import '../../dji_service.dart';
import '../hud_features.dart';
import '../product_profile.dart';
import '../state/key_state.dart';
import '../state/parse.dart';
import 'settings_spec.dart';

/// The settings sheet's tabs (plan P6, GO 4's MC / Vision / RC / HD / Battery /
/// Gimbal / General). Each row is one spec bound to a KeyManager key; rows
/// whose key the aircraft does not support hide themselves, so the same list
/// serves every product.
///
/// Out of scope here, with no public MSDK V4 endpoint (see the matrix): gain &
/// expo, max descent speed, the RC speed bar, RC type / factory reset.
abstract final class SettingsKeys {
  // Flight controller
  static const DjiKey goHomeHeight = DjiKey.flightController('GO_HOME_HEIGHT_IN_METERS');
  static const DjiKey smartRth = DjiKey.flightController('SMART_RETURN_TO_HOME_ENABLED');
  static const DjiKey failSafe = DjiKey.flightController('CONNECTION_FAIL_SAFE_BEHAVIOR');
  static const DjiKey maxHeight = DjiKey.flightController('MAX_FLIGHT_HEIGHT');
  static const DjiKey maxHeightRange = DjiKey.flightController('MAX_FLIGHT_HEIGHT_RANGE');
  static const DjiKey maxRadiusEnabled = DjiKey.flightController('MAX_FLIGHT_RADIUS_ENABLED');
  static const DjiKey maxRadius = DjiKey.flightController('MAX_FLIGHT_RADIUS');
  static const DjiKey maxRadiusRange = DjiKey.flightController('MAX_FLIGHT_RADIUS_RANGE');
  static const DjiKey novice = DjiKey.flightController('NOVICE_MODE_ENABLED');
  static const DjiKey multiMode = DjiKey.flightController('MULTI_MODE_OPEN');
  static const DjiKey leds = DjiKey.flightController('LEDS_ENABLED_SETTINGS');
  static const DjiKey escBeep = DjiKey.flightController('ESC_BEEPING_ENABLED');
  static const DjiKey imuCount = DjiKey.flightController('IMU_COUNT');
  static const DjiKey compassCount = DjiKey.flightController('COMPASS_COUNT');
  static const DjiKey lowBattery = DjiKey.flightController('LOW_BATTERY_WARNING_THRESHOLD');
  static const DjiKey criticalBattery = DjiKey.flightController('SERIOUS_LOW_BATTERY_WARNING_THRESHOLD');
  static const DjiKey fcSerial = DjiKey.flightController('SERIAL_NUMBER');

  // Flight assistant (vision)
  static const DjiKey collision = DjiKey.flightAssistant('COLLISION_AVOIDANCE_ENABLED');
  static const DjiKey activeAvoidance = DjiKey.flightAssistant('ACTIVE_OBSTACLE_AVOIDANCE_ENABLED');
  static const DjiKey upwardAvoidance = DjiKey.flightAssistant('UPWARDS_AVOIDANCE_ENABLED');
  static const DjiKey apas = DjiKey.flightAssistant('IS_ADVANCED_PILOT_ASSISTANT_SYSTEM_ENABLED');
  static const DjiKey rthAvoidance = DjiKey.flightAssistant('RTH_OBSTACLE_AVOIDANCE_ENABLED');
  static const DjiKey rthRemoteAvoidance = DjiKey.flightAssistant('RTH_REMOTE_OBSTACLE_AVOIDANCE_ENABLED');
  static const DjiKey vps = DjiKey.flightAssistant('VISION_ASSISTED_POSITIONING_ENABLED');
  static const DjiKey landingProtection = DjiKey.flightAssistant('LANDING_PROTECTION_ENABLED');
  static const DjiKey precisionLanding = DjiKey.flightAssistant('PRECISION_LANDING_ENABLED');
  static const DjiKey bottomLight = DjiKey.flightAssistant('BOTTOM_AUXILIARY_LIGHT_MODE');
  static const DjiKey gestureMode = DjiKey.flightAssistant('ACTIVE_TRACK_GESTURE_MODE_ENABLED');
  static const DjiKey palmControl = DjiKey.flightAssistant('ADVANCED_GESTURE_CONTROL_ENABLED');

