import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../bluetooth/bt_poller.dart';
import '../logging/app_log.dart';
import '../models/sensor_defs.dart';
import '../protocol/kpro_parser.dart';
import '../protocol/s300_parser.dart';
import '../protocol/sensor_state.dart';
import 'bt_provider.dart';
import 'settings_provider.dart';

// NEG8 is only an 8-bit checksum, so roughly 1 in 256 corrupted frames can
// still pass validation — rare, but enough to occasionally show an
// impossible value: a single flipped bit in the high byte of a 16-bit field
// can jump it into the tens of thousands. Clamp just the fields where that's
// possible (multi-byte reads whose units genuinely match sensorDefs — RPM,
// VSS, MAP, INJ) to their realistic range, the same bounds the dashboard's
// gauges already use for normalization. Single-byte fields (TPS, gear, ECT/
// IAT, etc.) are already bounded to 0-255 raw by construction and can't
// produce this kind of runaway spike, so they're left alone here.
SensorState _clampToRealisticRange(SensorState s) {
  double clampFor(String id, double value) {
    final def = sensorDefs.firstWhere((d) => d.id == id);
    return value.clamp(def.min, def.max);
  }

  return s.copyWith(
    rpm: clampFor('rpm', s.rpm),
    vss: clampFor('vss', s.vss),
    map: clampFor('map', s.map),
    inj: clampFor('inj', s.inj),
  );
}

/// Counts of what sensorStateProvider actually did with each frame it saw,
/// exposed for the debug screen so the live pipeline can be inspected
/// directly instead of inferred from symptoms.
class DecodeStats {
  final int decoded;
  final int decodeErrors;

  const DecodeStats({
    this.decoded = 0,
    this.decodeErrors = 0,
  });

  DecodeStats copyWith({int? decoded, int? decodeErrors}) => DecodeStats(
        decoded: decoded ?? this.decoded,
        decodeErrors: decodeErrors ?? this.decodeErrors,
      );
}

final decodeStatsProvider = StateProvider<DecodeStats>((ref) => const DecodeStats());

/// Emits a parsed [SensorState] for every live data frame received from the ECU.
/// Automatically picks S300 or KPro parser based on [settingsProvider].
final sensorStateProvider = StreamProvider<SensorState>((ref) async* {
  final ecuType = ref.watch(settingsProvider.select((s) => s.ecuType));
  final btNotifier = ref.watch(btProvider.notifier);

  // `await for` treats an error event as fatal; absorb errors upstream so the
  // loop keeps waiting for the next frame.
  final safeStream =
      btNotifier.frameStream.handleError((Object _, StackTrace __) {});

  // Adapter default frames are already filtered out in BtNotifier, so every
  // frame here is a real ECU reading. No "hold last value" logic any more:
  // a missing reading simply means the gauge keeps its last position until
  // the next real frame, and the UI shows a banner if data stops.
  await for (final frame in safeStream) {
    try {
      SensorState decoded =
          ecuType == EcuType.s300 ? parseS300(frame) : parseKPro(frame);
      decoded = _clampToRealisticRange(decoded);

      final s = ref.read(decodeStatsProvider);
      ref.read(decodeStatsProvider.notifier).state =
          s.copyWith(decoded: s.decoded + 1);
      yield decoded;
    } catch (e) {
      final s = ref.read(decodeStatsProvider);
      ref.read(decodeStatsProvider.notifier).state =
          s.copyWith(decodeErrors: s.decodeErrors + 1);
      if (s.decodeErrors < 5) AppLog.w('Frame decode error: $e');
      continue;
    }
  }
});

/// Last successfully parsed sensor state (never null after first frame).
/// Falls back to SensorState.zero() before any data arrives.
final latestSensorProvider = Provider<SensorState>((ref) {
  return ref.watch(sensorStateProvider).whenData((s) => s).value ??
      SensorState.zero();
});