Calendar Heatmap Chart

import { type ChartPoint, cell, defineChart } 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, scaleThreshold } from "d3-scale";
import { Calendar } from "lucide-react";

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

interface CalendarCellDatum {
    week: number;
    day: string;
    precipitation: number;
}

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

const weekdays = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"];

function generateDemoData(): CalendarCellDatum[] {
    const results: CalendarCellDatum[] = [];
    for (let w = 0; w < 12; w++) {
        for (let d = 0; d < 7; d++) {
            const val = Math.max(0, Math.sin(w * 0.5 + d * 0.8) * 12 + (w % 3) * 2 - 2);
            results.push({ week: w, day: weekdays[d], precipitation: val });
        }
    }
    return results;
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const d = points[0].datum as CalendarCellDatum;
    if (!d) return { title: "", rows: [] };
    return {
        title: `Week ${d.week + 1} (${d.day})`,
        rows: [
            {
                label: "Precipitation",
                value: `${d.precipitation.toFixed(1)} mm`,
                color: "var(--chart-1)",
            },
        ],
    };
}

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

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        cell(data, {
                            id: "calendar-cells",
                            x: "week",
                            y: "day",
                            color: "precipitation",
                            inset: 1.5,
                            radius: 3,
                        }),
                    ],
                    scales: {
                        x: {
                            scale: () => scaleBand<number>().paddingInner(0.06).paddingOuter(0.03),
                            axis: {
                                line: false,
                                label: "Week",
                                ticks: {
                                    size: 0,
                                    format: (v: number) => `W${v + 1}`,
                                },
                            },
                        },
                        y: {
                            scale: () => scaleBand<string>().domain(weekdays).paddingInner(0.06).paddingOuter(0.03),
                            axis: {
                                line: false,
                                ticks: { size: 0 },
                            },
                        },
                    },
                    color: {
                        scale: scaleThreshold<number, string>,
                        domain: [3, 7, 12],
                        range: ["var(--chart-5)", "var(--chart-4)", "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",
                    },
                },
                {
                    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],
    );

    return (
        <Card className="w-full max-w-xl">
            <CardHeader>
                <CardTitle>Daily Rainfall Calendar Matrix</CardTitle>
                <CardDescription>12-week calendar grid displaying daily rainfall intensity</CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[250px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={250}
                        ariaLabel="Daily Rainfall Calendar Matrix Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    Mid-week days show peak precipitation concentration{" "}
                    <Calendar className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    Cells map day-of-week rows against sequential weekly columns
                </div>
            </CardFooter>
        </Card>
    );
}

export default CalendarHeatmap;