const app = document.querySelector("#app");
const toast = document.querySelector("#toast");
const API = "/api/v1";

function showToast(message) {
  toast.textContent = message;
  toast.classList.add("show");
  clearTimeout(showToast.timer);
  showToast.timer = setTimeout(() => toast.classList.remove("show"), 3400);
}

function escapeHtml(value = "") {
  return String(value).replace(/[&<>"']/g, (char) => ({
    "&": "&amp;", "<": "&lt;", ">": "&gt;", '"': "&quot;", "'": "&#039;",
  })[char]);
}

function lessonId() {
  const match = location.pathname.match(/^\/lesson\/([^/]+)/);
  return match && match[1] !== "new" ? match[1] : null;
}

async function fetchLesson(id) {
  const response = await fetch(`${API}/sessions/${id}`);
  if (!response.ok) throw new Error("Lesson not found");
  return response.json();
}

function setActiveNavigation() {
  document.querySelectorAll("[data-nav]").forEach((link) => {
    link.classList.toggle("active", link.dataset.nav === location.pathname);
  });
}

function landingPage() {
  return `
    <section class="page">
      <div class="hero">
        <div class="hero-copy">
          <span class="eyebrow">Meet your adaptive AI teacher</span>
          <h1>Learn anything.<br><span class="gradient-text">Understand it deeply.</span></h1>
          <p class="lead">Gargi listens, explains, draws and adapts in real time&mdash;turning every question into a lesson made just for you.</p>
          <div class="hero-actions">
            <a class="btn btn-primary" href="/lesson/new">Start a lesson <span>&rarr;</span></a>
            <a class="btn btn-secondary" href="#how-it-works">See how it works <span>&darr;</span></a>
          </div>
          <div class="trust-row">
            <div class="avatar-stack"><span>AI</span><span>STEM</span><span>ART</span></div>
            <span>From quantum physics to poetry&mdash;ask freely.</span>
          </div>
        </div>
        <div class="hero-visual">
          <div class="logo-stage"><img src="/static/logo-mark.svg" alt="Gargi AI owl"></div>
          <div class="float-card float-one"><i>&#10022;</i><span>Adapts to your level</span></div>
          <div class="float-card float-two"><i>&#9673;</i><span>Natural voice lessons</span></div>
        </div>
      </div>
      <div id="how-it-works" class="section-heading">
        <div><span class="eyebrow">One classroom, many ways to learn</span><h2>Teaching that meets you<br>where you are.</h2></div>
        <p>Speak naturally, watch ideas take shape on the whiteboard, and check your understanding without leaving the lesson.</p>
      </div>
      <div class="feature-grid">
        <article class="feature-card"><div class="feature-icon">&#9673;</div><h3>Talk it through</h3><p>Ask questions in your own words. Gemini Live listens, understands and responds with a natural teaching voice.</p></article>
        <article class="feature-card"><div class="feature-icon">&#10022;</div><h3>See the idea</h3><p>Gargi turns explanations into diagrams, equations and step-by-step whiteboard notes.</p></article>
        <article class="feature-card"><div class="feature-icon">&#10003;</div><h3>Make it stick</h3><p>Quick adaptive quizzes uncover misconceptions and shape the next explanation around you.</p></article>
      </div>
    </section>`;
}

function setupPage() {
  return `
    <section class="page">
      <div class="page-intro">
        <span class="eyebrow">Your next lesson starts here</span>
        <h1>What are you <span class="gradient-text">curious about?</span></h1>
        <p class="lead">Give Gargi a topic and a little context. Your classroom will be ready in seconds.</p>
      </div>
      <div class="setup-shell">
        <form id="lesson-form" class="setup-card">
          <div class="form-grid">
            <div class="form-field full">
              <label for="topic">What would you like to learn?</label>
              <input id="topic" name="topic" required minlength="2" maxlength="200" placeholder="e.g. Why do planets stay in orbit?">
              <div class="suggestions">
                <button class="suggestion" type="button" data-topic="How black holes bend space and time">Black holes</button>
                <button class="suggestion" type="button" data-topic="How photosynthesis helps plants grow">Photosynthesis</button>
                <button class="suggestion" type="button" data-topic="The basics of probability">Probability</button>
              </div>
            </div>
            <div class="form-field">
              <label for="level">My current level</label>
              <select id="level" name="learner_level">
                <option value="beginner">Beginner - start from scratch</option>
                <option value="intermediate">Intermediate - I know the basics</option>
                <option value="advanced">Advanced - challenge me</option>
              </select>
            </div>
            <div class="form-field">
              <label for="language">Lesson language</label>
              <select id="language" name="language">
                <option value="en-US">English</option>
                <option value="hi-IN">Hindi</option>
              </select>
            </div>
            <div class="form-field full">
              <label for="objective">What do you want to understand? <span class="optional">(optional)</span></label>
              <textarea id="objective" name="objective" maxlength="500" placeholder="Tell Gargi what success looks like for this lesson..."></textarea>
            </div>
          </div>
          <div class="setup-footer">
            <p class="setup-note">No perfect prompt needed. Start broad and ask follow-up questions naturally inside the classroom.</p>
            <button class="btn btn-primary" type="submit">Create my classroom <span>&rarr;</span></button>
          </div>
        </form>
      </div>
    </section>`;
}

