using Nonemm.Contests;
using Nonemm.Core;
using Nonemm.Core.Calls;
using Nonemm.Core.Country;
using Nonemm.Storage;

namespace Nonemm.Session;

/// The running contest: the log, the score and what happens when a contact is
/// logged. One of these per contest, however many radios the station has.
/// What the operator is typing lives in `OperatingPosition`, one per radio.
///
/// No UI framework is referenced here, so the behaviour an operator judges the
/// logger by is tested with plain unit tests.
public sealed class ContestSession
{
    private readonly LogStore store;

    public ContestSession(
        LogStore store,
        Contest contest,
        ContestInstance instance,
        StationInfo me,
        CountryFile? countries,
        CallHistory? history = null)
    {
        this.store = store;
        Countries = countries;
        History = history ?? CallHistory.Empty;
        Contest = contest;
        Instance = instance;
        Me = me;
        Log = new ContestLog(contest, me, countries, instance.Entry) { History = History };
        Log.Restore(store.Qsos(instance.ContestNumber));
        Editor = new QsoEditor(contest, me, countries);
        Numbers = new SerialNumberPool { ByBand = contest.NumbersByBand(instance.Entry) };
        SeedNumbers();
    }

    public Contest Contest { get; }

    public ContestInstance Instance { get; }

    public StationInfo Me { get; }

    public ContestLog Log { get; }

    public QsoEditor Editor { get; }

    public CountryFile? Countries { get; }

    /// What was published about the stations in this contest before it started.
    public CallHistory History { get; }

    /// The serial numbers the whole entry has taken, one highest per band. A
    /// number is taken from here when the operator starts a contact, not when
    /// it is logged, and the other stations are told at once, so two operators
    /// typing at the same moment cannot send the same number.
    public SerialNumberPool Numbers { get; }

    public string Operator { get; set; } = "";

    /// The computer this station logs as, and which station of the entry it is.
    /// N1MM stamps every contact with both — `NetBiosName` and
    /// `NetworkedCompNr` — and a resync asks for the contacts of one computer
    /// by name, so a contact logged without it belongs to no station.
    public string StationName { get; set; } = "";

    public int StationNumber { get; set; } = 1;

    /// Starts the serial numbers again: the pool is filled from the log, so the
    /// next number is the highest number in it plus one. That is what N1MM's
    /// Reset Serial Numbers at all Stations does, at every station of the
    /// entry, and it leaves the contacts already logged with the numbers they
    /// were sent with.
    public void RestartNumbers()
    {
        SeedNumbers();
        NumbersRestarted?.Invoke(this, EventArgs.Empty);
    }

    /// The numbers have been started again, so a position holding one it took
    /// earlier has to let it go.
    public event EventHandler? NumbersRestarted;

    /// The number a contact on this band would carry. Nothing is taken by
    /// asking; `ReserveNumberOn` is what takes one.
    public int NextNumberOn(Band? band) => Numbers.Next(band);

    /// Takes the next number for a contact about to be worked on this band.
    public int ReserveNumberOn(Band? band) => Numbers.Take(band);

    public event EventHandler? Changed;

    public event EventHandler<Qso>? Logged;

    /// A contact that was edited, with the call and time it had before. The
    /// other stations need the old pair to find their copy of it.
    public event EventHandler<QsoChange>? Edited;

    public event EventHandler<Qso>? Deleted;

    /// Scores the contact, writes it and hands back what was stored: the
    /// timestamp can move by a second when another contact with the same call
    /// already holds it.
    public Qso Add(Qso qso)
    {
        Qso scored = Log.Add(Stamped(qso));
        Qso stored = store.Add(scored);
        if (stored.TimestampUtc != scored.TimestampUtc)
        {
            Log.Replace(stored);
        }
        RecordNumber(stored);
        Logged?.Invoke(this, stored);
        Changed?.Invoke(this, EventArgs.Empty);
        return stored;
    }

    /// Drops every contact one computer made inside a block of time, which is
    /// what a resync asks for before it sends the block again. Returns how many
    /// went.
    public int ClearFromNetwork(string computerName, DateTime fromUtc, TimeSpan length)
    {
        List<Qso> gone = Log.Qsos
            .Where(q =>
                string.Equals(q.StationName, computerName, StringComparison.OrdinalIgnoreCase)
                && q.TimestampUtc >= fromUtc
                && q.TimestampUtc < fromUtc + length)
            .ToList();
        foreach (Qso qso in gone)
        {
            store.Delete(qso.Id);
            Log.Remove(qso.Id);
        }
        if (gone.Count > 0)
        {
            Changed?.Invoke(this, EventArgs.Empty);
        }
        return gone.Count;
    }

    /// Scores the log again and writes the points and multiplier flags of the
    /// contacts from `fromUtc` on back to storage. Returns how many rows were
    /// written.
    ///
    /// The log in memory scores itself whenever it changes, so this is for the
    /// database: N1MM reads the stored points and flags rather than working
    /// them out, and a contact that arrived from another station after the one
    /// that took a multiplier leaves those columns behind.
    public int Rescore(DateTime fromUtc)
    {
        Log.Rescore();
        int written = 0;
        foreach (Qso qso in Log.Qsos.Where(q => q.TimestampUtc >= fromUtc))
        {
            store.Update(qso);
            written++;
        }
        Changed?.Invoke(this, EventArgs.Empty);
        return written;
    }

