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

namespace Nonemm.Session;

/// One radio and what the operator is typing on it. A single-radio station has
/// one of these; an SO2R station has two, sharing one `ContestSession` and so
/// one log, one score and one run of serial numbers.
public sealed class OperatingPosition
{
    public OperatingPosition(ContestSession session, int radioNumber = 1)
    {
        Session = session;
        RadioNumber = radioNumber;
        Entry = new EntryFields(session.Contest.ExchangeFieldsFor(session.Me));
        FillSentExchange();
        // N1MM fills the sent serial in again on every entry window when a
        // contact is logged, so the other radio is not left showing the number
        // that has just gone
        Session.Logged += (_, _) => FillSentExchange();
        Session.NumbersRestarted += (_, _) => LetTheNumberGo();
        Entry.CallStarted += (_, _) => ReserveNumber();
    }

    public ContestSession Session { get; }

    /// 1 or 2. Contacts record which radio made them.
    public int RadioNumber { get; }

    public EntryFields Entry { get; }

    /// With no radio connected this stays where it was last typed.
    public Frequency Frequency { get; private set; } = Bands.Band20M.Low;

    /// The band this position is on. A contest that numbers per band takes the
    /// serial number against it.
    public Band? Band => Bands.ForFrequency(Frequency);

    /// Where the radio transmits when working split, and zero when it is not.
    public Frequency TransmitFrequency { get; private set; } = Frequency.Zero;

    public Mode Mode { get; private set; } = Modes.Cw;

    /// True while the operator is calling CQ on this radio rather than
    /// searching. Each radio runs or searches on its own.
    public bool IsRunning
    {
        get => running;
        set
        {
            if (value && !running)
            {
                CqFrequency = Frequency;
            }
            running = value;
        }
    }

    private bool running;

    /// Where this radio last started running or sent a CQ. It stays after the
    /// radio goes back to searching, so the operator can return to it.
    public Frequency? CqFrequency { get; set; }

    /// How far, in hertz, the radio can move off the CQ frequency before the
    /// position goes back to searching.
    public long CqLeaveHertz { get; set; } = 3_000;

    /// The other operator's name and a note about the contact. Neither is part
    /// of any exchange: the name is what a contact being quick edited already
    /// held, and the note is what Ctrl+N asks for. Neither counts towards a
    /// complete exchange.
    public string OtherName { get; set; } = "";

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

    /// The time this station sent, `HHmm`, for a contest that exchanges it.
    /// Empty until the exchange has gone out.
    public string SentTime { get; private set; } = "";

    public Contest Contest => Session.Contest;

    public ContestInstance Instance => Session.Instance;

    public StationInfo Me => Session.Me;

    public ContestLog Log => Session.Log;

    public QsoEditor Editor => Session.Editor;

    /// The serial number this position sends. It is taken from the pool at the
    /// first character of the callsign and held until the contact is logged;
    /// before that it is what the next contact on this band would carry.
    public int SentNumber => reserved ?? Session.NextNumberOn(Band);

    private int? reserved;

    /// Takes this position's number, unless it has one already. N1MM takes it
    /// at the first character of the callsign rather than at logging, so the
    /// number is on the network while the contact is still being worked and
    /// the other operator's next number goes above it.
    private void ReserveNumber()
    {
        if (reserved is not null || !Contest.HasSerialNumbers)
        {
            return;
        }
        reserved = Session.ReserveNumberOn(Band);
        FillSentExchange();
        Session.NotifyChanged();
    }

    /// Gives up the number this position holds, so the next contact takes a
    /// fresh one. A wipe keeps it, as N1MM does: the contact is still to come.
    private void LetTheNumberGo()
    {
        reserved = null;
        FillSentExchange();
    }

    public void Tune(Frequency frequency, Mode? mode = null, Frequency? transmitFrequency = null)
    {
        bool modeChanged = mode is not null && mode.Category != Mode.Category;
        Frequency = frequency;
        Mode = mode ?? Mode;
        if (modeChanged)
        {
            FillSentExchange();
        }
        TransmitFrequency = transmitFrequency ?? TransmitFrequency;
        if (running && CqFrequency is { } cq && Math.Abs(frequency.Hertz - cq.Hertz) > CqLeaveHertz)
        {
            running = false;
        }
        Session.NotifyChanged();
    }

