const DEBOUNCE_MS = 420;
const SILENCE_MS = 500;
const SILENCE_TOKEN = "<|silence|>";
const BOUNDARY_PATTERN = /[\s.,!?;:)\]}"]$/;
const MODE_BASELINE = "baseline";
const MODE_INTERACTIVE_BASE = "interactive-base";
const MODE_INTERACTIVE_RL = "interactive-rl";
const MODES = [MODE_BASELINE, MODE_INTERACTIVE_BASE, MODE_INTERACTIVE_RL];

const authView = document.querySelector("#authView");
const appView = document.querySelector("#appView");
const authForm = document.querySelector("#authForm");
const authError = document.querySelector("#authError");
const accessCode = document.querySelector("#accessCode");
const modeButtons = Array.from(document.querySelectorAll("[data-mode]"));
const historyView = document.querySelector("#history");
const composer = document.querySelector("#composer");
const typedText = document.querySelector("#typedText");
const predictedText = document.querySelector("#predictedText");
const thinking = document.querySelector("#thinking");
const assistantResponse = document.querySelector("#assistantResponse");
const latencyAverage = document.querySelector("#latencyAverage");
const accuracyAverage = document.querySelector("#accuracyAverage");
const callList = document.querySelector("#callList");
const clearCalls = document.querySelector("#clearCalls");
const pageTabs = Array.from(document.querySelectorAll("[data-tab]"));
const tabPanels = Array.from(document.querySelectorAll("[data-panel]"));

const state = {
  mode: MODE_INTERACTIVE_RL,
  activeTab: "overview",
  history: [],
  typed: "",
  predictionAnchor: null,
  predictionModelUserText: "",
  predictedUserCompletion: "",
  remainingUserCompletion: "",
  assistantText: "",
  errorText: "",
  hasPrediction: false,
  predictionComplete: false,
  predictionTurnDone: false,
  inFlight: false,
  controller: null,
  requestSeq: 0,
  debounceTimer: null,
  silenceTimer: null,
  silenceAnchor: "",
  silenceTokenCount: 0,
  silenceStartedAt: null,
  activeCallNode: null,
  locked: false,
  lockedSeq: null,
  pendingCommitSeq: null,
  pendingCommitText: "",
  pendingCommitModelText: "",
  pendingLatency: null,
  latencyMeasurements: [],
  measuredLatencySeqs: new Set(),
  interactiveInferenceCount: 0,
  predictionAccuracies: [],
};

async function boot() {
  const response = await fetch("/api/session", { credentials: "same-origin" });
  const session = await response.json();
  if (session.authenticated) {
    showApp();
  } else {
    authView.classList.remove("hidden");
  }
}

authForm.addEventListener("submit", async (event) => {
  event.preventDefault();
  authError.textContent = "";
  const response = await fetch("/api/auth", {
    method: "POST",
    credentials: "same-origin",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ code: accessCode.value }),
  });
  const payload = await response.json();
  if (!response.ok) {
    authError.textContent = payload.error || "Could not sign in.";
    return;
  }
  accessCode.value = "";
  showApp();
});

composer.addEventListener("keydown", (event) => {
  if (event.key !== "Enter" || event.isComposing) {
    return;
  }
  event.preventDefault();
  void commitCurrentTurn("enter");
});

for (const button of modeButtons) {
  button.addEventListener("click", () => {
    setMode(button.dataset.mode);
  });
}

for (const tab of pageTabs) {
  tab.addEventListener("click", () => {
    setActiveTab(tab.dataset.tab);
  });
}

composer.addEventListener("input", () => {
  if (state.locked) {
    composer.value = state.typed;
    return;
  }

  state.typed = composer.value;
  resizeComposer();

  if (state.mode === MODE_BASELINE) {
    clearTimeout(state.debounceTimer);
    state.debounceTimer = null;
    stopSilenceLoop();
    clearPredictionState();
    render();
    return;
  }

  const contradictedTurnDone =
    state.hasPrediction &&
    state.predictionAnchor !== null &&
    normalizeInline(state.predictedUserCompletion) === "" &&
    state.typed.startsWith(state.predictionAnchor) &&
    state.typed.length > state.predictionAnchor.length;

