"use strict";

/* ============================================================
   Transmission Manager - frontend
   Vanilla SPA. Auto-refreshes on a selectable interval with in-place updates.
   ============================================================ */

const DEFAULT_REFRESH_MS = 3000;
const REFRESH_INTERVALS = new Set([1000, 3000, 5000, 10000]);
const TRANSMISSION_STATUSES = {
  0: "stopped",
  1: "check-wait",
  2: "checking",
  3: "download-wait",
  4: "downloading",
  5: "seed-wait",
  6: "seeding",
};

const state = {
  torrents: [],
  stats: {},
  session: null,
  filter: "",
  scheduledOnly: false,
  sortKey: "status",
  refreshMs: DEFAULT_REFRESH_MS,
  lastError: null,
};

const torrentCards = new Map();
const actionStates = new Map();
let syncInFlight = false;
let syncQueued = false;
let refreshTimer = null;
let speedControlPending = false;
let speedControlError = null;
let schedulerData = null;
let schedulerItems = new Map();
let schedulerError = "";
let schedulerLoadPromise = null;
let schedulerSettingsPending = false;
let schedulerHistoryLoading = false;
let schedulerHistoryLoaded = false;
let schedulerHistoryEvents = [];
let schedulerHistoryHasMore = false;
let schedulerHistoryLatestID = -1;
const schedulerActionPending = new Set();
const schedulerActionErrors = new Map();
const schedulerRows = new Map();

const $ = (sel) => document.querySelector(sel);

/* ---------- Fetching ---------- */
async function fetchJSON(url, options = {}) {
  const res = await fetch(url, { cache: "no-store", ...options });
  const text = await res.text();
  let data = null;
  if (text) {
    try {
      data = JSON.parse(text);
    } catch {
      data = text;
    }
  }
  if (!res.ok) {
    const message = data && data.error ? data.error : `HTTP ${res.status} for ${url}`;
    throw new Error(message);
  }
  return data;
}

async function loadTorrents() {
  const data = await fetchJSON("/api/torrents");
  state.torrents = (data && data.torrents) || [];
}

async function loadStats() {
  const data = await fetchJSON("/api/stats");
  state.stats = data || {};
}

async function loadSession() {
  const data = await fetchJSON("/api/session");
  state.session = data && typeof data === "object" ? data : null;
}

async function sync() {
  if (syncInFlight) {
    syncQueued = true;
    return;
  }

  syncInFlight = true;
  setSyncing(true);
  try {
    await Promise.all([loadTorrents(), loadStats(), loadSession()]);
    state.lastError = null;
    speedControlError = null;
  } catch (err) {
    state.lastError = err.message || String(err);
  } finally {
    renderAll();
    setSyncing(false);
    const updated = $("#last-updated");
    if (updated) updated.textContent = `updated ${formatTime(new Date())}`;
    syncInFlight = false;
  }

  if (syncQueued) {
    syncQueued = false;
    sync();
  }
}

function setSyncing(on) {
  const el = $("#refresh-indicator");
  if (!el) return;
  el.classList.toggle("syncing", on);
  updateRefreshMetadata(on);
}

function refreshLabel() {
  return `${state.refreshMs / 1000}s`;
}

function updateRefreshMetadata(syncing = false) {
  const label = refreshLabel();
  const indicator = $("#refresh-indicator");
  if (indicator) {
    indicator.title = `Auto-refreshes every ${label}`;
    indicator.setAttribute(
      "aria-label",
      syncing ? `Syncing; auto-refresh every ${label}` : `Auto-refresh active every ${label}`,
    );
  }

  const hint = $("#error-hint");
  if (hint) hint.textContent = `Retrying in ${label}...`;
}

function setRefreshInterval(ms) {
  state.refreshMs = REFRESH_INTERVALS.has(ms) ? ms : DEFAULT_REFRESH_MS;
  updateRefreshMetadata(syncInFlight);

  if (refreshTimer) clearInterval(refreshTimer);
  refreshTimer = setInterval(sync, state.refreshMs);
}

async function runTorrentAction(id, action) {
  const pendingText = action === "pause" ? "Pausing..." : "Resuming...";
  actionStates.set(id, { pending: action, error: null, pendingText });
  updateCardByID(id);

  try {
    await fetchJSON(`/api/torrents/${id}/${action}`, { method: "POST" });
    actionStates.delete(id);
    await sync();
    loadScheduler();
  } catch (err) {
    actionStates.set(id, {
      pending: null,
      error: err.message || String(err),
      pendingText: "",
    });
    updateCardByID(id);
  }
}

async function setAlternativeSpeed(enabled) {
  if (speedControlPending || !state.session) return;
  speedControlPending = true;
  speedControlError = null;
  renderHeader();

  try {
    await fetchJSON("/api/session/alternative-speed", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ enabled }),
    });
    await sync();
    speedControlPending = false;
    renderHeader();
  } catch (err) {
    speedControlError = err.message || String(err);
    speedControlPending = false;
    renderHeader();
  }
}

