using System;
using System.Collections.Generic;
using System.Globalization;

namespace HC_APTBS.Models
{
    /// <summary>
    /// Maps a motor RPM setpoint to the corresponding analogue control voltage
    /// required to drive the bench motor to that speed.
    ///
    /// <para>
    /// The lookup table is ordered by ascending RPM. <see cref="VoltageForRpm"/>
    /// performs a linear scan and returns the voltage of the last entry whose
    /// RPM is ≤ the requested value (step interpolation).
    /// </para>
    /// </summary>
    public class RpmVoltageRelation
    {
        /// <summary>Analogue voltage to apply to the motor controller (V).</summary>
        public double Voltage { get; set; }

        /// <summary>Target motor speed (RPM).</summary>
        public int Rpm { get; set; }

        /// <param name="voltage">Motor control voltage (V).</param>
        /// <param name="rpm">Corresponding motor speed (RPM).</param>
        public RpmVoltageRelation(double voltage, int rpm)
        {
            Voltage = voltage;
            Rpm     = rpm;
        }

        // ── Lookup ────────────────────────────────────────────────────────────────

        /// <summary>
        /// Returns the control voltage for the given <paramref name="targetRpm"/>
        /// by scanning the ordered <paramref name="table"/> for the closest lower entry.
        /// Returns 0 if the table is empty or no lower entry is found.
        /// </summary>
        /// <param name="targetRpm">Requested motor speed in RPM.</param>
        /// <param name="table">Ordered (ascending RPM) lookup table.</param>
        public static double VoltageForRpm(int targetRpm, IReadOnlyList<RpmVoltageRelation> table)
        {
            double previousVoltage = -1;
            foreach (var entry in table)
            {
                if (entry.Rpm == targetRpm)
                    return entry.Voltage;

                if (targetRpm < entry.Rpm)
                    return previousVoltage < 0 ? 0 : previousVoltage;

                previousVoltage = entry.Voltage;
            }
            return 0;
        }

        // ── Serialisation ─────────────────────────────────────────────────────────

        /// <summary>
        /// Serialises a list of relations to the compact pipe-separated storage format
        /// used in config.xml: <c>RPM|Voltage;RPM|Voltage;…</c>
        /// </summary>
        public static string Serialise(IReadOnlyList<RpmVoltageRelation> relations)
        {
            if (relations == null || relations.Count == 0) return string.Empty;

            var parts = new List<string>(relations.Count);
            foreach (var r in relations)
                parts.Add($"{r.Rpm}|{r.Voltage.ToString(CultureInfo.InvariantCulture)}");

            return string.Join(";", parts);
        }

        /// <summary>
        /// Deserialises a list of relations from the compact storage format.
        /// </summary>
        public static List<RpmVoltageRelation> Deserialise(string serialised)
        {
            var result = new List<RpmVoltageRelation>();
            if (string.IsNullOrWhiteSpace(serialised)) return result;

            foreach (var part in serialised.Split(';'))
            {
                var tokens = part.Split('|');
                if (tokens.Length != 2) continue;
                if (!int.TryParse(tokens[0], out int rpm)) continue;
                if (!double.TryParse(tokens[1], NumberStyles.Float,
                        CultureInfo.InvariantCulture, out double voltage)) continue;

                result.Add(new RpmVoltageRelation(voltage, rpm));
            }
            return result;
        }
    }
}