  // Remote controller
  static const DjiKey stickMode = DjiKey.remoteController('AIRCRAFT_MAPPING_STYLE');
  static const DjiKey chargeMobile = DjiKey.remoteController('CHARGE_MOBILE_MODE');
  static const DjiKey gimbalDialSpeed = DjiKey.remoteController('GIMBAL_CONTROL_SPEED_COEFFICIENT');
  static const DjiKey pairingState = DjiKey.remoteController('PAIRING_STATE');
  static const DjiKey startPairing = DjiKey.remoteController('START_PAIRING');
  static const DjiKey stopPairing = DjiKey.remoteController('STOP_PAIRING');
  static const DjiKey rcName = DjiKey.remoteController('DISPLAY_NAME');
  static const DjiKey rcSerial = DjiKey.remoteController('SERIAL_NUMBER');
  static const DjiKey rcFirmware = DjiKey.remoteController('FIRMWARE_VERSION');

  // Image transmission
  static const DjiKey uplink = DjiKey.airLink('UPLINK_SIGNAL_QUALITY');
  static const DjiKey downlink = DjiKey.airLink('DOWNLINK_SIGNAL_QUALITY');
  static const DjiKey osChannelMode = DjiKey.ocuSync('CHANNEL_SELECTION_MODE');
  static const DjiKey osBand = DjiKey.ocuSync('OCUSYNC_FREQUENCY_BAND');
  static const DjiKey osBands = DjiKey.ocuSync('OCUSYNC_SUPPORTED_FREQUENCY_BANDS');
  static const DjiKey osBandwidth = DjiKey.ocuSync('BANDWIDTH');
  static const DjiKey osChannel = DjiKey.ocuSync('FREQUENCY_POINT_INDEX');
  static const DjiKey osChannelRange = DjiKey.ocuSync('FREQUENCY_POINT_INDEX_VALID_RANGE');
  static const DjiKey osDataRate = DjiKey.ocuSync('DYNAMIC_DATA_RATE');
  static const DjiKey lbChannelMode = DjiKey.lightbridge('CHANNEL_SELECTION_MODE');
  static const DjiKey lbBand = DjiKey.lightbridge('LB_FREQUENCY_BAND');
  static const DjiKey lbBands = DjiKey.lightbridge('LB_SUPPORTED_FREQUENCY_BANDS');
  static const DjiKey lbChannel = DjiKey.lightbridge('LB_CHANNEL');
  static const DjiKey lbChannelRange = DjiKey.lightbridge('CHANNEL_RANGE');
  static const DjiKey lbDataRate = DjiKey.lightbridge('LB_DATA_RATE');
  static const DjiKey wifiSsid = DjiKey.wifi('SSID');
  static const DjiKey wifiBand = DjiKey.wifi('WIFI_FREQUENCY_BAND');
  static const DjiKey wifiChannel = DjiKey.wifi('CHANNEL_NUMBER');

  // Product
  static const DjiKey firmwarePackage = DjiKey.product('FIRMWARE_PACKAGE_VERSION');

  // Battery (per index)
  static DjiKey battery(String key, int i) => DjiKey.battery(key, index: i);
}

abstract final class SettingsTabs {
  static const String safety = 'safety';
  static const String vision = 'vision';
  static const String rc = 'rc';
  static const String transmission = 'transmission';
  static const String battery = 'battery';
  static const String gimbal = 'gimbal';
  static const String general = 'general';