function renderBoard(blocks = []) {
  if (!blocks.length) {
    return `<div class="empty-board"><div class="sketch">&#10022;</div><h3>Your ideas will appear here</h3><p>Start the conversation and Gargi will build diagrams, equations and notes around your questions.</p></div>`;
  }
  return blocks.map((block) => {
    if (block.type === "bullets") {
      return `<div class="board-block"><ul>${block.content.map((item) => `<li>${escapeHtml(item)}</li>`).join("")}</ul></div>`;
    }
    if (block.type === "mermaid") {
      return `<div class="board-block diagram"><span>Concept diagram</span>${renderMermaidDiagram(block.content)}</div>`;
    }
    if (block.type === "equation") {
      return renderEquation(block.content);
    }
    return `<div class="board-block ${block.type}">${escapeHtml(block.content)}</div>`;
  }).join("");
}

function readLatexGroup(source, start) {
  if (source[start] !== "{") return null;
  let depth = 0;
  for (let index = start; index < source.length; index++) {
    const char = source[index];
    if (char === "{" && source[index - 1] !== "\\") depth++;
    if (char === "}" && source[index - 1] !== "\\") depth--;
    if (depth === 0) return {content: source.slice(start + 1, index), end: index + 1};
  }
  return null;
}

function findLatexFraction(source) {
  const start = source.indexOf("\\frac");
  if (start < 0) return null;
  let cursor = start + "\\frac".length;
  while (/\s/.test(source[cursor])) cursor++;
  const numerator = readLatexGroup(source, cursor);
  if (!numerator) return null;
  cursor = numerator.end;
  while (/\s/.test(source[cursor])) cursor++;
  const denominator = readLatexGroup(source, cursor);
  if (!denominator) return null;
  return {start, end: denominator.end, numerator: numerator.content, denominator: denominator.content};
}

function formatLatexInline(source = "") {
  let output = String(source).trim().replace(/^\$|\$$/g, "");
  let textMatch = output.match(/\\text\s*\{/);
  while (textMatch) {
    const groupStart = textMatch.index + textMatch[0].lastIndexOf("{");
    const group = readLatexGroup(output, groupStart);
    if (!group) break;
    output = `${output.slice(0, textMatch.index)}${group.content}${output.slice(group.end)}`;
    textMatch = output.match(/\\text\s*\{/);
  }
  output = output
    .replace(/\\left|\\right/g, "")
    .replace(/\\times/g, "×")
    .replace(/\\cdot/g, "·")
    .replace(/\\leq?/g, "≤")
    .replace(/\\geq?/g, "≥")
    .replace(/\\neq/g, "≠")
    .replace(/\\approx/g, "≈")
    .replace(/\\pi/g, "π")
    .replace(/\\%/g, "%")
    .replace(/\s+/g, " ");
  return escapeHtml(output);
}

function renderEquation(source = "") {
  const equation = String(source).trim();
  const fraction = findLatexFraction(equation);
  if (!fraction) {
    return `<div class="board-block equation"><div class="equation-card"><span class="eq-inline">${formatLatexInline(equation)}</span></div></div>`;
  }
  const before = equation.slice(0, fraction.start).trim();
  const after = equation.slice(fraction.end).trim();
  return `
    <div class="board-block equation">
      <div class="equation-card">
        ${before ? `<span class="eq-prefix">${formatLatexInline(before)}</span>` : ""}
        <span class="eq-fraction" aria-label="${formatLatexInline(fraction.numerator)} over ${formatLatexInline(fraction.denominator)}">
          <span class="eq-top">${formatLatexInline(fraction.numerator)}</span>
          <span class="eq-bottom">${formatLatexInline(fraction.denominator)}</span>
        </span>
        ${after ? `<span class="eq-suffix">${formatLatexInline(after)}</span>` : ""}
      </div>
    </div>`;
}

function parseMermaidNode(raw = "") {
  const trimmed = raw.trim();
  const match = trimmed.match(/^([A-Za-z0-9_-]+)\s*(?:\[\s*([^\]]+?)\s*\]|\(\(\s*([^)]+?)\s*\)\)|\(\s*([^)]+?)\s*\)|\{\s*([^}]+?)\s*\})?$/);
  if (!match) return {id: trimmed, label: trimmed.replace(/_/g, " ")};
  const [, id, square, circle, round, brace] = match;
  return {id, label: square || circle || round || brace || id.replace(/_/g, " ")};
}

function renderMermaidDiagram(source = "") {
  const lines = String(source)
    .split(/\n|;/)
    .map((line) => line.trim())
    .filter(Boolean)
    .filter((line) => !/^(graph|flowchart)\s+/i.test(line));
  const edges = lines.map((line) => {
    const match = line.match(/^(.+?)\s*[-.=]+>\s*(?:\|(.+?)\|\s*)?(.+)$/) || line.match(/^(.+?)\s*--\s*(?:\|(.+?)\|\s*)?(.+)$/);
    if (!match) return null;
    const from = parseMermaidNode(match[1]);
    const label = match[2] || "";
    const to = parseMermaidNode(match[3]);
    return {from, label, to};
  }).filter(Boolean);

  if (!edges.length) return `<pre>${escapeHtml(source)}</pre>`;
  return `<div class="mermaid-flow">${edges.map((edge) => `
    <div class="flow-row">
      <div class="flow-node">${escapeHtml(edge.from.label)}</div>
      <div class="flow-link">${edge.label ? `<small>${escapeHtml(edge.label)}</small>` : ""}<b></b></div>
      <div class="flow-node">${escapeHtml(edge.to.label)}</div>
    </div>`).join("")}</div>`;
}

