using System;
using System.Globalization;
using System.Xml.Linq;

namespace HC_APTBS.Models
{
    /// <summary>
    /// Represents a single logical parameter exchanged over CAN.
    /// Each parameter occupies up to two bytes within a CAN frame identified by <see cref="MessageId"/>.
    ///
    /// <para><b>Bench params</b> use the simple calibration model:<br/>
    ///   Linear:  <c>eng = raw * Factor + Offset</c><br/>
    ///   Inverse: <c>eng = Factor / raw + Offset</c></para>
    ///
    /// <para><b>Pump params</b> (legacy) use the P1–P6 rational transfer function via
    /// <see cref="GetTransformResult"/>. Set <see cref="UseLegacyTransform"/> to enable.</para>
    /// </summary>
    public class CanBusParameter
    {
        // ── Frame addressing ─────────────────────────────────────────────────────

        /// <summary>CAN message identifier this parameter belongs to.</summary>
        public uint MessageId { get; set; }

        /// <summary>Index of the high byte within the 8-byte CAN payload.</summary>
        public ushort ByteH { get; set; }

        /// <summary>Index of the low byte within the 8-byte CAN payload.</summary>
        public ushort ByteL { get; set; }

        // ── Metadata ─────────────────────────────────────────────────────────────

        /// <summary>Human-readable parameter name used for lookup (see <see cref="BenchParameterNames"/>).</summary>
        public string Name { get; set; } = string.Empty;

        /// <summary>
        /// Sensor/encoding type selector. Used by the receive decoder to choose
        /// the correct bit-extraction formula (e.g. for temperature and RPM).
        /// </summary>
        public int Type { get; set; } = 0;

        // ── Simple calibration (bench params) ────────────────────────────────────

        /// <summary>Multiplication factor: <c>eng = raw * Factor + Offset</c>.</summary>
        public double Factor { get; set; } = 1.0;

        /// <summary>Additive offset: <c>eng = raw * Factor + Offset</c>.</summary>
        public double Offset { get; set; }

        /// <summary>When true, calibration uses <c>eng = Factor / raw + Offset</c>.</summary>
        public bool IsInverse { get; set; }

        // ── Legacy P1–P6 calibration (pump params) ───────────────────────────────

        /// <summary>Transfer function coefficient P1 (numerator multiplier).</summary>
        public double P1 { get; set; }

        /// <summary>Transfer function coefficient P2 (numerator offset).</summary>
        public double P2 { get; set; }

        /// <summary>Transfer function coefficient P3 (denominator multiplier).</summary>
        public double P3 { get; set; }

        /// <summary>Transfer function coefficient P4 (denominator offset).</summary>
        public double P4 { get; set; }

        /// <summary>Transfer function coefficient P5 (additive offset 1).</summary>
        public double P5 { get; set; }

        /// <summary>Transfer function coefficient P6 (additive offset 2).</summary>
        public double P6 { get; set; }

        /// <summary>
        /// When true, the calibration coefficients are set to the identity transform
        /// (P1=1, P4=1, all others 0) so the raw value passes through unchanged.
        /// </summary>
        public bool DisableCalibration { get; set; }

        /// <summary>
        /// When true, <see cref="GetTransformResult"/> is used instead of
        /// <see cref="Calibrate"/>. Enabled for pump params loaded via <see cref="FromXml"/>.
        /// </summary>
        public bool UseLegacyTransform { get; set; }

        // ── Runtime state ─────────────────────────────────────────────────────────

        /// <summary>Current decoded engineering-unit value (updated by the CAN read thread).</summary>
        public double Value { get; set; }

        /// <summary>
        /// True when <see cref="Value"/> has been updated since the last UI refresh tick.
        /// Reset to false by the consumer after reading.
        /// </summary>
        public bool NeedsUpdate { get; set; }

        /// <summary>
        /// True for receive-direction params (decoded from incoming CAN frames).
        /// False for transmit-direction params (packed into outgoing frames).
        /// </summary>
        public bool IsReceive { get; set; }

        /// <summary>
        /// Exponential moving average coefficient α ∈ (0, 1].
        /// α = 1 means no smoothing (pass-through); smaller values give more smoothing.
        /// </summary>
        public double Alpha { get; set; } = 1.0;

        // ── Convenience alias kept for cross-file compatibility ───────────────────

        /// <summary>Alias for <see cref="MessageId"/> — used by legacy call sites.</summary>
        public uint ID
        {
            get => MessageId;
            set => MessageId = value;
        }

        // ── Simple calibration ────────────────────────────────────────────────────

        /// <summary>
        /// Converts a raw CAN value to engineering units using Factor/Offset.
        /// </summary>
        public double Calibrate(double raw)
        {
            if (IsInverse)
                return raw != 0 ? Factor / raw + Offset : 0;
            return raw * Factor + Offset;
        }

