const STORAGE_KEY = "speedcode-typing-save-v1";

const FALLBACK_WORD_BANKS = {
  frontend: ["component", "props", "state", "effect", "dom", "render", "hook", "event", "layout", "style", "selector", "responsive", "hydration", "bundle", "asset", "router", "transition", "animation", "markup", "stylesheet"],
  backend: ["endpoint", "middleware", "request", "response", "session", "database", "query", "migration", "service", "worker", "queue", "cache", "auth", "token", "serializer", "controller", "schema", "webhook", "latency", "throughput"],
  systems: ["pointer", "thread", "mutex", "allocator", "kernel", "register", "syscall", "segment", "stack", "heap", "compiler", "linker", "interrupt", "buffer", "runtime", "ownership", "lifetime", "scheduler", "pipeline", "throughput"],
  "full-stack": ["frontend", "backend", "contract", "gateway", "orchestrator", "deployment", "container", "observability", "tracing", "monorepo", "api", "client", "server", "session", "render", "streaming", "database", "replica", "pipeline", "integration"]
};

const DIFFICULTY_CONFIG = {
  frontend: { xp_mult: 1.05, round_words: 44 },
  backend: { xp_mult: 1.15, round_words: 46 },
  systems: { xp_mult: 1.3, round_words: 50 },
  "full-stack": { xp_mult: 1.4, round_words: 54 }
};

const CHALLENGE_CONFIG = {
  casual: { xp_mult: 0.9, round_seconds: 75, words_mult: 0.9 },
  standard: { xp_mult: 1, round_seconds: 60, words_mult: 1 },
  intense: { xp_mult: 1.2, round_seconds: 52, words_mult: 1.15 },
  nightmare: { xp_mult: 1.4, round_seconds: 45, words_mult: 1.3 }
};

const PERKS = [
  { id: "combo-boost", name: "combo boost", unlock_level: 2, cost: 1, description: "earn 15% more xp while your best combo is 5 or higher." },
  { id: "accuracy-bounty", name: "accuracy bounty", unlock_level: 4, cost: 2, description: "if you finish with 96%+ accuracy, gain +30 bonus xp." },
  { id: "time-warp", name: "time warp", unlock_level: 6, cost: 2, description: "start rounds with +8 seconds for easier high-streak runs." },
  { id: "focus-engine", name: "focus engine", unlock_level: 8, cost: 3, description: "at 98%+ accuracy, your wpm contributes an extra 25% xp." }
];

const TRACK_REPO_PREFIXES = {
  frontend: ["vuejs/core/", "twbs/bootstrap/", "vercel/next.js/", "microsoft/TypeScript/"],
  backend: ["nodejs/node/", "python/cpython/", "golang/go/", "laravel/framework/"],
  systems: ["rust-lang/rust/", "redis/redis/", "torvalds/linux/", "llvm/llvm-project/"],
  "full-stack": ["vercel/next.js/", "remix-run/remix/", "microsoft/TypeScript/", "nodejs/node/"]
};

const DEFAULT_STATE = {
  profile_name: "rookie typer",
  difficulty: "full-stack",
  challenge: "standard",
  target_chars: [],
  index: 0,
  typed_chars: 0,
  correct_words: 0,
  wrong_words: 0,
  combo: 0,
  best_combo: 0,
  timer: null,
  elapsed_seconds: 0,
  round_seconds: 60,
  running: false,
  xp: 0,
  level: 1,
  shards: 0,
  last_round_xp: 0,
  owned_perks: [],
  round_nonce: 0,
  stats: { total_rounds: 0, best_wpm: 0, best_accuracy: 0, average_wpm: 0, average_accuracy: 0 },
  recent_rounds: []
};

const state = { ...DEFAULT_STATE, stats: { ...DEFAULT_STATE.stats }, recent_rounds: [] };
const q = (id) => document.getElementById(id);
const num = (v, d = 0) => (Number.isFinite(v) ? Number(v) : d);
const snake_or_camel = (obj, snake, camel, fallback = undefined) => (obj?.[snake] ?? obj?.[camel] ?? fallback);