  if (reconcilePrediction()) {
    if (state.predictionTurnDone) {
      queueCommitFromPrediction("accepted", performance.now());
    }
    render();
    return;
  }

  invalidatePrediction();
  if (!state.typed.trim()) {
    resetCurrentInteractiveMetrics();
    stopSilenceLoop();
    render();
    return;
  }

  const immediate = contradictedTurnDone || BOUNDARY_PATTERN.test(state.typed);
  if (immediate) {
    startSilenceLoop(state.typed);
  } else {
    stopSilenceLoop();
  }
  scheduleInference(
    contradictedTurnDone ? "continued" : immediate ? "boundary" : "pause",
    immediate ? 0 : DEBOUNCE_MS,
  );
  render();
});

clearCalls.addEventListener("click", () => {
  callList.replaceChildren();
});

function showApp() {
  authView.classList.add("hidden");
  appView.classList.remove("hidden");
  setActiveTab(state.activeTab);
  render();
}

function setActiveTab(tabName) {
  if (!tabPanels.some((panel) => panel.dataset.panel === tabName)) {
    return;
  }
  state.activeTab = tabName;
  for (const tab of pageTabs) {
    const active = tab.dataset.tab === tabName;
    tab.classList.toggle("active", active);
    tab.setAttribute("aria-selected", String(active));
  }
  for (const panel of tabPanels) {
    panel.classList.toggle("hidden", panel.dataset.panel !== tabName);
  }
  if (tabName !== "demo") {
    stopSilenceLoop();
  }
  if (tabName === "demo") {
    composer.focus();
  }
}

function setMode(mode) {
  if (
    state.locked ||
    !MODES.includes(mode) ||
    mode === state.mode
  ) {
    return;
  }

  invalidatePrediction();
  resetCurrentInteractiveMetrics();
  stopSilenceLoop();
  state.mode = mode;
  state.typed = composer.value;
  state.assistantText = "";
  state.errorText = "";
  render();
  composer.focus();

  if (isInteractiveMode(state.mode) && state.typed.trim()) {
    if (BOUNDARY_PATTERN.test(state.typed)) {
      startSilenceLoop(state.typed);
    }
    scheduleInference("mode", 0);
  }
}

function reconcilePrediction() {
  if (state.predictionAnchor === null || !state.hasPrediction) {
    return false;
  }
  if (state.typed === state.predictionAnchor) {
    state.remainingUserCompletion = state.predictedUserCompletion;
    state.predictionTurnDone = normalizeInline(state.remainingUserCompletion) === "";
    return true;
  }
  if (!state.typed.startsWith(state.predictionAnchor)) {
    return false;
  }

  const consumed = state.typed.slice(state.predictionAnchor.length);
  if (!state.predictedUserCompletion.startsWith(consumed)) {
    return false;
  }

  state.remainingUserCompletion = state.predictedUserCompletion.slice(consumed.length);
  state.predictionTurnDone = normalizeInline(state.remainingUserCompletion) === "";
  return true;
}

function invalidatePrediction() {
  state.requestSeq += 1;
  if (state.controller) {
    state.controller.abort();
    markCall(state.activeCallNode, "canceled", "canceled");
  }
  clearTimeout(state.debounceTimer);
  state.debounceTimer = null;
  stopSilenceLoop();
  state.inFlight = false;
  state.controller = null;
  state.activeCallNode = null;
  state.predictionAnchor = null;
  state.predictionModelUserText = "";
  state.predictedUserCompletion = "";
  state.remainingUserCompletion = "";
  state.assistantText = "";
  state.errorText = "";
  state.hasPrediction = false;
  state.predictionComplete = false;
  state.predictionTurnDone = false;
  state.pendingCommitSeq = null;
  state.pendingCommitText = "";
  state.pendingCommitModelText = "";
}

function scheduleInference(reason, delayMs) {
  clearTimeout(state.debounceTimer);
  state.debounceTimer = window.setTimeout(() => {
    void runInference(reason);
  }, delayMs);
}

