/**
 * @file MiniChart.tsx
 * @description The Administration page's small single-series charts: a bar
 * chart (a user's daily spend) and a line chart (System Health's CPU and
 * memory history), plain SVG in the app's theme tokens. One series each — the
 * card's title names it, so there is no legend — thin marks, rounded bar ends
 * on the baseline, a recessive grid with a max label, and a hover tooltip
 * (crosshair for the line, per bar for the bars) whose text is the caller's.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

import { useRef, useState, type MouseEvent } from "react";

export type ChartPoint = { x: string; y: number };

const H = 120;
const PAD_TOP = 14;
const PAD_BOTTOM = 18;

/**
 * @param props.points - In x order; `x` is the axis/tooltip label.
 * @param props.kind - `bar` or `line`.
 * @param props.format - Formats a value for the max label and the tooltip.
 * @param props.max - A fixed top (e.g. 100 for a percentage); else the data's max.
 * @param props.label - The chart's accessible name.
 */
export function MiniChart({
  points,
  kind,
  format,
  max,
  label,
  emptyText,
}: {
  points: ChartPoint[];
  kind: "bar" | "line";
  format: (v: number) => string;
  max?: number;
  label: string;
  emptyText?: string;
}) {
  const ref = useRef<SVGSVGElement>(null);
  const [hover, setHover] = useState<number | null>(null);
  if (points.length === 0)
    return (
      <div className="flex h-[120px] items-center justify-center text-xs text-fg-muted">
        {emptyText ?? "—"}
      </div>
    );

  const W = 600;
  const top = Math.max(max ?? 0, ...points.map((p) => p.y), 1e-9);
  const plotH = H - PAD_TOP - PAD_BOTTOM;
  const yOf = (v: number) => PAD_TOP + plotH - (v / top) * plotH;
  const step = W / points.length;
  const xOf = (i: number) =>
    kind === "bar" ? i * step + step / 2 : (i / Math.max(1, points.length - 1)) * W;

  const onMove = (e: MouseEvent<SVGSVGElement>) => {
    const r = ref.current?.getBoundingClientRect();
    if (!r || r.width === 0) return;
    const fx = ((e.clientX - r.left) / r.width) * W;
    const i =
      kind === "bar"
        ? Math.floor(fx / step)
        : Math.round((fx / W) * Math.max(1, points.length - 1));
    setHover(Math.max(0, Math.min(points.length - 1, i)));
  };

  const h = hover != null ? points[hover] : null;
  const barW = Math.max(2, Math.min(24, step - 2));
  const line = points
    .map((p, i) => `${i ? "L" : "M"}${xOf(i).toFixed(1)},${yOf(p.y).toFixed(1)}`)
    .join("");

  return (
    <div className="relative">
      <svg
        ref={ref}
        viewBox={`0 0 ${W} ${H}`}
        preserveAspectRatio="none"
        className="block h-[120px] w-full"
        role="img"
        aria-label={label}
        onMouseMove={onMove}
        onMouseLeave={() => setHover(null)}
      >
        {[0, 0.5, 1].map((f) => (
          <line
            key={f}
            x1={0}
            x2={W}
            y1={yOf(top * f)}
            y2={yOf(top * f)}
            className="stroke-border"
            strokeWidth={1}
            vectorEffect="non-scaling-stroke"
            strokeDasharray={f === 0 ? undefined : "3 3"}
          />
        ))}
        {kind === "bar" ? (
          points.map((p, i) => {
            const y = yOf(p.y);
            const bh = Math.max(0, PAD_TOP + plotH - y);
            const r = Math.min(4, barW / 2, bh);
            const x = xOf(i) - barW / 2;
            const base = PAD_TOP + plotH;
            // Rounded top only; the base sits flat on the axis.
            const d =
              bh <= 0
                ? ""
                : `M${x},${base}V${y + r}Q${x},${y} ${x + r},${y}H${x + barW - r}Q${x + barW},${y} ${x + barW},${y + r}V${base}Z`;
            return (
              <path key={i} d={d} className={hover === i ? "fill-accent" : "fill-accent-solid"} />
            );
          })
        ) : (
          <>
            <path
              d={`${line}L${W},${PAD_TOP + plotH}L0,${PAD_TOP + plotH}Z`}
              className="fill-accent-solid"
              opacity={0.12}
            />
            <path
              d={line}
              fill="none"
              className="stroke-accent-solid"
              strokeWidth={2}
              vectorEffect="non-scaling-stroke"
              strokeLinejoin="round"
            />
            {hover != null && (
              <line
                x1={xOf(hover)}
                x2={xOf(hover)}
                y1={PAD_TOP}
                y2={PAD_TOP + plotH}
                className="stroke-fg-muted"
                strokeWidth={1}
                vectorEffect="non-scaling-stroke"
              />
            )}
          </>
        )}
      </svg>
      <span className="pointer-events-none absolute left-0 top-0 text-[10px] text-fg-muted tabular-nums">
        {format(top)}
      </span>
      <div className="pointer-events-none flex justify-between text-[10px] text-fg-muted">
        <span>{points[0]!.x}</span>
        <span>{points[points.length - 1]!.x}</span>
      </div>
      {h && hover != null && (
        <div
          className="pointer-events-none absolute top-0 z-10 -translate-x-1/2 whitespace-nowrap rounded-md border border-border bg-surface-1 px-2 py-1 text-[11px] shadow-lg"
          style={{ left: `${Math.min(92, Math.max(8, (xOf(hover) / W) * 100))}%` }}
          role="status"
        >
          <div className="text-fg-muted">{h.x}</div>
          <div className="font-medium text-fg-primary tabular-nums">{format(h.y)}</div>
        </div>
      )}
    </div>
  );
}