"use client";

import { useCallback, useEffect, useRef, useState, type RefObject } from "react";
import {
  CHAPTER_META,
  FLASHCARDS,
  FORMULA_LOCK,
  NOTE_SECTIONS,
  QUIZ,
  matchChatReply,
  type Flashcard,
  type QuizQuestion,
} from "@/content/sslc/physics/sound-waves/oneshot";

const display = "var(--font-docdoe-display), Archivo, ui-sans-serif, system-ui, sans-serif";
const body = "var(--font-docdoe-sans), Onest, ui-sans-serif, system-ui, sans-serif";

type StepId = "watch" | "notes" | "chat" | "test";

const STEPS: { id: StepId; label: string }[] = [
  { id: "watch", label: "Watch" },
  { id: "notes", label: "Notes" },
  { id: "chat", label: "Chat" },
  { id: "test", label: "Test" },
];

const WATCH_UNLOCK_SEC = 20;
const LS_DONE = "docdoe.preview.sound-waves.chapterDone";

type ChatMsg = { role: "tutor" | "student"; text: string };

const CHIPS = ["Explain again", "Give example", "Exam trap", "Quiz me"] as const;

export function SoundWavesChapterLoop() {
  const [step, setStep] = useState<StepId>("watch");
  const [watchedEnough, setWatchedEnough] = useState(false);
  const [founderSkip, setFounderSkip] = useState(false);
  const notesUnlocked = watchedEnough || founderSkip;

  const videoRef = useRef<HTMLVideoElement | null>(null);

  const onTimeUpdate = useCallback(() => {
    const v = videoRef.current;
    if (!v) return;
    if (v.currentTime >= WATCH_UNLOCK_SEC) setWatchedEnough(true);
  }, []);

  const go = (id: StepId) => {
    if (id !== "watch" && !notesUnlocked && id === "notes") return;
    if ((id === "notes" || id === "chat" || id === "test") && !notesUnlocked) return;
    // Allow chat/test only after notes unlocked (same gate as notes for prototype simplicity)
    setStep(id);
  };

  const unlockAndNotes = () => {
    setFounderSkip(true);
    setStep("notes");
  };

  return (
    <div className="min-h-svh bg-[#10211c] text-[#f2f4f1]" style={{ fontFamily: body }}>
      <div className="border-b border-white/10 bg-[#0c1a16] px-4 py-3 sm:px-6">
        <div className="mx-auto max-w-[720px]">
          <p className="text-[11px] font-semibold uppercase tracking-[0.14em] text-[#c6e04a]">
            Sound Waves chapter loop preview
          </p>
          <p className="mt-1 text-[12px] leading-5 text-[#f2f4f1]/55">
            Sound Waves chapter loop preview · /home untouched
          </p>
        </div>
      </div>

      <div className="mx-auto w-full max-w-[720px] px-4 py-5 pb-24 sm:px-6 sm:py-8">
        <header className="mb-5">
          <p className="text-[12px] font-medium text-[#f2f4f1]/55 sm:text-[13px]">
            {CHAPTER_META.subject} · {CHAPTER_META.board}
          </p>
          <h1
            className="mt-1.5 text-[32px] font-semibold leading-none tracking-[-0.04em] text-[#f2f4f1] sm:text-[44px]"
            style={{ fontFamily: display }}
          >
            {CHAPTER_META.title}
          </h1>
        </header>

        <nav
          className="mb-6 flex gap-1 overflow-x-auto rounded-[14px] border border-white/10 bg-white/[0.04] p-1"
          aria-label="Chapter steps"
        >
          {STEPS.map((s, i) => {
            const locked = s.id !== "watch" && !notesUnlocked;
            const active = step === s.id;
            return (
              <button
                key={s.id}
                type="button"
                disabled={locked}
                onClick={() => go(s.id)}
                className={[
                  "min-h-10 flex-1 rounded-[10px] px-2 text-[12px] font-semibold sm:text-[13px]",
                  active
                    ? "bg-[#c6e04a] text-[#10211c]"
                    : locked
                      ? "cursor-not-allowed text-[#f2f4f1]/30"
                      : "text-[#f2f4f1]/70 hover:bg-white/[0.06]",
                ].join(" ")}
              >
                <span className="tabular-nums opacity-70">{i + 1}.</span> {s.label}
              </button>
            );
          })}
        </nav>