function startSilenceLoop(anchorText, delayMs = SILENCE_MS) {
  if (!isInteractiveMode(state.mode) || !anchorText.trim()) {
    stopSilenceLoop();
    return;
  }
  if (!BOUNDARY_PATTERN.test(anchorText)) {
    stopSilenceLoop();
    return;
  }
  if (state.silenceAnchor !== anchorText) {
    state.silenceAnchor = anchorText;
    state.silenceTokenCount = 0;
    state.silenceStartedAt = performance.now();
  }
  clearTimeout(state.silenceTimer);
  state.silenceTimer = window.setTimeout(() => {
    if (
      state.locked ||
      !isInteractiveMode(state.mode) ||
      composer.value !== state.silenceAnchor ||
      !BOUNDARY_PATTERN.test(composer.value)
    ) {
      stopSilenceLoop();
      return;
    }
    if (state.inFlight) {
      startSilenceLoop(state.silenceAnchor, 100);
      return;
    }
    const elapsedSilenceMs = performance.now() - (state.silenceStartedAt ?? performance.now());
    state.silenceTokenCount = Math.max(
      state.silenceTokenCount + 1,
      Math.floor(elapsedSilenceMs / SILENCE_MS),
    );
    void runInference(`silence x${state.silenceTokenCount}`, {
      userText: state.silenceAnchor,
      requestText: withSilenceTokens(
        state.silenceAnchor,
        state.silenceTokenCount,
      ),
    });
    startSilenceLoop(state.silenceAnchor);
  }, delayMs);
}

function stopSilenceLoop() {
  clearTimeout(state.silenceTimer);
  state.silenceTimer = null;
  state.silenceAnchor = "";
  state.silenceTokenCount = 0;
  state.silenceStartedAt = null;
}

function withSilenceTokens(text, count) {
  if (count <= 0) {
    return text;
  }
  return `${text}${" "}${Array(count).fill(SILENCE_TOKEN).join(" ")}`;
}

async function runInference(reason, options = {}) {
  const mode = options.mode ?? state.mode;
  const userText = options.userText ?? composer.value;
  const requestText = options.requestText ?? userText;
  const commitAfterResult = Boolean(options.commitAfterResult);
  const lockDuringRequest = Boolean(options.lockDuringRequest);
  const turnComplete = Boolean(options.turnComplete);
  const latencyStartedAt = options.latencyStartedAt;
  const latencySource = options.latencySource ?? reason;
  if (!requestText.trim()) {
    return null;
  }

  state.requestSeq += 1;
  const seq = state.requestSeq;
  if (state.controller) {
    state.controller.abort();
    markCall(state.activeCallNode, "canceled", "canceled");
  }
  const controller = new AbortController();
  state.controller = controller;
  state.inFlight = true;
  if (isInteractiveMode(mode)) {
    state.interactiveInferenceCount += 1;
  }
  state.activeCallNode = addCall({
    seq,
    reason: interactiveCallReason(mode, reason),
    text: userText,
  });
  if (typeof latencyStartedAt === "number") {
    beginLatencyMeasurement(seq, latencySource, latencyStartedAt);
  }
  if (lockDuringRequest) {
    lockComposer(seq);
  }
  render();

  let finalPrediction = null;
  let committed = false;

  try {
    const response = await fetch("/api/predict", {
      method: "POST",
      credentials: "same-origin",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({
        typed: requestText,
        history: state.history,
        turn_complete: turnComplete,
        model_variant: predictionVariantForMode(mode),
      }),
      signal: controller.signal,
    });

    if (response.status === 401) {
      authView.classList.remove("hidden");
      appView.classList.add("hidden");
      return null;
    }
    if (!response.ok || !response.body) {
      throw new Error(`Prediction failed with HTTP ${response.status}`);
    }

    await readEventStream(response.body, (event, data) => {
      if (seq !== state.requestSeq) {
        return;
      }
      if (event === "meta") {
        updateCallMeta(state.activeCallNode, data);
      }
      if (event === "parsed" || event === "result") {
        const eventTime = performance.now();
        const applied = applyPrediction(userText, data, requestText);
        if (event === "result") {
          finalPrediction = data;
        }
        if (
          applied &&
          !commitAfterResult &&
          data.user_completion_closed &&
          state.predictionTurnDone
        ) {
          queuePendingCommit(
            seq,
            composer.value,
            "predicted",
            eventTime,
            requestText,
          );
        }
        observeAssistantFirstToken(seq, eventTime);
      }
      if (event === "error") {
        throw new Error(data.error || "Prediction failed.");
      }
    });