  /// Custom row ids the sheet draws itself.
  static const String homePoint = 'homePoint';
  static const String leds = 'leds';
  static const String sensors = 'sensors';
  static const String stickDiagram = 'stickDiagram';
  static const String gimbalList = 'gimbalList';
  static const String showRoute = 'showRoute';
  static const String radarChart = 'radarChart';
  static const String stickPads = 'stickPads';
  static const String airSenseList = 'airSenseList';
  static const String sensingDistances = 'sensingDistances';
  static const String flyZoneList = 'flyZoneList';
  static const String flyZoneLicences = 'flyZoneLicences';
  static const String flyZoneDatabase = 'flyZoneDatabase';
  static const String clearRoute = 'clearRoute';
  static const String about = 'about';
  static const String developer = 'developer';

  static bool _isOn(KeyState s, DjiKey k) => asBool(s.value(k)) == true;
  static bool _manual(KeyState s, DjiKey k) => asString(s.value(k)) == 'MANUAL';

  static const List<(String, String)> _channelModes = <(String, String)>[('AUTO', 'Auto'), ('MANUAL', 'Custom')];

  /// The tabs for [p]; battery groups repeat per battery.
  static List<SettingsTab> all(ProductProfile p) => <SettingsTab>[
        SettingsTab(id: safety, label: 'Safety', icon: 'shield', rows: _safety),
        SettingsTab(id: vision, label: 'Vision', icon: 'obstacle', requires: HudFeatures.settingsVision, rows: _vision),
        SettingsTab(id: rc, label: 'Remote', icon: 'rc', rows: _rc),
        SettingsTab(id: transmission, label: 'Video link', icon: 'radio', rows: _transmission),
        SettingsTab(id: battery, label: 'Battery', icon: 'battery', rows: _battery(p)),
        SettingsTab(
          id: gimbal,
          label: 'Gimbal',
          icon: 'gimbal',
          requires: HudFeatures.gimbalSettings,
          rows: const <SettingSpec>[CustomSpec(id: gimbalList)],
        ),
        SettingsTab(id: general, label: 'General', icon: 'settings', rows: _general),
      ];

  // ── Safety / MC ─────────────────────────────────────────────────────────────
  static final List<SettingSpec> _safety = <SettingSpec>[
    const GroupSpec('RETURN TO HOME'),
    const CustomSpec(id: homePoint),
    const KeyNumberSpec(
      id: 'rthAltitude',
      label: 'RTH altitude',
      key: SettingsKeys.goHomeHeight,
      min: 20,
      max: 500,
      step: 10,
      unit: 'm',
      feet: true,
    ),
    const KeySwitchSpec(
      id: 'smartRth',
      label: 'Smart RTH',
      hint: 'Return home on its own when the battery only just covers the way back',
      key: SettingsKeys.smartRth,
    ),
    const KeyChoiceSpec(
      id: 'failSafe',
      label: 'RC signal lost',
      key: SettingsKeys.failSafe,
      options: <(String, String)>[('HOVER', 'Hover'), ('LANDING', 'Land'), ('GO_HOME', 'Return home')],
    ),
    const GroupSpec('LIMITS'),
    const KeyNumberSpec(
      id: 'maxAltitude',
      label: 'Max altitude',
      key: SettingsKeys.maxHeight,
      rangeKey: SettingsKeys.maxHeightRange,
      min: 20,
      max: 500,
      step: 10,
      unit: 'm',
      feet: true,
    ),
    const KeySwitchSpec(id: 'distanceLimit', label: 'Distance limit', key: SettingsKeys.maxRadiusEnabled),
    KeyNumberSpec(
      id: 'maxDistance',
      label: 'Max distance',
      key: SettingsKeys.maxRadius,
      rangeKey: SettingsKeys.maxRadiusRange,
      min: 15,
      max: 8000,
      step: 50,
      unit: 'm',
      feet: true,
      visibleWhen: (SettingsContext c) => _isOn(c.keys, SettingsKeys.maxRadiusEnabled),
    ),
    const KeySwitchSpec(
      id: 'beginner',
      label: 'Beginner mode',
      hint: 'Slow, and held within 30 m of home',
      key: SettingsKeys.novice,
      groundOnly: true,
    ),
    const GroupSpec('FLIGHT'),
    const KeySwitchSpec(
      id: 'multiMode',
      label: 'Multiple flight modes',
      hint: 'Lets the RC switch reach Sport / Atti / Tripod',
      key: SettingsKeys.multiMode,
    ),
    const CustomSpec(id: leds, keys: <DjiKey>[SettingsKeys.leds]),
    const KeySwitchSpec(id: 'escBeep', label: 'ESC beeping', key: SettingsKeys.escBeep),
    const GroupSpec('SENSORS'),
    const CustomSpec(id: sensors, keys: <DjiKey>[SettingsKeys.imuCount, SettingsKeys.compassCount]),
    GroupSpec('AIRSENSE', requires: HudFeatures.airSense),
    CustomSpec(id: airSenseList, requires: HudFeatures.airSense),
    GroupSpec('FLY ZONES', requires: HudFeatures.flyZones),
    CustomSpec(id: flyZoneList, requires: HudFeatures.flyZones),
    CustomSpec(id: flyZoneLicences, requires: HudFeatures.flyZones),
    CustomSpec(id: flyZoneDatabase, requires: HudFeatures.flyZones),
  ];

