/**
 * diagnostics_panel.js — Saltybot System Diagnostics Dashboard (Issue #562)
 *
 * Connects to rosbridge WebSocket and subscribes to:
 *   /diagnostics           diagnostic_msgs/DiagnosticArray  — everything
 *   /saltybot/balance_state std_msgs/String (JSON)           — motor cmd / state
 *
 * Diagnostic KeyValues decoded:
 *   battery_voltage_v, battery_current_a, battery_soc_pct
 *   cpu_temp_c, gpu_temp_c, board_temp_c
 *   motor_temp_l_c, motor_temp_r_c
 *   motor_current_l_a, motor_current_r_a
 *   ram_used_mb, ram_total_mb
 *   gpu_used_mb, gpu_total_mb
 *   disk_used_gb, disk_total_gb
 *   wifi_rssi_dbm, wifi_latency_ms
 *   mqtt_connected
 *
 * Auto-refresh: rosbridge subscriptions push at ~2 Hz; UI polls canvas draws
 * at the same rate and updates DOM elements.
 */

'use strict';

// ── Constants ─────────────────────────────────────────────────────────────────

const LIPO_MIN = 12.0;   // 4S empty
const LIPO_MAX = 16.8;   // 4S full

const BATT_HISTORY_MAX = 120;  // ~2 min at 1 Hz

// Alert thresholds
const THRESHOLDS = {
  voltage_warn:    13.6,
  voltage_crit:    13.0,
  soc_warn:        25,
  soc_crit:        10,
  cpu_temp_warn:   75,
  cpu_temp_crit:   90,
  gpu_temp_warn:   75,
  gpu_temp_crit:   90,
  motor_temp_warn: 70,
  motor_temp_crit: 85,
  ram_pct_warn:    80,
  ram_pct_crit:    95,
  disk_pct_warn:   80,
  disk_pct_crit:   95,
  rssi_warn:       -70,
  rssi_crit:       -80,
  latency_warn:    150,
  latency_crit:    500,
  current_warn:    8.0,
  current_crit:    12.0,
};

// ── State ─────────────────────────────────────────────────────────────────────

let ros = null;
let diagSub = null;
let balanceSub = null;

const state = {
  // Battery
  voltage:  null,
  current:  null,
  soc:      null,
  battHistory: [],   // [{ts, v}]

  // Temperatures
  cpuTemp:   null,
  gpuTemp:   null,
  boardTemp: null,
  motorTempL: null,
  motorTempR: null,

  // Motor
  motorCurrentL: null,
  motorCurrentR: null,
  motorCmdL:     null,
  motorCmdR:     null,
  balanceState:  'UNKNOWN',

  // Resources
  ramUsed:  null, ramTotal:  null,
  gpuUsed:  null, gpuTotal:  null,
  diskUsed: null, diskTotal: null,

  // Network
  rssi:       null,
  latency:    null,

  // MQTT
  mqttConnected: null,

  // ROS nodes (DiagnosticStatus array)
  nodes: [],

  // Overall health
  overallLevel: 3,  // 3=STALE by default
  lastUpdate: null,
};

// ── Utility ───────────────────────────────────────────────────────────────────

function numOrNull(s) {
  const n = parseFloat(s);
  return isNaN(n) ? null : n;
}

function pct(used, total) {
  if (!total || total === 0) return 0;
  return Math.min(100, Math.max(0, (used / total) * 100));
}

function socFromVoltage(v) {
  if (v == null || v <= 0) return null;
  return Math.max(0, Math.min(100, ((v - LIPO_MIN) / (LIPO_MAX - LIPO_MIN)) * 100));
}

function threshColor(value, warnThr, critThr, invert = false) {
  // invert: lower is worse (e.g. voltage, SOC, RSSI)
  if (value == null) return '#6b7280';
  const warn = invert ? value <= warnThr : value >= warnThr;
  const crit = invert ? value <= critThr : value >= critThr;
  if (crit) return '#ef4444';
  if (warn) return '#f59e0b';
  return '#22c55e';
}

function levelClass(level) {
  return ['ns-ok', 'ns-warn', 'ns-error', 'ns-stale'][level] ?? 'ns-stale';
}

function levelLabel(level) {
  return ['OK', 'WARN', 'ERROR', 'STALE'][level] ?? 'STALE';
}

function setBadgeClass(el, level) {
  el.className = 'sys-badge ' + ['badge-ok','badge-warn','badge-error','badge-stale'][level ?? 3];
}

