"use client";

import { useEffect, useId, useRef, useState, type PointerEvent } from "react";
import { useReducedMotion } from "motion/react";

type ReleaseNote = { kind: "new" | "fix" | "up"; text: string };
type Release = { version: string; date: string; title: string; notes: ReleaseNote[] };

type ChangelogWallProps = {
  /** Newest first. Each one is a poster on the wall. */
  releases?: Release[];
  /** Called with the release now on top. */
  onChange?: (release: Release, index: number) => void;
  /** Set the width here. Everything scales with it. */
  className?: string;
};

const RELEASES: Release[] = [
  {
    version: "4.2",
    date: "2 Nov 2026",
    title: "Offline mode",
    notes: [
      { kind: "new", text: "Works with no signal" },
      { kind: "up", text: "Search twice as fast" },
      { kind: "fix", text: "Double invoices are gone" },
    ],
  },
  {
    version: "4.1",
    date: "9 Sep 2026",
    title: "Team seats",
    notes: [
      { kind: "new", text: "Invite your whole team" },
      { kind: "new", text: "Roles for each member" },
      { kind: "fix", text: "CSV dates read right" },
    ],
  },
  {
    version: "4.0",
    date: "1 Jul 2026",
    title: "All new look",
    notes: [
      { kind: "new", text: "Dark theme" },
      { kind: "up", text: "Pages load in half the time" },
      { kind: "up", text: "Tamil and Hindi menus" },
    ],
  },
  {
    version: "3.9",
    date: "12 Apr 2026",
    title: "Reports",
    notes: [
      { kind: "new", text: "Monthly report by mail" },
      { kind: "fix", text: "Totals round the right way" },
    ],
  },
  {
    version: "3.8",
    date: "3 Feb 2026",
    title: "First print",
    notes: [
      { kind: "new", text: "Billing, stock and customers" },
      { kind: "new", text: "UPI payment links" },
    ],
  },
];

const PAPERS = [
  { bg: "#f2b632", ink: "#1b1a18", hot: "#c8321f" },
  { bg: "#d8402a", ink: "#fbf1dc", hot: "#1b1a18" },
  { bg: "#14756e", ink: "#fbf1dc", hot: "#f2b632" },
  { bg: "#f0e4c8", ink: "#1b1a18", hot: "#d8402a" },
  { bg: "#27306b", ink: "#fbf1dc", hot: "#f09aa8" },
];

const TAGS = { new: "NEW", fix: "FIX", up: "UP" };
const TILT = [-1.4, 1.1, -0.7, 1.6, -1.1];

// In cqw, measured from the bottom right corner: u leftwards, v upwards.
const PW = 84;
const PH = 54;
const REST = 9; // the corner that has come loose by itself
const END = PW + PH - 7; // what stays on the wall after a tear

const STOP = 2.6;
const rip = (s: number, c: number) => (Math.sin(s * 1.7) * 1.1 + Math.sin(s * 4.3 + 1) * 0.7) * Math.min(1, c / 9);
const at = ([u, v]: number[], pad = 0) => `${(PW - u + pad).toFixed(2)}cqw ${(PH - v + pad).toFixed(2)}cqw`;

/** The two shapes for a tear c long: what stays pasted, and the torn paper folded back over it. */
function tear(c: number) {
  const a = c <= PW ? [c, 0] : [PW, c - PW];
  const b = c <= PH ? [0, c] : [c - PH, PH];
  const line = [a];
  // Sampled on a fixed grid so the rough edge stays put as the tear moves.
  for (let s = Math.floor((a[0] - a[1]) / STOP) * STOP; s > b[0] - b[1]; s -= STOP) {
    const j = rip(s, c);
    line.push([(c + s) / 2 + j, (c - s) / 2 + j]);
  }
  line.push(b);

  const keep = [...(c < PW ? [[PW, 0]] : []), [PW, PH], ...(c < PH ? [[0, PH]] : [])];
  const gone = [...(c > PH ? [[0, PH]] : []), [0, 0], ...(c > PW ? [[PW, 0]] : [])];
  const back = [...line, ...gone].map(([u, v]) => [c - v, c - u]);
  return {
    keep: `polygon(${[...line.slice().reverse(), ...keep].map((p) => at(p)).join(",")})`,
    flap: `polygon(${back.map((p) => at(p, 100)).join(",")})`,
    fade: Math.max(0, Math.min(1, (END - c) / (END * 0.3))),
  };
}