  // ── Vision ──────────────────────────────────────────────────────────────────
  static final List<SettingSpec> _vision = <SettingSpec>[
    GroupSpec('OBSTACLE AVOIDANCE', requires: HudFeatures.settingsObstacle),
    CustomSpec(id: radarChart, requires: HudFeatures.visionRadar),
    KeySwitchSpec(
      id: 'collision',
      label: 'Obstacle avoidance',
      key: SettingsKeys.collision,
      requires: HudFeatures.settingsObstacle,
    ),
    KeySwitchSpec(
      id: 'activeAvoidance',
      label: 'Active obstacle avoidance',
      hint: 'Back away from obstacles that approach the aircraft',
      key: SettingsKeys.activeAvoidance,
      requires: HudFeatures.settingsObstacle,
    ),
    KeySwitchSpec(
      id: 'upwardAvoidance',
      label: 'Upward obstacle avoidance',
      key: SettingsKeys.upwardAvoidance,
      requires: HudFeatures.settingsObstacle,
    ),
    KeySwitchSpec(
      id: 'apas',
      label: 'APAS',
      hint: 'Fly around obstacles instead of braking',
      key: SettingsKeys.apas,
      requires: HudFeatures.settingsObstacle,
    ),
    KeySwitchSpec(
      id: 'rthAvoidance',
      label: 'RTH obstacle check',
      key: SettingsKeys.rthAvoidance,
      requires: HudFeatures.settingsObstacle,
    ),
    KeySwitchSpec(
      id: 'rthRemoteAvoidance',
      label: 'RTH remote obstacle check',
      key: SettingsKeys.rthRemoteAvoidance,
      requires: HudFeatures.settingsObstacle,
    ),
    CustomSpec(id: sensingDistances, requires: HudFeatures.settingsObstacle),
    const GroupSpec('POSITIONING & LANDING'),
    const KeySwitchSpec(id: 'vps', label: 'Vision positioning', key: SettingsKeys.vps),
    const KeySwitchSpec(
      id: 'landingProtection',
      label: 'Landing protection',
      hint: 'Checks the ground before landing',
      key: SettingsKeys.landingProtection,
    ),
    const KeySwitchSpec(
      id: 'precisionLanding',
      label: 'Precision landing',
      hint: 'RTH lands on the recorded take-off spot',
      key: SettingsKeys.precisionLanding,
    ),
    const KeyChoiceSpec(
      id: 'bottomLight',
      label: 'Bottom auxiliary light',
      key: SettingsKeys.bottomLight,
      options: <(String, String)>[('AUTO', 'Auto'), ('ON', 'On'), ('OFF', 'Off')],
    ),
    // Rows hide on aircraft whose flight assistant does not support the key.
    GroupSpec('GESTURES', requires: HudFeatures.settingsGestures),
    KeySwitchSpec(
      id: 'gestureMode',
      label: 'Gesture mode',
      hint: 'Raise your arms to be tracked; make a frame with your fingers for a photo',
      key: SettingsKeys.gestureMode,
      requires: HudFeatures.settingsGestures,
    ),
    KeySwitchSpec(
      id: 'palmControl',
      label: 'Palm control',
      hint: 'Guide the aircraft with your palm, a couple of metres away',
      key: SettingsKeys.palmControl,
      requires: HudFeatures.settingsGestures,
    ),
  ];

