosshair } from "lucide-react";

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

interface IndustryDatum {
    industry: string;
    date: Date;
    unemployed: number;
}

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

const industriesList = ["Trade", "Manufacturing", "Tech"];

function generateDemoData(): IndustryDatum[] {
    const results: IndustryDatum[] = [];
    const months = 12;

    for (let m = 0; m < months; m++) {
        const date = new Date(Date.UTC(2024, m, 1));
        industriesList.forEach((ind, idx) => {
            const base = 120 + idx * 40 + Math.sin(m * 0.5) * 35;
            results.push({
                industry: ind,
                date,
                unemployed: Math.round(base + (Math.random() - 0.5) * 15),
            });
        });
    }

    return results;
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const date = (points[0].datum as IndustryDatum)?.date;
    const dateObj = date ? (date instanceof Date ? date : new Date(date)) : null;
    const titleText =
        dateObj && !isNaN(dateObj.getTime())
            ? dateObj.toLocaleDateString("en-US", { month: "short", year: "numeric", timeZone: "UTC" })
            : "";

    const rows = points.map((p, idx) => {
        const d = p.datum as IndustryDatum;
        return {
            label: d.industry,
            value: `${d.unemployed}k`,
            color: `var(--chart-${idx + 1})`,
        };
    });

    return { title: titleText, rows };
}

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

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        lineY(data, {
                            id: "industry-lines",
                            x: "date",
                            y: "unemployed",
                            z: "industry",
                            color: "industry",
                            key: (row: IndustryDatum) =>
                                `${row.industry}:${row?.date ? (row.date instanceof Date ? row.date.getTime() : new Date(row.date).getTime()) : 0}`,
                            strokeWidth: 2,
                        }),
                        dot(data, {
                            id: "industry-points",
                            x: "date",
                            y: "unemployed",
                            z: "industry",
                            color: "industry",
                            key: (row: IndustryDatum) =>
                                `${row.industry}:${row?.date ? (row.date instanceof Date ? row.date.getTime() : new Date(row.date).getTime()) : 0}`,
                            r: 3.5,
                            stroke: "var(--background)",
                            strokeWidth: 1,
                        }),
                        focusGuideX(data, {
                            id: "axis-pointer-guide",
                            x: "date",
                            y: "unemployed",
                            z: "industry",
                            key: (row: IndustryDatum) =>
                                `${row.industry}:${row?.date ? (row.date instanceof Date ? row.date.getTime() : new Date(row.date).getTime()) : 0}`,
                            xRule: {
                                stroke: "var(--muted-foreground)",
                                strokeWidth: 1,
                                strokeDasharray: "4 4",
                            },
                        }),
                    ],
                    scales: {
                        x: {
                            scale: scaleUtc,
                            axis: {
                                ticks: {
                                    format: (v: any) => {
                                        const dateObj = v instanceof Date ? v : new Date(v);
                                        return isNaN(dateObj.getTime())
                                            ? ""
                                            : dateObj.toLocaleDateString("en-US", { month: "short", timeZone: "UTC" });
                                    },
                                },
                            },
                        },
                        y: {
                            scale: scaleLinear,
                            grid: true,
                            axis: { label: "Unemployed (Thousands)" },
                        },
                    },
                    color: {
                        domain: industriesList,
                        range: ["var(--chart-1)", "var(--chart-2)", "var(--chart-3)"],
                    },
                    focus: "group-x",
                    focusRing: false,
                    maxFocusDistance: Number.POSITIVE_INFINITY,
                    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>Snapped Axis Pointer Grouped Crosshair</CardTitle>
                <CardDescription>
                    ECharts-style vertical snapping axis pointer grouping multi-series metrics at X timeline steps
                </CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[250px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={250}
                        ariaLabel="Snapped Axis Pointer Grouped Crosshair Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    Crosshair line snaps to exact X positions comparing all 3 industries{" "}
                    <Crosshair className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    `focus: group-x` automatically locks pointer cursor to nearest temporal timestamp step
                </div>
            </CardFooter>
        </Card>
    );
}

export default EchartsAxisPointer;