/* ---------- Formatting helpers ---------- */
function humanSize(bytes) {
  if (bytes == null || isNaN(bytes) || bytes < 0) return "—";
  if (bytes === 0) return "0 B";
  const units = ["B", "KB", "MB", "GB", "TB", "PB"];
  const i = Math.min(Math.floor(Math.log(bytes) / Math.log(1024)), units.length - 1);
  const v = bytes / Math.pow(1024, i);
  const digits = i === 0 ? 0 : v < 10 ? 2 : v < 100 ? 1 : 0;
  return `${v.toFixed(digits)} ${units[i]}`;
}

function humanSpeed(bytesPerSec) {
  if (!bytesPerSec || bytesPerSec <= 0) return "0 kB/s";
  return humanSize(bytesPerSec) + "/s";
}

function humanRatio(ratio) {
  if (ratio == null || ratio < 0 || isNaN(ratio)) return "—";
  if (ratio === -1) return "∞";
  return ratio.toFixed(2);
}

function humanPct(p) {
  if (p == null || isNaN(p)) return 0;
  if (p < 0) return 0;
  if (p >= 1) return 1;
  return p;
}

function formatETA(sec) {
  if (sec == null || sec < 0 || isNaN(sec)) return "—";
  if (sec === 0) return "—";
  if (sec < 60) return `${sec}s`;
  const m = Math.floor(sec / 60);
  if (m < 60) return `${m}m ${sec % 60}s`;
  const h = Math.floor(m / 60);
  if (h < 24) return `${h}h ${m % 60}m`;
  const d = Math.floor(h / 24);
  return `${d}d ${h % 24}h`;
}

function formatDate(unix) {
  if (!unix || unix <= 0) return "—";
  const d = new Date(unix * 1000);
  if (isNaN(d.getTime())) return "—";
  return d.toLocaleDateString(undefined, {
    year: "numeric", month: "short", day: "numeric",
  });
}

function formatTime(d) {
  return d.toLocaleTimeString(undefined, { hour: "2-digit", minute: "2-digit", second: "2-digit" });
}

function formatDateTime(unix) {
  if (!unix) return "Never";
  const date = new Date(unix * 1000);
  return Number.isNaN(date.getTime()) ? "Never" : date.toLocaleString();
}

/* ---------- Scheduler ---------- */
function schedulerStatus(item) {
  if (!item.available) return { label: "Unavailable", key: "" };
  if (item.active) return item.status === 6
    ? { label: "Active", key: "active" }
    : { label: item.status === 5 ? "Queued" : "Starting", key: "waiting" };
  if (item.optedIn) return { label: "Waiting", key: "waiting" };
  return { label: "Available", key: "" };
}

function schedulerItemFor(torrent) {
  const hash = (torrent.hashString || "").toLowerCase();
  return schedulerItems.get(hash);
}

function renderScheduleControls() {
  const filter = $("#scheduled-filter");
  filter.disabled = !schedulerData;
  filter.setAttribute("aria-pressed", String(state.scheduledOnly));
  const count = schedulerData ? state.torrents.filter((torrent) => schedulerItemFor(torrent)?.optedIn).length : 0;
  setText(filter, schedulerData ? `Scheduled (${count})` : "Scheduled");

  const status = $("#schedule-status");
  const message = schedulerError || (schedulerData && schedulerData.error) || "";
  setText(status, message ? `Scheduler: ${message}` : "");
  status.classList.toggle("hidden", !message);
}

function createSchedulerRow() {
  const row = document.createElement("div");
  row.className = "scheduler-row";
  row.innerHTML = `<div class="scheduler-row-main"><span class="scheduler-row-name"></span><span class="scheduler-row-meta"></span></div>
    <div class="scheduler-row-controls"><span class="scheduler-state"></span><button type="button" class="scheduler-toggle"></button></div>`;
  return row;
}

function renderScheduler() {
  const error = $("#scheduler-error");
  const message = schedulerError || (schedulerData && schedulerData.error) || "";
  setText(error, message);
  error.classList.toggle("hidden", !message);
  if (!schedulerData) return;

  const slots = $("#scheduler-slots");
  if (document.activeElement !== slots && !schedulerSettingsPending) slots.value = String(schedulerData.maxActive);
  $("#scheduler-settings").querySelector("button").disabled = schedulerSettingsPending;

