"use client";

/**
 * PROCESS — "The Feedback Loop" as pinned scroll storytelling.
 * - GSAP ScrollTrigger pins the panel while the user scrolls through 4 steps.
 * - A single SVG glyph MORPHS between 4 shapes (MorphSVGPlugin) — magnifier
 *   (Audit) -> route/plan -> bolt (Execute) -> chart (Report) — the animated-SVG
 *   moment for this section.
 * - A progress rail + numbered steps light up in sync (scrub).
 * - prefers-reduced-motion: no pin, no morph; steps render as a static list.
 */
import { useEffect, useRef } from "react";
// Side-effect import registers ScrollTrigger + MorphSVGPlugin; gsap exposes both.
import { gsap } from "./gsap";
import { processSteps } from "../content";

// Four target paths for the morph (drawn on a 100x100 canvas).
const SHAPES = [
  // Audit — magnifying glass
  "M44 20a24 24 0 1 0 15 43l18 18 7-7-18-18A24 24 0 0 0 44 20Zm0 10a14 14 0 1 1 0 28 14 14 0 0 1 0-28Z",
  // Plan — connected route / nodes
  "M22 30a8 8 0 1 1 16 0 8 8 0 0 1-16 0Zm40 40a8 8 0 1 1 16 0 8 8 0 0 1-16 0ZM30 38v8a16 16 0 0 0 16 16h8a16 16 0 0 1 16 16v-2 2h-8a26 26 0 0 1-26-26v-8Z",
  // Execute — lightning bolt
  "M55 14 26 58h20l-6 30 32-46H50l9-28Z",
  // Report — bar chart trending up
  "M22 78V52h12v26Zm22 0V36h12v42Zm22 0V20h12v58ZM20 30 40 22l16 8 26-14",
];

export default function ProcessLoop() {
  const root = useRef<HTMLElement>(null);

  useEffect(() => {
    const el = root.current;
    if (!el) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (reduce) return;

    const ctx = gsap.context(() => {
      const morph = el.querySelector<SVGPathElement>(".loop-glyph__path");
      if (!morph) return;
      const steps = gsap.utils.toArray<HTMLElement>(".loop-step");
      const total = SHAPES.length;

      // One pinned, scrubbed timeline drives the morph + rotation + rail fill.
      const tl = gsap.timeline({
        scrollTrigger: {
          trigger: ".loop-pin",
          start: "top top",
          end: () => `+=${window.innerHeight * (total - 0.2)}`,
          pin: true,
          scrub: 0.6,
          anticipatePin: 1,
          onUpdate: (self) => {
            // Robust, independent active-step highlight tied to raw progress.
            const idx = Math.min(
              total - 1,
              Math.floor(self.progress * total + 0.0001)
            );
            steps.forEach((s, j) => s.classList.toggle("is-active", j === idx));
          },
        },
      });

      steps[0]?.classList.add("is-active");
      const counter = el.querySelector<HTMLElement>(".loop__count-cur");
      const node = el.querySelector<HTMLElement>(".loop-rail__node");

      SHAPES.forEach((shape, i) => {
        if (i === 0) return; // start shape already in markup
        const at = i - 1;
        // morph the glyph + a counter-rotation so it tumbles as it transforms,
        // and grow the rail fill (+ a node that rides the fill edge).
        tl.to(morph, { morphSVG: shape, duration: 1, ease: "power2.inOut" }, at)
          .to(".loop-glyph", { rotate: i * 5, duration: 1, ease: "power2.inOut" }, at)
          .to(
            ".loop-rail__fill",
            { scaleY: i / (total - 1), duration: 1, ease: "none" },
            at
          )
          .to(
            node,
            { top: `${(i / (total - 1)) * 100}%`, duration: 1, ease: "none" },
            at
          );
      });

      // separate light update so the counter is robust at every scroll position
      tl.eventCallback("onUpdate", () => {
        const idx = Math.min(total, Math.floor(tl.progress() * total) + 1);
        if (counter) counter.textContent = String(idx).padStart(2, "0");
      });
    }, el);

    return () => ctx.revert();
  }, []);

  return (
    <section ref={root} id="process" className="loop frame" data-invert aria-labelledby="loop-h">
      <div className="loop-pin">
        <div className="wrap loop__inner">
          <header className="sec-head loop__head">
            <div>
              <p className="kicker">
                <span className="kicker__dot" />
                The Feedback Loop
              </p>
              <h2 id="loop-h" className="display sec-head__title">
                How it works
              </h2>
            </div>
            <p className="loop__count" aria-hidden="true">
              <span className="loop__count-cur">01</span>
              <span className="loop__count-sep">/</span>
              <span className="loop__count-tot">0{processSteps.length}</span>
            </p>
          </header>

          <div className="loop__stage">
            {/* morphing glyph */}
            <div className="loop-glyph" aria-hidden="true">
              <svg viewBox="0 0 100 100">
                <path className="loop-glyph__path" d={SHAPES[0]} fill="url(#loopGrad)" />
                <defs>
                  <linearGradient id="loopGrad" x1="0" y1="0" x2="1" y2="1">
                    <stop offset="0%" stopColor="#3b82f6" />
                    <stop offset="50%" stopColor="#8b5cf6" />
                    <stop offset="100%" stopColor="#10b981" />
                  </linearGradient>
                </defs>
              </svg>
            </div>

            {/* steps + progress rail */}
            <div className="loop__steps">
              <div className="loop-rail" aria-hidden="true">
                <span className="loop-rail__fill" />
                <span className="loop-rail__node" />
              </div>
              <ol>
                {processSteps.map((p) => (
                  <li className="loop-step" key={p.n}>
                    <span className="loop-step__n">{p.n}</span>
                    <div>
                      <h3 className="loop-step__name">{p.name}</h3>
                      <p className="loop-step__desc">{p.desc}</p>
                    </div>
                  </li>
                ))}
              </ol>
            </div>
          </div>
        </div>
      </div>
    </section>
  );
}