    /// What the log says about what is typed now. Null when there is no call to
    /// judge yet.
    public Verdict? Verdict()
    {
        string call = Entry.Call.Trim();
        return call.Length == 0 ? null : Log.Judge(BuildQso(call));
    }

    /// The same on another band and mode, which is what the band panel asks for
    /// each of its cells.
    public Verdict? Verdict(Frequency frequency, Mode mode)
    {
        string call = Entry.Call.Trim();
        return call.Length == 0
            ? null
            : Log.Judge(BuildQso(call) with { Frequency = frequency, Mode = mode });
    }

    public CountryLookup? Country() =>
        Entry.Call.Trim().Length == 0 ? null : Session.Countries?.Find(Entry.Call.Trim());

    /// Every earlier contact with the call being typed, newest first.
    public IReadOnlyList<Qso> WorkedBefore() =>
        Entry.Call.Trim().Length == 0 ? [] : Log.WorkedBefore(Entry.Call.Trim());

    /// The frequency typed into the callsign box, if that is what it holds.
    public Frequency? PendingQsy() => FrequencyEntry.Parse(Entry.Call);

    /// The mode typed into the callsign box, if that is what it holds.
    public Mode? PendingMode() => ModeEntry.Parse(Entry.Call, Frequency);

    /// What working this call on the band and mode we are on would bring,
    /// judged from the call alone. A call that has not been worked has sent no
    /// exchange, so a contest scored on what the other station sends can be
    /// judged no further than this.
    public Verdict? JudgeCall(string call)
    {
        string wanted = call.Trim();
        return wanted.Length == 0
            ? null
            : Log.Judge(new Qso
            {
                Id = "",
                TimestampUtc = DateTime.UtcNow,
                Call = Callsign.Parse(wanted),
                Frequency = Frequency,
                Mode = Mode,
                ContestName = Contest.Name,
            });
    }

    /// The calls answering our CQ that have not been worked yet.
    public CallStack Stack { get; } = new();

    /// N1MM's {STACKANOTHER} and Ctrl+Alt+G: the call being typed goes on the
    /// stack and the entry is cleared, so the next caller can be copied. Only
    /// while running, and a dupe is not stacked. False when nothing was
    /// stacked.
    public bool StackAnother()
    {
        if (!IsRunning || !IsWorthStacking(Entry.Call.Trim()))
        {
            return false;
        }
        Verdict? worth = Verdict();
        if (worth is null || worth.IsDupe)
        {
            return false;
        }
        Stack.Add(Entry.Call.Trim(), worth.IsNewMultiplier);
        ClearEntry();
        return true;
    }

    /// N1MM's Alt+G: the call on top of the stack replaces what is typed.
    /// False when the stack is empty, and then the entry is left alone.
    public bool GrabStacked()
    {
        if (Stack.IsEmpty)
        {
            return false;
        }
        string call = Stack.Next();
        ClearEntry();
        Entry.Call = call;
        Entry.FocusOn(0);
        Session.NotifyChanged();
        return true;
    }

    /// N1MM's {SOCALLSTACK}: one key both stacks and unstacks. With a call
    /// typed and the stack holding one, the two are swapped — the stacked call
    /// comes off first, so the typed call cannot come straight back. With the
    /// box empty it takes the next call off; with the stack empty it puts the
    /// typed call on. Only while running, and a dupe or a frequency is left
    /// alone. False when there was nothing to do, which is what N1MM reports
    /// back to ESM.
    public bool SwapWithStack()
    {
        if (!IsRunning)
        {
            return false;
        }
        string call = Entry.Call.Trim();
        if (call.Length == 0)
        {
            return GrabStacked();
        }
        if (!IsWorthStacking(call) || Verdict() is not { IsDupe: false } worth)
        {
            return false;
        }
        bool isMultiplier = worth.IsNewMultiplier;
        string next = Stack.Next();
        Stack.Add(call, isMultiplier);
        ClearEntry();
        Entry.Call = next;
        Entry.FocusOn(0);
        Session.NotifyChanged();
        return next.Length > 0;
    }

    /// A frequency typed into the callsign box is a band change, not a call,
    /// and our own callsign is never stacked. N1MM refuses its own call only
    /// while the stack is empty.
    private bool IsWorthStacking(string call) =>
        call.Length >= CallStack.ShortestCall
        && !call.All(c => char.IsAsciiDigit(c) || c == '.')
        && !string.Equals(call, Me.Callsign, StringComparison.OrdinalIgnoreCase);

