/**
 * Rail: the device → camera tree of the events console.
 *
 * A device row carries the heartbeat verdict (online/offline, fps, temp, throttle, config
 * drift); the cameras that have reported events nest under it on hairline connectors, and a
 * camera node doubles as the stream's camera filter. app.js owns the polling, the filter state
 * and the per-camera aggregation — this file owns only the rail's DOM.
 *
 * XSS-safe: every dynamic value goes through textContent / setAttribute, never innerHTML.
 */
(function () {
  'use strict';

  var LEVELS = { critical: 'lv-critical', high: 'lv-high', warning: 'lv-warning', info: 'lv-info' };
  var LEVEL_TEXT = { critical: '위급', high: '높음', warning: '경고', info: '정보' };

  var collapsed = {};   // device_id -> true; survives the 5s re-render
  var lastSig = null;   // rendered signature; an unchanged poll must not rebuild the DOM
  var last = null;      // {root, summaryEl, model} for the collapse toggle's own re-render

  function ago(seconds) {
    if (seconds === null || seconds === undefined) return '응답 없음';
    if (seconds < 60) return Math.max(0, Math.round(seconds)) + '초 전';
    if (seconds < 3600) return Math.floor(seconds / 60) + '분 전';
    if (seconds < 86400) return Math.floor(seconds / 3600) + '시간 전';
    return Math.floor(seconds / 86400) + '일 전';
  }

  function deviceMeta(d) {
    // Liveness first, spelled out in words — the status dot is colour, and colour is never
    // allowed to carry state on its own (NF9). The verdict itself is the server's (computed
    // against the request clock), never re-derived here from a local clock.
    if (d.seconds_since === null || d.seconds_since === undefined) return '응답 없음';
    // fps/temp are the LAST values a dead device reported, so on an offline row they would read
    // as current telemetry ("0 fps" for a device that simply stopped talking). Liveness only.
    if (!d.online) return '오프라인 · ' + ago(d.seconds_since);
    var parts = ['온라인 · ' + ago(d.seconds_since)];
    if (d.fps !== null && d.fps !== undefined) parts.push((Math.round(d.fps * 10) / 10) + ' fps');
    if (d.temp !== null && d.temp !== undefined && d.temp > 0) parts.push(Math.round(d.temp) + '°');
    return parts.join(' · ');
  }

  function deviceWarn(d) {
    var w = [];
    if (d.throttle) w.push('과열 스로틀');
    if (d.config_drift) w.push('설정 미적용');
    return w.join(' · ');
  }

  /** Devices from the heartbeat API, each with its observed cameras nested underneath. */
  function groupsOf(model) {
    var groups = [], byId = {};
    (model.devices || []).forEach(function (d) {
      var id = String(d.device_id);
      var g = { id: id, label: d.name || id, state: d.online ? 'online' : 'offline',
                meta: deviceMeta(d), warn: deviceWarn(d), cams: [] };
      byId[id] = g;
      groups.push(g);
    });
    (model.cameras || []).forEach(function (c) {
      var g = byId[c.device_id];
      if (!g) {
        // A camera whose device is missing from /api/devices — it was deleted, or it is sending
        // events under an id nobody provisioned. Show it as its own unknown-device group: an
        // unattributed camera is exactly the thing an operator must be told about, never dropped.
        g = byId[c.device_id] = { id: c.device_id, label: c.device_id || '(장치 ID 없음)',
                                  state: 'unknown', meta: '', warn: '장치 목록에 없음 — 등록 확인', cams: [] };
        groups.push(g);
      }
      g.cams.push({
        key: c.key,
        id: c.camera_id,
        when: c.last_at ? ago(model.now - c.last_at) : '감지 없음',
        count: c.unacked,
        level: c.worst
      });
    });
    groups.forEach(function (g) {
      // Stable order: the rail is a target the operator clicks, so a camera must not jump
      // position because its event count changed.
      g.cams.sort(function (a, b) { return a.id < b.id ? -1 : (a.id > b.id ? 1 : 0); });
    });
    return groups;
  }

  /** Collapsed, unless this branch holds the camera the stream is currently filtered by —
   *  hiding that node would leave the operator filtered with no visible sign of by what. */
  function isCollapsed(g, selectedKey) {
    if (!collapsed[g.id]) return false;
    for (var i = 0; i < g.cams.length; i++) if (g.cams[i].key === selectedKey) return false;
    return true;
  }

  function signature(groups, model) {
    var parts = [model.stale ? 'S' : '-', model.loaded ? 'L' : '-', model.selectedKey || ''];
    groups.forEach(function (g) {
      parts.push(g.id + '|' + g.label + '|' + g.state + '|' + g.meta + '|' + g.warn
                 + '|' + (isCollapsed(g, model.selectedKey) ? 'c' : 'o'));
      g.cams.forEach(function (c) { parts.push(' ' + c.id + '|' + c.when + '|' + c.count + '|' + (c.level || '')); });
    });
    return parts.join('\n');
  }

  function el(tag, cls, text) {
    var n = document.createElement(tag);
    if (cls) n.className = cls;
    if (text !== undefined && text !== null) n.textContent = text;
    return n;
  }

  function buildDeviceHead(g, shut) {
    var head = el('button', 'device-head');
    head.type = 'button';
    head.setAttribute('data-node', 'd' + g.id);
    head.setAttribute('aria-expanded', shut ? 'false' : 'true');

    var line = el('span', 'device-line');
    line.appendChild(el('span', 'twisty')).setAttribute('aria-hidden', 'true');
    line.appendChild(el('span', 'dot')).setAttribute('aria-hidden', 'true');
    line.appendChild(el('span', 'device-name', g.label));
    line.appendChild(el('span', 'device-tally', g.cams.length + '대'));
    head.appendChild(line);

    if (g.meta) head.appendChild(el('span', 'device-meta', g.meta));
    if (g.warn) head.appendChild(el('span', 'device-warn', g.warn));