        {step === "watch" ? (
          <WatchStep
            videoRef={videoRef}
            onTimeUpdate={onTimeUpdate}
            notesUnlocked={notesUnlocked}
            onOpenNotes={() => setStep("notes")}
            onFounderSkip={unlockAndNotes}
          />
        ) : null}
        {step === "notes" ? <NotesStep onContinue={() => setStep("chat")} /> : null}
        {step === "chat" ? <ChatStep onContinue={() => setStep("test")} /> : null}
        {step === "test" ? <TestStep /> : null}
      </div>
    </div>
  );
}

function WatchStep({
  videoRef,
  onTimeUpdate,
  notesUnlocked,
  onOpenNotes,
  onFounderSkip,
}: {
  videoRef: RefObject<HTMLVideoElement | null>;
  onTimeUpdate: () => void;
  notesUnlocked: boolean;
  onOpenNotes: () => void;
  onFounderSkip: () => void;
}) {
  return (
    <section className="space-y-4">
      <p className="text-[14px] leading-6 text-[#f2f4f1]/75">
        Watch the class first. Notes open after.
      </p>
      <div className="overflow-hidden rounded-[16px] border border-white/10 bg-black">
        <video
          ref={videoRef}
          className="aspect-video w-full bg-black"
          controls
          playsInline
          preload="metadata"
          onTimeUpdate={onTimeUpdate}
          onPlay={onTimeUpdate}
        >
          <source src={CHAPTER_META.videoSrc} type="video/mp4" />
          <track
            kind="captions"
            src={CHAPTER_META.captionsSrc}
            srcLang="en"
            label="English"
            default
          />
        </video>
      </div>
      <div className="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
        <button
          type="button"
          onClick={onFounderSkip}
          className="text-left text-[12px] font-medium text-[#f2f4f1]/45 underline-offset-2 hover:text-[#f2f4f1]/70 hover:underline"
        >
          I&apos;ve watched — open notes
        </button>
        <button
          type="button"
          disabled={!notesUnlocked}
          onClick={onOpenNotes}
          className={[
            "inline-flex min-h-11 items-center justify-center rounded-full px-5 text-[14px] font-semibold",
            notesUnlocked
              ? "bg-[#c6e04a] text-[#10211c]"
              : "cursor-not-allowed bg-white/10 text-[#f2f4f1]/35",
          ].join(" ")}
        >
          Open notes
        </button>
      </div>
    </section>
  );
}

function NotesStep({ onContinue }: { onContinue: () => void }) {
  return (
    <section className="space-y-4">
      <p className="text-[12px] font-semibold uppercase tracking-[0.14em] text-[#c6e04a]">
        One-shot notes
      </p>
      <div className="max-h-[70vh] space-y-4 overflow-y-auto rounded-[16px] bg-[#f4f3ee] p-4 text-[#10211c] sm:p-5">
        {NOTE_SECTIONS.map((s) => (
          <article
            key={s.n}
            className="rounded-[14px] border border-[#10211c]/10 bg-[#f2f4f1] p-4"
          >
            <h2
              className="text-[17px] font-semibold tracking-[-0.02em]"
              style={{ fontFamily: display }}
            >
              <span className="tabular-nums text-[#10211c]/45">{s.n}.</span> {s.title}
            </h2>
            <p className="mt-2 text-[14px] leading-6 text-[#10211c]/85">{s.concept}</p>
            {s.formula ? (
              <pre className="mt-3 overflow-x-auto rounded-[10px] border border-[#10211c]/12 bg-[#10211c] px-3 py-2.5 font-mono text-[12px] leading-5 text-[#c6e04a] sm:text-[13px]">
                {s.formula}
              </pre>
            ) : null}
            {s.trap ? (
              <p className="mt-3 rounded-[10px] border border-amber-700/25 bg-amber-50 px-3 py-2 text-[13px] leading-5 text-amber-950">
                <span className="font-semibold">Trap · </span>
                {s.trap}
              </p>
            ) : null}
            {s.example ? (
              <p className="mt-3 text-[13px] leading-5 text-[#10211c]/70">
                <span className="font-semibold text-[#10211c]">Example · </span>
                {s.example}
              </p>
            ) : null}
          </article>
        ))}