const dom = {
  text_display: q("textDisplay"), new_round_btn: q("newRoundBtn"), settings_btn: q("settingsBtn"),
  close_settings_btn: q("closeSettingsBtn"), settings_modal: q("settingsModal"), reset_confirm_modal: q("resetConfirmModal"),
  cancel_reset_btn: q("cancelResetBtn"), confirm_reset_btn: q("confirmResetBtn"), play_again_btn: q("playAgainBtn"),
  results: q("results"), results_summary: q("resultsSummary"), wpm: q("wpm"), accuracy: q("accuracy"), combo: q("combo"),
  time: q("time"), profile_title: q("profileTitle"), level_text: q("levelText"), xp_text: q("xpText"), shard_text: q("shardText"),
  xp_fill: q("xpFill"), xp_gain: q("xpGain"), perks: q("perks"), profile_name: q("profileName"), difficulty_select: q("difficultySelect"),
  difficulty_bonus: q("difficultyBonus"), challenge_select: q("challengeSelect"), challenge_bonus: q("challengeBonus"),
  reset_progress_btn: q("resetProgressBtn"), snippet_source: q("snippetSource"),
  snippet_language: q("snippetLanguage"), code_editor: q("codeEditor"), code_snippet: q("codeSnippet"),
  tab_type_btn: q("tabTypeBtn"), tab_perks_btn: q("tabPerksBtn"),
  type_tab: q("typeTab"), perks_tab: q("perksTab")
};

if (!dom.text_display) dom.text_display = dom.code_snippet;

const detect_language = (source) => {
  const ext = (source || "").split(".").pop()?.toLowerCase();
  if (ext === "js" || ext === "mjs" || ext === "cjs") return "javascript";
  if (ext === "ts" || ext === "tsx") return "typescript";
  if (ext === "py") return "python";
  if (ext === "json") return "json";
  if (ext === "html") return "html";
  if (ext === "css") return "css";
  if (ext === "c" || ext === "h") return "c";
  if (ext === "cpp" || ext === "cc" || ext === "cxx" || ext === "hpp" || ext === "hh" || ext === "hxx") return "cpp";
  if (ext === "rs") return "rust";
  if (ext === "go") return "go";
  if (ext === "java") return "java";
  if (ext === "php") return "php";
  if (ext === "sql") return "sql";
  if (ext === "sh") return "shell";
  return "plaintext";
};

const prism_language_for = (language) => (
  language === "shell" ? "bash" :
  language === "html" ? "markup" :
  language
);

async function set_code_display(snippet, source) {
  const language = detect_language(source);
  const prism_language = prism_language_for(language);

  dom.snippet_language.textContent = `language: ${language}`;
  dom.code_snippet.className = `language-${prism_language || "plaintext"}`;
}

const xp_needed_for_level = (level) => 120 + (level - 1) * 60;
const sanitize_difficulty = (v) => {
  if (DIFFICULTY_CONFIG[v]) return v;
  if (v === "easy") return "frontend";
  if (v === "normal") return "backend";
  if (v === "hard") return "systems";
  if (v === "expert") return "full-stack";
  return "full-stack";
};
const sanitize_challenge = (v) => (CHALLENGE_CONFIG[v] ? v : "standard");
const source_matches_track = (source, track) => {
  const prefixes = TRACK_REPO_PREFIXES[track] || [];
  if (!source || !prefixes.length) return true;
  return prefixes.some((prefix) => source.startsWith(prefix));
};
const has_perk = (id) => state.owned_perks.includes(id);
const get_track_xp_mult = () => DIFFICULTY_CONFIG[state.difficulty].xp_mult;
const get_challenge_xp_mult = () => CHALLENGE_CONFIG[state.challenge].xp_mult;
const get_total_xp_mult = () => get_track_xp_mult() * get_challenge_xp_mult();
const get_round_word_count = () => Math.max(24, Math.floor(DIFFICULTY_CONFIG[state.difficulty].round_words * CHALLENGE_CONFIG[state.challenge].words_mult));
const get_round_seconds = () => CHALLENGE_CONFIG[state.challenge].round_seconds + (has_perk("time-warp") ? 8 : 0);
const open_settings = () => { dom.settings_modal.hidden = false; };
const close_settings = () => { dom.settings_modal.hidden = true; };
const open_reset_confirm = () => { dom.reset_confirm_modal.hidden = false; };
const close_reset_confirm = () => { dom.reset_confirm_modal.hidden = true; };
let levelup_animation_queue = Promise.resolve();
let xp_bar_animation_queue = Promise.resolve();