    /// The first entry box holding something that cannot be logged, and why.
    /// Null when everything typed can go in the log. The log window checks the
    /// same way, so a value refused here is refused there.
    public EntryProblem? EntryProblem() => ExchangeCheck.Problem(Entry, Mode);

    /// Logs what is typed and clears the entry. Throws when the entry is not
    /// complete or holds a value the contest will not take, so a caller that
    /// has not checked cannot lose an exchange or log nonsense.
    public Qso LogContact()
    {
        if (!IsEntryComplete)
        {
            throw new InvalidOperationException($"the exchange for {Entry.Call} is not complete");
        }
        if (EntryProblem() is { } problem)
        {
            throw new InvalidOperationException(problem.Message);
        }
        return Store();
    }

    /// Logs what is typed although the exchange is short or a box holds
    /// something the contest will not take, which is N1MM's `{FORCELOG}`. A
    /// contact in the log with a hole in it can be filled in afterwards; one
    /// that was never logged cannot. The callsign is still required, because a
    /// row with no callsign in it is not a contact.
    public Qso LogContactAnyway()
    {
        if (Entry.Call.Trim().Length == 0)
        {
            throw new InvalidOperationException("there is no callsign to log");
        }
        return Store();
    }

    private Qso Store()
    {
        StampSentTime();
        Qso stored = Session.Add(Noted(BuildQso(Entry.Call.Trim())));
        // the number went with the contact, so the next one starts again from
        // the pool
        reserved = null;
        Entry.Clear();
        FillSentExchange();
        OtherName = "";
        Comment = "";
        SentTime = "";
        return stored;
    }

    /// Notes the time the exchange went out, which the BARTG RTTY contest
    /// sends and logs. The first message of a contact sets it, so the time in
    /// the log is the time the other station copied, not the time the contact
    /// was logged. Does nothing for the contests that do not send a time.
    public void StampSentTime()
    {
        if (Contest.StampsSentTime && SentTime.Length == 0 && Entry.Call.Trim().Length > 2)
        {
            SentTime = DateTime.UtcNow.ToString("HHmm");
            Session.NotifyChanged();
        }
    }

    /// Puts what this station sends into the boxes that show it: the report
    /// and the serial number. N1MM keeps both filled in and steps over them,
    /// so the number going out is on the screen without being typed.
    public void FillSentExchange()
    {
        foreach (ExchangeField field in Entry.Exchange.Where(f => f.IsSent))
        {
            Entry.Set(
                field.Slot,
                field.Slot == ExchangeSlot.SentReport ? DefaultReport() : SentNumber.ToString());
        }
    }

    /// Puts the report the operator would send anyway into the report boxes
    /// that are empty: 599 on CW and digital modes, 59 on phone. N1MM does the
    /// same when the callsign box is left, which is why neither program stops
    /// on a report box.
    public bool FillReports()
    {
        bool filled = false;
        for (int at = 0; at < Entry.Exchange.Count; at++)
        {
            if (Entry.Exchange[at].Kind == ExchangeFieldKind.Report && Entry[at + 1].Trim().Length == 0)
            {
                Entry[at + 1] = DefaultReport();
                filled = true;
            }
        }
        if (filled)
        {
            Session.NotifyChanged();
        }
        return filled;
    }

    /// Fills what is already known about the station into the exchange boxes
    /// that are still empty. What the other station actually sends wins, so a
    /// box with something in it is left alone. A zone box takes the call
    /// history file first, then the zone logged on the last contact with the
    /// call, then the zone the country file gives for the callsign, which is
    /// what N1MM does. Returns true when anything was filled.
    public bool FillFromHistory()
    {
        CallHistoryEntry? known = Session.History.Find(Entry.Call);
        bool filled = false;
        for (int at = 0; at < Entry.Exchange.Count; at++)
        {
            ExchangeField field = Entry.Exchange[at];
            string value = known is null ? "" : ExchangeSlots.ValueFrom(known, field);
            if (value.Length == 0)
            {
                value = KnownZone(field);
            }
            if (value.Length == 0 || Entry[at + 1].Trim().Length > 0)
            {
                continue;
            }
            Entry[at + 1] = value;
            filled = true;
        }
        if (filled)
        {
            Session.NotifyChanged();
        }
        return filled;
    }