  const list = $("#scheduler-torrents");
  const items = schedulerData.torrents || [];
  const visible = new Set();
  items.forEach((item, index) => {
    visible.add(item.hashString);
    let row = schedulerRows.get(item.hashString);
    if (!row) {
      row = createSchedulerRow();
      schedulerRows.set(item.hashString, row);
    }
    row.dataset.hash = item.hashString;
    const name = row.querySelector(".scheduler-row-name");
    setText(name, item.name || item.hashString);
    name.title = item.name || item.hashString;
    setText(row.querySelector(".scheduler-row-meta"), item.optedIn
      ? `Last seeded: ${formatDateTime(item.lastSeededAt)} · Idle clock: ${formatDateTime(item.lastUploadAt)}`
      : "Not scheduled");
    const status = schedulerStatus(item);
    const badge = row.querySelector(".scheduler-state");
    badge.className = `scheduler-state ${status.key}`.trim();
    setText(badge, status.label);
    const button = row.querySelector(".scheduler-toggle");
    button.disabled = schedulerActionPending.has(item.hashString);
    button.setAttribute("aria-pressed", String(Boolean(item.optedIn)));
    button.setAttribute("aria-label", `${item.optedIn ? "Remove" : "Add"} ${item.name || "torrent"} ${item.optedIn ? "from" : "to"} scheduler`);
    setText(button, schedulerActionPending.has(item.hashString) ? "Saving..." : (item.optedIn ? "Opt out" : "Opt in"));
    const current = list.children[index];
    if (current !== row) list.insertBefore(row, current || null);
  });
  for (const [hash, row] of schedulerRows) {
    if (!visible.has(hash)) {
      row.remove();
      schedulerRows.delete(hash);
    }
  }
  $("#scheduler-empty").classList.toggle("hidden", items.length > 0);
  const active = items.filter((item) => item.active).length;
  const optedIn = items.filter((item) => item.optedIn).length;
  setText($("#scheduler-count"), `${active} / ${schedulerData.maxActive} active slots · ${optedIn} opted in`);
}

function renderSchedulerHistory() {
  const list = $("#scheduler-history");
  list.replaceChildren();
  for (const event of schedulerHistoryEvents) {
    const row = document.createElement("li");
    const description = document.createElement("span");
    const names = document.createElement("strong");
    const movement = event.fromName && event.toName
      ? `${event.fromName} → ${event.toName}`
      : (event.toName ? `${event.toName} activated` : `${event.fromName || "Torrent"} paused`);
    setText(names, movement);
    description.append(names, document.createTextNode(` · ${event.reason}`));
    const time = document.createElement("time");
    time.dateTime = new Date(event.happenedAt * 1000).toISOString();
    setText(time, formatDateTime(event.happenedAt));
    row.append(description, time);
    list.append(row);
  }
  $("#scheduler-history-empty").classList.toggle("hidden", schedulerHistoryEvents.length > 0);
  $("#scheduler-history-more").classList.toggle("hidden", !schedulerHistoryHasMore);
  $("#scheduler-history-more").disabled = schedulerHistoryLoading;
}

async function loadSchedulerHistory(reset = false) {
  if (schedulerHistoryLoading) return;
  schedulerHistoryLoading = true;
  try {
    const before = !reset && schedulerHistoryEvents.length
      ? `?before=${schedulerHistoryEvents[schedulerHistoryEvents.length - 1].id}` : "";
    const result = await fetchJSON(`/api/scheduler/history${before}`);
    schedulerHistoryEvents = reset ? (result.events || []) : schedulerHistoryEvents.concat(result.events || []);
    schedulerHistoryHasMore = Boolean(result.hasMore);
    schedulerHistoryLoaded = true;
    schedulerHistoryLatestID = schedulerData ? schedulerData.latestEventId : schedulerHistoryLatestID;
    schedulerError = "";
  } catch (err) {
    schedulerError = err.message || String(err);
    renderScheduler();
  } finally {
    schedulerHistoryLoading = false;
    renderSchedulerHistory();
  }
}

async function loadScheduler() {
  if (schedulerLoadPromise) return schedulerLoadPromise;
  schedulerLoadPromise = (async () => {
    try {
      schedulerData = await fetchJSON("/api/scheduler");
      schedulerItems = new Map((schedulerData.torrents || []).map((item) => [item.hashString.toLowerCase(), item]));
      schedulerError = "";
      renderScheduler();
      if (location.hash === "#scheduler" && (!schedulerHistoryLoaded || schedulerData.latestEventId !== schedulerHistoryLatestID)) {
        await loadSchedulerHistory(true);
      }
    } catch (err) {
      schedulerError = err.message || String(err);
      renderScheduler();
    } finally {
      renderScheduleControls();
      renderList();
    }
  })();
  try { await schedulerLoadPromise; } finally { schedulerLoadPromise = null; }
}

async function setSchedulerSlots(value) {
  if (schedulerSettingsPending) return;
  schedulerSettingsPending = true;
  renderScheduler();
  try {
    await fetchJSON("/api/scheduler/settings", {
      method: "POST", headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ maxActive: value }),
    });
    setText($("#scheduler-feedback"), "Active slots saved.");
    schedulerError = "";
    await loadScheduler();
  } catch (err) {
    schedulerError = err.message || String(err);
  } finally {
    schedulerSettingsPending = false;
    renderScheduler();
  }
}

