Moving Average Line

import { type ChartPoint, defineChart, lineY, rollingWindow, ruleY } 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 { scaleLinear, scaleUtc } from "d3-scale";
import { TrendingUp } from "lucide-react";

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

interface TempDatum {
    date: Date;
    high: number;
    low: number;
}

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

function generateDemoData(): TempDatum[] {
    const baseDate = new Date(2025, 0, 1);
    return Array.from({ length: 30 }, (_, i) => {
        const d = new Date(baseDate);
        d.setDate(baseDate.getDate() + i);
        return {
            date: d,
            high: 58 + Math.sin(i * 0.4) * 8 + (i % 5),
            low: 42 + Math.cos(i * 0.3) * 6 + (i % 3),
        };
    });
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const d = points[0].datum as any;
    if (!d) return { title: "", rows: [] };
    const dateStr = d.date ? d.date.toLocaleDateString("en-US", { month: "short", day: "numeric" }) : "";
    return {
        title: dateStr,
        rows: [
            { label: "High 7d Avg", value: `${d.high.toFixed(1)}°F`, color: "var(--chart-1)" },
            { label: "Low 7d Avg", value: `${d.low.toFixed(1)}°F`, color: "var(--chart-2)" },
        ],
    };
}

export function MovingAverageLine() {
    const rawData = useMemo(() => generateDemoData(), []);

    const data = useMemo(() => {
        return rollingWindow(rawData, {
            size: 7,
            partial: false,
            outputs: {
                high: { value: "high", reduce: "mean" },
                low: { value: "low", reduce: "mean" },
            },
        });
    }, [rawData]);

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        lineY(data, {
                            id: "ma-low",
                            x: "date",
                            y: "low",
                            stroke: "var(--chart-2)",
                            strokeWidth: 2.25,
                        }),
                        lineY(data, {
                            id: "ma-high",
                            x: "date",
                            y: "high",
                            stroke: "var(--chart-1)",
                            strokeWidth: 2.25,
                        }),
                        ruleY([32], {
                            stroke: "var(--border)",
                            strokeDasharray: "4 4",
                        }),
                    ],
                    scales: {
                        x: {
                            scale: scaleUtc,
                            axis: {
                                line: false,
                                label: "Date",
                                ticks: {
                                    size: 0,
                                    padding: 10,
                                    format: (d: Date) => d.toLocaleDateString("en-US", { month: "short", day: "numeric" }),
                                },
                            },
                        },
                        y: {
                            scale: scaleLinear().domain([30, 75]),
                            grid: true,
                            axis: {
                                line: false,
                                label: "7-Day Moving Avg (°F)",
                                ticks: { size: 0 },
                            },
                        },
                    },
                    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>Smoothed Temperature Trends</CardTitle>
                <CardDescription>
                    7-day rolling window moving average for daily high and low temperatures
                </CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[250px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={250}
                        ariaLabel="Smoothed Temperature Trends Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    Moving average dampens short-term daily volatility{" "}
                    <TrendingUp className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    Dashed threshold line indicates freezing baseline (32°F)
                </div>
            </CardFooter>
        </Card>
    );
}

export default MovingAverageLine;