    if (seq === state.requestSeq) {
      markCall(state.activeCallNode, "done", "done");
    }

    if (seq === state.requestSeq && finalPrediction) {
      const pendingText =
        state.pendingCommitSeq === seq ? state.pendingCommitText : "";
      const pendingModelText =
        state.pendingCommitSeq === seq ? state.pendingCommitModelText : "";
      const shouldCommit = commitAfterResult || Boolean(pendingText);
      if (shouldCommit) {
        committed = commitPrediction(
          pendingText || userText,
          finalPrediction,
          pendingModelText || requestText,
        );
      }
    }

    return finalPrediction;
  } catch (error) {
    if (error.name === "AbortError") {
      return null;
    }
    markCall(state.activeCallNode, "error", "error");
    state.errorText = error.message || "Prediction failed.";
    clearPendingLatency(seq);
    return null;
  } finally {
    if (seq === state.requestSeq) {
      state.inFlight = false;
      state.controller = null;
      state.activeCallNode = null;
      if (!committed && state.lockedSeq === seq) {
        unlockComposer(seq);
      }
      render();
    }
  }
}

function applyPrediction(anchor, parsed, modelUserText = anchor) {
  const currentText = composer.value;
  const predictedCompletion = removeEchoedUserPrefix(
    currentText,
    parsed.user_completion || "",
  );
  let remainingCompletion = predictedCompletion;
  const isSilenceRefresh =
    modelUserText.includes(SILENCE_TOKEN) &&
    state.hasPrediction &&
    state.predictionAnchor === anchor;

  if (currentText !== anchor) {
    if (!currentText.startsWith(anchor)) {
      return false;
    }
    const consumedCompletion = currentText.slice(anchor.length);
    if (!predictedCompletion.startsWith(consumedCompletion)) {
      return false;
    }
    remainingCompletion = predictedCompletion.slice(consumedCompletion.length);
  }

  if (
    isSilenceRefresh &&
    !parsed.complete &&
    isRegressiveRefresh(
      state.remainingUserCompletion,
      remainingCompletion,
      state.assistantText,
      parsed.assistant_response || "",
    )
  ) {
    return false;
  }

  state.predictionAnchor = anchor;
  state.predictionModelUserText = modelUserText;
  state.predictedUserCompletion = predictedCompletion;
  state.remainingUserCompletion = remainingCompletion;
  state.assistantText = parsed.assistant_response || "";
  state.errorText = "";
  state.hasPrediction =
    Boolean(parsed.has_user_completion_tag) ||
    Boolean(parsed.has_assistant_response_tag);
  state.predictionComplete = Boolean(parsed.complete);
  state.predictionTurnDone =
    Boolean(parsed.user_completion_closed) &&
    normalizeInline(state.remainingUserCompletion) === "";
  render();
  return true;
}

function removeEchoedUserPrefix(userText, predictedCompletion) {
  const normalizedUser = normalizeInline(stripSilenceTokens(userText)).toLowerCase();
  if (!normalizedUser || !predictedCompletion.trim()) {
    return predictedCompletion;
  }

  let bestEnd = 0;
  for (let end = 1; end <= predictedCompletion.length; end += 1) {
    const prefix = normalizeInline(predictedCompletion.slice(0, end)).toLowerCase();
    if (prefix && normalizedUser.endsWith(prefix)) {
      bestEnd = end;
    }
  }

  return bestEnd ? predictedCompletion.slice(bestEnd).trimStart() : predictedCompletion;
}

function isRegressiveRefresh(
  previousUserCompletion,
  nextUserCompletion,
  previousAssistant,
  nextAssistant,
) {
  return (
    isRegressiveText(previousUserCompletion, nextUserCompletion) ||
    isRegressiveText(previousAssistant, nextAssistant)
  );
}

