Gradient Track Slider

"use client";

import { useState } from "react";
import type { CSSProperties } from "react";
import { motion, useReducedMotion } from "motion/react";

type CSSVars = CSSProperties & Record<`--${string}`, string>;

type SliderId = "temp" | "tint" | "sat" | "exposure";

interface Stop {
  at: number;
  rgb: [number, number, number];
}

interface SliderDef {
  id: SliderId;
  label: string;
  hint: string;
  gradient: string;
  stops: Stop[];
  ends: [string, string];
  descriptor: (v: number) => string;
}

interface Preset {
  id: string;
  name: string;
  values: Record<SliderId, number>;
}

const MIN = -100;
const MAX = 100;
const THUMB = 22;

const SLIDERS: SliderDef[] = [
  {
    id: "temp",
    label: "Temperature",
    hint: "white balance",
    gradient: "linear-gradient(90deg, #3b82f6 0%, #e2e8f0 50%, #f59e0b 100%)",
    stops: [
      { at: 0, rgb: [59, 130, 246] },
      { at: 0.5, rgb: [226, 232, 240] },
      { at: 1, rgb: [245, 158, 11] },
    ],
    ends: ["Cool", "Warm"],
    descriptor: (v) =>
      v === 0 ? "neutral" : v > 0 ? (v > 60 ? "hot" : "warm") : v < -60 ? "icy" : "cool",
  },
  {
    id: "tint",
    label: "Tint",
    hint: "green / magenta",
    gradient: "linear-gradient(90deg, #10b981 0%, #e2e8f0 50%, #ec4899 100%)",
    stops: [
      { at: 0, rgb: [16, 185, 129] },
      { at: 0.5, rgb: [226, 232, 240] },
      { at: 1, rgb: [236, 72, 153] },
    ],
    ends: ["Green", "Magenta"],
    descriptor: (v) => (v === 0 ? "neutral" : v > 0 ? "magenta" : "green"),
  },
  {
    id: "sat",
    label: "Saturation",
    hint: "muted / vivid",
    gradient: "linear-gradient(90deg, #94a3b8 0%, #818cf8 50%, #7c3aed 100%)",
    stops: [
      { at: 0, rgb: [148, 163, 184] },
      { at: 0.5, rgb: [129, 140, 248] },
      { at: 1, rgb: [124, 58, 237] },
    ],
    ends: ["Muted", "Vivid"],
    descriptor: (v) =>
      v <= -100 ? "grayscale" : v === 0 ? "normal" : v > 0 ? "vivid" : "muted",
  },
  {
    id: "exposure",
    label: "Exposure",
    hint: "shadow / highlight",
    gradient: "linear-gradient(90deg, #171717 0%, #787878 50%, #fafafa 100%)",
    stops: [
      { at: 0, rgb: [23, 23, 23] },
      { at: 0.5, rgb: [120, 120, 120] },
      { at: 1, rgb: [250, 250, 250] },
    ],
    ends: ["Shadow", "Highlight"],
    descriptor: (v) => (v === 0 ? "neutral" : v > 0 ? "brighter" : "darker"),
  },
];

const PRESETS: Preset[] = [
  { id: "neutral", name: "Neutral", values: { temp: 0, tint: 0, sat: 0, exposure: 0 } },
  { id: "golden", name: "Golden Hour", values: { temp: 58, tint: 10, sat: 20, exposure: 8 } },
  { id: "arctic", name: "Arctic", values: { temp: -46, tint: -8, sat: -10, exposure: 12 } },
  { id: "vintage", name: "Vintage", values: { temp: 24, tint: 16, sat: -32, exposure: -6 } },
  { id: "noir", name: "Noir", values: { temp: -4, tint: 0, sat: -100, exposure: -10 } },
];

