using Avalonia.Threading;
using Nonemm.Core;
using Nonemm.Network;

namespace Nonemm.App;

/// The log as a resync reads it. The link asks these questions on a socket
/// thread and the log is only touched where the windows are, so every answer is
/// fetched on the window thread and waited for.
///
/// The wait is short — a block is an hour of contacts out of a list already in
/// memory — and nothing on the window thread waits on the socket thread, so
/// there is nothing here for the two to deadlock over.
internal sealed class SessionContactLog : ContactLog
{
    private readonly AppSession session;

    internal SessionContactLog(AppSession session) => this.session = session;

    public string ContestName => Ask(() => session.Logging?.Contest.Name ?? "");

    public string MyCall => Ask(() => session.Settings.Station.Callsign);

    public string ContestSubType => Ask(() => session.Logging?.Instance.SubType ?? "");

    public string CountryFileVersion => Ask(() => session.Countries?.Version ?? "");

    public IReadOnlyList<Qso> Contacts(string computerName, DateTime fromUtc, TimeSpan length) =>
        Ask(() => session.Logging is not { } logging
            ? []
            : logging.Log.Qsos
                .Where(q =>
                    string.Equals(q.StationName, computerName, StringComparison.OrdinalIgnoreCase)
                    && q.TimestampUtc >= fromUtc
                    && q.TimestampUtc < fromUtc + length)
                .OrderBy(q => q.TimestampUtc)
                .ThenBy(q => q.Call.Text, StringComparer.Ordinal)
                .ToList());

    public DateTime LastContactUtc(string computerName) =>
        Ask(() => session.Logging is not { } logging
            ? default
            : logging.Log.Qsos
                .Where(q => string.Equals(q.StationName, computerName, StringComparison.OrdinalIgnoreCase))
                .Select(q => q.TimestampUtc)
                .DefaultIfEmpty(default)
                .Max());

    public DateTime FirstContactUtc =>
        Ask(() => session.Logging is not { } logging
            ? default
            : logging.Log.Qsos.Select(q => q.TimestampUtc).DefaultIfEmpty(default).Min());

    private static T Ask<T>(Func<T> question) =>
        Dispatcher.UIThread.CheckAccess() ? question() : Dispatcher.UIThread.Invoke(question);
}