function classroomPage(lesson) {
  const artifact = lesson.artifacts.at(-1);
  const messages = lesson.messages.length
    ? lesson.messages.map((message) => `<div class="message ${message.role}"><strong>${message.role === "student" ? "You" : "Gargi"}</strong><span>${escapeHtml(message.text)}</span></div>`).join("")
    : `<div class="transcript-empty">Your conversation will appear here.<br>Use the microphone or type a question below.</div>`;
  return `
    <section class="page classroom-page">
      <div class="lesson-bar">
        <div class="lesson-title">
          <div class="mini-mark"><img src="/static/logo-mark.svg" width="30" alt=""></div>
          <div><h1>${escapeHtml(lesson.topic)}</h1><p>${escapeHtml(lesson.learner_level)} &middot; ${escapeHtml(lesson.language)} &middot; Adaptive lesson</p></div>
        </div>
        <div class="lesson-actions">
          <span id="live-status" class="status-pill connecting">Connecting</span>
          <a id="quiz-link" class="btn btn-secondary ${artifact ? "" : "hidden"}" href="#quiz">Take quiz</a>
          <a class="btn btn-ghost" href="/lesson/${lesson.id}/summary">End lesson</a>
        </div>
      </div>
      <div class="classroom-grid">
        <section id="teacher-panel" class="class-panel teacher-panel">
          <div class="teacher-top"><span>GARGI &middot; LIVE TEACHER</span><span>Gemini Live</span></div>
          <div id="avatar-mount" class="avatar-placeholder" aria-label="Live2D avatar mount">
            <div class="voice-rings"><i></i><i></i><i></i></div>
            <canvas id="avatar-canvas" aria-hidden="true"></canvas>
            <img id="avatar-fallback" src="/static/logo-mark.svg" alt="Gargi avatar placeholder">
            <span id="avatar-label">Loading Haru Live2D...</span>
          </div>
          <div class="voice-control">
            <button id="mic-button" class="mic-button" aria-label="Start voice question"><span class="mic-icon">&#9673;</span></button>
            <p id="mic-label">Tap to ask Gargi a question</p>
            <small>Tap again when you finish speaking</small>
          </div>
        </section>
        <section class="class-panel whiteboard-panel">
          <div class="panel-head"><h2>Interactive whiteboard</h2><span id="board-status">Updates after each answer</span></div>
          <div id="whiteboard" class="whiteboard-content">${renderBoard(artifact?.whiteboard_blocks)}</div>
          <script id="classroom-quiz-data" type="application/json">${JSON.stringify(artifact?.quiz || []).replace(/</g, "\\u003c")}</script>
          <script id="classroom-board-data" type="application/json">${JSON.stringify(artifact?.whiteboard_blocks || []).replace(/</g, "\\u003c")}</script>
        </section>
        <aside class="class-panel side-panel">
          <div class="panel-head"><h2>Conversation</h2><span id="message-count">${lesson.messages.length} messages</span></div>
          <div id="transcript" class="transcript">${messages}</div>
          <div class="ask-box">
            <form id="ask-form">
              <input id="ask-input" maxlength="4000" placeholder="Type a question..." autocomplete="off">
              <button class="send-btn" aria-label="Send question">&#10148;</button>
            </form>
          </div>
        </aside>
      </div>
    </section>`;
}

function emptyState(title, copy) {
  return `<section class="page"><div class="surface empty-state"><img src="/static/logo-mark.svg" alt=""><h2>${title}</h2><p class="lead empty-copy">${copy}</p><a class="btn btn-primary" href="/lesson/new">Start a new lesson</a></div></section>`;
}

function quizPage(lesson) {
  const quiz = lesson.artifacts.at(-1)?.quiz || [];
  if (!quiz.length) return emptyState("No quiz yet", "Ask Gargi a question first. Your adaptive quiz appears after the explanation.");
  return `
    <section class="page quiz-shell">
      <div class="page-intro"><span class="eyebrow">Knowledge check</span><h1>Let us make it <span class="gradient-text">stick.</span></h1><p class="lead">Three quick questions based on your latest conversation.</p></div>
      <div class="progress-row"><span id="progress-label"></span><div class="progress-track"><div id="progress-fill" class="progress-fill"></div></div><span id="score-label">0 correct</span></div>
      <div id="quiz-card" class="surface quiz-card"></div>
      <script id="quiz-data" type="application/json">${JSON.stringify(quiz).replace(/</g, "\\u003c")}</script>
    </section>`;
}