        <article className="rounded-[14px] border-2 border-[#10211c] bg-[#10211c] p-4 text-[#f2f4f1]">
          <h2
            className="text-[15px] font-semibold uppercase tracking-[0.12em] text-[#c6e04a]"
            style={{ fontFamily: display }}
          >
            Chapter formula lock
          </h2>
          <p className="mt-1 text-[12px] text-[#f2f4f1]/55">
            Write these without looking.
          </p>
          <ul className="mt-3 space-y-2">
            {FORMULA_LOCK.map((line) => (
              <li
                key={line}
                className="rounded-[8px] bg-white/[0.06] px-3 py-2 font-mono text-[13px] text-[#c6e04a]"
              >
                {line}
              </li>
            ))}
          </ul>
        </article>
      </div>
      <button
        type="button"
        onClick={onContinue}
        className="inline-flex min-h-11 w-full items-center justify-center rounded-full bg-[#c6e04a] px-5 text-[14px] font-semibold text-[#10211c] sm:w-auto"
      >
        Continue to study chat
      </button>
    </section>
  );
}

function ChatStep({ onContinue }: { onContinue: () => void }) {
  const [messages, setMessages] = useState<ChatMsg[]>([
    {
      role: "tutor",
      text: `Locked to ${CHAPTER_META.contextLock}. Ask a trap, a formula, or tap a chip.`,
    },
  ]);
  const [draft, setDraft] = useState("");
  const bottomRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    bottomRef.current?.scrollIntoView({ behavior: "smooth" });
  }, [messages]);

  const send = (text: string) => {
    const cleaned = text.trim();
    if (!cleaned) return;
    const reply = matchChatReply(cleaned);
    setMessages((m) => [...m, { role: "student", text: cleaned }, { role: "tutor", text: reply }]);
    setDraft("");
  };

  return (
    <section className="space-y-3">
      <div className="flex items-center justify-between gap-2">
        <p className="text-[12px] font-semibold uppercase tracking-[0.14em] text-[#c6e04a]">
          Study chat
        </p>
        <span className="rounded-full border border-white/12 bg-white/[0.06] px-2.5 py-1 text-[11px] font-medium text-[#f2f4f1]/70">
          {CHAPTER_META.contextLock}
        </span>
      </div>

      <div className="flex max-h-[52vh] flex-col overflow-hidden rounded-[16px] border border-white/10 bg-[#0c1a16]">
        <div className="flex-1 space-y-3 overflow-y-auto p-3 sm:p-4">
          {messages.map((m, i) => (
            <div
              key={`${i}-${m.role}`}
              className={[
                "max-w-[92%] whitespace-pre-wrap rounded-[14px] px-3 py-2.5 text-[14px] leading-6",
                m.role === "tutor"
                  ? "bg-[#f2f4f1] text-[#10211c]"
                  : "ml-auto bg-white/[0.08] text-[#f2f4f1]",
              ].join(" ")}
            >
              {m.role === "tutor" ? (
                <p className="mb-1 text-[10px] font-semibold uppercase tracking-[0.12em] text-[#10211c]/45">
                  Tutor
                </p>
              ) : null}
              {m.text}
            </div>
          ))}
          <div ref={bottomRef} />
        </div>

        <div className="flex flex-wrap gap-1.5 border-t border-white/10 px-3 py-2">
          {CHIPS.map((c) => (
            <button
              key={c}
              type="button"
              onClick={() => send(c)}
              className="rounded-full border border-white/12 bg-white/[0.05] px-2.5 py-1 text-[11px] font-medium text-[#f2f4f1]/75"
            >
              {c}
            </button>
          ))}
        </div>