// ── Connection ────────────────────────────────────────────────────────────────

function connect() {
  const url = document.getElementById('ws-input').value.trim();
  if (!url) return;
  if (ros) ros.close();

  ros = new ROSLIB.Ros({ url });

  ros.on('connection', () => {
    document.getElementById('conn-dot').className = 'connected';
    document.getElementById('conn-label').textContent = url;
    setupSubscriptions();
  });

  ros.on('error', (err) => {
    document.getElementById('conn-dot').className = 'error';
    document.getElementById('conn-label').textContent = 'ERROR: ' + (err?.message || err);
    teardown();
  });

  ros.on('close', () => {
    document.getElementById('conn-dot').className = '';
    document.getElementById('conn-label').textContent = 'Disconnected';
    teardown();
  });
}

function setupSubscriptions() {
  // /diagnostics — throttle 500ms → ~2 Hz
  diagSub = new ROSLIB.Topic({
    ros, name: '/diagnostics',
    messageType: 'diagnostic_msgs/DiagnosticArray',
    throttle_rate: 500,
  });
  diagSub.subscribe(onDiagnostics);

  // /saltybot/balance_state
  balanceSub = new ROSLIB.Topic({
    ros, name: '/saltybot/balance_state',
    messageType: 'std_msgs/String',
    throttle_rate: 500,
  });
  balanceSub.subscribe(onBalanceState);
}

function teardown() {
  if (diagSub)    { diagSub.unsubscribe();    diagSub    = null; }
  if (balanceSub) { balanceSub.unsubscribe(); balanceSub = null; }
  state.overallLevel = 3;
  state.lastUpdate   = null;
  render();
}

// ── Message handlers ──────────────────────────────────────────────────────────

function onDiagnostics(msg) {
  const statuses = msg.status ?? [];
  state.nodes = [];
  let overallLevel = 0;

  for (const status of statuses) {
    const kv = {};
    for (const { key, value } of (status.values ?? [])) {
      kv[key] = value;
    }

    // Battery
    if ('battery_voltage_v'  in kv) state.voltage = numOrNull(kv.battery_voltage_v);
    if ('battery_current_a'  in kv) state.current = numOrNull(kv.battery_current_a);
    if ('battery_soc_pct'    in kv) state.soc     = numOrNull(kv.battery_soc_pct);

    // Temperatures
    if ('cpu_temp_c'         in kv) state.cpuTemp    = numOrNull(kv.cpu_temp_c);
    if ('gpu_temp_c'         in kv) state.gpuTemp    = numOrNull(kv.gpu_temp_c);
    if ('board_temp_c'       in kv) state.boardTemp  = numOrNull(kv.board_temp_c);
    if ('motor_temp_l_c'     in kv) state.motorTempL = numOrNull(kv.motor_temp_l_c);
    if ('motor_temp_r_c'     in kv) state.motorTempR = numOrNull(kv.motor_temp_r_c);

    // Motor current
    if ('motor_current_l_a'  in kv) state.motorCurrentL = numOrNull(kv.motor_current_l_a);
    if ('motor_current_r_a'  in kv) state.motorCurrentR = numOrNull(kv.motor_current_r_a);

    // Resources
    if ('ram_used_mb'        in kv) state.ramUsed   = numOrNull(kv.ram_used_mb);
    if ('ram_total_mb'       in kv) state.ramTotal  = numOrNull(kv.ram_total_mb);
    if ('gpu_used_mb'        in kv) state.gpuUsed   = numOrNull(kv.gpu_used_mb);
    if ('gpu_total_mb'       in kv) state.gpuTotal  = numOrNull(kv.gpu_total_mb);
    if ('disk_used_gb'       in kv) state.diskUsed  = numOrNull(kv.disk_used_gb);
    if ('disk_total_gb'      in kv) state.diskTotal = numOrNull(kv.disk_total_gb);

