using GeoVLog.Core.Models;
using System;
using System.Globalization;
using System.Text;

namespace GeoVLog.Core.Parsers;

/// <summary>
/// Parser for the GEM GSM-90 VLF dual-station measurement line.
/// Produces two <see cref="VlfReading"/> objects per input line.
/// </summary>
internal static class VlfParser
{
    public static bool TryParse(ReadOnlySpan<byte> msg, DateTime arrivalUtc, out VlfReading[] readings)
    {
        readings = Array.Empty<VlfReading>();
        var line = Encoding.ASCII.GetString(msg).Trim();
        if (string.IsNullOrWhiteSpace(line))
            return false;

        string[] parts = line.Split(',', StringSplitOptions.None);
        if (parts.Length != 22)
            return false;

        for (int i = 0; i < parts.Length; i++)
            parts[i] = parts[i].Trim();

        if (!TryParseConsoleTime(parts[0], arrivalUtc.Date, out DateTime consoleTime))
            return false;

        if (!double.TryParse(parts[1], NumberStyles.Float, CultureInfo.InvariantCulture, out double freq1))
            return false;
        if (!double.TryParse(parts[2], NumberStyles.Float, CultureInfo.InvariantCulture, out double tf1))
            return false;
        if (!double.TryParse(parts[3], NumberStyles.Float, CultureInfo.InvariantCulture, out double ip1))
            return false;
        if (!double.TryParse(parts[4], NumberStyles.Float, CultureInfo.InvariantCulture, out double op1))
            return false;
        if (!int.TryParse(parts[5], NumberStyles.Integer, CultureInfo.InvariantCulture, out int h11))
            return false;
        if (!int.TryParse(parts[6], NumberStyles.Integer, CultureInfo.InvariantCulture, out int h21))
            return false;
        if (!int.TryParse(parts[7], NumberStyles.Integer, CultureInfo.InvariantCulture, out int gain1))
            return false;

        if (!double.TryParse(parts[8], NumberStyles.Float, CultureInfo.InvariantCulture, out double freq2))
            return false;
        if (!double.TryParse(parts[9], NumberStyles.Float, CultureInfo.InvariantCulture, out double tf2))
            return false;
        if (!double.TryParse(parts[10], NumberStyles.Float, CultureInfo.InvariantCulture, out double ip2))
            return false;
        if (!double.TryParse(parts[11], NumberStyles.Float, CultureInfo.InvariantCulture, out double op2))
            return false;
        if (!int.TryParse(parts[12], NumberStyles.Integer, CultureInfo.InvariantCulture, out int h12))
            return false;
        if (!int.TryParse(parts[13], NumberStyles.Integer, CultureInfo.InvariantCulture, out int h22))
            return false;
        if (!int.TryParse(parts[14], NumberStyles.Integer, CultureInfo.InvariantCulture, out int gain2))
            return false;

        if (!double.TryParse(parts[15], NumberStyles.Float, CultureInfo.InvariantCulture, out double pitch))
            return false;
        if (!double.TryParse(parts[16], NumberStyles.Float, CultureInfo.InvariantCulture, out double roll))
            return false;
        if (!double.TryParse(parts[17], NumberStyles.Float, CultureInfo.InvariantCulture, out double tilt))
            return false;
        if (!int.TryParse(parts[18], NumberStyles.Integer, CultureInfo.InvariantCulture, out int samples))
            return false;
        if (!double.TryParse(parts[19], NumberStyles.Float, CultureInfo.InvariantCulture, out double vmain))
            return false;
        if (!int.TryParse(parts[20], NumberStyles.Integer, CultureInfo.InvariantCulture, out int vdig))
            return false;
        if (!double.TryParse(parts[21], NumberStyles.Float, CultureInfo.InvariantCulture, out double temp))
            return false;

        readings = new[]
        {
            new VlfReading
            {
                TimestampUtc = arrivalUtc,
                ConsoleTimeUtc = consoleTime,
                Channel = 0,
                RawLine = line,
                FrequencyKHz = freq1,
                TotalField_pT = tf1,
                InPhase_pct = ip1,
                QuadPhase_pct = op1,
                H1 = h11,
                H2 = h21,
                Gain = gain1,
                PitchDeg = pitch,
                RollDeg = roll,
                TiltDeg = tilt,
                Samples = samples,
                VmainVolt = vmain,
                VdigMilliV = vdig,
                TempDegC = temp
            },
            new VlfReading
            {
                TimestampUtc = arrivalUtc,
                ConsoleTimeUtc = consoleTime,
                Channel = 1,
                RawLine = line,
                FrequencyKHz = freq2,
                TotalField_pT = tf2,
                InPhase_pct = ip2,
                QuadPhase_pct = op2,
                H1 = h12,
                H2 = h22,
                Gain = gain2,
                PitchDeg = pitch,
                RollDeg = roll,
                TiltDeg = tilt,
                Samples = samples,
                VmainVolt = vmain,
                VdigMilliV = vdig,
                TempDegC = temp
            }
        };

        return true;
    }

    private static bool TryParseConsoleTime(string value, DateTime date, out DateTime result)
    {
        result = default;
        if (value.Length < 6)
            return false;
        if (!int.TryParse(value.Substring(0, 2), out int hh))
            return false;
        if (!int.TryParse(value.Substring(2, 2), out int mm))
            return false;
        if (!double.TryParse(value.Substring(4), NumberStyles.Float, CultureInfo.InvariantCulture, out double ss))
            return false;
        int sec = (int)Math.Floor(ss);
        int ms = (int)Math.Round((ss - sec) * 1000.0);
        result = new DateTime(date.Year, date.Month, date.Day, hh, mm, sec, DateTimeKind.Utc).AddMilliseconds(ms);
        return true;
    }
}