async function setSchedulerOptIn(hash, enabled) {
  if (schedulerActionPending.has(hash)) return;
  schedulerActionPending.add(hash);
  schedulerActionErrors.delete(hash);
  renderScheduler();
  renderList();
  try {
    await fetchJSON(`/api/scheduler/torrents/${hash}/opt-in`, {
      method: "POST", headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ enabled }),
    });
    schedulerError = "";
    if (schedulerLoadPromise) await schedulerLoadPromise;
    await loadScheduler();
  } catch (err) {
    schedulerError = err.message || String(err);
    schedulerActionErrors.set(hash, schedulerError);
  } finally {
    schedulerActionPending.delete(hash);
    renderScheduler();
    renderScheduleControls();
    renderList();
  }
}

function activateTab(name) {
  const selected = name === "scheduler" ? "scheduler" : "torrents";
  for (const tabName of ["torrents", "scheduler"]) {
    const tab = $(`#tab-${tabName}`);
    const active = tabName === selected;
    tab.classList.toggle("active", active);
    tab.setAttribute("aria-selected", String(active));
    tab.tabIndex = active ? 0 : -1;
    $(`#panel-${tabName}`).hidden = !active;
  }
  if (selected === "scheduler") loadScheduler();
}

function peerStatus(t) {
  const peers = Array.isArray(t.peers) ? t.peers : [];
  const connected = t.peersConnected || peers.length || 0;
  const at100 = peers.filter((p) => p && p.progress === 1.0).length;
  if (connected === 0) return { connected: 0, at100: 0, label: "no peers" };
  return {
    connected,
    at100,
    label: `${at100}/${connected} @ 100%`,
  };
}

/* ---------- Torrent status classification ---------- */
function classify(t) {
  if (t.error && t.error !== 0) {
    return { key: "error", label: "Error", dot: true };
  }
  const tr = TRANSMISSION_STATUSES[t.status];
  switch (tr) {
    case "downloading": return { key: "downloading", label: "Downloading", dot: true };
    case "seeding":     return { key: "seeding", label: "Seeding", dot: true };
    case "stopped":
      if (t.isFinished || (t.percentDone >= 1.0)) return { key: "finished", label: "Finished", dot: false };
      return { key: "paused", label: "Paused", dot: false };
    case "checking":      return { key: "checking", label: "Verifying", dot: true };
    case "check-wait":    return { key: "queued", label: "Queued", dot: true };
    case "download-wait": return { key: "queued", label: "Queued ↓", dot: true };
    case "seed-wait":     return { key: "queued", label: "Queued ↑", dot: true };
    default:
      if (t.isFinished || (t.percentDone >= 1.0)) return { key: "finished", label: "Finished", dot: false };
      return { key: "idle", label: "Idle", dot: false };
  }
}

function actionForStatus(cls) {
  const pausable = ["checking", "downloading", "queued", "seeding"].includes(cls.key);
  if (pausable) {
    return { action: "pause", label: "Pause", pendingText: "Pausing..." };
  }
  return { action: "resume", label: "Resume", pendingText: "Resuming..." };
}

/* ---------- Sorting ---------- */
const STATUS_RANK = { error: 0, downloading: 1, seeding: 2, queued: 3, checking: 4, finished: 5, paused: 6, idle: 7 };

function compareName(a, b) {
  return (a.name || "").localeCompare(b.name || "");
}

function activitySpeed(t) {
  return (t.rateDownload || 0) + (t.rateUpload || 0);
}

function availabilityValue(t) {
  if (typeof t.availability === "number" && Number.isFinite(t.availability)) {
    return t.availability;
  }

  const pieces = Array.isArray(t.availability) ? t.availability : [];
  if (!pieces.length) return null;

  const counts = [];
  let min = Infinity;
  for (const piece of pieces) {
    const raw = Number(piece);
    if (!Number.isFinite(raw)) continue;
    const count = raw < 0 ? 1 : raw;
    counts.push(count);
    if (count < min) min = count;
  }

  if (!counts.length) return null;

  let aboveMin = 0;
  for (const count of counts) {
    if (count > min) aboveMin += 1;
  }

  return min + (aboveMin / counts.length);
}

function availabilitySortValue(t) {
  const value = availabilityValue(t);
  return value == null ? -1 : value;
}

function humanAvailability(value) {
  if (value == null || !Number.isFinite(value) || value < 0) return "—";
  return `${value.toFixed(value < 10 ? 2 : 1)}x`;
}