        /// <summary>
        /// Converts an engineering value back to raw CAN value (for transmit).
        /// </summary>
        public double CalibrateReverse(double eng)
        {
            if (IsInverse)
            {
                double denom = eng - Offset;
                return denom != 0 ? Factor / denom : 0;
            }
            return Factor != 0 ? (eng - Offset) / Factor : 0;
        }

        // ── Legacy P1–P6 transfer function (pump params) ─────────────────────────

        /// <summary>
        /// Applies the P1–P6 rational transfer function to <see cref="Value"/>.
        /// Used only by pump params (<see cref="UseLegacyTransform"/> = true).
        /// </summary>
        public double GetTransformResult()
        {
            if (IsReceive)
            {
                return (-P2 - P3 * P5 - P4 * P6 + P4 * Value)
                     / (P1 + P3 * P5 + P3 * P6 - P3 * Value);
            }

            return ((P1 * Value + P2) / (P3 * Value + P4)) + P5 + P6;
        }

        /// <summary>
        /// Returns the raw CAN value for transmission.
        /// Delegates to simple or legacy calibration depending on param type.
        /// </summary>
        public double GetTransmitValue()
        {
            if (UseLegacyTransform)
                return GetTransformResult();
            return CalibrateReverse(Value);
        }

        /// <summary>
        /// Resets calibration coefficients to the identity transform so the raw value
        /// passes through unchanged.
        /// </summary>
        public void SetIdentityCalibration()
        {
            P1 = 1; P2 = 0; P3 = 0; P4 = 1; P5 = 0; P6 = 0;
            DisableCalibration = true;
        }

        // ── XML serialisation ─────────────────────────────────────────────────────

        /// <summary>
        /// Deserialises a pump CAN parameter from an XML element inside the
        /// <c>&lt;Params&gt;</c> section of a pump definition.
        /// </summary>
        public static CanBusParameter FromXml(XElement xe)
        {
            var p = new CanBusParameter
            {
                Name      = xe.Name.LocalName,
                MessageId = uint.Parse(xe.Attribute("busid")?.Value ?? "0",
                                NumberStyles.HexNumber),
                ByteH     = ushort.Parse(xe.Attribute("byteh")?.Value ?? "0"),
                ByteL     = ushort.Parse(xe.Attribute("bytel")?.Value ?? "0"),
                Type      = int.Parse(xe.Attribute("type")?.Value ?? "0"),
                IsReceive = !string.Equals(xe.Attribute("send")?.Value, "true",
                                StringComparison.OrdinalIgnoreCase),
                Alpha     = ParseDecimal(xe.Attribute("filter")?.Value, 1.0),
                DisableCalibration = string.Equals(xe.Attribute("disableparams")?.Value,
                                         "true", StringComparison.OrdinalIgnoreCase),
                UseLegacyTransform = true
            };

            if (p.DisableCalibration)
            {
                p.SetIdentityCalibration();
            }
            else
            {
                p.P1 = ParseDecimal(xe.Attribute("p1")?.Value, 1.0);
                p.P2 = ParseDecimal(xe.Attribute("p2")?.Value, 0.0);
                p.P3 = ParseDecimal(xe.Attribute("p3")?.Value, 0.0);
                p.P4 = ParseDecimal(xe.Attribute("p4")?.Value, 1.0);
                p.P5 = ParseDecimal(xe.Attribute("p5")?.Value, 0.0);
                p.P6 = ParseDecimal(xe.Attribute("p6")?.Value, 0.0);
            }

            return p;
        }

        /// <summary>Parses a decimal string that may use comma or dot as separator.</summary>
        internal static double ParseDecimal(string? value, double fallback)
        {
            if (string.IsNullOrEmpty(value)) return fallback;
            return double.Parse(value.Replace(',', '.'), CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Serialises this parameter to an XML element using the pump-param format
        /// (<c>busid</c>, <c>p1–p6</c>, <c>send</c>, <c>disableparams</c>).
        /// Used when persisting pump definitions to <c>pumps.xml</c>.
        /// </summary>
        public XElement ToPumpXml()
        {
            var elm = new XElement(Name,
                new XAttribute("busid", MessageId.ToString("X")),
                new XAttribute("byteh", ByteH),
                new XAttribute("bytel", ByteL),
                new XAttribute("type",  Type));