  // ── Remote controller ───────────────────────────────────────────────────────
  static final List<SettingSpec> _rc = <SettingSpec>[
    const GroupSpec('STICKS'),
    const KeyChoiceSpec(
      id: 'stickMode',
      label: 'Stick mode',
      key: SettingsKeys.stickMode,
      options: <(String, String)>[('STYLE_1', 'Mode 1'), ('STYLE_2', 'Mode 2'), ('STYLE_3', 'Mode 3')],
      groundOnly: true,
    ),
    const CustomSpec(id: stickDiagram, keys: <DjiKey>[SettingsKeys.stickMode]),
    const KeyNumberSpec(
      id: 'gimbalDialSpeed',
      label: 'Gimbal dial speed',
      key: SettingsKeys.gimbalDialSpeed,
      min: 0,
      max: 100,
      step: 5,
    ),
    const GroupSpec('CONTROLLER'),
    const KeyChoiceSpec(
      id: 'chargeMobile',
      label: 'Charge mobile device',
      key: SettingsKeys.chargeMobile,
      options: <(String, String)>[('NEVER', 'Never'), ('INTELLIGENT', 'Smart'), ('ALWAYS', 'Always')],
    ),
    const KeyReadoutSpec(id: 'pairingState', label: 'Linking', key: SettingsKeys.pairingState),
    KeyActionSpec(
      id: 'startPairing',
      label: 'Link remote controller',
      hint: 'Then press the link button on the aircraft',
      key: SettingsKeys.startPairing,
      button: 'Link',
      groundOnly: true,
      confirmTitle: 'Link remote controller',
      confirmText: 'The current link drops until the aircraft is linked again. '
          'After sliding, press the aircraft\'s link button.',
      visibleWhen: (SettingsContext c) => asString(c.keys.value(SettingsKeys.pairingState)) != 'PAIRING',
    ),
    KeyActionSpec(
      id: 'stopPairing',
      label: 'Linking…',
      key: SettingsKeys.stopPairing,
      button: 'Stop',
      visibleWhen: (SettingsContext c) => asString(c.keys.value(SettingsKeys.pairingState)) == 'PAIRING',
    ),
    const KeyReadoutSpec(id: 'rcName', label: 'Name', key: SettingsKeys.rcName),
    const KeyReadoutSpec(id: 'rcSerial', label: 'Serial number', key: SettingsKeys.rcSerial),
    const KeyReadoutSpec(id: 'rcFirmware', label: 'Firmware', key: SettingsKeys.rcFirmware),
  ];

