Ridgeline Density

import { type ChartPoint, binX, d3Curve, defineChart, normalize, ridgelineY, 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, scalePoint } from "d3-scale";
import { curveBasis } from "d3-shape";
import { Layers } from "lucide-react";

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

interface EpisodeDatum {
    season: number;
    rating: number;
}

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

const seasonsList = [1, 2, 3, 4, 5];
const ratingBoundaries = [4, 5, 6, 7, 8, 9, 10];

function generateDemoData(): EpisodeDatum[] {
    const results: EpisodeDatum[] = [];

    seasonsList.forEach((s) => {
        const meanRating = 9.2 - s * 0.4;
        for (let ep = 0; ep < 25; ep++) {
            const r = Math.max(4, Math.min(10, meanRating + (Math.random() - 0.45) * 1.8));
            results.push({ season: s, rating: Number(r.toFixed(1)) });
        }
    });

    return results;
}

function shadcnTooltipContent<TDatum>(points: readonly ChartPoint<TDatum>[]) {
    if (points.length === 0) return { title: "", rows: [] };
    const d = points[0].datum as { season: number; x: number; height: number };
    if (!d) return { title: "", rows: [] };
    return {
        title: `Season ${d.season} (Rating ${d.x?.toFixed(1)})`,
        rows: [{ label: "Density Height", value: `${(d.height * 100).toFixed(1)}%`, color: "var(--chart-1)" }],
    };
}

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

    const rows = useMemo(() => {
        const bins = binX(data, {
            value: "rating",
            by: "season",
            thresholds: ratingBoundaries,
            outputs: { count: { reduce: "count" } },
        });

        return normalize(bins, {
            value: "count",
            by: "season",
            basis: "max",
            as: "height",
        });
    }, [data]);

    const overlap = 0.75;

    const definition = useMemo(
        () =>
            defineChart(
                {
                    renderer: motionRenderer,
                    marks: [
                        ruleY(seasonsList, {
                            id: "season-guides",
                            stroke: "var(--border)",
                            strokeOpacity: 0.7,
                        }),
                        ridgelineY(rows, {
                            id: "rating-ridges",
                            x: "x",
                            y: "season",
                            height: "height",
                            key: (row: { season: number; x: number }) => `${row.season}:${row.x}`,
                            overlap,
                            color: "season",
                            fillOpacity: 0.45,
                            strokeWidth: 1.5,
                            curve: d3Curve(curveBasis),
                        }),
                    ],
                    scales: {
                        x: {
                            scale: scaleLinear().domain([4, 10]),
                            grid: true,
                            axis: { label: "IMDb Rating Score" },
                        },
                        y: {
                            scale: scalePoint<number>().domain(seasonsList).padding(overlap),
                            reverse: true,
                            axis: {
                                ticks: {
                                    values: seasonsList,
                                    format: (s: number) => `Season ${s}`,
                                },
                            },
                        },
                    },
                    color: {
                        range: [
                            "var(--chart-1)",
                            "var(--chart-2)",
                            "var(--chart-3)",
                            "var(--chart-4)",
                            "var(--chart-5)",
                        ],
                    },
                    margin: { top: 24, right: 24, bottom: 32, left: 65 },
                    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),
                    },
                },
            ),
        [rows],
    );

    return (
        <Card className="w-full max-w-xl">
            <CardHeader>
                <CardTitle>Overlapping Ridgeline Density Plot</CardTitle>
                <CardDescription>
                    Stacked density ridge mountain plots comparing ratings distribution per season
                </CardDescription>
            </CardHeader>
            <CardContent>
                <div className="h-[250px] w-full">
                    <Chart
                        definition={definition}
                        renderer={motionRenderer}
                        height={250}
                        ariaLabel="Overlapping Ridgeline Density Plot Chart"
                    />
                </div>
            </CardContent>
            <CardFooter className="flex-col items-start gap-2 text-sm">
                <div className="flex items-center gap-2 leading-none font-medium">
                    Season 1 displays peak density concentrated at higher 8.8 rating{" "}
                    <Layers className="h-4 w-4 text-emerald-500" />
                </div>
                <div className="text-muted-foreground leading-none">
                    Partial Y-axis overlapping ridgelines economize vertical space in multi-series KDE plots
                </div>
            </CardFooter>
        </Card>
    );
}

export default RidgelineDensity;