const SCENE =
  "radial-gradient(130% 90% at 18% 12%, rgba(254,240,138,0.95), rgba(254,240,138,0) 55%)," +
  "radial-gradient(120% 100% at 85% 15%, rgba(244,114,182,0.85), rgba(244,114,182,0) 50%)," +
  "radial-gradient(140% 120% at 50% 120%, rgba(16,185,129,0.85), rgba(16,185,129,0) 55%)," +
  "linear-gradient(150deg, #4f46e5 0%, #0ea5e9 42%, #14b8a6 78%, #f59e0b 100%)";

const EASE = [0.22, 1, 0.36, 1] as const;

function clamp255(n: number): number {
  return Math.max(0, Math.min(255, Math.round(n)));
}

function sampleStops(stops: Stop[], t: number): string {
  const c = Math.min(1, Math.max(0, t));
  for (let i = 0; i < stops.length - 1; i++) {
    const a = stops[i];
    const b = stops[i + 1];
    if (c >= a.at && c <= b.at) {
      const span = b.at - a.at || 1;
      const lt = (c - a.at) / span;
      const r = Math.round(a.rgb[0] + (b.rgb[0] - a.rgb[0]) * lt);
      const g = Math.round(a.rgb[1] + (b.rgb[1] - a.rgb[1]) * lt);
      const bl = Math.round(a.rgb[2] + (b.rgb[2] - a.rgb[2]) * lt);
      return `rgb(${r}, ${g}, ${bl})`;
    }
  }
  const last = stops[stops.length - 1].rgb;
  return `rgb(${last[0]}, ${last[1]}, ${last[2]})`;
}

function signed(v: number): string {
  return v > 0 ? `+${v}` : `${v}`;
}

export default function GradientTrackSlider() {
  const prefersReduced = useReducedMotion();
  const reduce = prefersReduced === true;

  const [values, setValues] = useState<Record<SliderId, number>>({
    temp: 0,
    tint: 0,
    sat: 0,
    exposure: 0,
  });
  const [activePreset, setActivePreset] = useState<string | null>("neutral");

  function update(id: SliderId, next: number) {
    setValues((prev) => ({ ...prev, [id]: next }));
    setActivePreset(null);
  }

  function applyPreset(p: Preset) {
    setValues(p.values);
    setActivePreset(p.id);
  }

  const warmth = values.temp / 100;
  const tn = values.tint / 100;
  const castR = clamp255(128 + warmth * 95 + tn * 45);
  const castG = clamp255(128 - tn * 55 - Math.abs(warmth) * 4);
  const castB = clamp255(128 - warmth * 95 + tn * 45);
  const castRgb = `rgb(${castR}, ${castG}, ${castB})`;
  const washOpacity = Math.min(0.7, (Math.abs(warmth) + Math.abs(tn)) * 0.55);

  const sceneFilter =
    `saturate(${(1 + values.sat / 100).toFixed(2)}) ` +
    `brightness(${(1 + values.exposure / 160).toFixed(2)}) ` +
    `contrast(${(1 + Math.abs(values.exposure) / 400).toFixed(2)})`;

  const lookName = activePreset
    ? PRESETS.find((p) => p.id === activePreset)?.name ?? "Custom"
    : "Custom";

  const reveal = (delay: number) => ({
    initial: reduce ? false : { opacity: 0, y: 12 },
    animate: { opacity: 1, y: 0 },
    transition: { duration: 0.5, ease: EASE, delay: reduce ? 0 : delay },
  });