    // Spoken name: everything the row shows, in reading order and without the visual
    // separators. It must stay a superset of the visible text — a shorter label would hide
    // exactly the fields (오프라인, 과열 스로틀) that this rail exists to surface.
    var spoken = [g.label];
    if (g.meta) spoken.push(g.meta.split(' · ').join(', '));
    spoken.push('카메라 ' + g.cams.length + '대');
    if (g.warn) spoken.push(g.warn);
    head.setAttribute('aria-label', spoken.join(', '));
    return head;
  }

  function buildCamNode(c, onSelect, selectedKey) {
    var node = el('button', 'cam-node');
    node.type = 'button';
    node.setAttribute('data-node', 'c' + c.key);
    node.setAttribute('aria-pressed', c.key === selectedKey ? 'true' : 'false');
    node.appendChild(el('span', 'cam-id', c.id));
    node.appendChild(el('span', 'cam-when', c.when));
    if (c.count > 0) {
      node.appendChild(el('span', 'cam-count ' + (LEVELS[c.level] || 'lv-info'), String(c.count)));
    }
    node.setAttribute('aria-label',
      c.id + ' 카메라, 마지막 감지 ' + c.when
      + (c.count > 0 ? ', 미확인 ' + (LEVEL_TEXT[c.level] || '') + ' 포함 ' + c.count + '건' : ', 미확인 없음')
      + ' — 이 카메라만 보기');
    node.addEventListener('click', function () { onSelect(c.key); });
    return node;
  }

  function renderSummary(summaryEl, groups, model) {
    if (!summaryEl) return;
    summaryEl.textContent = '';
    if (!model.loaded) { summaryEl.textContent = '장치 상태 확인 중…'; return; }
    // "장치" counts REGISTERED devices only — an unknown-device group is not a device the
    // operator has, it is a discrepancy, and it gets its own count rather than padding this one.
    var cams = 0, known = 0, down = 0, unknown = 0;
    groups.forEach(function (g) {
      cams += g.cams.length;
      if (g.state === 'unknown') { unknown += 1; return; }
      known += 1;
      if (g.state === 'offline') down += 1;
    });
    summaryEl.appendChild(document.createTextNode('장치 ' + known + ' · 카메라 ' + cams));
    if (down > 0) summaryEl.appendChild(el('span', 'is-down', ' · 오프라인 ' + down));
    if (unknown > 0) summaryEl.appendChild(el('span', 'is-down', ' · 미등록 ' + unknown));
  }

  function render(root, summaryEl, model) {
    if (!root) return;
    last = { root: root, summaryEl: summaryEl, model: model };

    var groups = groupsOf(model);
    var sig = signature(groups, model);
    if (sig === lastSig) return;   // nothing visible changed: keep the DOM, and the focus in it
    lastSig = sig;

    // The tree is rebuilt, not patched, so a node the operator is tabbing through would lose
    // focus on any change. Remember which node held it and hand focus back to its replacement.
    var active = document.activeElement;
    var refocus = (active && root.contains(active)) ? active.getAttribute('data-node') : null;

    renderSummary(summaryEl, groups, model);

    root.textContent = '';
    root.className = 'device-tree' + (model.stale ? ' is-stale' : '') + (groups.length === 0 ? ' is-empty' : '');
    if (model.stale) {
      // A frozen panel is worse than an empty one: a camera that dies while the poll is down
      // would keep showing "온라인". Say the state is old instead of quietly implying it is live.
      root.appendChild(el('div', 'device-stale-note', '상태 갱신 지연 — 마지막으로 확인된 상태입니다'));
    }
    if (groups.length === 0) {
      root.appendChild(document.createTextNode(
        model.loaded ? '등록된 장치가 없습니다. 관리자가 장치를 등록하면 여기에 표시됩니다.' : '불러오는 중…'));
      return;
    }

    var frag = document.createDocumentFragment();
    groups.forEach(function (g) {
      var shut = isCollapsed(g, model.selectedKey);
      var node = el('div', 'device-node'
        + (g.state === 'offline' ? ' is-offline' : '')
        + (g.state === 'unknown' ? ' is-unknown' : '')
        + (shut ? ' is-collapsed' : ''));
      var head = buildDeviceHead(g, shut);
      head.addEventListener('click', function () { toggle(g.id); });
      node.appendChild(head);

      if (!shut) {
        if (g.cams.length === 0) {
          node.appendChild(el('div', 'cam-empty', '수신된 감지 이벤트 없음'));
        } else {
          var list = el('ul', 'cam-list');
          g.cams.forEach(function (c) {
            var item = el('li', 'cam-item');
            item.appendChild(buildCamNode(c, model.onSelect, model.selectedKey));
            list.appendChild(item);
          });
          node.appendChild(list);
        }
      }
      frag.appendChild(node);
    });
    root.appendChild(frag);

    if (refocus) {
      var nodes = root.querySelectorAll('[data-node]');
      for (var i = 0; i < nodes.length; i++) {
        if (nodes[i].getAttribute('data-node') === refocus) { nodes[i].focus(); break; }
      }
    }
  }

  function toggle(deviceId) {
    if (collapsed[deviceId]) delete collapsed[deviceId];
    else collapsed[deviceId] = true;
    if (!last) return;
    lastSig = null;   // collapse state is part of the signature; force the rebuild
    render(last.root, last.summaryEl, last.model);
  }

  window.DeviceTree = { render: render };
})();