function isRegressiveText(previous, next) {
  if (!previous) {
    return false;
  }
  return previous.startsWith(next) && previous !== next;
}

async function commitCurrentTurn(reason) {
  if (state.locked) {
    return;
  }

  const userText = composer.value;
  if (!userText.trim()) {
    return;
  }
  const turnStoppedAt = performance.now();

  state.typed = userText;

  clearTimeout(state.debounceTimer);
  state.debounceTimer = null;

  if (state.mode === MODE_BASELINE) {
    await commitBaselineTurn(userText, turnStoppedAt);
    return;
  }

  reconcilePrediction();

  if (
    state.hasPrediction &&
    state.predictionTurnDone &&
    state.inFlight
  ) {
    queuePendingCommit(state.requestSeq, userText, reason, turnStoppedAt);
    return;
  }

  if (
    state.hasPrediction &&
    state.predictionTurnDone &&
    state.assistantText.trim()
  ) {
    beginLatencyMeasurement(state.requestSeq, reason, turnStoppedAt);
    observeAssistantFirstToken(state.requestSeq, turnStoppedAt);
    if (state.controller) {
      state.controller.abort();
      markCall(state.activeCallNode, "canceled", "canceled");
    }
    state.requestSeq += 1;
    commitPrediction(
      userText,
      { assistant_response: state.assistantText },
      state.predictionModelUserText || userText,
    );
    render();
    return;
  }

  invalidatePrediction();
  state.typed = userText;
  composer.value = userText;
  resizeComposer();

  await runInference(reason, {
    userText,
    requestText: userText,
    commitAfterResult: true,
    lockDuringRequest: true,
    turnComplete: true,
    latencyStartedAt: turnStoppedAt,
    latencySource: reason,
  });
}

async function commitBaselineTurn(userText, turnStoppedAt) {
  invalidatePrediction();
  state.typed = userText;
  composer.value = userText;
  resizeComposer();

  await runBaselineResponse(userText, turnStoppedAt);
}

async function runBaselineResponse(userText, latencyStartedAt) {
  state.requestSeq += 1;
  const seq = state.requestSeq;
  const controller = new AbortController();
  state.controller = controller;
  state.inFlight = true;
  state.activeCallNode = addCall({
    seq,
    reason: "non-interactive",
    text: userText,
  });
  state.assistantText = "";
  state.errorText = "";
  beginLatencyMeasurement(seq, "baseline", latencyStartedAt);
  lockComposer(seq);
  render();

  let assistantText = "";
  let committed = false;

  try {
    const response = await fetch("/api/respond", {
      method: "POST",
      credentials: "same-origin",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ typed: userText, history: state.history }),
      signal: controller.signal,
    });

    if (response.status === 401) {
      authView.classList.remove("hidden");
      appView.classList.add("hidden");
      return null;
    }
    if (!response.ok || !response.body) {
      throw new Error(`Response failed with HTTP ${response.status}`);
    }

    await readEventStream(response.body, (event, data) => {
      if (seq !== state.requestSeq) {
        return;
      }
      if (event === "meta") {
        updateCallMeta(state.activeCallNode, data);
      }
      if (event === "delta") {
        assistantText += data.text || "";
        state.assistantText = assistantText;
        observeAssistantFirstToken(seq, performance.now());
        render();
      }
      if (event === "result") {
        assistantText = data.assistant_response || assistantText;
        state.assistantText = assistantText;
        observeAssistantFirstToken(seq, performance.now());
        render();
      }
      if (event === "error") {
        throw new Error(data.error || "Response failed.");
      }
    });

    if (seq === state.requestSeq) {
      markCall(state.activeCallNode, "done", "done");
      committed = commitPrediction(userText, { assistant_response: assistantText });
    }

    return assistantText;
  } catch (error) {
    if (error.name === "AbortError") {
      return null;
    }
    markCall(state.activeCallNode, "error", "error");
    state.errorText = error.message || "Response failed.";
    clearPendingLatency(seq);
    return null;
  } finally {
    if (seq === state.requestSeq) {
      state.inFlight = false;
      state.controller = null;
      state.activeCallNode = null;
      if (!committed && state.lockedSeq === seq) {
        unlockComposer(seq);
      }
      render();
    }
  }
}