function sortTorrents(list) {
  const key = state.sortKey;
  const sorted = list.slice();
  const availabilityValues = key === "availability"
    ? new Map(sorted.map((t) => [t, availabilitySortValue(t)]))
    : null;
  sorted.sort((a, b) => {
    switch (key) {
      case "name":
        return compareName(a, b);
      case "progress":
        return (b.percentDone || 0) - (a.percentDone || 0) || compareName(a, b);
      case "ratio":
        return (b.uploadRatio || 0) - (a.uploadRatio || 0) || compareName(a, b);
      case "size":
        return (b.totalSize || 0) - (a.totalSize || 0) || compareName(a, b);
      case "speed":
        return (activitySpeed(b) - activitySpeed(a))
          || ((b.rateDownload || 0) - (a.rateDownload || 0))
          || ((b.rateUpload || 0) - (a.rateUpload || 0))
          || compareName(a, b);
      case "availability":
        return (availabilityValues.get(b) - availabilityValues.get(a))
          || ((b.percentDone || 0) - (a.percentDone || 0))
          || compareName(a, b);
      case "status": {
        const ra = STATUS_RANK[classify(a).key] ?? 99;
        const rb = STATUS_RANK[classify(b).key] ?? 99;
        if (ra !== rb) return ra - rb;
        return (b.percentDone || 0) - (a.percentDone || 0) || compareName(a, b);
      }
      default:
        return 0;
    }
  });
  return sorted;
}

/* ---------- Rendering ---------- */
function renderHeader() {
  const torrents = state.torrents || [];
  let dl = 0, ul = 0;
  for (const t of torrents) {
    dl += t.rateDownload || 0;
    ul += t.rateUpload || 0;
  }
  $("#stat-torrents").textContent = String(torrents.length);
  $("#stat-dl").textContent = humanSpeed(dl);
  $("#stat-ul").textContent = humanSpeed(ul);
  renderSpeedControls();
}

function sessionValue(session, kebab, snake) {
  if (!session) return null;
  if (session[kebab] != null) return session[kebab];
  return snake ? session[snake] : null;
}

function sessionSpeedBytes(session) {
  const units = session && session.units;
  const value = units && (units["speed-bytes"] ?? units.speed_bytes ?? units.speedBytes);
  return Number.isFinite(Number(value)) && Number(value) > 0 ? Number(value) : 1000;
}

function activeSpeedCap(session, direction) {
  const enabled = Boolean(sessionValue(session, "alt-speed-enabled", "alt_speed_enabled"));
  const alt = direction === "down"
    ? sessionValue(session, "alt-speed-down", "alt_speed_down")
    : sessionValue(session, "alt-speed-up", "alt_speed_up");
  const normalEnabled = Boolean(sessionValue(
    session,
    direction === "down" ? "speed-limit-down-enabled" : "speed-limit-up-enabled",
    direction === "down" ? "speed_limit_down_enabled" : "speed_limit_up_enabled",
  ));
  const normal = direction === "down"
    ? sessionValue(session, "speed-limit-down", "speed_limit_down")
    : sessionValue(session, "speed-limit-up", "speed_limit_up");
  const value = enabled ? alt : (normalEnabled ? normal : null);
  const number = Number(value);
  return Number.isFinite(number) && number > 0 ? number * sessionSpeedBytes(session) : null;
}

function renderSpeedControls() {
  const toggle = $("#alt-speed-toggle");
  const toggleState = $("#alt-speed-state");
  const status = $("#speed-control-status");
  if (!toggle || !toggleState || !status) return;

  const session = state.session;
  const enabled = Boolean(sessionValue(session, "alt-speed-enabled", "alt_speed_enabled"));
  toggle.disabled = !session || speedControlPending;
  toggle.setAttribute("aria-pressed", String(enabled));
  toggle.classList.toggle("is-saving", speedControlPending);
  setText(toggleState, !session ? (state.lastError ? "Unavailable" : "Loading...") : (speedControlPending ? "Saving..." : (enabled ? "On" : "Off")));

  const caps = [
    { id: "speed-cap-down", value: activeSpeedCap(session, "down") },
    { id: "speed-cap-up", value: activeSpeedCap(session, "up") },
  ];
  for (const cap of caps) {
    const el = $("#" + cap.id);
    if (!el) continue;
    el.classList.toggle("hidden", cap.value == null);
    const valueEl = el.querySelector("strong");
    if (valueEl && cap.value != null) setText(valueEl, humanSpeed(cap.value));
  }
  setText(status, speedControlError || "");
}

function initial(name) {
  const n = (name || "").trim();
  if (!n) return "?";
  const base = n.replace(/\.[a-z0-9]+$/i, "");
  const m = base.match(/[A-Za-z0-9]/);
  return m ? m[0].toUpperCase() : "?";
}