        <form
          className="flex gap-2 border-t border-white/10 p-3"
          onSubmit={(e) => {
            e.preventDefault();
            send(draft);
          }}
        >
          <input
            value={draft}
            onChange={(e) => setDraft(e.target.value)}
            placeholder="Ask about Sound Waves…"
            className="min-h-11 flex-1 rounded-full border border-white/12 bg-white/[0.06] px-4 text-[14px] text-[#f2f4f1] outline-none placeholder:text-[#f2f4f1]/35 focus:border-[#c6e04a]/50"
          />
          <button
            type="submit"
            className="inline-flex min-h-11 min-w-11 items-center justify-center rounded-full bg-[#c6e04a] px-4 text-[13px] font-semibold text-[#10211c]"
          >
            Send
          </button>
        </form>
      </div>

      <button
        type="button"
        onClick={onContinue}
        className="inline-flex min-h-11 w-full items-center justify-center rounded-full bg-[#c6e04a] px-5 text-[14px] font-semibold text-[#10211c] sm:w-auto"
      >
        Continue to exam test
      </button>
    </section>
  );
}

function TestStep() {
  const [qi, setQi] = useState(0);
  const [selected, setSelected] = useState<number | null>(null);
  const [revealed, setRevealed] = useState(false);
  const [score, setScore] = useState(0);
  const [phase, setPhase] = useState<"quiz" | "score" | "cards">("quiz");
  const [cardIndex, setCardIndex] = useState(0);
  const [flipped, setFlipped] = useState(false);
  const [knowCount, setKnowCount] = useState(0);
  const [done, setDone] = useState(() => {
    if (typeof window === "undefined") return false;
    try {
      return window.localStorage.getItem(LS_DONE) === "1";
    } catch {
      return false;
    }
  });

  const q: QuizQuestion = QUIZ[qi];
  const card: Flashcard = FLASHCARDS[cardIndex];
  const total = QUIZ.length;

  const submitChoice = (idx: number) => {
    if (revealed) return;
    setSelected(idx);
    setRevealed(true);
    if (idx === q.answerIndex) setScore((s) => s + 1);
  };

  const nextQ = () => {
    if (qi + 1 >= total) {
      setPhase("score");
      return;
    }
    setQi((i) => i + 1);
    setSelected(null);
    setRevealed(false);
  };

  const retryType = () => {
    setSelected(null);
    setRevealed(false);
    if (selected === q.answerIndex) setScore((s) => Math.max(0, s - 1));
  };

  const markDone = () => {
    try {
      localStorage.setItem(LS_DONE, "1");
      setDone(true);
    } catch {
      setDone(true);
    }
  };

  const advanceCard = (know: boolean) => {
    if (know) setKnowCount((c) => c + 1);
    setFlipped(false);
    if (cardIndex + 1 >= FLASHCARDS.length) {
      setCardIndex(0);
      return;
    }
    setCardIndex((i) => i + 1);
  };

  const scoreLine = `${score} / ${total}`;

  if (phase === "quiz") {
    return (
      <section className="space-y-4">
        <div className="flex items-center justify-between">
          <p className="text-[12px] font-semibold uppercase tracking-[0.14em] text-[#c6e04a]">
            Exam test
          </p>
          <span className="text-[12px] tabular-nums text-[#f2f4f1]/55">
            {qi + 1} / {total}
          </span>
        </div>
        <div className="rounded-[16px] bg-[#f4f3ee] p-4 text-[#10211c] sm:p-5">
          <p className="text-[15px] font-semibold leading-6" style={{ fontFamily: display }}>
            {q.prompt}
          </p>
          <div className="mt-4 space-y-2">
            {q.choices.map((c, idx) => {
              const isSel = selected === idx;
              const isAns = idx === q.answerIndex;
              let cls =
                "w-full rounded-[12px] border border-[#10211c]/12 bg-[#f2f4f1] px-3 py-3 text-left text-[14px] leading-5";
              if (revealed && isAns) cls += " border-[#10211c] bg-[#c6e04a]/35";
              if (revealed && isSel && !isAns) cls += " border-red-700/40 bg-red-50";
              if (!revealed) cls += " hover:border-[#10211c]/35";
              return (
                <button
                  key={c}
                  type="button"
                  disabled={revealed}
                  onClick={() => submitChoice(idx)}
                  className={cls}
                >
                  {c}
                </button>
              );
            })}
          </div>
          {revealed ? (
            <div className="mt-4 space-y-3">
              <p className="rounded-[10px] border border-[#10211c]/12 bg-white px-3 py-2 text-[13px] leading-5">
                <span className="font-semibold">Fix · </span>
                {q.fix}
              </p>
              <div className="flex flex-wrap gap-2">
                <button
                  type="button"
                  onClick={retryType}
                  className="min-h-10 rounded-full border border-[#10211c]/20 px-4 text-[13px] font-semibold"
                >
                  Retry this type
                </button>
                <button
                  type="button"
                  onClick={nextQ}
                  className="min-h-10 rounded-full bg-[#10211c] px-4 text-[13px] font-semibold text-[#c6e04a]"
                >
                  {qi + 1 >= total ? "See score" : "Next"}
                </button>
              </div>
            </div>
          ) : null}
        </div>
      </section>
    );
  }