function set_side_tab(tab) {
  const show_type = tab === "type";
  const show_perks = tab === "perks";

  if (dom.type_tab) dom.type_tab.hidden = !show_type;
  if (dom.perks_tab) dom.perks_tab.hidden = !show_perks;

  if (dom.tab_type_btn) {
    dom.tab_type_btn.classList.toggle("active", show_type);
    dom.tab_type_btn.setAttribute("aria-selected", show_type ? "true" : "false");
  }
  if (dom.tab_perks_btn) {
    dom.tab_perks_btn.classList.toggle("active", show_perks);
    dom.tab_perks_btn.setAttribute("aria-selected", show_perks ? "true" : "false");
  }
}

function play_levelup_milestone(level) {
  const overlay = q("levelUpOverlay");
  const text = q("levelUpText");
  const kicker = q("levelUpKicker");
  if (!overlay || !text) return Promise.resolve();

  return new Promise((resolve) => {
    const tier = Math.min(4, Math.max(1, Math.floor(level / 5)));
    overlay.dataset.tier = String(tier);
    text.textContent = `level ${level}`;
    if (kicker) kicker.textContent = level >= 20 ? "legend milestone unlocked" : "milestone unlocked";
    overlay.hidden = false;
    overlay.classList.remove("active");
    void overlay.offsetWidth;
    overlay.classList.add("active");

    setTimeout(() => {
      overlay.classList.remove("active");
      overlay.hidden = true;
      resolve();
    }, 2250);
  });
}

function queue_levelup_milestones(levels) {
  if (!Array.isArray(levels) || !levels.length) return;
  levelup_animation_queue = levelup_animation_queue.then(async () => {
    for (const level of levels) {
      await play_levelup_milestone(level);
    }
  });
}

function play_xp_level_ping() {
  const bar = dom.xp_fill?.parentElement;
  if (!bar || !dom.xp_fill) return Promise.resolve();

  return new Promise((resolve) => {
    bar.classList.remove("level-ping");
    dom.xp_fill.classList.remove("level-ping");
    void bar.offsetWidth;
    bar.classList.add("level-ping");
    dom.xp_fill.classList.add("level-ping");

    setTimeout(() => {
      bar.classList.remove("level-ping");
      dom.xp_fill.classList.remove("level-ping");
      resolve();
    }, 340);
  });
}

function queue_xp_level_pings(count) {
  const pings = Math.max(0, Math.floor(count));
  if (!pings) return;

  xp_bar_animation_queue = xp_bar_animation_queue.then(async () => {
    for (let i = 0; i < pings; i += 1) {
      await play_xp_level_ping();
    }
  });
}

function save_progress() {
  localStorage.setItem(STORAGE_KEY, JSON.stringify({
    profile_name: state.profile_name,
    difficulty: state.difficulty,
    challenge: state.challenge,
    xp: state.xp,
    level: state.level,
    shards: state.shards,
    last_round_xp: state.last_round_xp,
    owned_perks: state.owned_perks,
    stats: state.stats,
    recent_rounds: state.recent_rounds
  }));
}

function load_progress() {
  const raw = localStorage.getItem(STORAGE_KEY);
  if (!raw) return;
  try {
    const parsed = JSON.parse(raw);
    state.profile_name = String(snake_or_camel(parsed, "profile_name", "profileName", DEFAULT_STATE.profile_name)).trim().slice(0, 24) || DEFAULT_STATE.profile_name;
    state.difficulty = sanitize_difficulty(parsed.difficulty);
    state.challenge = sanitize_challenge(parsed.challenge);
    state.xp = Math.max(0, Math.floor(num(parsed.xp)));
    state.level = Math.max(1, Math.floor(num(parsed.level, 1)));
    state.shards = Math.max(0, Math.floor(num(parsed.shards)));
    state.last_round_xp = Math.max(0, Math.floor(num(snake_or_camel(parsed, "last_round_xp", "lastRoundXp"))));