    // Network
    if ('wifi_rssi_dbm'      in kv) state.rssi     = numOrNull(kv.wifi_rssi_dbm);
    if ('wifi_latency_ms'    in kv) state.latency  = numOrNull(kv.wifi_latency_ms);

    // MQTT
    if ('mqtt_connected'     in kv) state.mqttConnected = kv.mqtt_connected === 'true';

    // Node health
    state.nodes.push({
      name:    status.name || status.hardware_id || 'unknown',
      level:   status.level ?? 3,
      message: status.message || '',
    });

    overallLevel = Math.max(overallLevel, status.level ?? 0);
  }

  state.overallLevel = overallLevel;
  state.lastUpdate   = new Date();

  // Battery history
  if (state.voltage != null) {
    state.battHistory.push({ ts: Date.now(), v: state.voltage });
    if (state.battHistory.length > BATT_HISTORY_MAX) {
      state.battHistory.shift();
    }
  }

  // Derive SOC from voltage if not provided
  if (state.soc == null && state.voltage != null) {
    state.soc = socFromVoltage(state.voltage);
  }

  render();
  flashRefreshDot();
}

function onBalanceState(msg) {
  try {
    const data = JSON.parse(msg.data);
    state.balanceState  = data.state  ?? 'UNKNOWN';
    state.motorCmdL     = data.motor_cmd ?? null;
    state.motorCmdR     = data.motor_cmd ?? null;  // single motor_cmd field
  } catch (_) {}
}

// ── Refresh indicator ─────────────────────────────────────────────────────────

function flashRefreshDot() {
  const dot = document.getElementById('refresh-dot');
  dot.classList.add('pulse');
  setTimeout(() => dot.classList.remove('pulse'), 400);
}

// ── Sparkline canvas ──────────────────────────────────────────────────────────

function drawSparkline() {
  const canvas = document.getElementById('batt-sparkline');
  if (!canvas) return;
  const ctx = canvas.getContext('2d');
  const W = canvas.width = canvas.offsetWidth || 300;
  const H = canvas.height;

  ctx.clearRect(0, 0, W, H);
  ctx.fillStyle = '#0a0a1a';
  ctx.fillRect(0, 0, W, H);

  const data = state.battHistory;
  if (data.length < 2) {
    ctx.fillStyle = '#374151';
    ctx.font = '10px Courier New';
    ctx.textAlign = 'center';
    ctx.fillText('Awaiting battery data…', W / 2, H / 2 + 4);
    return;
  }

  const vMin = LIPO_MIN - 0.2;
  const vMax = LIPO_MAX + 0.2;

  // Grid lines
  ctx.strokeStyle = '#1e3a5f';
  ctx.lineWidth = 0.5;
  [0.25, 0.5, 0.75].forEach((f) => {
    const y = H - f * H;
    ctx.beginPath(); ctx.moveTo(0, y); ctx.lineTo(W, y); ctx.stroke();
  });

  // Plot
  ctx.lineWidth = 1.5;
  ctx.beginPath();
  data.forEach((pt, i) => {
    const x = (i / (data.length - 1)) * W;
    const y = H - ((pt.v - vMin) / (vMax - vMin)) * H;
    i === 0 ? ctx.moveTo(x, y) : ctx.lineTo(x, y);
  });

  const lastV = data[data.length - 1].v;
  ctx.strokeStyle = threshColor(lastV, THRESHOLDS.voltage_warn, THRESHOLDS.voltage_crit, true);
  ctx.stroke();

  // Fill under
  ctx.lineTo(W, H); ctx.lineTo(0, H); ctx.closePath();
  ctx.fillStyle = 'rgba(6,182,212,0.06)';
  ctx.fill();