function createCard() {
  const card = document.createElement("article");
  card.className = "card is-new";
  card.innerHTML = `
    <div class="card-top">
      <div class="favicon" data-field="initial"></div>
      <div class="card-body">
        <div class="card-name" data-field="name"></div>
        <div class="card-meta">
          <span class="schedule-badge" data-field="schedule-badge"></span>
          <span class="meta-item"><span class="meta-label">Size</span> <span data-field="size"></span></span>
          <span class="meta-item"><span class="meta-label">Ratio</span> <span data-field="ratio"></span></span>
          <span class="meta-item"><span class="meta-label">Peers</span> <span data-field="peers"></span></span>
          <span class="meta-item done-meta hidden" data-field="done-meta-wrap"><span class="meta-label">Done</span> <span data-field="done-meta"></span></span>
        </div>
      </div>
      <div class="card-actions">
        <div class="card-status-col">
          <span class="badge" data-field="badge"><span class="dotb"></span><span data-field="status-label"></span></span>
          <span class="pct" data-field="pct"></span>
        </div>
        <button type="button" class="card-schedule-toggle hidden" data-schedule-button></button>
        <button type="button" class="action-btn" data-action-button></button>
      </div>
    </div>

    <div class="progress-wrap">
      <div class="progress-bar" data-field="progress"></div>
    </div>

    <div class="card-bottom">
      <div class="stat-cell">
        <span class="k">Downloaded</span>
        <span class="v" data-field="downloaded"></span>
      </div>
      <div class="stat-cell">
        <span class="k">Uploaded</span>
        <span class="v" data-field="uploaded"></span>
      </div>
      <div class="stat-cell">
        <span class="k">↓ Speed</span>
        <span class="v" data-field="download-speed"></span>
      </div>
      <div class="stat-cell">
        <span class="k">↑ Speed</span>
        <span class="v" data-field="upload-speed"></span>
      </div>
      <div class="stat-cell">
        <span class="k">ETA</span>
        <span class="v" data-field="eta"></span>
      </div>
      <div class="stat-cell">
        <span class="k">Availability</span>
        <span class="v mono" data-field="availability"></span>
      </div>
      <div class="stat-cell">
        <span class="k">Peers @ 100%</span>
        <span class="v mono" data-field="peers-100"></span>
      </div>
      <div class="stat-cell">
        <span class="k">Finished</span>
        <span class="v" data-field="finished"></span>
      </div>
    </div>

    <div class="action-error hidden" data-field="action-error"></div>
    <div class="error-string hidden" data-field="error-string"></div>
  `;
  card.addEventListener("animationend", () => card.classList.remove("is-new"), { once: true });
  return card;
}

function field(card, name) {
  return card.querySelector(`[data-field="${name}"]`);
}

function setText(el, value) {
  const text = value == null ? "" : String(value);
  if (el.textContent !== text) el.textContent = text;
}

function setValueClass(el, className) {
  el.classList.remove("accent", "success", "warn", "dim");
  if (className) el.classList.add(className);
}

function updateCard(card, t) {
  const id = Number(t.id);
  const cls = classify(t);
  const pct = humanPct(t.percentDone);
  const pctText = (pct * 100).toFixed(pct === 1 ? 0 : 1) + "%";
  const isDone = pct >= 1.0;
  const ps = peerStatus(t);
  const availability = availabilityValue(t);
  const dl = t.rateDownload || 0;
  const ul = t.rateUpload || 0;
  const eta = (dl > 0 && !isDone) ? formatETA(t.eta) : (isDone ? "—" : "∞");
  const hasError = cls.key === "error";

  let barClass = "";
  if (hasError) barClass = "error";
  else if (isDone) barClass = "done";
  else if (cls.key === "paused" || cls.key === "finished") barClass = "paused";

  card.dataset.id = String(id);
  card.classList.toggle("is-error", hasError);
  setText(field(card, "initial"), initial(t.name));

  const nameEl = field(card, "name");
  setText(nameEl, t.name || "Unnamed torrent");
  nameEl.title = t.name || "";

  setText(field(card, "size"), humanSize(t.totalSize));
  setText(field(card, "ratio"), humanRatio(t.uploadRatio));
  setText(field(card, "peers"), ps.label);

  const doneMetaWrap = field(card, "done-meta-wrap");
  doneMetaWrap.classList.toggle("hidden", !t.doneDate);
  setText(field(card, "done-meta"), formatDate(t.doneDate));

  const badge = field(card, "badge");
  badge.className = `badge ${cls.key}`;
  setText(field(card, "status-label"), cls.label);
  setText(field(card, "pct"), pctText);

