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

namespace Nonemm.Contests;

/// The contacts of one contest, with the indexes that answer "worked before?"
/// and "new multiplier?" while the operator types.
public sealed class ContestLog
{
    private readonly Contest contest;
    private readonly StationInfo me;
    private readonly CountryFile? countries;
    private readonly List<Qso> qsos = [];
    private readonly Dictionary<string, DateTime> workedKeys = new(StringComparer.Ordinal);

    /// How many QTC lines have gone with each station, either way. It is kept
    /// here rather than counted when a station is judged, because the bandmap
    /// judges every spot it holds on every pass.
    private readonly Dictionary<string, int> trafficWith = new(StringComparer.OrdinalIgnoreCase);
    private readonly HashSet<string> claimedMultipliers = new(StringComparer.Ordinal);
    private readonly Dictionary<ScoreKey, ScoreTally> rows = [];
    private ScoreTally tally = new();

    public ContestLog(
        Contest contest,
        StationInfo me,
        CountryFile? countries,
        ContestEntry? entry = null)
    {
        this.contest = contest;
        this.me = me;
        this.countries = countries;
        Entry = entry ?? new ContestEntry();
    }

    /// The categories and sent exchange of the running entry. The operator can
    /// change them while the contest is open, and the score follows.
    public ContestEntry Entry { get; set; }

    /// The call history file, for a contest that counts a multiplier from it.
    /// The session sets it when the operator loads one.
    public CallHistory History { get; set; } = CallHistory.Empty;

    public Contest Contest => contest;

    public IReadOnlyList<Qso> Qsos => qsos;

    /// The contacts alone. In WAE the log also holds QTC traffic, and a QTC
    /// row is not a contact: its report columns hold the time and callsign of
    /// the contact being reported. Anything that writes contacts out — the
    /// ADIF export — takes these rather than every row.
    public IEnumerable<Qso> Contacts => qsos.Where(contest.IsContact);

    public ScoreTally Tally => tally;

    /// The same score split the way N1MM's score window splits it: a row per
    /// band, and per kind of row as well where the contest has kinds. The
    /// rows add up to `Tally`.
    public IReadOnlyDictionary<ScoreKey, ScoreTally> Rows => rows;

    public int TotalScore => contest.TotalScore(tally, Entry);

    /// How many QTC lines have already gone with this station, either way.
    public int TrafficWith(string call) =>
        trafficWith.TryGetValue(call.Trim(), out int count) ? count : 0;

    /// What logging this contact right now would do, without logging it.
    public Verdict Judge(Qso candidate)
    {
        if (!candidate.IsClaimed)
        {
            return new Verdict(false, 0, []);
        }
        QsoContext context = ContextFor(candidate);
        if (!contest.IsContact(candidate))
        {
            return new Verdict(false, contest.PointsFor(context), []);
        }
        int trafficLeft = contest.TrafficLeft(context, TrafficWith(candidate.Call.Text));
        if (IsWorked(candidate))
        {
            return Verdict.Dupe with { TrafficLeft = trafficLeft };
        }
        List<Multiplier> newOnes = [];
        foreach (Multiplier multiplier in contest.MultipliersFor(context))
        {
            if (!claimedMultipliers.Contains(MultiplierKey(multiplier, candidate)))
            {
                newOnes.Add(multiplier);
            }
        }
        // a contest can pay a bonus for a new multiplier, so the flags have to
        // be set before the points are worked out
        QsoContext scored = ContextFor(ApplyMultiplierFlags(candidate, newOnes));
        return new Verdict(
            false,
            IsContestMode(candidate) ? contest.PointsFor(scored) : 0,
            newOnes,
            trafficLeft);
    }

    /// Adds the contact and returns it with points and multiplier flags filled in.
    public Qso Add(Qso qso)
    {
        Verdict verdict = Judge(qso);
        Qso scored = ApplyVerdict(qso, verdict);
        qsos.Add(scored);
        Index(scored, verdict);
        return scored;
    }

    /// Loads contacts read back from storage. Points and multiplier flags in
    /// the stored rows are ignored and worked out again from the rules.
    public void Restore(IEnumerable<Qso> stored)
    {
        qsos.AddRange(stored);
        Rebuild();
    }

    /// Adds a contact that may be older than ones already logged, which is what
    /// a contact from another station of the entry can be, and scores the log
    /// again: the earlier of two contacts is the one that claims a multiplier.
    public void Insert(Qso qso)
    {
        qsos.Add(qso);
        Rebuild();
    }

    public void Remove(string id)
    {
        qsos.RemoveAll(q => q.Id == id);
        Rebuild();
    }

    public void Replace(Qso qso)
    {
        int at = qsos.FindIndex(q => q.Id == qso.Id);
        if (at < 0)
        {
            throw new InvalidOperationException($"no contact with id {qso.Id} in the log");
        }
        qsos[at] = qso;
        Rebuild();
    }