function summaryPage(lesson) {
  const latest = lesson.artifacts.at(-1);
  const score = lesson.quiz_attempts.length ? Math.round(lesson.quiz_attempts.at(-1).score * 100) : 0;
  return `
    <section class="page summary-shell">
      <div class="summary-hero">
        <span class="eyebrow summary-eyebrow">Lesson snapshot</span>
        <h1>Curiosity looks good on you.</h1>
        <p>${escapeHtml(lesson.topic)} &middot; ${Math.floor(lesson.messages.length / 2)} conversation turns</p>
        <div class="hero-actions"><a class="btn btn-secondary" href="/lesson/${lesson.id}">Continue lesson</a><a class="btn summary-new" href="/lesson/new">Learn something new</a></div>
      </div>
      <div class="summary-grid">
        <article class="surface summary-card">
          <h3>What you explored</h3>
          <p>${escapeHtml(latest?.summary || lesson.objective || "Start a conversation to build your lesson summary.")}</p>
          <div class="stat-row">
            <div class="stat"><strong>${Math.floor(lesson.messages.length / 2)}</strong><span>Questions</span></div>
            <div class="stat"><strong>${lesson.artifacts.length}</strong><span>Explanations</span></div>
            <div class="stat"><strong>${score}%</strong><span>Quiz score</span></div>
          </div>
        </article>
        <article class="surface summary-card">
          <h3>Understanding improved</h3>
          ${lesson.misconceptions.length ? `<ul>${lesson.misconceptions.map((item) => `<li>${escapeHtml(item)}</li>`).join("")}</ul>` : "<p>Gargi will track and clarify misconceptions as your lesson develops.</p>"}
        </article>
        <article class="surface summary-card">
          <h3>Suggested next step</h3>
          <p>${escapeHtml(latest?.suggested_follow_up || "Continue the lesson and ask for a practical example.")}</p>
          <a class="btn btn-secondary" href="/lesson/${lesson.id}">Keep exploring &rarr;</a>
        </article>
        <article class="surface summary-card">
          <h3>Lesson details</h3>
          <p><strong>Level:</strong> ${escapeHtml(lesson.learner_level)}<br><strong>Language:</strong> ${escapeHtml(lesson.language)}<br><strong>Status:</strong> ${escapeHtml(lesson.status)}</p>
          ${latest ? `<a class="btn btn-secondary" href="/lesson/${lesson.id}/quiz">Review quiz &rarr;</a>` : ""}
        </article>
      </div>
    </section>`;
}

async function render() {
  setActiveNavigation();
  try {
    if (location.pathname === "/") app.innerHTML = landingPage();
    else if (location.pathname === "/lesson/new") app.innerHTML = setupPage();
    else {
      const lesson = await fetchLesson(lessonId());
      if (location.pathname.endsWith("/quiz")) app.innerHTML = quizPage(lesson);
      else if (location.pathname.endsWith("/summary")) app.innerHTML = summaryPage(lesson);
      else app.innerHTML = classroomPage(lesson);
    }
    bindPage();
  } catch {
    app.innerHTML = emptyState("We could not find that classroom", "The lesson may have ended or the link is no longer available.");
  }
}

function bindPage() {
  document.querySelectorAll("[data-topic]").forEach((button) => {
    button.addEventListener("click", () => { document.querySelector("#topic").value = button.dataset.topic; });
  });

  document.querySelector("#lesson-form")?.addEventListener("submit", async (event) => {
    event.preventDefault();
    const button = event.submitter;
    button.disabled = true;
    button.textContent = "Preparing classroom...";
    try {
      const response = await fetch(`${API}/sessions`, {
        method: "POST",
        headers: {"Content-Type": "application/json"},
        body: JSON.stringify(Object.fromEntries(new FormData(event.currentTarget))),
      });
      if (!response.ok) throw new Error("Could not create the lesson.");
      location.href = `/lesson/${(await response.json()).id}`;
    } catch (error) {
      showToast(error.message);
      button.disabled = false;
      button.innerHTML = "Create my classroom <span>&rarr;</span>";
    }
  });

  const quizData = document.querySelector("#quiz-data");
  if (quizData) initializeQuiz(JSON.parse(quizData.textContent));
  initializeClassroom();
}

function initializeQuiz(quiz) {
  let index = 0;
  let correct = 0;
  const id = lessonId();
  const card = document.querySelector("#quiz-card");

  function showQuestion() {
    const question = quiz[index];
    const answers = question.type === "multiple_choice"
      ? question.options.map((option) => `<label class="answer-option"><input type="radio" name="answer" value="${escapeHtml(option)}"><span>${escapeHtml(option)}</span></label>`).join("")
      : `<div class="form-field"><textarea id="short-answer" placeholder="Explain in your own words..."></textarea></div>`;
    card.innerHTML = `<span class="question-number">Question ${index + 1}</span><h2 class="question-title">${escapeHtml(question.question)}</h2><div class="answer-list">${answers}</div><div class="quiz-actions"><a class="btn btn-ghost" href="/lesson/${id}">Back to class</a><button id="submit-answer" class="btn btn-primary">Check answer</button></div>`;
    document.querySelector("#progress-label").textContent = `Question ${index + 1} of ${quiz.length}`;
    document.querySelector("#progress-fill").style.width = `${((index + 1) / quiz.length) * 100}%`;
    document.querySelectorAll(".answer-option").forEach((option) => option.addEventListener("click", () => {
      document.querySelectorAll(".answer-option").forEach((item) => item.classList.remove("selected"));
      option.classList.add("selected");
    }));
    document.querySelector("#submit-answer").addEventListener("click", async () => {
      const answer = question.type === "multiple_choice"
        ? document.querySelector('input[name="answer"]:checked')?.value
        : document.querySelector("#short-answer")?.value.trim();
      if (!answer) return showToast("Choose or write an answer first.");
      const response = await fetch(`${API}/sessions/${id}/quiz/${question.id}/answer`, {
        method: "POST", headers: {"Content-Type": "application/json"}, body: JSON.stringify({answer}),
      });
      if (!response.ok) return showToast("The answer could not be checked.");
      const result = await response.json();
      if (result.is_correct) correct++;
      document.querySelector("#score-label").textContent = `${correct} correct`;
      card.innerHTML = `<span class="question-number">${result.is_correct ? "Nicely done" : "Let us clarify it"}</span><h2 class="question-title">${result.is_correct ? "That is correct." : `Expected answer: ${escapeHtml(result.expected_answer)}`}</h2><p class="lead">${escapeHtml(result.explanation)}</p><div class="quiz-actions"><span></span><button id="next-question" class="btn btn-primary">${index === quiz.length - 1 ? "View lesson summary" : "Next question"} &rarr;</button></div>`;
      document.querySelector("#next-question").addEventListener("click", () => {
        if (index === quiz.length - 1) location.href = `/lesson/${id}/summary`;
        else { index++; showQuestion(); }
      });
    });
  }
  showQuestion();
}