    const owned = snake_or_camel(parsed, "owned_perks", "ownedPerks", []);
    state.owned_perks = Array.isArray(owned) ? owned.filter((id) => PERKS.some((p) => p.id === id)) : [];

    const stats = parsed.stats || {};
    state.stats = {
      total_rounds: Math.max(0, Math.floor(num(snake_or_camel(stats, "total_rounds", "totalRounds")))),
      best_wpm: Math.max(0, Math.floor(num(snake_or_camel(stats, "best_wpm", "bestWpm")))),
      best_accuracy: Math.max(0, Math.floor(num(snake_or_camel(stats, "best_accuracy", "bestAccuracy")))),
      average_wpm: Math.max(0, num(snake_or_camel(stats, "average_wpm", "averageWpm"))),
      average_accuracy: Math.max(0, num(snake_or_camel(stats, "average_accuracy", "averageAccuracy")))
    };

    const rounds = snake_or_camel(parsed, "recent_rounds", "recentRounds", []);
    state.recent_rounds = Array.isArray(rounds)
      ? rounds.slice(0, 20).map((r) => ({
        stamp: num(r.stamp, Date.now()),
        wpm: num(r.wpm),
        accuracy: num(r.accuracy),
        best_combo: num(snake_or_camel(r, "best_combo", "bestCombo")),
        xp: num(r.xp),
        difficulty: sanitize_difficulty(r.difficulty),
        challenge: sanitize_challenge(r.challenge)
      }))
      : [];
  } catch {
    localStorage.removeItem(STORAGE_KEY);
  }
}

function pick_words() {
  const round_words = get_round_word_count();
  const pool = FALLBACK_WORD_BANKS[state.difficulty];
  return Array.from({ length: round_words }, () => pool[Math.floor(Math.random() * pool.length)]);
}

function tokenize_snippet(snippet, max_words) {
  const language = "plaintext";
  return tokenize_snippet_with_syntax(snippet, max_words, language);
}

function tokenize_snippet_with_syntax(snippet, max_words, language) {
  const source = String(snippet || "").replace(/\r/g, "");
  const words = [];
  const tokens = [];
  const prism_language = prism_language_for(language || "plaintext");
  const grammar = window.Prism?.languages?.[prism_language];

  const tokenize_plain = () => {
    const parts = source.split(/(\s+)/);
    for (const part of parts) {
      if (!part) continue;
      if (/^\s+$/.test(part)) {
        if (tokens.length) tokens.push({ type: "space", text: part });
        continue;
      }
      if (words.length >= max_words) break;
      const word = part.trim();
      if (!word) continue;
      const index = words.length;
      words.push(word);
      tokens.push({ type: "word", text: word, index, syntax_class: "" });
    }
    while (tokens.length && tokens[tokens.length - 1].type === "space") tokens.pop();
    return { words, tokens };
  };

  if (!window.Prism || !grammar) {
    return tokenize_plain();
  }

  let highlighted = "";
  try {
    highlighted = window.Prism.highlight(source, grammar, prism_language);
  } catch {
    return tokenize_plain();
  }
  const root = document.createElement("div");
  root.innerHTML = highlighted;

  const push_text = (text, syntax_class) => {
    const parts = text.split(/(\s+)/);
    for (const part of parts) {
      if (!part) continue;
      if (/^\s+$/.test(part)) {
        if (tokens.length) tokens.push({ type: "space", text: part });
        continue;
      }
      if (words.length >= max_words) return false;
      const word = part.trim();
      if (!word) continue;
      const index = words.length;
      words.push(word);
      tokens.push({ type: "word", text: word, index, syntax_class: syntax_class || "" });
    }
    return words.length < max_words;
  };