function Poster({ release, paper }: { release: Release; paper: (typeof PAPERS)[number] }) {
  return (
    <div className="absolute inset-0 flex gap-[3cqw] px-[4cqw] py-[3.6cqw]" style={{ background: paper.bg, color: paper.ink }}>
      <div className="flex w-[30cqw] shrink-0 flex-col justify-between">
        <span className="font-mono text-[2.6cqw] font-bold tracking-[0.2em] uppercase">Release</span>
        <span className="block leading-[0.86]" style={{ fontFamily: "Impact, Haettenschweiler, 'Arial Narrow', sans-serif", fontSize: "17.5cqw", color: paper.hot, letterSpacing: "-0.01em" }}>
          {release.version}
        </span>
        <span className="font-mono text-[2.9cqw] font-semibold">{release.date}</span>
      </div>
      <div className="min-w-0 flex-1 border-l-[0.5cqw] pl-[3cqw]" style={{ borderColor: paper.ink }}>
        <p className="m-0 text-[5.2cqw] leading-[1.08] font-extrabold uppercase" style={{ fontFamily: "'Arial Narrow', 'Roboto Condensed', Arial, sans-serif" }}>
          {release.title}
        </p>
        <ul className="m-0 mt-[1.5cqw] list-none p-0">
          {release.notes.map((note) => (
            <li key={note.text} className="flex items-baseline gap-[1.2cqw] text-[3.1cqw] leading-[1.18] font-semibold" style={{ marginTop: "1.3cqw" }}>
              <span className="shrink-0 rounded-[0.5cqw] px-[0.8cqw] py-[0.1cqw] font-mono text-[2.3cqw] font-bold" style={{ background: paper.ink, color: paper.bg }}>
                {TAGS[note.kind]}
              </span>
              <span>{note.text}</span>
            </li>
          ))}
        </ul>
      </div>
      {/* Wheat paste: slack paper dries in soft ridges. */}
      <div
        className="pointer-events-none absolute inset-0"
        style={{ background: "linear-gradient(97deg, transparent 12%, #ffffff1f 14%, transparent 17%, transparent 52%, #00000017 54%, transparent 57%, transparent 80%, #ffffff17 82%, transparent 85%), linear-gradient(176deg, transparent 38%, #0000000f 40%, transparent 43%)" }}
      />
    </div>
  );
}

/* ChangelogWall: every release is a poster pasted over the last one on a brick wall. The newest has one corner come loose; pull it, or press Older, and it rips away along a rough edge to show the release under it, leaving a scrap behind. */
export function ChangelogWall({ releases = RELEASES, onChange, className = "w-full max-w-2xl" }: ChangelogWallProps) {
  const reduce = useReducedMotion();
  const id = useId().replace(/[^a-zA-Z0-9]/g, "");
  const wall = useRef<HTMLDivElement>(null);
  const raf = useRef(0);
  const busy = useRef(false);
  const drag = useRef<{ x: number; y: number; moved: boolean; c: number } | null>(null);
  const [top, setTop] = useState(0);
  const last = releases.length - 1;

  useEffect(() => () => cancelAnimationFrame(raf.current), []);

  const paint = (i: number, c: number) => {
    const root = wall.current;
    if (!root) return;
    const t = tear(c);
    const keep = root.querySelector<HTMLElement>(`[data-poster="${i}"]`);
    const flap = root.querySelector<HTMLElement>(`[data-flap="${i}"]`);
    if (keep) keep.style.clipPath = t.keep;
    if (flap) {
      flap.style.clipPath = t.flap;
      flap.style.opacity = String(t.fade);
    }
  };

  const run = (i: number, from: number, to: number, ms: number, done?: () => void) => {
    cancelAnimationFrame(raf.current);
    const begun = performance.now();
    const tick = (now: number) => {
      const p = ms ? Math.min(1, (now - begun) / ms) : 1;
      paint(i, from + (to - from) * (p * p * (3 - 2 * p)));
      if (p < 1) raf.current = requestAnimationFrame(tick);
      else done?.();
    };
    raf.current = requestAnimationFrame(tick);
  };

  const show = (i: number) => {
    busy.current = false;
    setTop(i);
    const r = releases[i];
    if (r) onChange?.(r, i);
  };

  const older = (from = REST) => {
    if (busy.current || top >= last) return;
    busy.current = true;
    run(top, from, END, reduce ? 0 : 620, () => show(top + 1));
  };

  const newer = () => {
    if (busy.current || top <= 0) return;
    busy.current = true;
    const i = top - 1;
    run(i, END, REST, reduce ? 0 : 480, () => show(i));
  };

  const down = (e: PointerEvent<HTMLElement>) => {
    if (busy.current) return;
    e.currentTarget.setPointerCapture(e.pointerId);
    drag.current = { x: e.clientX, y: e.clientY, moved: false, c: REST };
  };

  const move = (e: PointerEvent<HTMLElement>) => {
    const d = drag.current;
    const root = wall.current;
    if (!d || !root) return;
    const pull = d.x - e.clientX + (d.y - e.clientY);
    if (Math.abs(pull) > 5) d.moved = true;
    d.c = Math.max(REST, Math.min(END, REST + (pull / root.offsetWidth) * 100 * 0.85));
    paint(top, d.c);
  };

  const up = () => {
    const d = drag.current;
    drag.current = null;
    if (!d) return;
    if (!d.moved || d.c > REST + 15) {
      older(d.c);
    } else {
      busy.current = true;
      run(top, d.c, REST, 240, () => {
        busy.current = false;
      });
    }
  };

