using Nonemm.Core;
using Nonemm.Core.Country;

namespace Nonemm.Session;

/// Where the station being worked is from here: the beam heading, the heading
/// the long way round, how far away it is, and when the sun rises and sets
/// there. N1MM writes the same line under its entry window.
///
/// The position comes from the grid square if the contest exchanges one and the
/// operator has copied it, and from the country file otherwise, which puts the
/// station in the middle of its country. That is close enough to point a beam
/// with, and it is what N1MM does.
public sealed record StationPath(
    double Heading,
    double DistanceKm,
    DateTime? Sunrise,
    DateTime? Sunset)
{
    /// The heading the long way round, which a big antenna is sometimes better
    /// off using.
    public double LongPath => (Heading + 180.0) % 360.0;

    /// Null when there is nothing to work out a path from: no station in the
    /// callsign box, no country file, or no position for either end.
    public static StationPath? For(OperatingPosition session, DateTime nowUtc)
    {
        if (Mine(session) is not { } here || Theirs(session) is not { } there)
        {
            return null;
        }
        (DateTime Rise, DateTime Set)? sun = SunTimes.For(there.Latitude, there.Longitude, nowUtc);
        return new StationPath(
            GridSquare.Bearing(here.Latitude, here.Longitude, there.Latitude, there.Longitude),
            GridSquare.DistanceKm(here.Latitude, here.Longitude, there.Latitude, there.Longitude),
            sun?.Rise,
            sun?.Set);
    }

    private static (double Latitude, double Longitude)? Mine(OperatingPosition session) =>
        Place(session.Me.GridSquare) ?? Place(session.Session.Countries?.Find(session.Me.Callsign));

    private static (double Latitude, double Longitude)? Theirs(OperatingPosition session)
    {
        if (session.Entry.Call.Trim().Length == 0)
        {
            return null;
        }
        return Place(session.Entry.ValueOf(Contests.ExchangeSlot.GridSquare))
            ?? Place(session.Session.History.Find(session.Entry.Call)?.GridSquare ?? "")
            ?? Place(session.Country());
    }

    private static (double Latitude, double Longitude)? Place(string grid) =>
        GridSquare.TryParse(grid, out GridSquare square) ? (square.Latitude, square.Longitude) : null;

    private static (double Latitude, double Longitude)? Place(CountryLookup? country) =>
        country is null ? null : (country.Latitude, country.Longitude);
}