function queueCommitFromPrediction(source = "predicted", startedAt = performance.now()) {
  if (
    !state.hasPrediction ||
    !state.predictionTurnDone ||
    !state.typed.trim()
  ) {
    return false;
  }

  if (state.inFlight) {
    queuePendingCommit(
      state.requestSeq,
      state.typed,
      source,
      startedAt,
      state.predictionModelUserText || state.typed,
    );
    return true;
  }

  if (state.assistantText.trim()) {
    beginLatencyMeasurement(state.requestSeq, source, startedAt);
    observeAssistantFirstToken(state.requestSeq, startedAt);
    commitPrediction(
      state.typed,
      { assistant_response: state.assistantText },
      state.predictionModelUserText || state.typed,
    );
    return true;
  }

  return false;
}

function queuePendingCommit(
  seq,
  userText,
  source = "predicted",
  startedAt = performance.now(),
  modelUserText = userText,
) {
  if (!userText.trim()) {
    return;
  }
  state.pendingCommitSeq = seq;
  state.pendingCommitText = userText;
  state.pendingCommitModelText = modelUserText;
  beginLatencyMeasurement(seq, source, startedAt);
  observeAssistantFirstToken(seq, startedAt);
  lockComposer(seq);
  render();
}

function commitPrediction(userText, prediction, modelUserText = userText) {
  const committedModelUser = modelUserText.trimEnd();
  const committedAssistant = (prediction.assistant_response || "").trim();
  if (!committedModelUser.trim()) {
    return false;
  }
  if (!committedAssistant) {
    state.errorText = "Assistant prediction was empty.";
    return false;
  }
  observeAssistantFirstToken(null, performance.now());
  if (isInteractiveMode(state.mode)) {
    recordPredictionAccuracy(state.interactiveInferenceCount);
  }

  state.history.push({ role: "user", content: committedModelUser });
  state.history.push({ role: "assistant", content: committedAssistant });
  state.history = state.history.slice(-24);

  state.typed = "";
  composer.value = "";
  resizeComposer();
  stopSilenceLoop();
  clearPredictionState();
  resetCurrentInteractiveMetrics();
  unlockComposer();
  renderHistory();
  return true;
}

function clearPredictionState() {
  state.predictionAnchor = null;
  state.predictionModelUserText = "";
  state.predictedUserCompletion = "";
  state.remainingUserCompletion = "";
  state.assistantText = "";
  state.errorText = "";
  state.hasPrediction = false;
  state.predictionComplete = false;
  state.predictionTurnDone = false;
  state.pendingCommitSeq = null;
  state.pendingCommitText = "";
  state.pendingCommitModelText = "";
}

function lockComposer(seq) {
  state.locked = true;
  state.lockedSeq = seq;
}

function unlockComposer(seq = null) {
  if (seq !== null && state.lockedSeq !== seq) {
    return;
  }
  state.locked = false;
  state.lockedSeq = null;
  state.pendingCommitSeq = null;
  state.pendingCommitText = "";
  state.pendingCommitModelText = "";
  window.requestAnimationFrame(() => {
    if (!state.locked && !appView.classList.contains("hidden")) {
      composer.focus();
    }
  });
}

function beginLatencyMeasurement(seq, source, startedAt) {
  if (state.measuredLatencySeqs.has(seq)) {
    return;
  }
  if (
    state.pendingLatency &&
    state.pendingLatency.seq === seq &&
    !state.pendingLatency.recorded
  ) {
    return;
  }
  state.pendingLatency = {
    seq,
    source,
    startedAt,
    recorded: false,
  };
}

function observeAssistantFirstToken(seq = null, observedAt = performance.now()) {
  if (!state.pendingLatency || state.pendingLatency.recorded) {
    return false;
  }
  if (seq !== null && state.pendingLatency.seq !== seq) {
    return false;
  }
  if (!state.assistantText.trim()) {
    return false;
  }