  // Labels
  ctx.fillStyle = '#374151';
  ctx.font = '9px Courier New';
  ctx.textAlign = 'left';
  ctx.fillText(`${LIPO_MAX}V`, 2, 10);
  ctx.fillText(`${LIPO_MIN}V`, 2, H - 2);
}

// ── Gauge helpers ─────────────────────────────────────────────────────────────

function setGauge(barId, pctVal, color) {
  const el = document.getElementById(barId);
  if (!el) return;
  el.style.width = `${Math.max(0, Math.min(100, pctVal))}%`;
  el.style.background = color;
}

function setText(id, text) {
  const el = document.getElementById(id);
  if (el) el.textContent = text ?? '—';
}

function setColor(id, color) {
  const el = document.getElementById(id);
  if (el) el.style.color = color;
}

function setTempBox(id, tempC, warnT, critT) {
  const box = document.getElementById(id + '-box');
  const val = document.getElementById(id + '-val');
  const bar = document.getElementById(id + '-bar');
  const color = threshColor(tempC, warnT, critT);

  if (val)  { val.textContent = tempC != null ? tempC.toFixed(0) + '°C' : '—'; val.style.color = color; }
  if (bar)  {
    const p = tempC != null ? Math.min(100, (tempC / 100) * 100) : 0;
    bar.style.width = p + '%';
    bar.style.background = color;
  }
  if (box && tempC != null) {
    box.style.borderColor = tempC >= critT ? '#991b1b' : tempC >= warnT ? '#92400e' : '#1e3a5f';
  }
}

// ── RSSI bars ─────────────────────────────────────────────────────────────────

function rssiToLevel(dBm) {
  if (dBm == null) return { label: 'N/A', color: '#374151', bars: 0 };
  if (dBm >= -50)  return { label: 'Excellent', color: '#22c55e', bars: 5 };
  if (dBm >= -60)  return { label: 'Good',      color: '#3b82f6', bars: 4 };
  if (dBm >= -70)  return { label: 'Fair',      color: '#f59e0b', bars: 3 };
  if (dBm >= -80)  return { label: 'Weak',      color: '#ef4444', bars: 2 };
  return             { label: 'Poor',      color: '#7f1d1d', bars: 1 };
}

function drawRssiBars() {
  const container = document.getElementById('rssi-bars');
  if (!container) return;
  const lv = rssiToLevel(state.rssi);
  const BAR_H = [4, 8, 12, 16, 20];

  container.innerHTML = '';
  for (let i = 0; i < 5; i++) {
    const bar = document.createElement('div');
    bar.className = 'rssi-bar';
    bar.style.height = BAR_H[i] + 'px';
    bar.style.width  = '7px';
    bar.style.background = i < lv.bars ? lv.color : '#1f2937';
    container.appendChild(bar);
  }
}

// ── Node list renderer ────────────────────────────────────────────────────────

function renderNodes() {
  const container = document.getElementById('node-list');
  if (!container) return;

  if (state.nodes.length === 0) {
    container.innerHTML = '<div style="color:#374151;font-size:10px;text-align:center;padding:8px">No /diagnostics data yet</div>';
    return;
  }

  container.innerHTML = state.nodes.map((n) => `
    <div class="node-row">
      <span class="node-name">${n.name}</span>
      <div style="display:flex;align-items:center;gap:6px">
        ${n.message ? `<span style="color:#4b5563;font-size:9px;max-width:120px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap" title="${n.message}">${n.message}</span>` : ''}
        <span class="node-status ${levelClass(n.level)}">${levelLabel(n.level)}</span>
      </div>
    </div>
  `).join('');
}

// ── Overall status bar ────────────────────────────────────────────────────────

function updateStatusBar() {
  const lvl = state.overallLevel;
  const badge = document.getElementById('system-badge');
  const labels = ['HEALTHY', 'DEGRADED', 'FAULT', 'STALE'];
  if (badge) {
    badge.textContent = labels[lvl] ?? 'STALE';
    setBadgeClass(badge, lvl);
  }