  const scheduleItem = schedulerItemFor(t);
  const scheduled = Boolean(scheduleItem && scheduleItem.optedIn);
  const scheduleBadge = field(card, "schedule-badge");
  scheduleBadge.classList.toggle("is-scheduled", scheduled);
  setText(scheduleBadge, !schedulerData ? (schedulerError ? "Schedule unavailable" : "Schedule loading") : scheduled
    ? `Scheduled · ${schedulerStatus(scheduleItem).label}` : "Not scheduled");
  scheduleBadge.title = !schedulerData
    ? (schedulerError ? "Scheduler state is unavailable" : "Loading scheduler state")
    : (!scheduleItem ? "Torrent must be complete and error-free before scheduling" : "");
  const scheduleButton = card.querySelector("[data-schedule-button]");
  const schedulable = Boolean(scheduleItem && (scheduleItem.available || scheduled));
  scheduleButton.classList.toggle("hidden", !schedulable);
  scheduleButton.disabled = schedulerActionPending.has((t.hashString || "").toLowerCase());
  scheduleButton.setAttribute("aria-pressed", String(scheduled));
  scheduleButton.setAttribute("aria-label", `${scheduled ? "Remove" : "Add"} ${t.name || "torrent"} ${scheduled ? "from" : "to"} scheduler`);
  setText(scheduleButton, scheduleButton.disabled ? "Saving..." : (scheduled ? "Unschedule" : "Schedule"));

  const progress = field(card, "progress");
  progress.className = `progress-bar ${barClass}`.trim();
  progress.style.width = `${(pct * 100).toFixed(2)}%`;

  setText(field(card, "downloaded"), isDone ? `${humanSize(t.downloadedEver)} / ${humanSize(t.totalSize)}` : humanSize(t.downloadedEver));
  setText(field(card, "uploaded"), humanSize(t.uploadedEver));

  const dlEl = field(card, "download-speed");
  setText(dlEl, humanSpeed(dl));
  setValueClass(dlEl, dl > 0 ? "accent" : "dim");

  const ulEl = field(card, "upload-speed");
  setText(ulEl, humanSpeed(ul));
  setValueClass(ulEl, ul > 0 ? "success" : "dim");

  setText(field(card, "eta"), eta);

  const availabilityEl = field(card, "availability");
  setText(availabilityEl, humanAvailability(availability));
  setValueClass(availabilityEl, availability == null ? "dim" : availability >= 1 ? "success" : "warn");

  setText(field(card, "peers-100"), `${ps.at100}/${ps.connected}`);
  setText(field(card, "finished"), formatDate(t.doneDate));

  const errorEl = field(card, "error-string");
  const errorText = hasError && t.errorString ? t.errorString : "";
  setText(errorEl, errorText);
  errorEl.classList.toggle("hidden", !errorText);

  const action = actionForStatus(cls);
  const actionState = actionStates.get(id);
  const button = card.querySelector("[data-action-button]");
  button.dataset.action = action.action;
  button.classList.toggle("pause", action.action === "pause");
  button.classList.toggle("resume", action.action === "resume");
  button.disabled = Boolean(actionState && actionState.pending);
  button.setAttribute("aria-label", `${action.label} ${t.name || "torrent"}`);
  setText(button, actionState && actionState.pending ? actionState.pendingText : action.label);

  const actionError = field(card, "action-error");
  const actionErrorText = (actionState && actionState.error) || schedulerActionErrors.get((t.hashString || "").toLowerCase()) || "";
  setText(actionError, actionErrorText);
  actionError.classList.toggle("hidden", !actionErrorText);
}

function updateCardByID(id) {
  const card = torrentCards.get(String(id));
  const torrent = (state.torrents || []).find((t) => Number(t.id) === id);
  if (card && torrent) updateCard(card, torrent);
}

function reconcileCards(torrents) {
  const list = $("#torrents");
  const visible = new Set();

  torrents.forEach((t, index) => {
    const id = String(t.id);
    visible.add(id);

    let card = torrentCards.get(id);
    if (!card) {
      card = createCard();
      torrentCards.set(id, card);
    }

    updateCard(card, t);

    const current = list.children[index];
    if (current !== card) {
      list.insertBefore(card, current || null);
    }
  });

  for (const [id, card] of torrentCards) {
    if (!visible.has(id)) {
      card.remove();
      torrentCards.delete(id);
      actionStates.delete(Number(id));
    }
  }
}

function renderList() {
  const empty = $("#empty-state");
  const errEl = $("#error-state");
  const errMsg = $("#error-msg");

  errEl.classList.toggle("hidden", !state.lastError);
  if (state.lastError) {
    errMsg.textContent = state.lastError;
  }

  if (state.lastError && (!state.torrents || state.torrents.length === 0)) {
    reconcileCards([]);
    empty.classList.add("hidden");
    return;
  }

  let torrents = sortTorrents(state.torrents || []);
  if (state.scheduledOnly) torrents = torrents.filter((t) => schedulerItemFor(t)?.optedIn);
  const f = state.filter.trim().toLowerCase();
  if (f) torrents = torrents.filter((t) => (t.name || "").toLowerCase().includes(f));

  reconcileCards(torrents);
  empty.classList.toggle("hidden", torrents.length !== 0 || Boolean(state.lastError));
  setText($("#empty-title"), state.filter ? "No matching torrents" : (state.scheduledOnly ? "No scheduled torrents" : "No torrents"));
  setText($("#empty-sub"), state.filter ? "Try a different filter." : (state.scheduledOnly
    ? "Schedule a completed torrent here to see it in this view."
    : "Add torrents to your Transmission client to see them here."));
}

function renderAll() {
  renderHeader();
  renderScheduleControls();
  renderList();
}