    /// Whose contact this is. A contact that already names a station keeps it.
    private Qso Stamped(Qso qso) =>
        StationName.Length == 0 || qso.StationName.Length > 0
            ? qso
            : qso with { StationName = StationName, NetworkedComputerNumber = StationNumber };

    public void Delete(string id)
    {
        Qso? gone = Log.Qsos.FirstOrDefault(q => q.Id == id);
        store.Delete(id);
        Log.Remove(id);
        if (gone is not null)
        {
            Deleted?.Invoke(this, gone);
        }
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// Changes one field of a logged contact. A refused edit leaves the log
    /// alone and the caller gets the reason back.
    public QsoEdit Edit(string id, QsoField field, string text) =>
        EditWith(id, before => Editor.Apply(before, field, text));

    /// Replaces a logged contact with one the caller has already built and
    /// checked. The edit contact dialog changes many fields at once and comes
    /// in this way.
    public void Update(Qso qso) => EditWith(qso.Id, _ => QsoEdit.Accept(qso));

    public void NotifyChanged() => Changed?.Invoke(this, EventArgs.Empty);

    /// A contact worked by another station of a multi-operator entry. It is
    /// scored here from the rules rather than trusting what the sender worked
    /// out, and it raises no `Logged`, so it does not go back out to the other
    /// stations. False when we already hold it.
    public bool AddFromNetwork(Qso qso)
    {
        if (Log.Qsos.Any(q => q.Id == qso.Id))
        {
            return false;
        }
        Qso arrived = store.Add(FromNetwork(qso));
        Log.Insert(arrived);
        RecordNumber(arrived);
        Changed?.Invoke(this, EventArgs.Empty);
        return true;
    }

    /// An edit made at another station. False when we do not hold the contact
    /// it changes.
    public bool ReplaceFromNetwork(Qso qso, string oldCall, DateTime oldTimestampUtc)
    {
        if (Find(qso.Id, oldCall, oldTimestampUtc) is not { } old)
        {
            return false;
        }
        Qso replacement = FromNetwork(qso) with { Id = old.Id };
        store.Update(replacement);
        Log.Replace(replacement);
        Changed?.Invoke(this, EventArgs.Empty);
        return true;
    }

    /// A contact deleted at another station. False when we do not hold it.
    public bool DeleteFromNetwork(string id, string call, DateTime timestampUtc)
    {
        if (Find(id, call, timestampUtc) is not { } gone)
        {
            return false;
        }
        store.Delete(gone.Id);
        Log.Remove(gone.Id);
        Changed?.Invoke(this, EventArgs.Empty);
        return true;
    }

    private Qso FromNetwork(Qso qso) => qso with
    {
        ContestNumber = Instance.ContestNumber,
        IsOriginal = false,
    };

    /// N1MM keys a contact on its call and time, so a message from N1MM carries
    /// no id we would recognise. Fall back to that pair when the id misses.
    private Qso? Find(string id, string call, DateTime timestampUtc) =>
        Log.Qsos.FirstOrDefault(q => id.Length > 0 && q.Id == id)
        ?? Log.Qsos.FirstOrDefault(q =>
            string.Equals(q.Call.Text, call, StringComparison.OrdinalIgnoreCase)
            && q.TimestampUtc == timestampUtc);

    private QsoEdit EditWith(string id, Func<Qso, QsoEdit> change)
    {
        Qso before = Log.Qsos.FirstOrDefault(q => q.Id == id)
            ?? throw new InvalidOperationException($"no contact with id {id} in the log");
        QsoEdit edit = change(before);
        if (edit.Result is not null)
        {
            store.Update(edit.Result);
            Log.Replace(edit.Result);
            Edited?.Invoke(this, new QsoChange(edit.Result, before.Call.Text, before.TimestampUtc));
            Changed?.Invoke(this, EventArgs.Empty);
        }
        return edit;
    }

    /// Fills the pool from the numbers the log already holds. A contest whose
    /// `ResetSNEverySession` is set starts over in each session, so only the
    /// contacts of the session we are in count.
    private void SeedNumbers()
    {
        IEnumerable<Qso> counted = Contest.ResetsSerialNumbersEachSession
            ? Log.Qsos.Where(q =>
                Contest.SessionOf(q.TimestampUtc) == Contest.SessionOf(DateTime.UtcNow))
            : Log.Qsos;
        Numbers.SeedFrom(counted.Where(Contest.IsContact));
    }

    /// The sent number of a contact, and nothing else. A WAE QTC row carries
    /// the serial of the contact it reports in the same column, and that
    /// number was sent by the station being reported rather than by us, so
    /// taking it would push our own numbers up. N1MM leaves the QTC rows out
    /// of the same query, in `QSONrsByBand`.
    private void RecordNumber(Qso qso)
    {
        if (Contest.IsContact(qso))
        {
            Numbers.Record(qso.SentNumber, qso.Band);
        }
    }
}