  return (
    <section className="relative w-full overflow-hidden bg-slate-50 px-5 py-16 text-slate-900 dark:bg-zinc-950 dark:text-slate-100 sm:px-8 sm:py-24">
      <style>{`
        .sgt-range {
          -webkit-appearance: none;
          appearance: none;
          width: 100%;
          height: 24px;
          background: transparent;
          cursor: pointer;
        }
        .sgt-range:focus { outline: none; }
        .sgt-range::-webkit-slider-runnable-track {
          height: 12px;
          border-radius: 999px;
          background: var(--sgt-grad);
          box-shadow: inset 0 1px 2px rgba(0,0,0,0.35), inset 0 0 0 1px rgba(255,255,255,0.14);
        }
        .sgt-range::-webkit-slider-thumb {
          -webkit-appearance: none;
          appearance: none;
          width: 22px;
          height: 22px;
          margin-top: -5px;
          border-radius: 999px;
          background: var(--sgt-thumb);
          border: 3px solid #ffffff;
          box-shadow: 0 2px 6px rgba(0,0,0,0.35), 0 0 0 1px rgba(0,0,0,0.18);
          transition: transform 0.12s ease, box-shadow 0.12s ease;
        }
        .sgt-range:active::-webkit-slider-thumb { transform: scale(1.14); }
        .sgt-range:focus-visible::-webkit-slider-thumb {
          box-shadow: 0 0 0 4px rgba(99,102,241,0.55), 0 2px 6px rgba(0,0,0,0.35);
        }
        .sgt-range::-moz-range-track {
          height: 12px;
          border-radius: 999px;
          background: var(--sgt-grad);
          box-shadow: inset 0 1px 2px rgba(0,0,0,0.35), inset 0 0 0 1px rgba(255,255,255,0.14);
        }
        .sgt-range::-moz-range-thumb {
          width: 22px;
          height: 22px;
          border-radius: 999px;
          background: var(--sgt-thumb);
          border: 3px solid #ffffff;
          box-shadow: 0 2px 6px rgba(0,0,0,0.35), 0 0 0 1px rgba(0,0,0,0.18);
          transition: transform 0.12s ease, box-shadow 0.12s ease;
        }
        .sgt-range:active::-moz-range-thumb { transform: scale(1.14); }
        .sgt-range:focus-visible::-moz-range-thumb {
          box-shadow: 0 0 0 4px rgba(99,102,241,0.55), 0 2px 6px rgba(0,0,0,0.35);
        }
        @keyframes sgtc-sheen {
          0% { transform: translateX(-130%) skewX(-16deg); }
          100% { transform: translateX(230%) skewX(-16deg); }
        }
        .sgtc-sheen { animation: sgtc-sheen 7s linear infinite; }
        @media (prefers-reduced-motion: reduce) {
          .sgtc-sheen { animation: none; }
          .sgt-range::-webkit-slider-thumb { transition: none; }
          .sgt-range::-moz-range-thumb { transition: none; }
        }
      `}</style>

      <div
        aria-hidden="true"
        className="pointer-events-none absolute inset-0"
        style={{
          background:
            "radial-gradient(48% 40% at 12% 8%, rgba(99,102,241,0.16), transparent 70%)," +
            "radial-gradient(46% 44% at 90% 100%, rgba(236,72,153,0.14), transparent 70%)",
        }}
      />

      <div className="relative mx-auto w-full max-w-3xl">
        <motion.header {...reveal(0)} className="mb-8 sm:mb-10">
          <div className="flex items-center gap-2.5">
            <span className="flex h-8 w-8 items-center justify-center rounded-lg bg-slate-900 text-white dark:bg-white dark:text-slate-900">
              <svg viewBox="0 0 24 24" className="h-4 w-4" fill="none" stroke="currentColor" strokeWidth={2} strokeLinecap="round" aria-hidden="true">
                <path d="M4 7h9" />
                <path d="M17 7h3" />
                <circle cx="15" cy="7" r="2" />
                <path d="M4 17h3" />
                <path d="M11 17h9" />
                <circle cx="9" cy="17" r="2" />
              </svg>
            </span>
            <span className="font-mono text-[11px] font-medium uppercase tracking-[0.22em] text-slate-500 dark:text-slate-400">
              Color Grade · v2
            </span>
          </div>
          <h2 className="mt-4 font-serif text-3xl font-semibold tracking-tight text-slate-900 dark:text-white sm:text-4xl">
            Grade the frame.
          </h2>
          <p className="mt-2 max-w-lg text-sm leading-relaxed text-slate-600 dark:text-slate-400">
            Four gradient tracks, one live look. Drag, or steer with the arrow keys — every
            track shows exactly what it does to the picture.
          </p>
        </motion.header>