  const latencyMs = Math.max(
    0,
    Math.round(observedAt - state.pendingLatency.startedAt),
  );
  state.latencyMeasurements.push({
    latencyMs,
    source: state.pendingLatency.source,
  });
  state.latencyMeasurements = state.latencyMeasurements.slice(-100);
  state.measuredLatencySeqs.add(state.pendingLatency.seq);
  state.pendingLatency.recorded = true;
  state.pendingLatency = null;
  renderLatencyAverage();
  return true;
}

function clearPendingLatency(seq) {
  if (!state.pendingLatency) {
    return;
  }
  if (seq === null || state.pendingLatency.seq === seq) {
    state.pendingLatency = null;
  }
}

function renderLatencyAverage() {
  if (!latencyAverage) {
    return;
  }
  if (!state.latencyMeasurements.length) {
    latencyAverage.textContent = "avg ttft --";
    return;
  }

  const total = state.latencyMeasurements.reduce(
    (sum, measurement) => sum + measurement.latencyMs,
    0,
  );
  const average = total / state.latencyMeasurements.length;
  latencyAverage.textContent =
    `avg ttft ${formatLatency(average)} (${state.latencyMeasurements.length})`;
}

function recordPredictionAccuracy(inferenceCount) {
  const score = predictionAccuracyScore(inferenceCount);
  if (score === null) {
    return;
  }
  state.predictionAccuracies.push(score);
  state.predictionAccuracies = state.predictionAccuracies.slice(-100);
  renderAccuracyAverage();
}

function predictionAccuracyScore(inferenceCount) {
  if (!inferenceCount) {
    return null;
  }
  return 1 / inferenceCount;
}

function resetCurrentInteractiveMetrics() {
  state.interactiveInferenceCount = 0;
}

function renderAccuracyAverage() {
  if (!accuracyAverage) {
    return;
  }
  accuracyAverage.classList.toggle("hidden", state.mode === MODE_BASELINE);
  if (!state.predictionAccuracies.length) {
    accuracyAverage.textContent = "avg accuracy --";
    return;
  }

  const total = state.predictionAccuracies.reduce(
    (sum, score) => sum + score,
    0,
  );
  const average = total / state.predictionAccuracies.length;
  accuracyAverage.textContent =
    `avg accuracy ${formatPercent(average)} (${state.predictionAccuracies.length})`;
}

function formatPercent(value) {
  return `${Math.round(value * 100)}%`;
}

function formatLatency(milliseconds) {
  if (milliseconds < 1000) {
    return `${Math.round(milliseconds)} ms`;
  }
  if (milliseconds < 10_000) {
    return `${(milliseconds / 1000).toFixed(1)} s`;
  }
  return `${Math.round(milliseconds / 1000)} s`;
}

function normalizeInline(text) {
  return text.replace(/\s+/g, " ").trim();
}

function stripSilenceTokens(text) {
  return text.replaceAll(SILENCE_TOKEN, "").replace(/\s+/g, " ").trimStart();
}

function isInteractiveMode(mode) {
  return mode === MODE_INTERACTIVE_BASE || mode === MODE_INTERACTIVE_RL;
}

function predictionVariantForMode(mode) {
  return mode === MODE_INTERACTIVE_RL ? "rl" : "base";
}

function interactiveCallReason(mode, reason) {
  const prefix = mode === MODE_INTERACTIVE_RL ? "interactive-rl" : "interactive";
  return `${prefix} ${reason}`;
}

async function readEventStream(body, onEvent) {
  const reader = body.getReader();
  const decoder = new TextDecoder();
  let buffer = "";

  while (true) {
    const { value, done } = await reader.read();
    if (done) {
      break;
    }
    buffer += decoder.decode(value, { stream: true });
    const frames = buffer.split("\n\n");
    buffer = frames.pop() || "";
    for (const frame of frames) {
      const parsed = parseSseFrame(frame);
      if (parsed) {
        onEvent(parsed.event, parsed.data);
      }
    }
  }

  if (buffer.trim()) {
    const parsed = parseSseFrame(buffer);
    if (parsed) {
      onEvent(parsed.event, parsed.data);
    }
  }
}