    /// The zone to suggest for a zone box: the one on the newest earlier
    /// contact with this call that has one, else the country file's zone.
    /// Empty for any other box.
    private string KnownZone(ExchangeField field)
    {
        if (field.Kind is not (ExchangeFieldKind.CqZone or ExchangeFieldKind.ItuZone))
        {
            return "";
        }
        string logged = WorkedBefore()
            .Select(qso => ExchangeSlots.ValueOf(qso, field.Slot))
            .FirstOrDefault(value => value.Length > 0) ?? "";
        if (logged.Length > 0)
        {
            return logged;
        }
        CountryLookup? their = Country();
        int zone = their is null ? 0 : field.Kind == ExchangeFieldKind.CqZone ? their.CqZone : their.ItuZone;
        return zone > 0 ? zone.ToString() : "";
    }

    /// Moves to the next box the operator types in. On top of the report boxes
    /// the entry itself steps over, a contest can say a box is not for this
    /// station: CQ WW RTTY asks only the US and Canada for a state.
    /// True when everything this contest asks for this station has been typed.
    /// A box the walk steps over is not asked for, so it does not hold the
    /// contact up: `MoveFocus` and this read the same rule.
    public bool IsEntryComplete => Entry.IsComplete(Applies);

    private bool Applies(ExchangeField field) => !Contest.SkipsField(field, Country());

    public void MoveFocus(bool forward)
    {
        CountryLookup? their = Country();
        for (int step = 0; step < Entry.FieldCount; step++)
        {
            if (forward)
            {
                Entry.Advance();
            }
            else
            {
                Entry.Retreat();
            }
            if (Entry.Focus == 0 || !Contest.SkipsField(Entry.Exchange[Entry.Focus - 1], their))
            {
                return;
            }
        }
    }

    /// The logged contact the boxes are re-editing, or null while a new one is
    /// being typed. N1MM calls this quick edit: Ctrl+Q steps back through the
    /// log, Ctrl+A forward, Enter writes the changes back and Esc leaves.
    public Qso? Editing { get; private set; }

    private TypedEntry? held;
    private TypedEntry? wiped;

    /// Steps one contact back or forward and loads it into the boxes. False
    /// when the log has nothing that way; stepping forward past the newest
    /// contact leaves quick edit instead.
    public bool QuickEdit(bool forward)
    {
        IReadOnlyList<Qso> qsos = Log.Qsos;
        if (qsos.Count == 0)
        {
            return false;
        }
        int at = Editing is null ? qsos.Count : IndexOf(Editing.Id);
        int wanted = forward ? at + 1 : at - 1;
        if (wanted < 0 || at < 0)
        {
            return false;
        }
        if (wanted >= qsos.Count)
        {
            LeaveQuickEdit();
            return true;
        }
        held ??= Typed();
        Editing = qsos[wanted];
        LoadFrom(Editing);
        Session.NotifyChanged();
        return true;
    }

    /// Puts the boxes back to the contact that was being typed.
    public void LeaveQuickEdit()
    {
        if (Editing is null)
        {
            return;
        }
        Editing = null;
        if (held is { } typed)
        {
            PutBack(typed);
            held = null;
        }
        Session.NotifyChanged();
    }

    /// Writes the boxes back to the contact being quick edited and leaves quick
    /// edit. Null when no contact is being edited. Throws on a value the
    /// contest will not take, the same as logging a new contact does.
    public Qso? SaveQuickEdit()
    {
        if (Editing is null)
        {
            return null;
        }
        if (EntryProblem() is { } problem)
        {
            throw new InvalidOperationException(problem.Message);
        }
        Qso saved = Noted(ApplyExchange(CountryFields.Apply(
            Editing with { Call = Callsign.Parse(Entry.Call.Trim()) }, Session.Countries)));
        Session.Update(saved);
        LeaveQuickEdit();
        return saved;
    }

    /// The contact as it would be logged now, for the dialog that edits the one
    /// in progress.
    public Qso InProgress() => Noted(BuildQso(Entry.Call.Trim()));

    /// Fills the boxes from a contact, as quick edit does.
    public void LoadFrom(Qso qso)
    {
        Entry.Call = qso.Call.Text;
        for (int at = 0; at < Entry.Exchange.Count; at++)
        {
            Entry[at + 1] = QsoExchange.ValueOf(qso, Entry.Exchange[at].Slot);
        }
        OtherName = Entry.Exchange.Any(f => f.Slot == ExchangeSlot.Name) ? "" : qso.Name;
        Comment = qso.Comment;
    }

    private int IndexOf(string id)
    {
        for (int at = 0; at < Log.Qsos.Count; at++)
        {
            if (Log.Qsos[at].Id == id)
            {
                return at;
            }
        }
        return -1;
    }