  // Individual badges
  updateBattBadge();
  updateTempBadge();
  updateNetBadge();

  const upd = document.getElementById('last-update');
  if (upd && state.lastUpdate) {
    upd.textContent = 'Updated ' + state.lastUpdate.toLocaleTimeString();
  }
}

function updateBattBadge() {
  const el = document.getElementById('batt-badge');
  if (!el) return;
  const v = state.voltage;
  if (v == null)             { el.textContent = 'NO DATA'; setBadgeClass(el, 3); return; }
  if (v <= THRESHOLDS.voltage_crit) { el.textContent = 'CRITICAL'; setBadgeClass(el, 2); }
  else if (v <= THRESHOLDS.voltage_warn) { el.textContent = 'LOW'; setBadgeClass(el, 1); }
  else                       { el.textContent = 'OK'; setBadgeClass(el, 0); }
}

function updateTempBadge() {
  const el = document.getElementById('temp-badge');
  if (!el) return;
  const temps = [state.cpuTemp, state.gpuTemp, state.motorTempL, state.motorTempR].filter(t => t != null);
  if (temps.length === 0)    { el.textContent = 'NO DATA'; setBadgeClass(el, 3); return; }
  const max = Math.max(...temps);
  if (max >= THRESHOLDS.cpu_temp_crit) { el.textContent = 'CRITICAL'; setBadgeClass(el, 2); }
  else if (max >= THRESHOLDS.cpu_temp_warn) { el.textContent = 'HOT'; setBadgeClass(el, 1); }
  else                       { el.textContent = 'OK'; setBadgeClass(el, 0); }
}

function updateNetBadge() {
  const el = document.getElementById('net-badge');
  if (!el) return;
  const r = state.rssi;
  if (r == null)                   { el.textContent = 'NO DATA'; setBadgeClass(el, 3); return; }
  if (r <= THRESHOLDS.rssi_crit)   { el.textContent = 'POOR'; setBadgeClass(el, 2); }
  else if (r <= THRESHOLDS.rssi_warn) { el.textContent = 'WEAK'; setBadgeClass(el, 1); }
  else                             { el.textContent = 'OK'; setBadgeClass(el, 0); }
}

// ── Main render ───────────────────────────────────────────────────────────────

function render() {
  // ── Battery ──
  const v    = state.voltage;
  const soc  = state.soc ?? socFromVoltage(v);
  const vColor = threshColor(v, THRESHOLDS.voltage_warn, THRESHOLDS.voltage_crit, true);
  const sColor = threshColor(soc, THRESHOLDS.soc_warn, THRESHOLDS.soc_crit, true);

  setText('batt-voltage', v != null ? v.toFixed(2) + ' V' : '—');
  setColor('batt-voltage', vColor);
  setText('batt-soc', soc != null ? soc.toFixed(0) + ' %' : '—');
  setColor('batt-soc', sColor);
  setText('batt-current', state.current != null ? state.current.toFixed(2) + ' A' : '—');

  setGauge('batt-soc-bar', soc ?? 0, sColor);
  setGauge('batt-volt-bar', v != null ? ((v - LIPO_MIN) / (LIPO_MAX - LIPO_MIN)) * 100 : 0, vColor);

  drawSparkline();

  // ── Temperatures ──
  setTempBox('cpu-temp', state.cpuTemp, THRESHOLDS.cpu_temp_warn, THRESHOLDS.cpu_temp_crit);
  setTempBox('gpu-temp', state.gpuTemp, THRESHOLDS.gpu_temp_warn, THRESHOLDS.gpu_temp_crit);
  setTempBox('board-temp', state.boardTemp, 60, 80);
  setTempBox('motor-temp-l', state.motorTempL, THRESHOLDS.motor_temp_warn, THRESHOLDS.motor_temp_crit);
  setTempBox('motor-temp-r', state.motorTempR, THRESHOLDS.motor_temp_warn, THRESHOLDS.motor_temp_crit);