function initializeClassroom() {
  const form = document.querySelector("#ask-form");
  if (!form) return;

  const id = lessonId();
  const panel = document.querySelector("#teacher-panel");
  const status = document.querySelector("#live-status");
  const transcript = document.querySelector("#transcript");
  const board = document.querySelector("#whiteboard");
  const boardStatus = document.querySelector("#board-status");
  const quizLink = document.querySelector("#quiz-link");
  const micButton = document.querySelector("#mic-button");
  const micLabel = document.querySelector("#mic-label");
  const messageCount = document.querySelector("#message-count");
  const avatarMount = document.querySelector("#avatar-mount");
  const avatarCanvas = document.querySelector("#avatar-canvas");
  const avatarFallback = document.querySelector("#avatar-fallback");
  const avatarLabel = document.querySelector("#avatar-label");
  const protocol = location.protocol === "https:" ? "wss:" : "ws:";

  let socket;
  let socketReady = false;
  let recording = false;
  let mediaStream;
  let captureContext;
  let micNode;
  let micSource;
  let playbackContext;
  let nextPlayTime = 0;
  let activeSources = 0;
  let playbackSources = new Set();
  let startingMicrophone = false;
  let pendingTyped = "";
  let currentQuiz = JSON.parse(document.querySelector("#classroom-quiz-data")?.textContent || "[]");
  let currentBoardBlocks = JSON.parse(document.querySelector("#classroom-board-data")?.textContent || "[]");
  let heardLiveAudioThisTurn = false;
  let fallbackSpeechText = "";
  let fallbackSpeechBuffer = "";
  let fallbackSpeechTimer;
  let fallbackLipSyncTimer;
  let live2dApp;
  let live2dModel;

  function setState(name, label) {
    panel.dataset.state = name;
    status.className = `status-pill ${name}`;
    status.textContent = label;
    micLabel.textContent = name === "listening" ? "Listening... tap when finished" : label;
  }

  function updateCount() {
    const count = transcript.querySelectorAll(".message").length;
    messageCount.textContent = `${count} message${count === 1 ? "" : "s"}`;
  }

  function appendMessage(role, text, merge = false) {
    transcript.querySelector(".transcript-empty")?.remove();
    const last = transcript.lastElementChild;
    if (merge && last?.classList.contains(role)) {
      last.querySelector("span").textContent += text;
    } else {
      transcript.insertAdjacentHTML("beforeend", `<div class="message ${role}"><strong>${role === "student" ? "You" : "Gargi"}</strong><span>${escapeHtml(text)}</span></div>`);
    }
    transcript.scrollTop = transcript.scrollHeight;
    updateCount();
  }

  function showWhiteboard() {
    board.innerHTML = renderBoard(currentBoardBlocks);
    boardStatus.textContent = currentBoardBlocks.length ? "Whiteboard view" : "Updates after each answer";
    quizLink.textContent = "Take quiz";
    quizLink.href = "#quiz";
  }

  function showInlineQuiz() {
    if (!currentQuiz.length) return showToast("Ask Gargi a question first. Your quiz appears after the explanation.");
    let index = 0;
    let correct = 0;
    boardStatus.textContent = "Quiz in whiteboard";
    quizLink.textContent = "Whiteboard";
    quizLink.href = "#whiteboard";
    board.innerHTML = `
      <div class="inline-quiz">
        <div class="progress-row"><span id="inline-progress-label"></span><div class="progress-track"><div id="inline-progress-fill" class="progress-fill"></div></div><span id="inline-score-label">0 correct</span></div>
        <div id="inline-quiz-card" class="surface quiz-card"></div>
      </div>`;
    const card = board.querySelector("#inline-quiz-card");

