Waterfall Chart

import { type ChartPoint, barY, defineChart, 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 { scaleBand, scaleLinear } from "d3-scale";
import { TrendingDown } from "lucide-react";

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

interface WaterfallItemDatum {
    step: string;
    start: number;
    end: number;
    kind: "increase" | "decrease" | "total";
}

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

function generateDemoData(): WaterfallItemDatum[] {
    return [
        { step: "Start Revenue", start: 0, end: 100, kind: "increase" },
        { step: "New Sales", start: 100, end: 145, kind: "increase" },
        { step: "Churn", start: 145, end: 125, kind: "decrease" },
        { step: "Discounts", start: 125, end: 110, kind: "decrease" },
        { step: "Upsells", start: 110, end: 140, kind: "increase" },
        { step: "Net Total", start: 0, end: 140, kind: "total" },
    ];
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const d = points[0].datum as WaterfallItemDatum;
    if (!d) return { title: "", rows: [] };
    const diff = d.end - d.start;
    const isTotal = d.kind === "total";
    return {
        title: d.step,
        rows: [
            {
                label: isTotal ? "Total Value" : "Variance",
                value: isTotal ? `$${d.end}k` : `${diff > 0 ? "+" : ""}$${diff}k`,
                color: points[0].color || "var(--chart-1)",
            },
        ],
    };
}

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

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        barY(data, {
                            id: "waterfall-bars",
                            x: "step",
                            y1: "start",
                            y2: "end",
                            color: "kind",
                            inset: 1.5,
                            radius: 3,
                        }),
                        ruleY([0], { stroke: "var(--border)" }),
                    ],
                    scales: {
                        x: {
                            scale: () => scaleBand<string>().padding(0.2),
                            axis: {
                                line: false,
                                ticks: { size: 0, padding: 10 },
                            },
                        },
                        y: {
                            scale: scaleLinear().domain([0, 170]),
                            grid: true,
                            axis: {
                                line: false,
                                label: "Revenue ($k)",
                                ticks: { size: 0 },
                            },
                        },
                    },
                    color: {
                        domain: ["increase", "decrease", "total"],
                        range: ["var(--chart-1)", "var(--chart-2)", "var(--chart-3)"],
                    },
                    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>Revenue Waterfall Bridge</CardTitle>
                <CardDescription>Sequential waterfall bridge analyzing net revenue variance drivers</CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[250px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={250}
                        ariaLabel="Revenue Waterfall Bridge Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    Net ending revenue expanded +$40k over fiscal period{" "}
                    <TrendingDown className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    Green bars reflect gains; Red bars depict losses; Blue bar shows net ending total
                </div>
            </CardFooter>
        </Card>
    );
}

export default WaterfallChart;