  const brick = `url(#${id}b)`;
  const current = releases[top];

  return (
    <div className={`@container ${className}`}>
      <div ref={wall} className="relative overflow-hidden rounded-[1.4cqw] select-none" style={{ paddingTop: "74cqw", background: "#6a3528" }}>
        <svg className="absolute inset-0 size-full" aria-hidden>
          <defs>
            <pattern id={`${id}b`} width="96" height="48" patternUnits="userSpaceOnUse">
              <rect width="96" height="48" fill="#3f2019" />
              <rect x="1" y="1" width="46" height="22" fill="#8b4733" />
              <rect x="49" y="1" width="46" height="22" fill="#7c3d2c" />
              <rect x="-23" y="25" width="46" height="22" fill="#7a3b2b" />
              <rect x="25" y="25" width="46" height="22" fill="#94503a" />
              <rect x="73" y="25" width="46" height="22" fill="#7a3b2b" />
            </pattern>
          </defs>
          <rect width="100%" height="100%" fill={brick} />
        </svg>
        <div className="absolute inset-0" style={{ background: "radial-gradient(90% 70% at 50% 20%, transparent 40%, #0007), linear-gradient(180deg, #ffffff10, transparent 40%)" }} aria-hidden />

        <div className="absolute top-[3.5cqw] left-[8cqw]" style={{ width: `${PW}cqw`, height: `${PH}cqw` }} aria-hidden>
          {releases.map((release, i) => {
            if (i > top + 2) return null;
            const torn = i < top;
            const live = i === top && i < last;
            const shape = torn ? tear(END) : live ? tear(REST) : null;
            return (
              <div key={release.version} className="absolute inset-0" style={{ zIndex: releases.length - i, transform: `rotate(${TILT[i % TILT.length]}deg)`, pointerEvents: i === top ? undefined : "none" }}>
                <div data-poster={i} className="absolute inset-0" style={{ clipPath: shape?.keep, boxShadow: "0 0.4cqw 1.2cqw #0006" }}>
                  <Poster release={release} paper={PAPERS[i % PAPERS.length]} />
                </div>
                {/* Back of the paper, folded over the tear. */}
                <div className="pointer-events-none absolute inset-0" style={{ filter: "drop-shadow(-0.4cqw -0.4cqw 0.7cqw #0007)" }}>
                  <div
                    data-flap={i}
                    className="absolute top-[-100cqw] left-[-100cqw] h-[300cqw] w-[300cqw]"
                    style={{ clipPath: shape?.flap ?? "none", opacity: shape?.fade ?? 0, background: "repeating-linear-gradient(135deg, #e9e1cf 0 1.4cqw, #dcd3bd 1.4cqw 2.2cqw)" }}
                  />
                </div>
                {i === top && i < last && (
                  <span
                    onPointerDown={down}
                    onPointerMove={move}
                    onPointerUp={up}
                    onPointerCancel={up}
                    className="absolute right-0 bottom-0 size-[20cqw] cursor-grab touch-none active:cursor-grabbing"
                  />
                )}
              </div>
            );
          })}
        </div>

        <div className="absolute inset-x-[8cqw] bottom-[2.8cqw] flex items-center justify-between gap-[2cqw]" style={{ zIndex: releases.length + 2 }}>
          <p className="m-0 rounded-[0.6cqw] px-[2.2cqw] py-[1cqw] font-mono text-[2.9cqw] font-bold" style={{ background: "#efe8d6", color: "#26211b", boxShadow: "0 0.4cqw 0.8cqw #0006" }} role="status">
            v{current?.version} · {top + 1} of {releases.length}
          </p>
          <div className="flex gap-[1.6cqw]">
            <button type="button" onClick={newer} disabled={top === 0} className="min-h-6 cursor-pointer rounded-[0.6cqw] px-[2.6cqw] py-[1cqw] font-mono text-[2.9cqw] font-bold disabled:cursor-default disabled:opacity-45" style={{ background: "#efe8d6", color: "#26211b", boxShadow: "0 0.4cqw 0.8cqw #0006" }}>
              Newer
            </button>
            <button type="button" onClick={() => older()} disabled={top === last} className="min-h-6 cursor-pointer rounded-[0.6cqw] px-[2.6cqw] py-[1cqw] font-mono text-[2.9cqw] font-bold disabled:cursor-default disabled:opacity-45" style={{ background: "#f2b632", color: "#1b1a18", boxShadow: "0 0.4cqw 0.8cqw #0006" }}>
              Tear for older
            </button>
          </div>
        </div>
      </div>

      <ol className="sr-only">
        {releases.map((r) => (
          <li key={r.version}>
            Version {r.version}, {r.date}. {r.title}. {r.notes.map((n) => `${TAGS[n.kind]}: ${n.text}`).join(". ")}.
          </li>
        ))}
      </ol>
    </div>
  );
}