  const walk = (node, active_class) => {
    if (words.length >= max_words) return;
    if (node.nodeType === Node.TEXT_NODE) {
      push_text(node.nodeValue || "", active_class);
      return;
    }
    if (node.nodeType !== Node.ELEMENT_NODE) return;
    const element = node;
    const class_name = element.className && String(element.className).includes("token") ? String(element.className) : active_class;
    for (const child of Array.from(element.childNodes)) {
      if (words.length >= max_words) break;
      walk(child, class_name);
    }
  };

  for (const child of Array.from(root.childNodes)) {
    if (words.length >= max_words) break;
    walk(child, "");
  }

  while (tokens.length && tokens[tokens.length - 1].type === "space") tokens.pop();
  return { words, tokens };
}

function chars_from_tokens(tokens) {
  const chars = [];
  for (const token of tokens || []) {
    const text = String(token.text || "");
    const syntax_class = token.type === "word" ? (token.syntax_class || "") : "";
    for (const ch of text) {
      chars.push({ ch, syntax_class });
    }
  }
  return chars;
}

const normalize_token = (value) => String(value || "")
  .normalize("NFKC")
  .replace(/[\u200B-\u200D\uFEFF]/g, "")
  .replace(/[‘’]/g, "'")
  .replace(/[“”]/g, '"')
  .replace(/[–—]/g, "-")
  .trim()
  .toLowerCase();

async function load_snippet_words() {
  const max_words = get_round_word_count();

  for (let i = 0; i < 6; i += 1) {
    try {
      const params = new URLSearchParams({ track: state.difficulty, d: state.difficulty, t: `${Date.now()}-${i}` });
      const res = await fetch(`/api/snippet?${params.toString()}`, { cache: "no-store" });
      if (!res.ok) continue;
      const data = await res.json();
      const source = data.source || "github";
      if (!source_matches_track(source, state.difficulty)) continue;

      const snippet = String(data.snippet || "");
      const language = detect_language(source);
      const parsed = tokenize_snippet_with_syntax(snippet, max_words, language);
      const words = parsed.words;
      const tokens = parsed.tokens;
      if (words.length < 12) continue;

      return { words, tokens, snippet, source, track: data.track || state.difficulty };
    } catch {
      continue;
    }
  }

  return null;
}

function render_words() {
  dom.text_display.innerHTML = "";
  const fragment = document.createDocumentFragment();
  state.target_chars.forEach((item, idx) => {
    const span = document.createElement("span");
    span.className = `char-unit${item.syntax_class ? ` ${item.syntax_class}` : ""}`;

    if (idx < state.index) {
      const typed = state.user_chars?.[idx] || "";
      const correct = normalize_token(typed) === normalize_token(item.ch);
      span.classList.add(correct ? "char-ok" : "char-bad");
      span.textContent = item.ch;
    } else if (idx === state.index) {
      span.classList.add("char-current");
      span.textContent = item.ch;
    } else {
      span.textContent = item.ch;
    }

    fragment.appendChild(span);
  });

  dom.text_display.appendChild(fragment);
}

function render_perks() {
  dom.perks.innerHTML = "";
  PERKS.forEach((perk) => {
    const level_ready = state.level >= perk.unlock_level;
    const owned = has_perk(perk.id);
    const can_buy = level_ready && !owned && state.shards >= perk.cost;
    const card = document.createElement("article");
    card.className = "perk";
    card.innerHTML = `<h3>${perk.name} · lv ${perk.unlock_level}</h3>
      <p>${perk.description}</p>
      <div class="perk-actions">
        <span class="perk-cost">cost: ${perk.cost} shard${perk.cost > 1 ? "s" : ""}</span>
        <button class="perk-buy" data-perk-id="${perk.id}" ${can_buy ? "" : "disabled"}>${owned ? "owned" : level_ready ? "buy" : "locked"}</button>
      </div>
      <span class="status ${owned ? "active" : level_ready ? "unlocked" : "locked"}">${owned ? "active" : level_ready ? "shop open" : "locked"}</span>`;
    dom.perks.appendChild(card);
  });
}