/* ---------- Events ---------- */
function wireEvents() {
  document.querySelectorAll(".app-tab").forEach((tab) => {
    tab.addEventListener("click", () => { location.hash = tab.id === "tab-scheduler" ? "scheduler" : "torrents"; });
    tab.addEventListener("keydown", (event) => {
      if (!["ArrowLeft", "ArrowRight", "Home", "End"].includes(event.key)) return;
      event.preventDefault();
      const next = event.key === "Home" ? "torrents"
        : event.key === "End" ? "scheduler"
          : (tab.id === "tab-torrents" ? "scheduler" : "torrents");
      location.hash = next;
      $(`#tab-${next}`).focus();
    });
  });
  window.addEventListener("hashchange", () => activateTab(location.hash.slice(1)));

  $("#scheduler-settings").addEventListener("submit", (event) => {
    event.preventDefault();
    const value = Number($("#scheduler-slots").value);
    if (!Number.isInteger(value) || value < 1 || value > 100) {
      schedulerError = "Active slots must be a whole number from 1 to 100.";
      renderScheduler();
      return;
    }
    setSchedulerSlots(value);
  });
  $("#scheduler-torrents").addEventListener("click", (event) => {
    const button = event.target.closest(".scheduler-toggle");
    if (!button || button.disabled) return;
    const hash = button.closest(".scheduler-row").dataset.hash;
    const item = schedulerData && schedulerData.torrents.find((t) => t.hashString === hash);
    if (item) setSchedulerOptIn(hash, !item.optedIn);
  });
  $("#scheduler-history-more").addEventListener("click", () => loadSchedulerHistory(false));

  const filterInput = $("#filter");
  filterInput.addEventListener("input", (e) => {
    state.filter = e.target.value;
    renderList();
  });
  $("#scheduled-filter").addEventListener("click", () => {
    state.scheduledOnly = !state.scheduledOnly;
    renderScheduleControls();
    renderList();
  });

  document.querySelectorAll(".sort-btn").forEach((btn) => {
    btn.addEventListener("click", () => {
      document.querySelectorAll(".sort-btn").forEach((b) => b.classList.remove("active"));
      btn.classList.add("active");
      state.sortKey = btn.dataset.sort;
      renderList();
    });
  });

  const refreshSelect = $("#refresh-interval");
  if (refreshSelect) {
    refreshSelect.value = String(state.refreshMs);
    refreshSelect.addEventListener("change", (e) => {
      const next = Number(e.target.value);
      if (!REFRESH_INTERVALS.has(next)) {
        e.target.value = String(state.refreshMs);
        return;
      }
      setRefreshInterval(next);
    });
  }

  const speedToggle = $("#alt-speed-toggle");
  if (speedToggle) {
    speedToggle.addEventListener("click", () => {
      const enabled = !Boolean(sessionValue(state.session, "alt-speed-enabled", "alt_speed_enabled"));
      setAlternativeSpeed(enabled);
    });
  }

  $("#torrents").addEventListener("click", (e) => {
    const scheduleButton = e.target.closest("[data-schedule-button]");
    if (scheduleButton && !scheduleButton.disabled) {
      const card = scheduleButton.closest(".card");
      const torrent = (state.torrents || []).find((t) => String(t.id) === card.dataset.id);
      const item = torrent && schedulerItemFor(torrent);
      if (item) setSchedulerOptIn(item.hashString, !item.optedIn);
      return;
    }
    const button = e.target.closest("[data-action-button]");
    if (!button || button.disabled) return;

    const card = button.closest(".card");
    const id = Number(card && card.dataset.id);
    const action = button.dataset.action;
    if (!id || !["pause", "resume"].includes(action)) return;

    runTorrentAction(id, action);
  });

  document.addEventListener("visibilitychange", () => {
    if (!document.hidden) {
      sync();
      loadScheduler();
    }
  });
}

/* ---------- Init ---------- */
function boot() {
  wireEvents();
  activateTab(location.hash.slice(1));
  setRefreshInterval(state.refreshMs);
  setInterval(() => {
    if (!document.hidden) loadScheduler();
  }, 10000);
  sync();
  if (location.hash !== "#scheduler") loadScheduler();
}

document.addEventListener("DOMContentLoaded", boot);