  // ── Motor current ──
  const curL = state.motorCurrentL;
  const curR = state.motorCurrentR;
  const curColorL = threshColor(curL, THRESHOLDS.current_warn, THRESHOLDS.current_crit);
  const curColorR = threshColor(curR, THRESHOLDS.current_warn, THRESHOLDS.current_crit);

  setText('motor-cur-l', curL != null ? curL.toFixed(2) + ' A' : '—');
  setColor('motor-cur-l', curColorL);
  setText('motor-cur-r', curR != null ? curR.toFixed(2) + ' A' : '—');
  setColor('motor-cur-r', curColorR);
  setGauge('motor-bar-l', curL != null ? (curL / THRESHOLDS.current_crit) * 100 : 0, curColorL);
  setGauge('motor-bar-r', curR != null ? (curR / THRESHOLDS.current_crit) * 100 : 0, curColorR);
  setText('motor-cmd-l', state.motorCmdL != null ? state.motorCmdL.toString() : '—');
  setText('motor-cmd-r', state.motorCmdR != null ? state.motorCmdR.toString() : '—');
  setText('balance-state', state.balanceState);

  // ── Resources ──
  const ramPct  = pct(state.ramUsed,  state.ramTotal);
  const gpuPct  = pct(state.gpuUsed,  state.gpuTotal);
  const diskPct = pct(state.diskUsed, state.diskTotal);

  setText('ram-val',
    state.ramUsed != null ? `${state.ramUsed.toFixed(0)} / ${state.ramTotal?.toFixed(0) ?? '?'} MB` : '—');
  setGauge('ram-bar', ramPct, threshColor(ramPct, THRESHOLDS.ram_pct_warn, THRESHOLDS.ram_pct_crit));

  setText('gpu-val',
    state.gpuUsed != null ? `${state.gpuUsed.toFixed(0)} / ${state.gpuTotal?.toFixed(0) ?? '?'} MB` : '—');
  setGauge('gpu-bar', gpuPct, threshColor(gpuPct, 70, 90));

  setText('disk-val',
    state.diskUsed != null ? `${state.diskUsed.toFixed(1)} / ${state.diskTotal?.toFixed(1) ?? '?'} GB` : '—');
  setGauge('disk-bar', diskPct, threshColor(diskPct, THRESHOLDS.disk_pct_warn, THRESHOLDS.disk_pct_crit));

  // ── WiFi ──
  const rLevel = rssiToLevel(state.rssi);
  setText('rssi-val', state.rssi != null ? state.rssi + ' dBm' : '—');
  setColor('rssi-val', rLevel.color);
  setText('rssi-label', rLevel.label);
  setColor('rssi-label', rLevel.color);
  setText('latency-val', state.latency != null ? state.latency.toFixed(0) + ' ms' : '—');
  setColor('latency-val', threshColor(state.latency, THRESHOLDS.latency_warn, THRESHOLDS.latency_crit));
  drawRssiBars();

  // ── MQTT ──
  const mqttDot = document.getElementById('mqtt-dot');
  const mqttLbl = document.getElementById('mqtt-label');
  if (mqttDot) {
    mqttDot.className = 'mqtt-dot ' + (state.mqttConnected ? 'connected' : 'disconnected');
  }
  if (mqttLbl) {
    mqttLbl.textContent = state.mqttConnected === null ? 'No data'
      : state.mqttConnected ? 'Broker connected'
      : 'Broker disconnected';
    mqttLbl.style.color = state.mqttConnected ? '#4ade80' : '#f87171';
  }

  // ── Nodes ──
  renderNodes();

  // ── Status bar ──
  updateStatusBar();
}

// ── Init ──────────────────────────────────────────────────────────────────────

document.getElementById('btn-connect').addEventListener('click', connect);
document.getElementById('ws-input').addEventListener('keydown', (e) => {
  if (e.key === 'Enter') connect();
});

const stored = localStorage.getItem('diag_ws_url');
if (stored) document.getElementById('ws-input').value = stored;
document.getElementById('ws-input').addEventListener('change', (e) => {
  localStorage.setItem('diag_ws_url', e.target.value);
});

// Initial render (blank state)
render();

// Periodic sparkline resize + redraw on window resize
window.addEventListener('resize', drawSparkline);