  // ── Image transmission ──────────────────────────────────────────────────────
  static final List<SettingSpec> _transmission = <SettingSpec>[
    const KeyReadoutSpec(id: 'uplink', label: 'Control signal', key: SettingsKeys.uplink, format: _percent),
    const KeyReadoutSpec(id: 'downlink', label: 'Video signal', key: SettingsKeys.downlink, format: _percent),
    // OcuSync
    GroupSpec('OCUSYNC', requires: HudFeatures.linkOcuSync),
    KeyReadoutSpec(id: 'osDataRate', label: 'Video bitrate', key: SettingsKeys.osDataRate, format: _mbps, requires: HudFeatures.linkOcuSync),
    KeyChoiceSpec(
      id: 'osChannelMode',
      label: 'Channel mode',
      key: SettingsKeys.osChannelMode,
      options: _channelModes,
      requires: HudFeatures.linkOcuSync,
    ),
    KeyChoiceSpec(
      id: 'osBand',
      label: 'Frequency band',
      key: SettingsKeys.osBand,
      supportedKey: SettingsKeys.osBands,
      options: const <(String, String)>[
        ('FREQUENCY_BAND_DUAL', 'Dual'),
        ('FREQUENCY_BAND_2_DOT_4_GHZ', '2.4 GHz'),
        ('FREQUENCY_BAND_5_DOT_8_GHZ', '5.8 GHz'),
        ('FREQUENCY_BAND_5_DOT_7_GHZ', '5.7 GHz'),
      ],
      requires: HudFeatures.linkOcuSync,
    ),
    KeyChoiceSpec(
      id: 'osBandwidth',
      label: 'Bandwidth',
      key: SettingsKeys.osBandwidth,
      options: const <(String, String)>[('Bandwidth10MHz', '10 MHz'), ('Bandwidth20MHz', '20 MHz'), ('Bandwidth40MHZ', '40 MHz')],
      requires: HudFeatures.linkOcuSync,
      visibleWhen: (SettingsContext c) => _manual(c.keys, SettingsKeys.osChannelMode),
    ),
    KeyNumberSpec(
      id: 'osChannel',
      label: 'Channel',
      key: SettingsKeys.osChannel,
      rangeKey: SettingsKeys.osChannelRange,
      min: 0,
      max: 100,
      requires: HudFeatures.linkOcuSync,
      visibleWhen: (SettingsContext c) => _manual(c.keys, SettingsKeys.osChannelMode),
    ),
    // Lightbridge
    GroupSpec('LIGHTBRIDGE', requires: HudFeatures.linkLightbridge),
    KeyChoiceSpec(
      id: 'lbChannelMode',
      label: 'Channel mode',
      key: SettingsKeys.lbChannelMode,
      options: _channelModes,
      requires: HudFeatures.linkLightbridge,
    ),
    KeyChoiceSpec(
      id: 'lbBand',
      label: 'Frequency band',
      key: SettingsKeys.lbBand,
      supportedKey: SettingsKeys.lbBands,
      options: const <(String, String)>[
        ('FREQUENCY_BAND_2_DOT_4_GHZ', '2.4 GHz'),
        ('FREQUENCY_BAND_5_DOT_8_GHZ', '5.8 GHz'),
        ('FREQUENCY_BAND_5_DOT_7_GHZ', '5.7 GHz'),
      ],
      requires: HudFeatures.linkLightbridge,
    ),
    KeyNumberSpec(
      id: 'lbChannel',
      label: 'Channel',
      key: SettingsKeys.lbChannel,
      rangeKey: SettingsKeys.lbChannelRange,
      min: 0,
      max: 40,
      requires: HudFeatures.linkLightbridge,
      visibleWhen: (SettingsContext c) => _manual(c.keys, SettingsKeys.lbChannelMode),
    ),
    KeyChoiceSpec(
      id: 'lbDataRate',
      label: 'Video bitrate',
      key: SettingsKeys.lbDataRate,
      options: const <(String, String)>[
        ('BANDWIDTH_4_MBPS', '4 Mbps'),
        ('BANDWIDTH_6_MBPS', '6 Mbps'),
        ('BANDWIDTH_8_MBPS', '8 Mbps'),
        ('BANDWIDTH_10_MBPS', '10 Mbps'),
      ],
      requires: HudFeatures.linkLightbridge,
    ),
    // Wi-Fi
    GroupSpec('WI-FI', requires: HudFeatures.linkWifi),
    KeyReadoutSpec(id: 'wifiSsid', label: 'Network', key: SettingsKeys.wifiSsid, requires: HudFeatures.linkWifi),
    KeyChoiceSpec(
      id: 'wifiBand',
      label: 'Frequency band',
      key: SettingsKeys.wifiBand,
      options: const <(String, String)>[
        ('FREQUENCY_BAND_2_DOT_4_GHZ', '2.4 GHz'),
        ('FREQUENCY_BAND_5_GHZ', '5 GHz'),
        ('FREQUENCY_BAND_DUAL', 'Dual'),
      ],
      requires: HudFeatures.linkWifi,
      // 2.4-only hardware reports ONLY_2_DOT_4: nothing to choose.
      visibleWhen: (SettingsContext c) => asString(c.keys.value(SettingsKeys.wifiBand)) != 'FREQUENCY_BAND_ONLY_2_DOT_4',
    ),
    KeyReadoutSpec(id: 'wifiChannel', label: 'Channel', key: SettingsKeys.wifiChannel, requires: HudFeatures.linkWifi),
  ];