    /// Clears the boxes, keeping what was in them for `RestoreWiped`. An entry
    /// with nothing typed in it is not worth keeping, so a second wipe does not
    /// throw the first one away.
    public void Wipe()
    {
        if (!Entry.IsEmpty)
        {
            wiped = Typed();
        }
        ClearEntry();
    }

    /// N1MM's Alt+W and its Wipe button: one key both ways. With something in
    /// the boxes it clears them; with the boxes empty it puts back what the
    /// last wipe cleared.
    public void WipeOrRestore()
    {
        if (!RestoreWiped())
        {
            Wipe();
        }
    }

    /// Puts back what the last wipe cleared. False when no wipe
    /// has anything to put back, or when the boxes have something in them
    /// again — N1MM restores into an empty entry only, so nothing typed since
    /// the wipe is lost.
    public bool RestoreWiped()
    {
        if (wiped is not { } typed || !Entry.IsEmpty)
        {
            return false;
        }
        PutBack(typed);
        Entry.FocusOn(0);
        Session.NotifyChanged();
        return true;
    }

    /// Wipes without keeping anything: the call has gone somewhere else, such
    /// as onto the call stack, so there is nothing to put back.
    private void ClearEntry()
    {
        Editing = null;
        held = null;
        Entry.Clear();
        FillSentExchange();
        OtherName = "";
        Comment = "";
        SentTime = "";
        Session.NotifyChanged();
    }

    private TypedEntry Typed() => new(
        Entry.Call,
        [.. Enumerable.Range(1, Entry.FieldCount - 1).Select(f => Entry[f])],
        OtherName,
        Comment,
        SentTime);

    private void PutBack(TypedEntry typed)
    {
        Entry.Call = typed.Call;
        // the contest can have changed since, and with it the boxes there are
        for (int field = 1; field < Entry.FieldCount && field <= typed.Values.Count; field++)
        {
            Entry[field] = typed.Values[field - 1];
        }
        OtherName = typed.Name;
        Comment = typed.Comment;
        SentTime = typed.SentTime;
    }

    /// The name and comment boxes fill the log columns of the same names. A
    /// contest that exchanges a name has already filled that column, and what
    /// was exchanged wins.
    private Qso Noted(Qso qso) => qso with
    {
        Name = qso.Name.Length > 0 ? qso.Name : OtherName.Trim(),
        Comment = qso.Comment.Length > 0 ? qso.Comment : Comment.Trim(),
        MiscText = qso.MiscText.Length > 0 ? qso.MiscText : SentTime,
    };

    /// The report an operator sends without thinking about it: 599 on CW and
    /// digital modes, 59 on phone.
    public string DefaultReport() => Mode.Category switch
    {
        ModeCategory.Cw => "599",
        ModeCategory.Phone => "59",
        _ => "599",
    };

    private Qso BuildQso(string call)
    {
        Qso qso = new()
        {
            Id = Qso.NewId(),
            TimestampUtc = DateTime.UtcNow.AddTicks(-(DateTime.UtcNow.Ticks % TimeSpan.TicksPerSecond)),
            Call = Callsign.Parse(call),
            Frequency = Frequency,
            QsxFrequency = TransmitFrequency,
            Mode = Mode,
            RadioNumber = RadioNumber,
            ContestName = Contest.Name,
            ContestNumber = Instance.ContestNumber,
            SentReport = DefaultReport(),
            SentNumber = SentNumber,
            Operator = Session.Operator.Length > 0 ? Session.Operator : Me.Callsign,
            IsRunQso = IsRunning,
        };
        return ApplyExchange(CountryFields.Apply(qso, Session.Countries));
    }

    private Qso ApplyExchange(Qso qso)
    {
        foreach (ExchangeField field in Entry.Exchange)
        {
            qso = ExchangeSlots.Apply(qso, field.Slot, Entry.ValueOf(field.Slot).Trim());
        }
        return Entry.Exchange.Any(f => f.Slot == ExchangeSlot.Exchange1)
            ? Contest.FromExchange1(qso, Entry.ValueOf(ExchangeSlot.Exchange1).Trim())
            : qso;
    }
}