function parseSseFrame(frame) {
  const lines = frame.split(/\r?\n/);
  let event = "message";
  const dataLines = [];
  for (const line of lines) {
    if (line.startsWith("event:")) {
      event = line.slice(6).trim();
    }
    if (line.startsWith("data:")) {
      dataLines.push(line.slice(5).trimStart());
    }
  }
  if (!dataLines.length) {
    return null;
  }
  return { event, data: JSON.parse(dataLines.join("\n")) };
}

function render() {
  renderMode();
  renderHistory();
  renderLatencyAverage();
  renderAccuracyAverage();
  composer.disabled = state.locked;
  appView.classList.toggle("locked", state.locked);
  typedText.textContent = state.typed;
  predictedText.textContent =
    isInteractiveMode(state.mode)
      ? stripSilenceTokens(state.remainingUserCompletion)
      : "";
  const isThinking =
    state.inFlight &&
    !state.assistantText.trim() &&
    (state.mode === MODE_BASELINE || !normalizeInline(state.remainingUserCompletion));
  thinking.classList.toggle("active", isThinking);
  thinking.innerHTML = isThinking
    ? "<span>.</span><span>.</span><span>.</span>"
    : "";

  assistantResponse.textContent = state.errorText || state.assistantText;
  assistantResponse.className = "assistant-response";
  if (state.errorText) {
    assistantResponse.classList.add("error");
    return;
  }
  if (
    (isInteractiveMode(state.mode) && state.hasPrediction && state.predictionTurnDone) ||
    (state.mode === MODE_BASELINE && state.assistantText.trim())
  ) {
    assistantResponse.classList.add("ready");
  }
}

function renderMode() {
  for (const button of modeButtons) {
    const active = button.dataset.mode === state.mode;
    button.classList.toggle("active", active);
    button.setAttribute("aria-pressed", String(active));
    button.disabled = state.locked;
  }
}

function renderHistory() {
  historyView.replaceChildren();
  historyView.classList.toggle("empty", state.history.length === 0);

  for (const message of state.history) {
    const row = document.createElement("div");
    row.className = `history-line ${message.role}`;

    const role = document.createElement("span");
    role.className = "history-role";
    role.textContent = message.role === "user" ? "user" : "assistant";

    const content = document.createElement("div");
    content.className = "history-content";
    content.textContent =
      message.role === "user" ? stripSilenceTokens(message.content) : message.content;

    row.append(role, content);
    historyView.append(row);
  }
}

function resizeComposer() {
  composer.style.height = "auto";
  composer.style.height = `${Math.max(78, composer.scrollHeight)}px`;
}

function addCall({ seq, reason, text }) {
  const node = document.createElement("div");
  node.className = "call-item running";
  node.dataset.seq = String(seq);
  node.dataset.status = "starting";

  const prompt = document.createElement("span");
  prompt.className = "call-prompt";
  prompt.textContent = ">";

  const label = document.createElement("span");
  label.className = "call-label";
  label.textContent = `#${seq} ${reason}`;

  const meta = document.createElement("div");
  meta.className = "call-meta";
  meta.textContent = "starting";

  const separator = document.createElement("span");
  separator.className = "call-separator";
  separator.textContent = "::";

  const preview = document.createElement("div");
  preview.className = "call-preview";
  preview.textContent = stripSilenceTokens(text);

  node.append(prompt, label, meta, separator, preview);
  callList.prepend(node);
  return node;
}

function updateCallMeta(node, data) {
  if (!node) {
    return;
  }
  const meta = node.querySelector(".call-meta");
  const model = data.model || "model";
  const chars = data.chars ?? 0;
  const turns = data.history_turns ?? 0;
  node.dataset.model = model;
  node.dataset.chars = String(chars);
  node.dataset.turns = String(turns);
  node.dataset.status = "running";
  meta.textContent = `${model} ${chars}c ${turns}t running`;
}

function markCall(node, className, label) {
  if (!node) {
    return;
  }
  node.classList.remove("running", "done", "error", "canceled");
  node.classList.add(className);
  node.dataset.status = label;
  const meta = node.querySelector(".call-meta");
  if (meta) {
    const model = node.dataset.model || "model";
    const chars = node.dataset.chars || "?";
    const turns = node.dataset.turns || "0";
    meta.textContent = `${model} ${chars}c ${turns}t ${label}`;
  }
}

void boot();