  // ── Battery ─────────────────────────────────────────────────────────────────
  static List<SettingSpec> _battery(ProductProfile p) {
    final int n = p.batteryCount.clamp(1, 6);
    return <SettingSpec>[
      const GroupSpec('WARNINGS'),
      KeyNumberSpec(
        id: 'lowBattery',
        label: 'Low battery warning',
        key: SettingsKeys.lowBattery,
        min: 15,
        max: 50,
        unit: '%',
        bounds: (KeyState s, int lo, int hi) {
          final int? critical = asInt(s.value(SettingsKeys.criticalBattery));
          return (critical == null ? lo : (critical + 5).clamp(lo, hi), hi);
        },
      ),
      KeyNumberSpec(
        id: 'criticalBattery',
        label: 'Critical battery warning',
        hint: 'The aircraft lands on its own at this level',
        key: SettingsKeys.criticalBattery,
        min: 10,
        max: 45,
        unit: '%',
        bounds: (KeyState s, int lo, int hi) {
          final int? low = asInt(s.value(SettingsKeys.lowBattery));
          return (lo, low == null ? hi : (low - 5).clamp(lo, hi));
        },
      ),
      for (int i = 0; i < n; i++) ..._batteryRows(i, n),
    ];
  }

  static List<SettingSpec> _batteryRows(int i, int n) {
    DjiKey k(String key) => SettingsKeys.battery(key, i);
    return <SettingSpec>[
      GroupSpec(n == 1 ? 'BATTERY' : 'BATTERY ${i + 1}'),
      KeyReadoutSpec(id: 'cells$i', label: 'Cell voltages', key: k('CELL_VOLTAGES'), format: formatCells),
      KeyReadoutSpec(id: 'temperature$i', label: 'Temperature', key: k('TEMPERATURE'), format: _celsius),
      KeyReadoutSpec(id: 'discharges$i', label: 'Charge cycles', key: k('NUMBER_OF_DISCHARGES')),
      KeyReadoutSpec(id: 'capacity$i', label: 'Full charge capacity', key: k('FULL_CHARGE_CAPACITY'), format: _mah),
      KeyReadoutSpec(id: 'lifetime$i', label: 'Battery life', key: k('LIFETIME_REMAINING'), format: _percent),
      KeyNumberSpec(
        id: 'selfDischarge$i',
        label: 'Self-discharge after',
        hint: 'Storage: the battery drains to ~60 % after this many idle days',
        key: k('SELF_DISCHARGE_IN_DAYS'),
        min: 1,
        max: 10,
        unit: 'd',
      ),
      KeyReadoutSpec(id: 'batterySerial$i', label: 'Serial number', key: k('SERIAL_NUMBER')),
      KeyReadoutSpec(id: 'batteryFirmware$i', label: 'Firmware', key: k('FIRMWARE_VERSION')),
    ];
  }

  // ── General ─────────────────────────────────────────────────────────────────
  static final List<SettingSpec> _general = <SettingSpec>[
    const GroupSpec('MAP'),
    const CustomSpec(id: showRoute),
    const CustomSpec(id: clearRoute),
    GroupSpec('ON-SCREEN STICKS', requires: HudFeatures.virtualSticks),
    CustomSpec(id: stickPads, requires: HudFeatures.virtualSticks),
    const GroupSpec('ABOUT'),
    const CustomSpec(id: about, keys: <DjiKey>[SettingsKeys.firmwarePackage, SettingsKeys.fcSerial]),
    const GroupSpec('DEVELOPER'),
    const CustomSpec(id: developer),
  ];

  static String _percent(Object? v) => v is num ? '${v.round()} %' : formatValue(v);
  static String _mbps(Object? v) => v is num ? '${v.toStringAsFixed(1)} Mbps' : formatValue(v);
  static String _celsius(Object? v) => v is num ? '${v.toStringAsFixed(1)} °C' : formatValue(v);
  static String _mah(Object? v) => v is num ? '${v.round()} mAh' : formatValue(v);
}