    function showQuestion() {
      const question = currentQuiz[index];
      const answers = question.type === "multiple_choice"
        ? question.options.map((option) => `<label class="answer-option"><input type="radio" name="inline-answer" value="${escapeHtml(option)}"><span>${escapeHtml(option)}</span></label>`).join("")
        : `<div class="form-field"><textarea id="inline-short-answer" placeholder="Explain in your own words..."></textarea></div>`;
      card.innerHTML = `<span class="question-number">Question ${index + 1}</span><h2 class="question-title">${escapeHtml(question.question)}</h2><div class="answer-list">${answers}</div><div class="quiz-actions"><button id="inline-back-board" class="btn btn-ghost" type="button">Back to whiteboard</button><button id="inline-submit-answer" class="btn btn-primary" type="button">Check answer</button></div>`;
      board.querySelector("#inline-progress-label").textContent = `Question ${index + 1} of ${currentQuiz.length}`;
      board.querySelector("#inline-progress-fill").style.width = `${((index + 1) / currentQuiz.length) * 100}%`;
      board.querySelectorAll(".answer-option").forEach((option) => option.addEventListener("click", () => {
        board.querySelectorAll(".answer-option").forEach((item) => item.classList.remove("selected"));
        option.classList.add("selected");
      }));
      board.querySelector("#inline-back-board").addEventListener("click", showWhiteboard);
      board.querySelector("#inline-submit-answer").addEventListener("click", async () => {
        const answer = question.type === "multiple_choice"
          ? board.querySelector('input[name="inline-answer"]:checked')?.value
          : board.querySelector("#inline-short-answer")?.value.trim();
        if (!answer) return showToast("Choose or write an answer first.");
        const response = await fetch(`${API}/sessions/${id}/quiz/${question.id}/answer`, {
          method: "POST", headers: {"Content-Type": "application/json"}, body: JSON.stringify({answer}),
        });
        if (!response.ok) return showToast("The answer could not be checked.");
        const result = await response.json();
        if (result.is_correct) correct++;
        board.querySelector("#inline-score-label").textContent = `${correct} correct`;
        card.innerHTML = `<span class="question-number">${result.is_correct ? "Nicely done" : "Let us clarify it"}</span><h2 class="question-title">${result.is_correct ? "That is correct." : `Expected answer: ${escapeHtml(result.expected_answer)}`}</h2><p class="lead">${escapeHtml(result.explanation)}</p><div class="quiz-actions"><button id="inline-review-board" class="btn btn-ghost" type="button">Review whiteboard</button><button id="inline-next-question" class="btn btn-primary" type="button">${index === currentQuiz.length - 1 ? "Finish quiz" : "Next question"} &rarr;</button></div>`;
        board.querySelector("#inline-review-board").addEventListener("click", showWhiteboard);
        board.querySelector("#inline-next-question").addEventListener("click", () => {
          if (index === currentQuiz.length - 1) {
            showToast(`Quiz complete: ${correct}/${currentQuiz.length} correct.`);
            showWhiteboard();
          } else {
            index++;
            showQuestion();
          }
        });
      });
    }

    showQuestion();
  }

  function setAvatarMouth(level = 0) {
    if (!live2dModel?.internalModel?.coreModel) return;
    try {
      const coreModel = live2dModel.internalModel.coreModel;
      const value = Math.max(0, Math.min(1, level));
      if (typeof coreModel.setParameterValueById === "function") {
        coreModel.setParameterValueById("ParamMouthOpenY", value);
      }
    } catch {}
  }

  function stopFallbackLipSync() {
    clearInterval(fallbackLipSyncTimer);
    fallbackLipSyncTimer = null;
    panel.style.setProperty("--talk-level", "0");
    setAvatarMouth(0);
  }

  function startFallbackLipSync() {
    clearInterval(fallbackLipSyncTimer);
    fallbackLipSyncTimer = setInterval(() => {
      const level = 0.18 + Math.random() * 0.62;
      panel.style.setProperty("--talk-level", level.toFixed(2));
      setAvatarMouth(level);
    }, 90);
  }

  async function initializeLive2DAvatar() {
    if (!avatarCanvas || !avatarMount || !window.PIXI?.live2d?.Live2DModel) {
      if (avatarLabel) avatarLabel.textContent = "Live2D runtime unavailable";
      return;
    }
    try {
      live2dApp = new PIXI.Application({
        view: avatarCanvas,
        resizeTo: avatarMount,
        backgroundAlpha: 0,
        antialias: true,
        autoDensity: true,
      });
      live2dModel = await PIXI.live2d.Live2DModel.from("/static/vendor/live2d/haru/haru_greeter_t03.model3.json", {
        autoInteract: true,
      });
      live2dModel.anchor.set(0.5, 0.52);
      live2dApp.stage.addChild(live2dModel);

      const fitModel = () => {
        const width = live2dApp.renderer.width;
        const height = live2dApp.renderer.height;
        if (!width || !height) return;
        live2dModel.scale.set(1);
        live2dModel.position.set(width / 2, height * 0.78);
        const scale = Math.min(width / live2dModel.width, height / live2dModel.height) * 1.68;
        live2dModel.scale.set(scale);
      };
      fitModel();
      window.addEventListener("resize", fitModel);
      avatarFallback?.classList.add("hidden");
      avatarMount.classList.add("live2d-ready");
      avatarLabel.textContent = "Haru Live2D teacher ready";
      live2dModel.on("hit", () => live2dModel.motion("Tap"));
    } catch (error) {
      console.warn("Live2D avatar failed to load", error);
      avatarLabel.textContent = "Live2D fallback active";
    }
  }

  async function ensurePlaybackContext() {
    playbackContext ||= new AudioContext({sampleRate: 24000});
    if (playbackContext.state === "suspended") await playbackContext.resume();
  }

