import 'dart:typed_data';
import 'sensor_state.dart';
import 'temp_table.dart';
import 'neg8.dart';

bool isS300PlaceholderFrame(Uint8List frame) {
  if (frame.length != 128) return false;

  // Diagnostic signature observed in the S300 Bluetooth stream. Do not use
  // this to drop frames globally; current captures show real changing data can
  // still be carried in frames with this prefix.
  return frame[0] == 0x1B &&
      frame[1] == 0x00 &&
      frame[2] == 0x14 &&
      frame[3] == 0x00 &&
      frame[4] == 0x00 &&
      frame[5] == 0xFF &&
      frame[6] == 0xFF &&
      frame[7] == 0xF2 &&
      frame[8] == 0x03 &&
      frame[9] == 0x18 &&
      frame[10] == 0x00 &&
      frame[11] == 0x00 &&
      frame[12] == 0x10 &&
      frame[13] == 0x00 &&
      frame[14] == 0x00 &&
      frame[15] == 0x00 &&
      frame[16] == 0xC4;
}

/// Parses a 128-byte S300 ECU response frame into a [SensorState].
/// Throws [ArgumentError] if frame length is wrong, or if [validateChecksum]
/// is true and the NEG8 checksum fails.
SensorState parseS300(Uint8List frame, {bool validateChecksum = true}) {
  if (frame.length != 128) {
    throw ArgumentError('S300 frame must be 128 bytes, got ${frame.length}');
  }
  if (validateChecksum && !validateFrame(frame)) {
    throw ArgumentError('S300 frame NEG8 checksum failed');
  }

  // Some S300 Bluetooth frames carry live RPM in the tail payload at 82..83,
  // while the header bytes stay fixed at 1b 00 14 00 and decode to a bogus
  // 4864 rpm. Prefer the tail value when it looks like real engine speed.
  final bool hasTailPayload = _hasS300TailPayload(frame);
  final int rpmRaw =
      hasTailPayload ? _readUint16LE(frame, 82) : _readUint16BE(frame, 2);
  final double rpm = (hasTailPayload ? rpmRaw - 1089 : rpmRaw - 256)
      .clamp(0, 12000)
      .toDouble();

  // VSS: bytes 5..6 little-endian pulse period.
  final int vssRaw = _readUint16LE(frame, 5);
  final double vss =
      (vssRaw < 893 || vssRaw == 0xFFFF) ? 0.0 : 144256.0 / vssRaw;

  // MAP: bytes 7..8 little-endian. SManager displays this as gauge pressure
  // in its "/psi column rather than raw absolute kPa.
  final int mapRaw = _readUint16LE(frame, 7);
  final double map = ((mapRaw / 10.0) - 103.8) * 0.1450377377;

  // TPS: byte 9
  final int tpsRaw = frame[9];
  final double tps = ((tpsRaw - 25) * 100.0 / (239 - 25)).clamp(0.0, 100.0);

  // INJ: bytes 10..11 little-endian timer ticks.
  final int injRaw = _readUint16LE(frame, 10);
  final double inj = injRaw / 240.5;

  // IGN: byte 12 — SManager-aligned degrees.
  final double ign = (frame[12] - 66) / 2.0;

  // O2: byte 16, 0..5V scaled over 8-bit ADC range.
  final double o2 = frame[16] * 5.0 / 256.0;

  // SW bitmaps
  final int sw1 = frame[0x11]; // +17
  final int sw2 = frame[0x12]; // +18
  final int sw3 = frame[0x13]; // +19
  final int sw5 = frame[0x43]; // +67

  // Gear: byte 0x27 = +39 decimal... wait, +27 hex = decimal 39
  final int gear = frame[0x27];

  // Strim: byte 0x29 hex = 41 decimal
  final double strim = frame[0x29].toDouble();

  // Ltrim: byte 0x2B hex = 43 decimal
  final double ltrim = frame[0x2B].toDouble();

  // PA: byte 0x3C hex = 60 decimal
  final double pa = frame[0x3C].toDouble();

  // ECT: byte 0x2D hex = 45 decimal
  final double ect = (tempXlt[frame[0x2D]] + 40).toDouble();

  // IAT: byte 0x2E hex = 46 decimal
  final double iat = (tempXlt[frame[0x2E]] + 40).toDouble();

  // BAT: byte 0x24 hex = 36 decimal
  final double bat = frame[0x24] * 26.0 / 270.0;

  // ERR bytes: 0x31..0x34 (4 bytes for S300)
  final List<int> errBytes = [
    frame[0x31],
    frame[0x32],
    frame[0x33],
    frame[0x34],
  ];

  // Eth: byte 0x38 hex = 56 decimal
  final double eth = frame[0x38].toDouble();

  // AFR: byte 0x34 overlaps with ERR03 in the spec — use it as raw AFR
  final double afr = frame[0x34].toDouble();

  // AIN0–AIN7: decimal offsets 82..97 (uint16 BE each)
  final double ain0 = _readUint16BE(frame, 82).toDouble();
  final double ain1 = _readUint16BE(frame, 84).toDouble();
  final double ain2 = _readUint16BE(frame, 86).toDouble();
  final double ain3 = _readUint16BE(frame, 88).toDouble();
  final double ain4 = _readUint16BE(frame, 90).toDouble();
  final double ain5 = _readUint16BE(frame, 92).toDouble();
  final double ain6 = _readUint16BE(frame, 94).toDouble();
  final double ain7 = _readUint16BE(frame, 96).toDouble();

  // Flags
  // SW1 bit3 = REVL
  final bool revLimit = (sw1 & 0x08) != 0;
  // SW2 bit5 = MIL
  final bool mil = (sw2 & 0x20) != 0;
  // SW2 bit2 = Fuel (cut)
  final bool fuelCut = (sw2 & 0x04) != 0;
  // SW2 bit7 = ALTC → fanOut; also SW5 bit0 = FANC
  final bool fanOut = (sw2 & 0x80) != 0 || (sw5 & 0x01) != 0;
  // SW2 bit1..0 = VTS (VTEC solenoid — nonzero = active)
  final bool vtec = (sw2 & 0x03) != 0;
  // Knock = KRtrd > 0 (byte 13)
  final bool knock = frame[13] > 0;
  // SW3 bit7 = LnchC
  final bool launch = (sw3 & 0x80) != 0;

  return SensorState(
    rpm: rpm,
    vss: vss,
    map: map,
    tps: tps,
    inj: inj,
    ign: ign,
    ect: ect,
    iat: iat,
    bat: bat,
    o2: o2,
    gear: gear,
    eth: eth,
    pa: pa,
    afr: afr,
    strim: strim,
    ltrim: ltrim,
    ain0: ain0,
    ain1: ain1,
    ain2: ain2,
    ain3: ain3,
    ain4: ain4,
    ain5: ain5,
    ain6: ain6,
    ain7: ain7,
    mil: mil,
    fuelCut: fuelCut,
    fanOut: fanOut,
    vtec: vtec,
    knock: knock,
    revLimit: revLimit,
    launch: launch,
    errBytes: errBytes,
    timestamp: DateTime.now(),
  );
}

int _readUint16BE(Uint8List frame, int offset) {
  return (frame[offset] << 8) | frame[offset + 1];
}

int _readUint16LE(Uint8List frame, int offset) {
  return frame[offset] | (frame[offset + 1] << 8);
}

bool _hasS300TailPayload(Uint8List frame) {
  if (!isS300PlaceholderFrame(frame)) return false;
  final rpm = _readUint16LE(frame, 82);
  return rpm > 300 && rpm < 12000;
}