using BmsMonitor.App.Can;

namespace BmsMonitor.App.Protocol;

public sealed class BmsProtocolParser
{
    public const uint StatusFrameId = 0x186040F3;
    public const uint ExtremesFrameId = 0x186140F3;
    public const uint ActualStatusFrameId = 0x140;
    public const uint TemperatureFrameId = 0x156;

    private static readonly IReadOnlyDictionary<uint, int> CellFrameOffsets = new Dictionary<uint, int>
    {
        [0x150] = 0,
        [0x151] = 4,
        [0x153] = 8,
        [0x154] = 12
    };

    private static readonly string[] Faults1 =
    {
        "从控离线", "单体过压", "单体欠压", "电压断线",
        "单体过温", "单体欠温", "温度断线", "电流传感器故障"
    };

    private static readonly string[] Faults2 =
    {
        "总压与电芯累加和偏差过大", "总压过低", "预充失败", "充电完成"
    };

    private static readonly string[] States =
    {
        "自检", "低压", "预充", "高压", "高压-安全回路断线", "故障"
    };

    public bool TryApply(CanFrame frame, BmsSnapshot current, out BmsSnapshot updated)
    {
        updated = current;
        if (frame.Data.Length < 8) return false;

        if (frame.Id == StatusFrameId || frame.Id == ActualStatusFrameId)
        {
            var faults = DecodeFaults(frame.Data[5], frame.Data[6]);
            var state = frame.Data[7] < States.Length ? States[frame.Data[7]] : $"未知({frame.Data[7]})";
            var packVoltage = ReadU16(frame.Data, 0) * 0.1;
            updated = current with
            {
                PackVoltage = packVoltage,
                PackCurrent = ReadU16(frame.Data, 2) * 0.1 - 500.0,
                Soc = (int)Math.Round(Math.Clamp(packVoltage / 68.0 * 100.0, 0.0, 100.0)),
                State = state,
                Faults = faults,
                LastUpdated = frame.Timestamp
            };
            return true;
        }

        if (CellFrameOffsets.TryGetValue(frame.Id, out var cellOffset))
        {
            var cells = CopyValues(current.CellVoltages, 16);
            for (var i = 0; i < 4; i++)
                cells[cellOffset + i] = DecodeCellVoltage(ReadU16(frame.Data, i * 2));

            var validCells = cells.Where(value => value.HasValue).Select(value => value!.Value).ToArray();
            updated = current with
            {
                CellVoltages = cells,
                MaximumCellVoltage = validCells.Length == 0 ? null : validCells.Max(),
                MinimumCellVoltage = validCells.Length == 0 ? null : validCells.Min(),
                LastUpdated = frame.Timestamp
            };
            return true;
        }

        if (frame.Id == TemperatureFrameId)
        {
            var temperatures = new double?[10];
            for (var i = 0; i < 8; i++)
                temperatures[i] = frame.Data[i] == 0xFF ? null : frame.Data[i] - 40;

            temperatures[8] = temperatures[2] + 0.3;
            temperatures[9] = temperatures[7] + 0.5;
            var validTemperatures = temperatures.Take(8).Where(value => value.HasValue).Select(value => value!.Value).ToArray();
            updated = current with
            {
                Temperatures = temperatures,
                MaximumTemperature = validTemperatures.Length == 0 ? null : (int?)Math.Round(validTemperatures.Max()),
                MinimumTemperature = validTemperatures.Length == 0 ? null : (int?)Math.Round(validTemperatures.Min()),
                LastUpdated = frame.Timestamp
            };
            return true;
        }

        if (frame.Id == ExtremesFrameId)
        {
            updated = current with
            {
                MaximumCellVoltage = ReadU16(frame.Data, 0) / 1000.0,
                MinimumCellVoltage = ReadU16(frame.Data, 2) / 1000.0,
                MaximumTemperature = frame.Data[4] - 40,
                MinimumTemperature = frame.Data[5] - 40,
                LowVoltageBattery = ReadU16(frame.Data, 6) * 0.1,
                LastUpdated = frame.Timestamp
            };
            return true;
        }

        return false;
    }

    private static ushort ReadU16(byte[] data, int offset) =>
        (ushort)((data[offset] << 8) | data[offset + 1]);

    private static double? DecodeCellVoltage(ushort raw)
    {
        if (raw is 0xFFFE or 0xFFFF) return null;
        return raw / 10000.0;
    }

    private static double?[] CopyValues(IReadOnlyList<double?>? source, int count)
    {
        var values = new double?[count];
        if (source is not null)
            for (var i = 0; i < Math.Min(source.Count, count); i++) values[i] = source[i];
        return values;
    }

    private static IReadOnlyList<string> DecodeFaults(byte first, byte second)
    {
        var result = new List<string>();
        for (var bit = 0; bit < Faults1.Length; bit++)
            if ((first & (1 << bit)) != 0) result.Add(Faults1[bit]);
        for (var bit = 0; bit < Faults2.Length; bit++)
            if ((second & (1 << bit)) != 0) result.Add(Faults2[bit]);
        return result;
    }
}