  async function playPcm(buffer) {
    await ensurePlaybackContext();
    heardLiveAudioThisTurn = true;
    window.speechSynthesis?.cancel();
    clearTimeout(fallbackSpeechTimer);
    fallbackSpeechBuffer = "";
    stopFallbackLipSync();
    const pcm = new Int16Array(buffer);
    const samples = new Float32Array(pcm.length);
    let sum = 0;
    for (let index = 0; index < pcm.length; index++) {
      samples[index] = pcm[index] / 32768;
      sum += samples[index] * samples[index];
    }
    const rms = Math.sqrt(sum / Math.max(samples.length, 1));
    const talkLevel = Math.min(1, rms * 8);
    panel.style.setProperty("--talk-level", talkLevel.toFixed(2));
    setAvatarMouth(talkLevel);
    const audio = playbackContext.createBuffer(1, samples.length, 24000);
    audio.copyToChannel(samples, 0);
    const source = playbackContext.createBufferSource();
    source.buffer = audio;
    source.connect(playbackContext.destination);
    nextPlayTime = Math.max(nextPlayTime, playbackContext.currentTime + 0.04);
    source.start(nextPlayTime);
    nextPlayTime += audio.duration;
    playbackSources.add(source);
    activeSources = playbackSources.size;
    setState("speaking", "Gargi is speaking");
    source.onended = () => {
      playbackSources.delete(source);
      activeSources = playbackSources.size;
      if (activeSources <= 0 && !recording) {
        panel.style.setProperty("--talk-level", "0");
        setAvatarMouth(0);
        setState("ready", "Gargi is ready");
      }
    };
  }

  async function startMicrophone() {
    if (startingMicrophone || recording) return;
    if (!socketReady) return showToast("The live classroom is still connecting.");
    if (!navigator.mediaDevices?.getUserMedia) return showToast("This browser does not support microphone capture.");
    startingMicrophone = true;
    try {
      await ensurePlaybackContext();
      stopPlayback(false);
      mediaStream = await navigator.mediaDevices.getUserMedia({
        audio: {channelCount: 1, echoCancellation: true, noiseSuppression: true, autoGainControl: true},
      });
      captureContext = new AudioContext();
      await captureContext.audioWorklet.addModule("/static/mic-processor.js");
      micSource = captureContext.createMediaStreamSource(mediaStream);
      micNode = new AudioWorkletNode(captureContext, "gargi-mic-processor");
      const silentGain = captureContext.createGain();
      silentGain.gain.value = 0;
      micNode.port.onmessage = (event) => {
        if (recording && socket?.readyState === WebSocket.OPEN) socket.send(event.data);
      };
      micSource.connect(micNode);
      micNode.connect(silentGain).connect(captureContext.destination);
      heardLiveAudioThisTurn = false;
      fallbackSpeechText = "";
      fallbackSpeechBuffer = "";
      clearTimeout(fallbackSpeechTimer);
      recording = true;
      micButton.classList.add("recording");
      setState("listening", "Listening");
    } catch (error) {
      showToast(error.name === "NotAllowedError" ? "Microphone permission was denied." : "The microphone could not start.");
      await stopMicrophone(false);
    } finally {
      startingMicrophone = false;
    }
  }

  function stopPlayback(updateState = true) {
    window.speechSynthesis?.cancel();
    clearTimeout(fallbackSpeechTimer);
    fallbackSpeechBuffer = "";
    stopFallbackLipSync();
    playbackSources.forEach((source) => {
      source.onended = null;
      try { source.stop(); } catch {}
      try { source.disconnect(); } catch {}
    });
    playbackSources.clear();
    activeSources = 0;
    nextPlayTime = playbackContext?.currentTime || 0;
    panel.style.setProperty("--talk-level", "0");
    setAvatarMouth(0);
    if (updateState && !recording) setState("ready", "Gargi is ready");
  }

  function speakBrowserFallback(text, cancelExisting = false) {
    if (!window.speechSynthesis || !text.trim()) return;
    if (cancelExisting) window.speechSynthesis.cancel();
    const utterance = new SpeechSynthesisUtterance(text.trim());
    utterance.lang = "en-US";
    utterance.rate = 0.95;
    utterance.pitch = 1.08;
    const voices = window.speechSynthesis.getVoices();
    utterance.voice =
      voices.find((voice) => /Jenny|Aria|Zira|Samantha|Female/i.test(voice.name)) ||
      voices.find((voice) => voice.lang?.startsWith("en")) ||
      null;
    utterance.onstart = () => {
      startFallbackLipSync();
      setState("speaking", "Gargi is speaking");
    };
    utterance.onend = () => {
      if (!window.speechSynthesis.speaking) stopFallbackLipSync();
      if (!recording) setState("ready", "Ask a follow-up");
    };
    utterance.onerror = stopFallbackLipSync;
    window.speechSynthesis.speak(utterance);
  }

  function flushFallbackSpeech(force = false) {
    if (heardLiveAudioThisTurn || !fallbackSpeechBuffer.trim()) return;
    const source = fallbackSpeechBuffer.trimStart();
    let textToSpeak = "";
    let remaining = source;

    if (force) {
      textToSpeak = source;
      remaining = "";
    } else {
      const sentenceEnd = Math.max(source.lastIndexOf("."), source.lastIndexOf("?"), source.lastIndexOf("!"));
      if (sentenceEnd >= 0) {
        textToSpeak = source.slice(0, sentenceEnd + 1);
        remaining = source.slice(sentenceEnd + 1);
      } else if (source.length > 130) {
        const splitAt = Math.max(source.lastIndexOf(","), source.lastIndexOf(" "));
        textToSpeak = source.slice(0, splitAt > 30 ? splitAt : source.length);
        remaining = source.slice(textToSpeak.length);
      }
    }

