// Shared quiz engine for lessons. Two question types, both graded client-side, no server.
//
// Recall (free-recall self-check — best for storage strength):
//   <div class="q" data-type="recall" data-topic="Ownership">
//     <p class="topic">Ownership</p>
//     <p class="prompt">...question...</p>
//     <button class="reveal-btn">Show answer</button>
//     <div class="answer hidden">...answer text...</div>
//     <div class="grade hidden">
//       <button data-grade="hit">Got it</button>
//       <button data-grade="miss">Missed it</button>
//     </div>
//   </div>
//
// Multiple choice (instant feedback):
//   <div class="q" data-type="mcq" data-topic="Enums">
//     <p class="topic">Enums</p>
//     <p class="prompt">...question...</p>
//     <div class="options">
//       <button class="opt" data-correct="true">...</button>
//       <button class="opt" data-correct="false">...</button>
//     </div>
//     <div class="explain hidden">...explanation...</div>
//   </div>
//
// Bottom of page needs:
//   <div id="summary"><div id="summary-body"></div><p id="summary-total"></p>
//     <button id="report-btn">Copy report</button><pre id="report-output" class="hidden"></pre></div>

(function () {
  function all(sel, ctx) {
    return Array.from((ctx || document).querySelectorAll(sel));
  }

  function initRecall(q) {
    var revealBtn = q.querySelector(".reveal-btn");
    var answer = q.querySelector(".answer");
    var grade = q.querySelector(".grade");
    if (!revealBtn || !answer || !grade) return;
    revealBtn.addEventListener("click", function () {
      answer.classList.remove("hidden");
      grade.classList.remove("hidden");
      revealBtn.classList.add("hidden");
    });
    all("button", grade).forEach(function (btn) {
      btn.addEventListener("click", function () {
        q.dataset.result = btn.dataset.grade === "hit" ? "hit" : "miss";
        q.classList.add("graded");
        all("button", grade).forEach(function (b) {
          b.disabled = true;
        });
        btn.classList.add(btn.dataset.grade === "hit" ? "opt-correct" : "opt-incorrect");
        updateSummary();
      });
    });
  }

  function initMcq(q) {
    var opts = all(".opt", q);
    var explain = q.querySelector(".explain");
    opts.forEach(function (opt) {
      opt.addEventListener("click", function () {
        if (q.classList.contains("graded")) return;
        var correct = opt.dataset.correct === "true";
        q.classList.add("graded");
        q.dataset.result = correct ? "hit" : "miss";
        opts.forEach(function (o) {
          o.disabled = true;
          if (o.dataset.correct === "true") o.classList.add("correct");
        });
        if (!correct) opt.classList.add("incorrect");
        if (explain) explain.classList.remove("hidden");
        updateSummary();
      });
    });
  }

  function byTopic() {
    var map = {};
    all(".q").forEach(function (q) {
      var topic = q.dataset.topic || "General";
      map[topic] = map[topic] || { hit: 0, graded: 0, total: 0 };
      map[topic].total++;
      if (q.dataset.result) {
        map[topic].graded++;
        if (q.dataset.result === "hit") map[topic].hit++;
      }
    });
    return map;
  }

  function updateSummary() {
    var body = document.getElementById("summary-body");
    var total = document.getElementById("summary-total");
    var reportBtn = document.getElementById("report-btn");
    if (!body) return;
    var map = byTopic();
    var lines = [];
    var sumHit = 0,
      sumGraded = 0,
      sumAll = 0;
    Object.keys(map).forEach(function (topic) {
      var t = map[topic];
      sumHit += t.hit;
      sumGraded += t.graded;
      sumAll += t.total;
      var pct = t.graded ? Math.round((100 * t.hit) / t.graded) : null;
      lines.push(
        topic +
          ": " +
          t.hit +
          "/" +
          t.graded +
          (t.graded < t.total ? " (of " + t.total + ")" : "") +
          (pct === null ? "" : " — " + pct + "%")
      );
    });
    body.textContent = lines.join("\n");
    if (total) total.textContent = sumGraded + " of " + sumAll + " answered, " + sumHit + " correct.";
    if (reportBtn) reportBtn.disabled = sumGraded === 0;
  }

  function buildReport() {
    var map = byTopic();
    var weak = [];
    var solid = [];
    Object.keys(map).forEach(function (topic) {
      var t = map[topic];
      var entry = topic + " (" + t.hit + "/" + t.total + ")";
      if (t.hit < t.total) weak.push(entry);
      else solid.push(entry);
    });
    var lines = ["Rust diagnostic result:"];
    lines.push(weak.length ? "Weak: " + weak.join(", ") : "Weak: none");
    lines.push(solid.length ? "Solid: " + solid.join(", ") : "Solid: none");
    return lines.join("\n");
  }

  document.addEventListener("DOMContentLoaded", function () {
    all(".q").forEach(function (q) {
      if (q.dataset.type === "recall") initRecall(q);
      if (q.dataset.type === "mcq") initMcq(q);
    });
    updateSummary();
    var reportBtn = document.getElementById("report-btn");
    if (reportBtn) {
      reportBtn.addEventListener("click", function () {
        var report = buildReport();
        var out = document.getElementById("report-output");
        if (out) {
          out.textContent = report;
          out.classList.remove("hidden");
        }
        if (navigator.clipboard) navigator.clipboard.writeText(report).catch(function () {});
      });
    }
  });
})();