function render_settings() {
  dom.profile_name.value = state.profile_name;
  dom.difficulty_select.value = state.difficulty;
  if (dom.challenge_select) dom.challenge_select.value = state.challenge;
  dom.difficulty_bonus.textContent = `track xp bonus: x${get_track_xp_mult().toFixed(2)}`;
  if (dom.challenge_bonus) {
    const words_percent = Math.round(CHALLENGE_CONFIG[state.challenge].words_mult * 100);
    dom.challenge_bonus.textContent = `challenge xp bonus: x${get_challenge_xp_mult().toFixed(2)} · round: ${get_round_seconds()}s · snippet size: ${words_percent}%`;
  }
}

function render_progress() {
  const level_need = xp_needed_for_level(state.level);
  dom.profile_title.textContent = state.profile_name;
  dom.level_text.textContent = `level ${state.level}`;
  dom.xp_text.textContent = `${state.xp} / ${level_need} xp`;
  dom.shard_text.textContent = `perk shards: ${state.shards}`;
  dom.xp_fill.style.width = `${Math.min((state.xp / level_need) * 100, 100)}%`;
  dom.xp_gain.textContent = `+${state.last_round_xp} xp last round`;
  render_settings();
  render_perks();
}

function update_live_stats() {
  const elapsed = Math.max(state.elapsed_seconds / 60, 1 / 60);
  const wpm = Math.round((state.typed_chars / 5) / elapsed);
  const total = state.correct_words + state.wrong_words;
  const accuracy = total ? Math.round((state.correct_words / total) * 100) : 100;
  dom.wpm.textContent = String(wpm);
  dom.accuracy.textContent = `${accuracy}%`;
  dom.combo.textContent = `x${state.combo}`;
}

function update_timer() {
  const remaining = Math.max(state.round_seconds - state.elapsed_seconds, 0);
  dom.time.textContent = `${remaining}s`;
  dom.time.style.color = remaining <= 10 ? "#ffd587" : "";
}

function start_timer() {
  if (state.running) return;
  state.running = true;
  state.timer = setInterval(() => {
    state.elapsed_seconds += 1;
    update_timer();
    update_live_stats();
    if (state.elapsed_seconds >= state.round_seconds) finish_round();
  }, 1000);
}

function award_xp(summary) {
  let xp = 35 + Math.floor(summary.wpm * 1.4) + Math.floor(summary.accuracy * 0.55) + Math.floor(summary.best_combo * 2.5);
  if (has_perk("combo-boost") && summary.best_combo >= 5) xp = Math.floor(xp * 1.15);
  if (has_perk("accuracy-bounty") && summary.accuracy >= 96) xp += 30;
  if (has_perk("focus-engine") && summary.accuracy >= 98) xp += Math.floor(summary.wpm * 0.25);
  xp = Math.floor(xp * get_total_xp_mult());

  let pending = xp;
  let level_ups = 0;
  const milestone_levels = [];
  while (pending > 0) {
    const need = xp_needed_for_level(state.level) - state.xp;
    if (pending >= need) {
      pending -= need;
      state.level += 1;
      state.xp = 0;
      level_ups += 1;
      if (state.level % 5 === 0) milestone_levels.push(state.level);
    } else {
      state.xp += pending;
      pending = 0;
    }
  }
  state.shards += level_ups;
  state.last_round_xp = xp;
  return { xp, milestone_levels, level_ups };
}

function track_round(summary, earned_xp) {
  const s = state.stats;
  s.total_rounds += 1;
  s.best_wpm = Math.max(s.best_wpm, summary.wpm);
  s.best_accuracy = Math.max(s.best_accuracy, summary.accuracy);
  s.average_wpm = ((s.average_wpm * (s.total_rounds - 1)) + summary.wpm) / s.total_rounds;
  s.average_accuracy = ((s.average_accuracy * (s.total_rounds - 1)) + summary.accuracy) / s.total_rounds;
  state.recent_rounds.unshift({ stamp: Date.now(), wpm: summary.wpm, accuracy: summary.accuracy, best_combo: summary.best_combo, xp: earned_xp, difficulty: state.difficulty, challenge: state.challenge });
  state.recent_rounds = state.recent_rounds.slice(0, 20);
}