  if (phase === "score") {
    return (
      <section className="space-y-4">
        <p className="text-[12px] font-semibold uppercase tracking-[0.14em] text-[#c6e04a]">
          Score
        </p>
        <div className="rounded-[16px] bg-[#f4f3ee] p-5 text-[#10211c]">
          <p className="text-[40px] font-semibold tracking-[-0.04em]" style={{ fontFamily: display }}>
            {scoreLine}
          </p>
          <p className="mt-2 text-[14px] text-[#10211c]/70">
            Next: flashcards from the chapter formula lock.
          </p>
          <button
            type="button"
            onClick={() => setPhase("cards")}
            className="mt-4 inline-flex min-h-11 items-center justify-center rounded-full bg-[#c6e04a] px-5 text-[14px] font-semibold text-[#10211c]"
          >
            Open flashcards
          </button>
        </div>
      </section>
    );
  }

  return (
    <section className="space-y-4">
      <div className="flex items-center justify-between">
        <p className="text-[12px] font-semibold uppercase tracking-[0.14em] text-[#c6e04a]">
          Formula flashcards
        </p>
        <span className="text-[12px] tabular-nums text-[#f2f4f1]/55">
          {cardIndex + 1} / {FLASHCARDS.length} · know {knowCount}
        </span>
      </div>
      <button
        type="button"
        onClick={() => setFlipped((f) => !f)}
        className="flex min-h-[180px] w-full flex-col items-center justify-center rounded-[16px] border border-white/10 bg-[#f4f3ee] px-4 py-8 text-center text-[#10211c]"
      >
        <span className="text-[11px] font-semibold uppercase tracking-[0.14em] text-[#10211c]/45">
          {flipped ? "Answer" : "Tap to flip"}
        </span>
        <span
          className="mt-3 text-[18px] font-semibold leading-7 sm:text-[20px]"
          style={{ fontFamily: display }}
        >
          {flipped ? (
            <span className="inline-block rounded-[10px] bg-[#10211c] px-3 py-2 font-mono text-[16px] text-[#c6e04a]">
              {card.back}
            </span>
          ) : (
            card.front
          )}
        </span>
      </button>
      <div className="flex gap-2">
        <button
          type="button"
          onClick={() => advanceCard(false)}
          className="min-h-11 flex-1 rounded-full border border-white/15 text-[14px] font-semibold text-[#f2f4f1]/80"
        >
          Again
        </button>
        <button
          type="button"
          onClick={() => advanceCard(true)}
          className="min-h-11 flex-1 rounded-full bg-[#c6e04a] text-[14px] font-semibold text-[#10211c]"
        >
          Know
        </button>
      </div>
      <button
        type="button"
        onClick={markDone}
        className="inline-flex min-h-11 w-full items-center justify-center rounded-full border border-[#c6e04a]/40 px-5 text-[14px] font-semibold text-[#c6e04a]"
      >
        {done ? "Tonight’s chapter step marked done ✓" : "Mark tonight’s chapter step done"}
      </button>
      <p className="text-[11px] text-[#f2f4f1]/40">localStorage only · account progress untouched</p>
    </section>
  );
}