Themed Monotone Interactive Area

import { type ChartPoint, areaY, crosshair, d3Curve, defineChart, dot, lineY } from "@tanstack/charts";
import { focusGroupX } from "@tanstack/charts/focus";
import { motion } from "@tanstack/charts/motion";
import { tooltip } from "@tanstack/charts/tooltip";
import { Chart } from "@tanstack/react-charts/core";
import { useMemo, useState } from "react";

import { scaleLinear, scaleUtc } from "d3-scale";
import { curveMonotoneX } from "d3-shape";
import { TrendingUp } from "lucide-react";

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

interface VisitorRow {
    id: string;
    date: Date;
    visitors: number;
}

type RangeOption = "7d" | "30d" | "90d";

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

const smoothCurve = d3Curve(curveMonotoneX);

function generateDemoData(daysCount: number): VisitorRow[] {
    const results: VisitorRow[] = [];
    const baseDate = new Date(Date.UTC(2024, 5, 1)).getTime();
    let currentVisitors = 450;

    for (let i = 0; i < daysCount; i++) {
        currentVisitors += Math.floor(Math.sin(i * 0.3) * 40 + (Math.random() - 0.45) * 60);
        const visitors = Math.max(150, currentVisitors);
        const date = new Date(baseDate + i * 24 * 60 * 60 * 1000);
        results.push({
            id: `v-${i}`,
            date,
            visitors,
        });
    }
    return results;
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const d = points[0].datum as VisitorRow;
    if (!d) return { title: "", rows: [] };
    return {
        title: d.date.toLocaleDateString("en-US", { month: "short", day: "numeric", timeZone: "UTC" }),
        rows: [{ label: "Daily Visitors", value: `${d.visitors.toLocaleString()}`, color: "var(--chart-1)" }],
    };
}

export function ThemedInteractiveArea() {
    const [range, setRange] = useState<RangeOption>("30d");

    const daysCount = range === "7d" ? 7 : range === "30d" ? 30 : 90;
    const data = useMemo(() => generateDemoData(daysCount), [daysCount]);

    const firstDate = data[0].date;
    const lastDate = data[data.length - 1].date;

    const yMaximum = useMemo(() => {
        const max = Math.max(...data.map((d) => d.visitors));
        return Math.ceil(max * 1.1);
    }, [data]);

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        areaY(data, {
                            id: "visitor-area",
                            x: "date",
                            y: "visitors",
                            key: "id",
                            fill: "url(#themed-area-gradient)",
                            fillOpacity: 1,
                            curve: smoothCurve,
                        }),
                        lineY(data, {
                            id: "visitor-line",
                            x: "date",
                            y: "visitors",
                            key: "id",
                            stroke: "var(--chart-1)",
                            strokeWidth: 2.5,
                            curve: smoothCurve,
                        }),
                        dot(data, {
                            id: "visitor-points",
                            x: "date",
                            y: "visitors",
                            key: "id",
                            r: 3.5,
                            fill: "var(--chart-1)",
                            stroke: "var(--background)",
                            strokeWidth: 1.5,
                        }),
                        crosshair<Date, number>({
                            id: "visitor-crosshair",
                            x: {
                                stroke: "var(--muted-foreground)",
                                strokeOpacity: 0.4,
                                strokeWidth: 1,
                                strokeDasharray: "3 3",
                            },
                            y: false,
                        }),
                    ],
                    scales: {
                        x: {
                            scale: scaleUtc().domain([firstDate, lastDate]),
                            axis: {
                                ticks: {
                                    format: (v: Date) =>
                                        v.toLocaleDateString("en-US", {
                                            month: "short",
                                            day: "numeric",
                                            timeZone: "UTC",
                                        }),
                                },
                            },
                        },
                        y: {
                            scale: scaleLinear().domain([0, yMaximum]),
                            grid: true,
                            axis: { label: "Visitors" },
                        },
                    },
                    gradients: [
                        {
                            id: "themed-area-gradient",
                            x1: 0,
                            y1: 0,
                            x2: 0,
                            y2: 1,
                            stops: [
                                { offset: 0, color: "var(--chart-1)", opacity: 0.35 },
                                { offset: 0.7, color: "var(--chart-1)", opacity: 0.1 },
                                { offset: 1, color: "var(--chart-1)", opacity: 0 },
                            ],
                        },
                    ],
                    focus: focusGroupX,
                    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, firstDate, lastDate],
    );

    return (
        <Card className="w-full max-w-xl">
            <CardHeader className="flex flex-row items-center justify-between space-y-0 pb-2">
                <div>
                    <CardTitle>Daily Traffic & Visitors</CardTitle>
                    <CardDescription>
                        Smooth monotone curved area chart with smooth period range toggles
                    </CardDescription>
                </div>
                <div className="flex items-center space-x-1">
                    {(["7d", "30d", "90d"] as RangeOption[]).map((r) => (
                        <Button
                            key={r}
                            size="sm"
                            variant={range === r ? "default" : "outline"}
                            className="h-7 px-2 text-xs uppercase"
                            onClick={() => setRange(r)}>
                            {r}
                        </Button>
                    ))}
                </div>
            </CardHeader>
            <CardContent>
                <div className="h-[230px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={230}
                        ariaLabel="Daily Traffic & Visitors Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    Traffic up +14.2% in selected {range} window <TrendingUp className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    Gradient fill definition smoothly updates across 7d, 30d, and 90d presets
                </div>
            </CardFooter>
        </Card>
    );
}

export default ThemedInteractiveArea;