function set_current_word(jump_to_next_line = false) {
  const node = dom.text_display.querySelectorAll(".char-unit")[state.index];
  if (!node) return;
  node.scrollIntoView({ block: jump_to_next_line ? "start" : "nearest", behavior: "smooth" });
}

function finish_round() {
  clearInterval(state.timer);
  state.running = false;

  const elapsed_m = Math.max(state.elapsed_seconds / 60, 1 / 60);
  const wpm = Math.round((state.typed_chars / 5) / elapsed_m);
  const total = state.correct_words + state.wrong_words;
  const accuracy = total ? Math.round((state.correct_words / total) * 100) : 100;
  const summary = { wpm, accuracy, best_combo: state.best_combo };

  const reward = award_xp(summary);
  const earned_xp = reward.xp;
  queue_levelup_milestones(reward.milestone_levels);
  queue_xp_level_pings(reward.level_ups);
  track_round(summary, earned_xp);
  render_progress();
  update_live_stats();
  save_progress();

  dom.results.hidden = false;
  dom.results_summary.textContent = `you reached ${wpm} wpm with ${accuracy}% accuracy and earned ${earned_xp} xp!`;
}

async function reset_round() {
  clearInterval(state.timer);
  state.round_nonce += 1;
  const nonce = state.round_nonce;

  const loaded = await load_snippet_words();
  const fallback_words = pick_words();
  const fallback_snippet = fallback_words.join(" ");
  const fallback_parsed = tokenize_snippet_with_syntax(fallback_snippet, get_round_word_count(), "plaintext");
  const tokens = loaded?.tokens || fallback_parsed.tokens;
  const chars = chars_from_tokens(tokens);
  const source_label = loaded?.source ? `source: ${loaded.source}${loaded.track ? ` · track: ${loaded.track}` : ""}` : "source: local fallback";
  const snippet = loaded?.snippet || fallback_snippet;

  if (nonce !== state.round_nonce) return;

  Object.assign(state, {
    target_chars: chars,
    index: 0,
    user_chars: [],
    typed_chars: 0,
    correct_words: 0,
    wrong_words: 0,
    combo: 0,
    best_combo: 0,
    elapsed_seconds: 0,
    round_seconds: get_round_seconds(),
    running: false
  });

  set_code_display(snippet, loaded?.source || "fallback.txt");
  dom.snippet_source.textContent = source_label;
  render_words();
  update_live_stats();
  update_timer();
  dom.results.hidden = true;
}

function set_profile_name(value) {
  state.profile_name = value.trim().slice(0, 24) || DEFAULT_STATE.profile_name;
  render_progress();
  save_progress();
}

function set_difficulty(value) {
  state.difficulty = sanitize_difficulty(value);
  render_progress();
  reset_round();
  save_progress();
}

function set_challenge(value) {
  state.challenge = sanitize_challenge(value);
  render_progress();
  reset_round();
  save_progress();
}

function buy_perk(perk_id) {
  const perk = PERKS.find((p) => p.id === perk_id);
  if (!perk || has_perk(perk_id) || state.level < perk.unlock_level || state.shards < perk.cost) return;
  state.shards -= perk.cost;
  state.owned_perks.push(perk.id);
  render_progress();
  reset_round();
  save_progress();
}

function reset_progress() {
  localStorage.removeItem(STORAGE_KEY);
  clearInterval(state.timer);
  Object.assign(state, {
    ...DEFAULT_STATE,
    stats: { ...DEFAULT_STATE.stats },
    recent_rounds: [],
    owned_perks: []
  });
  render_progress();
  reset_round();
  save_progress();
}

function submit_typed_word() {
  return;
}

function can_capture_typing(target) {
  if (target instanceof HTMLInputElement) return true;
  if (target instanceof HTMLTextAreaElement) return true;
  if (target instanceof HTMLSelectElement) return true;
  if (target instanceof HTMLElement && target.isContentEditable) return true;
  return false;
}