    fallbackSpeechBuffer = remaining.trimStart();
    if (textToSpeak.trim()) speakBrowserFallback(textToSpeak, false);
  }

  function scheduleRealtimeFallbackSpeech() {
    if (heardLiveAudioThisTurn) return;
    clearTimeout(fallbackSpeechTimer);
    const delay = /[.!?]\s*$/.test(fallbackSpeechBuffer.trim()) ? 80 : 520;
    fallbackSpeechTimer = setTimeout(() => flushFallbackSpeech(false), delay);
  }

  async function stopMicrophone(sendEnd = true) {
    if (!recording && !mediaStream && !captureContext) return;
    const contextToClose = captureContext;
    recording = false;
    micButton.classList.remove("recording");
    if (sendEnd && socket?.readyState === WebSocket.OPEN) {
      socket.send(JSON.stringify({type: "audio_end"}));
      setState("thinking", "Gargi is thinking");
    } else {
      setState("ready", "Gargi is ready");
    }
    if (micNode?.port) micNode.port.onmessage = null;
    micNode?.disconnect();
    micSource?.disconnect();
    mediaStream?.getTracks().forEach((track) => track.stop());
    mediaStream = captureContext = micNode = micSource = null;
    if (contextToClose && contextToClose.state !== "closed") {
      contextToClose.close().catch(() => {});
    }
  }

  socket = new WebSocket(`${protocol}//${location.host}${API}/sessions/${id}/live`);
  socket.binaryType = "arraybuffer";
  socket.onopen = () => setState("connecting", "Connecting");
  socket.onmessage = async (event) => {
    if (event.data instanceof ArrayBuffer) {
      if (recording) return;
      return playPcm(event.data);
    }
    const message = JSON.parse(event.data);
    if (message.type === "ready") {
      socketReady = true;
      setState("ready", "Gargi is ready");
    } else if (message.type === "input_transcription") {
      const text = message.text.trim();
      if (pendingTyped && text.toLowerCase() === pendingTyped.toLowerCase()) pendingTyped = "";
      else if (text) appendMessage("student", text, true);
    } else if (message.type === "output_transcription") {
      fallbackSpeechText += message.text;
      fallbackSpeechBuffer += message.text;
      scheduleRealtimeFallbackSpeech();
      appendMessage("teacher", message.text, true);
      if (!recording) setState("speaking", "Gargi is speaking");
    } else if (message.type === "lesson_payload") {
      currentBoardBlocks = message.whiteboard_blocks || [];
      currentQuiz = message.quiz || [];
      board.innerHTML = renderBoard(message.whiteboard_blocks);
      boardStatus.textContent = "Updated just now";
      quizLink.classList.remove("hidden");
      showToast(message.fallback ? (message.notice || "Fallback whiteboard and quiz are ready.") : "Whiteboard and quiz are ready.");
    } else if (message.type === "interrupted") {
      stopPlayback(false);
      setState(recording ? "listening" : "ready", recording ? "Listening" : "Gargi is ready");
    } else if (message.type === "turn_complete") {
      if (!heardLiveAudioThisTurn && fallbackSpeechText.trim()) {
        clearTimeout(fallbackSpeechTimer);
        flushFallbackSpeech(true);
      }
      heardLiveAudioThisTurn = false;
      fallbackSpeechText = "";
      fallbackSpeechBuffer = "";
      if (activeSources <= 0) setState("ready", "Ask a follow-up");
    } else if (message.type === "error") {
      const retry = message.retry_delay ? ` Try again in ${message.retry_delay}.` : "";
      showToast(`${message.message || "The live classroom hit a problem."}${retry}`);
      setState("error", "Connection problem");
    }
  };
  socket.onclose = () => {
    socketReady = false;
    setState("error", "Voice disconnected");
  };
  socket.onerror = () => showToast("Could not connect to the live classroom.");

  initializeLive2DAvatar();

  quizLink?.addEventListener("click", (event) => {
    event.preventDefault();
    if (quizLink.textContent === "Whiteboard") showWhiteboard();
    else showInlineQuiz();
  });

  micButton.addEventListener("click", () => recording ? stopMicrophone(true) : startMicrophone());
  form.addEventListener("submit", async (event) => {
    event.preventDefault();
    const input = document.querySelector("#ask-input");
    const text = input.value.trim();
    if (!text) return;
    if (!socketReady) return showToast("The live classroom is still connecting.");
    await ensurePlaybackContext();
    heardLiveAudioThisTurn = false;
    fallbackSpeechText = "";
    fallbackSpeechBuffer = "";
    clearTimeout(fallbackSpeechTimer);
    pendingTyped = text;
    appendMessage("student", text);
    socket.send(JSON.stringify({type: "text", text}));
    input.value = "";
    setState("thinking", "Gargi is thinking");
  });

  window.addEventListener("beforeunload", () => {
    if (socket?.readyState === WebSocket.OPEN) socket.send(JSON.stringify({type: "close"}));
    stopPlayback(false);
    stopFallbackLipSync();
    live2dApp?.destroy(true);
    mediaStream?.getTracks().forEach((track) => track.stop());
  });
}

render();