            if (!IsReceive)
                elm.Add(new XAttribute("send", "true"));
            if (Alpha != 1.0)
                elm.Add(new XAttribute("filter", Alpha.ToString(CultureInfo.InvariantCulture)));
            if (DisableCalibration)
            {
                elm.Add(new XAttribute("disableparams", "true"));
            }
            else
            {
                elm.Add(new XAttribute("p1", P1.ToString(CultureInfo.InvariantCulture)));
                elm.Add(new XAttribute("p2", P2.ToString(CultureInfo.InvariantCulture)));
                elm.Add(new XAttribute("p3", P3.ToString(CultureInfo.InvariantCulture)));
                elm.Add(new XAttribute("p4", P4.ToString(CultureInfo.InvariantCulture)));
                elm.Add(new XAttribute("p5", P5.ToString(CultureInfo.InvariantCulture)));
                elm.Add(new XAttribute("p6", P6.ToString(CultureInfo.InvariantCulture)));
            }

            return elm;
        }

        /// <summary>Serialises this parameter to an XML element for persistence in bench.xml.</summary>
        public XElement ToXml()
        {
            var elm = new XElement(Name,
                new XAttribute("id",        MessageId.ToString("X")),
                new XAttribute("byteh",     ByteH),
                new XAttribute("bytel",     ByteL),
                new XAttribute("direction", IsReceive ? "rx" : "tx"));

            if (Alpha != 1.0)
                elm.Add(new XAttribute("filter", Alpha));
            if (Factor != 1.0)
                elm.Add(new XAttribute("factor", Factor));
            if (Offset != 0.0)
                elm.Add(new XAttribute("offset", Offset));
            if (IsInverse)
                elm.Add(new XAttribute("type", "inverse"));

            return elm;
        }
    }

    // ── Well-known parameter name constants ──────────────────────────────────────

    /// <summary>String constants for bench CAN parameter names.</summary>
    public static class BenchParameterNames
    {
        public const string Rpm              = "RPM";
        public const string Counter          = "Counter";
        public const string BaudRate         = "BaudRate";
        public const string BenchRpm         = "BenchRPM";
        public const string BenchCounter     = "BenchCounter";
        public const string Temp             = "BenchTemp";
        public const string TempIn           = "T-in";
        public const string TempOut          = "T-out";
        public const string Temp4            = "T4";
        public const string QDelivery        = "QDelivery";
        public const string QOver            = "QOver";
        public const string ElectronicMsg    = "ElectronicMsg";
        public const string EncoderResolution  = "EncoderResolution";
        public const string PsgEncoderValue    = "PSGEncoderValue";
        public const string PsgEncoderWorking  = "PSGEncoderWorking";
        public const string InjEncoderValue    = "InyectorEncoderValue";
        public const string InjEncoderWorking  = "InyectorEncoderWorking";
        public const string ManualEncoderValue = "ManualEncoderValue";
        public const string Alarms           = "Alarms";
        public const string Pressure         = "Pressure";
        public const string AnalogSensor2    = "AnalogicSensor2";
    }

    /// <summary>String constants for pump CAN parameter names.</summary>
    public static class PumpParameterNames
    {
        public const string MemoryRequest = "MemoryRequest";
        public const string Me            = "me";
        public const string Fbkw          = "FBKW";
        public const string PreIn         = "mepi";
        public const string Rpm           = "RPM";
        public const string Temp          = "Temp";
        public const string Tein          = "Tein";
        public const string TestUnlock    = "TestUnlock";
        public const string TestImmo      = "TestImmo";
        public const string Status        = "Status";
        public const string Empf3         = "Empf3";
    }

    /// <summary>String constants for K-Line / KWP data dictionary keys.</summary>
    public static class KlineKeys
    {
        public const string PumpId          = "pumpID";
        public const string SerialNumber    = "SerialNumber";
        public const string ModelReference  = "ModelReference";
        public const string PumpControl     = "PumpControl";
        public const string ModelIndex      = "ModelIndex";
        public const string DataRecord      = "DataRecord";
        public const string SwVersion1      = "SWV1";
        public const string SwVersion2      = "SWV2";
        public const string Dfi             = "dfi";
        public const string Errors          = "ErrorCodes";
        public const string Result          = "result";
        public const string NoErrors        = "No fault codes";
        public const string ConnectError    = "CON ERROR";
    }

    /// <summary>Relay name constants — mirror the bench XML definition.</summary>
    public static class RelayNames
    {
        public const string Electronic    = "Electronic";
        public const string OilPump       = "OilPump";
        public const string DepositCooler = "DepositCooler";
        public const string DepositHeater = "DepositHeater";
        public const string DirectionRight = "Reserve";
        public const string Counter       = "Counter";
        public const string DirectionLeft  = "Direction";
        public const string TinCooler     = "TinCooler";
        public const string Pulse4Signal  = "Pulse4Signal";
        public const string Flasher       = "Flasher";
    }
}