        <div className="rounded-3xl border border-slate-200/80 bg-white/85 p-4 shadow-xl shadow-slate-900/5 backdrop-blur-sm dark:border-zinc-800 dark:bg-zinc-900/70 dark:shadow-black/40 sm:p-6">
          <div className="grid gap-6 lg:grid-cols-[1.05fr_1fr] lg:gap-8">
            <motion.div {...reveal(0.06)} className="min-h-[260px]">
              <div className="relative h-full min-h-[240px] overflow-hidden rounded-2xl border border-slate-200/70 dark:border-zinc-800">
                <div
                  className="absolute inset-0 transition-[filter] duration-200 ease-out"
                  style={{ background: SCENE, filter: sceneFilter }}
                />
                <div
                  aria-hidden="true"
                  className="absolute inset-0 transition-opacity duration-200 ease-out"
                  style={{
                    background: castRgb,
                    opacity: washOpacity,
                    mixBlendMode: "soft-light",
                  }}
                />
                <div className="pointer-events-none absolute inset-0 overflow-hidden">
                  <div
                    aria-hidden="true"
                    className="sgtc-sheen absolute -inset-y-4 left-0 w-1/4"
                    style={{
                      background:
                        "linear-gradient(90deg, transparent, rgba(255,255,255,0.28), transparent)",
                    }}
                  />
                </div>
                <div
                  aria-hidden="true"
                  className="absolute inset-x-0 bottom-0 h-24"
                  style={{
                    background: "linear-gradient(to top, rgba(0,0,0,0.55), transparent)",
                  }}
                />
                <div className="absolute inset-x-0 bottom-0 flex items-end justify-between gap-3 p-4">
                  <div>
                    <p className="font-mono text-[10px] uppercase tracking-[0.24em] text-white/70">
                      Live preview
                    </p>
                    <p className="mt-0.5 font-serif text-lg font-medium text-white">
                      {lookName}
                    </p>
                  </div>
                  <div className="flex items-center gap-2 rounded-full bg-black/35 px-2.5 py-1.5 backdrop-blur-sm">
                    <span
                      className="h-4 w-4 rounded-full ring-1 ring-white/40"
                      style={{ background: castRgb }}
                    />
                    <span className="font-mono text-[11px] text-white/85">cast</span>
                  </div>
                </div>
              </div>
            </motion.div>

            <div className="flex flex-col">
              <motion.div {...reveal(0.12)} className="mb-5">
                <div className="mb-2.5 flex items-baseline justify-between">
                  <span className="font-mono text-[11px] font-medium uppercase tracking-[0.18em] text-slate-500 dark:text-slate-400">
                    Looks
                  </span>
                  <span className="font-mono text-[11px] text-slate-400 dark:text-slate-500">
                    {activePreset ? "preset" : "custom"}
                  </span>
                </div>
                <div className="flex flex-wrap gap-2">
                  {PRESETS.map((p) => {
                    const on = activePreset === p.id;
                    return (
                      <button
                        key={p.id}
                        type="button"
                        aria-pressed={on}
                        onClick={() => applyPreset(p)}
                        className={
                          "rounded-full border px-3 py-1.5 text-xs font-medium transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-indigo-500 focus-visible:ring-offset-2 focus-visible:ring-offset-white dark:focus-visible:ring-offset-zinc-900 " +
                          (on
                            ? "border-transparent bg-slate-900 text-white dark:bg-white dark:text-slate-900"
                            : "border-slate-200 bg-slate-50 text-slate-600 hover:border-slate-300 hover:bg-slate-100 dark:border-zinc-700 dark:bg-zinc-800/60 dark:text-slate-300 dark:hover:border-zinc-600 dark:hover:bg-zinc-800")
                        }
                      >
                        {p.name}
                      </button>
                    );
                  })}
                </div>
              </motion.div>

