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

namespace HC_APTBS.Models
{
    /// <summary>
    /// Calibration parameters for an analogue sensor channel.
    /// Maps a raw ADC counts value (from the bench CAN bus) to an
    /// engineering-unit value using a voltage-range to value-range linear mapping,
    /// then applies a gain and offset correction.
    ///
    /// <para>
    /// The bench ADC uses a 10-bit (1024-step) range over 0–5 V.
    /// Conversion: V = (rawCanBusValue × 5000 / 1024) / 1000
    /// Engineering value = V × ((MaxVal − MinVal) / (MaxVolt − MinVolt)) × Gain + Offset
    /// </para>
    /// </summary>
    public class SensorConfiguration
    {
        /// <summary>1-based sensor channel number.</summary>
        public short Number { get; set; } = 1;

        /// <summary>Display name for the sensor (e.g. "Pressure").</summary>
        public string SensorName { get; set; } = "Sensor";

        /// <summary>Minimum input voltage at the sensor connector (V).</summary>
        public double MinVolt { get; set; } = 0;

        /// <summary>Maximum input voltage at the sensor connector (V).</summary>
        public double MaxVolt { get; set; } = 5;

        /// <summary>Engineering-unit value corresponding to <see cref="MinVolt"/>.</summary>
        public double MinVal { get; set; } = 0;

        /// <summary>Engineering-unit value corresponding to <see cref="MaxVolt"/>.</summary>
        public double MaxVal { get; set; } = 15;

        /// <summary>Multiplicative gain correction applied after the range mapping.</summary>
        public double Gain { get; set; } = 1;

        /// <summary>Additive offset correction applied after the gain.</summary>
        public double Offset { get; set; } = 0;

        /// <summary>
        /// Static logging hook used by runtime guards and <see cref="TryParse"/>.
        /// Wired at app startup to <c>IAppLogger.Warning</c>. Left null keeps the
        /// Models layer DI-free and testable. Signature: (source, message).
        /// </summary>
        public static Action<string, string>? WarningLogger { get; set; }

        /// <summary>Set once per instance after the first zero-range warning, to prevent hot-loop log spam.</summary>
        private bool _warnedRangeZero;

        /// <summary>
        /// Converts a raw CAN bus ADC count to a calibrated engineering-unit value.
        /// Returns 0 and warns once if <c>MaxVolt == MinVolt</c>.
        /// </summary>
        /// <param name="rawCanBusValue">10-bit ADC count from the CAN frame.</param>
        /// <returns>Calibrated value in engineering units.</returns>
        public double GetValueFromRaw(double rawCanBusValue)
        {
            double range = MaxVolt - MinVolt;
            if (range == 0.0)
            {
                if (!_warnedRangeZero)
                {
                    WarningLogger?.Invoke(nameof(SensorConfiguration),
                        $"MaxVolt == MinVolt for sensor '{SensorName}' (channel {Number}). Returning 0.");
                    _warnedRangeZero = true;
                }
                return 0.0;
            }

            // Convert ADC counts → volts (10-bit ADC, 5 V reference)
            double volts = rawCanBusValue * 5000.0 / 1024.0 / 1000.0;

            // Map voltage range → engineering-unit range
            double value = volts * ((MaxVal - MinVal) / range);

            return value * Gain + Offset;
        }

        /// <summary>Serialises this sensor configuration to XML.</summary>
        public XElement ToXml()
            => new XElement("sensor",
                   new XAttribute("num",  Number),
                   new XAttribute("name", SensorName),
                   new XElement("Gain",   Gain),
                   new XElement("Offset", Offset),
                   new XElement("MinVolt", MinVolt),
                   new XElement("MaxVolt", MaxVolt),
                   new XElement("MinVal",  MinVal),
                   new XElement("MaxVal",  MaxVal));

        /// <summary>Deserialises a sensor configuration from XML.</summary>
        public static SensorConfiguration FromXml(XElement element)
        {
            var sc = new SensorConfiguration();
            TryParse(element.Attribute("num")?.Value,   "num",     v => sc.Number     = short.Parse(v, CultureInfo.InvariantCulture));
            TryParse(element.Attribute("name")?.Value,  "name",    v => sc.SensorName = v);
            TryParse(element.Element("Gain")?.Value,    "Gain",    v => sc.Gain       = ParseInvariant(v));
            TryParse(element.Element("Offset")?.Value,  "Offset",  v => sc.Offset     = ParseInvariant(v));
            TryParse(element.Element("MinVolt")?.Value, "MinVolt", v => sc.MinVolt    = ParseInvariant(v));
            TryParse(element.Element("MaxVolt")?.Value, "MaxVolt", v => sc.MaxVolt    = ParseInvariant(v));
            TryParse(element.Element("MinVal")?.Value,  "MinVal",  v => sc.MinVal     = ParseInvariant(v));
            TryParse(element.Element("MaxVal")?.Value,  "MaxVal",  v => sc.MaxVal     = ParseInvariant(v));
            return sc;
        }

        /// <summary>Parses a decimal under <see cref="CultureInfo.InvariantCulture"/>, tolerating comma separators.</summary>
        private static double ParseInvariant(string v)
            => double.Parse(v.Replace(',', '.'), CultureInfo.InvariantCulture);

        /// <summary>Creates the default pressure sensor calibration for channel 1.</summary>
        public static SensorConfiguration DefaultPressureSensor()
            => new SensorConfiguration
            {
                Number     = 1,
                SensorName = "Pressure",
                Offset     = -4.1,
                MinVolt    = 0.5,
                MaxVolt    = 3.2,
                MinVal     = 0,
                MaxVal     = 20
            };

        private static void TryParse(string? value, string fieldName, Action<string> assign)
        {
            if (string.IsNullOrEmpty(value)) return;
            try { assign(value!); }
            catch (Exception ex)
            {
                WarningLogger?.Invoke(nameof(SensorConfiguration),
                    $"Skipped malformed '{fieldName}' value '{value}': {ex.Message}");
            }
        }
    }
}