function handle_typing_keydown(e) {
  if (!dom.settings_modal.hidden || !dom.reset_confirm_modal.hidden) return;
  if (!dom.results.hidden || state.index >= state.target_chars.length) return;
  if (can_capture_typing(e.target)) return;
  if (e.ctrlKey || e.metaKey || e.altKey) return;

  if (e.key === "Backspace") {
    e.preventDefault();
    if (state.index <= 0) return;
    state.index -= 1;
    const removed = state.user_chars[state.index];
    state.user_chars[state.index] = "";
    if (removed) {
      const expected = state.target_chars[state.index]?.ch || "";
      const correct = normalize_token(removed) === normalize_token(expected);
      if (correct) state.correct_words = Math.max(0, state.correct_words - 1);
      else state.wrong_words = Math.max(0, state.wrong_words - 1);
    }
    state.combo = 0;
    render_words();
    return;
  }

  let typed_char = "";
  if (e.key === "Enter") typed_char = "\n";
  else if (e.key === "Tab") typed_char = "\t";
  else if (e.key.length === 1) typed_char = e.key;
  else return;

  e.preventDefault();
  if (!state.running) start_timer();

  const expected = state.target_chars[state.index]?.ch || "";
  state.user_chars[state.index] = typed_char;
  state.typed_chars += 1;
  let completed_line = false;

  const correct = normalize_token(typed_char) === normalize_token(expected);
  if (correct) {
    state.correct_words += 1;
    state.combo += 1;
    state.best_combo = Math.max(state.best_combo, state.combo);
  } else {
    state.wrong_words += 1;
    state.combo = 0;
  }

  state.index += 1;

  while (state.index < state.target_chars.length && state.target_chars[state.index].ch === "\n") {
    state.user_chars[state.index] = "\n";
    state.correct_words += 1;
    state.combo += 1;
    state.best_combo = Math.max(state.best_combo, state.combo);
    state.index += 1;
    completed_line = true;
  }

  if (completed_line) {
    while (state.index < state.target_chars.length) {
      const ch = state.target_chars[state.index].ch;
      if (ch !== " " && ch !== "\t") break;
      state.user_chars[state.index] = ch;
      state.correct_words += 1;
      state.combo += 1;
      state.best_combo = Math.max(state.best_combo, state.combo);
      state.index += 1;
    }
  }

  render_words();
  update_live_stats();
  if (state.index >= state.target_chars.length) return finish_round();
  set_current_word(completed_line);
}

dom.new_round_btn.addEventListener("click", reset_round);
dom.play_again_btn.addEventListener("click", reset_round);
dom.settings_btn.addEventListener("click", open_settings);
dom.close_settings_btn.addEventListener("click", close_settings);
dom.tab_type_btn?.addEventListener("click", () => set_side_tab("type"));
dom.tab_perks_btn?.addEventListener("click", () => set_side_tab("perks"));
dom.profile_name.addEventListener("change", (e) => set_profile_name(e.target.value));
dom.difficulty_select.addEventListener("change", (e) => set_difficulty(e.target.value));
dom.challenge_select?.addEventListener("change", (e) => set_challenge(e.target.value));
dom.reset_progress_btn.addEventListener("click", open_reset_confirm);
dom.cancel_reset_btn.addEventListener("click", close_reset_confirm);
dom.confirm_reset_btn.addEventListener("click", () => {
  reset_progress();
  close_reset_confirm();
  close_settings();
});
dom.settings_modal.addEventListener("click", (e) => e.target === dom.settings_modal && close_settings());
dom.reset_confirm_modal.addEventListener("click", (e) => e.target === dom.reset_confirm_modal && close_reset_confirm());
document.addEventListener("keydown", (e) => {
  if (e.key !== "Escape") return;
  if (!dom.reset_confirm_modal.hidden) return close_reset_confirm();
  if (!dom.settings_modal.hidden) close_settings();
});
document.addEventListener("keydown", handle_typing_keydown);

dom.perks.addEventListener("click", (e) => {
  const target = e.target;
  if (!(target instanceof HTMLButtonElement)) return;
  const perk_id = target.dataset.perkId;
  if (perk_id) buy_perk(perk_id);
});

load_progress();
render_progress();
set_side_tab("type");
reset_round();