              <ul className="space-y-6">
                {SLIDERS.map((def, i) => {
                  const v = values[def.id];
                  const t = (v - MIN) / (MAX - MIN);
                  const thumb = sampleStops(def.stops, t);
                  const trackStyle: CSSVars = {
                    "--sgt-grad": def.gradient,
                    "--sgt-thumb": thumb,
                  };
                  return (
                    <motion.li key={def.id} {...reveal(0.18 + i * 0.06)}>
                      <div className="flex items-baseline justify-between gap-3">
                        <label
                          htmlFor={`sgt-${def.id}`}
                          className="flex items-baseline gap-2 text-sm font-medium text-slate-800 dark:text-slate-100"
                        >
                          {def.label}
                          <span className="font-mono text-[10px] font-normal uppercase tracking-wide text-slate-400 dark:text-slate-500">
                            {def.hint}
                          </span>
                        </label>
                        <span className="font-mono text-sm tabular-nums text-slate-900 dark:text-white">
                          {signed(v)}
                          <span className="ml-1.5 text-xs text-slate-400 dark:text-slate-500">
                            {def.descriptor(v)}
                          </span>
                        </span>
                      </div>

                      <div className="group relative mt-3">
                        <div
                          aria-hidden="true"
                          className="pointer-events-none absolute -top-9 z-10 -translate-x-1/2 translate-y-1 rounded-md bg-slate-900 px-2 py-1 font-mono text-[11px] tabular-nums text-white opacity-0 shadow-lg transition duration-150 group-hover:translate-y-0 group-hover:opacity-100 group-focus-within:translate-y-0 group-focus-within:opacity-100 dark:bg-white dark:text-slate-900"
                          style={{ left: `calc(11px + ${t} * (100% - ${THUMB}px))` }}
                        >
                          {signed(v)}
                        </div>
                        <input
                          id={`sgt-${def.id}`}
                          type="range"
                          className="sgt-range"
                          min={MIN}
                          max={MAX}
                          step={1}
                          value={v}
                          style={trackStyle}
                          onChange={(e) => update(def.id, Number(e.currentTarget.value))}
                          aria-valuetext={`${signed(v)}, ${def.descriptor(v)}`}
                        />
                      </div>

                      <div className="mt-1.5 grid grid-cols-3 font-mono text-[10px] uppercase tracking-wide text-slate-400 dark:text-slate-500">
                        <span className="text-left">{def.ends[0]}</span>
                        <span className="text-center">0</span>
                        <span className="text-right">{def.ends[1]}</span>
                      </div>
                    </motion.li>
                  );
                })}
              </ul>

              <motion.div
                {...reveal(0.18 + SLIDERS.length * 0.06)}
                className="mt-7 flex items-center justify-between gap-3 border-t border-slate-200 pt-4 dark:border-zinc-800"
              >
                <p className="min-w-0 truncate font-mono text-[11px] text-slate-500 dark:text-slate-400">
                  T {signed(values.temp)} · Ti {signed(values.tint)} · S {signed(values.sat)}{" "}
                  · E {signed(values.exposure)}
                </p>
                <button
                  type="button"
                  onClick={() => applyPreset(PRESETS[0])}
                  className="inline-flex shrink-0 items-center gap-1.5 rounded-full border border-slate-200 bg-white px-3 py-1.5 text-xs font-medium text-slate-700 transition-colors hover:bg-slate-100 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-indigo-500 focus-visible:ring-offset-2 focus-visible:ring-offset-white dark:border-zinc-700 dark:bg-zinc-800/60 dark:text-slate-200 dark:hover:bg-zinc-800 dark:focus-visible:ring-offset-zinc-900"
                >
                  <svg viewBox="0 0 24 24" className="h-3.5 w-3.5" fill="none" stroke="currentColor" strokeWidth={2} strokeLinecap="round" strokeLinejoin="round" aria-hidden="true">
                    <path d="M3 12a9 9 0 1 0 3-6.7" />
                    <path d="M3 4v4h4" />
                  </svg>
                  Reset
                </button>
              </motion.div>
            </div>
          </div>
        </div>
      </div>
    </section>
  );
}