    /// A station worked before, under the contest's dupe rule. A contest with
    /// a dupe window — N1MM's `DupeQSOMinutesAgo` — lets the same station be
    /// worked again once the window has passed.
    public bool IsWorked(Qso candidate)
    {
        if (contest.DupeScope == DupeScope.Never || !contest.IsContact(candidate))
        {
            return false;
        }
        if (!workedKeys.TryGetValue(DupeKey(candidate), out DateTime last))
        {
            return false;
        }
        return contest.DupeWindow is not { } window
            || (candidate.TimestampUtc - last).Duration() < window;
    }

    /// Every contact with this call, newest first.
    public IReadOnlyList<Qso> WorkedBefore(string call) =>
        qsos.Where(q => string.Equals(q.Call.Text, call, StringComparison.OrdinalIgnoreCase))
            .OrderByDescending(q => q.TimestampUtc)
            .ToList();

    /// A contact in a mode the contest does not run — a tuning carrier logged
    /// by accident, or a CW contact in an SSB contest — scores nothing. It
    /// still brings its multiplier, which is what N1MM logs. A contest with no
    /// mode of its own takes every mode.
    private bool IsContestMode(Qso qso) =>
        contest.Modes.Count == 0 || contest.Modes.Contains(qso.Mode.Category);

    /// A maritime or aeronautical mobile belongs to no country, and the
    /// contest still has to know which continent it is working, so the call it
    /// is signing from is looked up when the call as sent places nowhere. What
    /// that country counts for is the contest's decision.
    private QsoContext ContextFor(Qso qso) =>
        new(qso, countries?.Find(qso.Call) ?? countries?.Find(qso.Call.Station), me, Entry)
        {
            History = History,
        };

    private Qso ApplyVerdict(Qso qso, Verdict verdict) =>
        ApplyMultiplierFlags(qso, verdict.NewMultipliers) with
        {
            Points = verdict.Points,
            ContactType = ContactTypeOf(qso),
        };

    /// N1MM's contact type column, which it writes in `Contact.IsDupe`: `D`
    /// for a station already worked, `N` for one this entry may not work at
    /// all, and empty for an ordinary contact. Every contest is marked the
    /// same way; what changes between them is what counts as a dupe and which
    /// stations are workable, and both of those come from the contest here as
    /// they do there.
    ///
    /// Traffic keeps an empty column, which is what N1MM's QTC window writes:
    /// its `IsDupe` only marks a row while the program is logging contacts.
    private string ContactTypeOf(Qso qso)
    {
        if (!contest.IsContact(qso))
        {
            return "";
        }
        // a mark that came with the contact stands: N1MM marks a contact when
        // it logs or edits it and never clears the mark in a pass over the
        // log, so a row that arrived from another station or from an N1MM
        // database keeps what it was given
        if (IsWorked(qso) || qso.ContactType.Equals("D", StringComparison.OrdinalIgnoreCase))
        {
            return "D";
        }
        // N1MM adds our own callsign to whatever the contest says
        bool workable = contest.IsWorkable(ContextFor(qso))
                        && !qso.Call.Text.Equals(me.Callsign, StringComparison.OrdinalIgnoreCase);
        return workable ? "" : "N";
    }

    private static Qso ApplyMultiplierFlags(Qso qso, IReadOnlyList<Multiplier> claimed) => qso with
    {
        IsMultiplier1 = claimed.Any(m => m.Index == 1),
        IsMultiplier2 = claimed.Any(m => m.Index == 2),
        IsMultiplier3 = claimed.Any(m => m.Index == 3),
    };

    /// Adds the contact to the score and to the indexes that answer "worked
    /// before?" and "new multiplier?". An unclaimed contact enters neither:
    /// N1MM scores it as zero and leaves it out of both searches, so it takes
    /// nothing away from a later contact with the same call or multiplier. A
    /// contact marked as a dupe is the other way round — N1MM searches for
    /// dupes and multipliers among it, and leaves it out of the score alone.
    private void Index(Qso qso, Verdict verdict)
    {
        if (!qso.IsClaimed)
        {
            return;
        }
        bool counts = qso.IsInScore;
        ScoreTally row = RowFor(qso);
        if (counts)
        {
            tally.AddQso(verdict.Points);
            row.AddQso(verdict.Points);
        }
        if (!contest.IsContact(qso))
        {
            string station = qso.Call.Text.Trim();
            trafficWith[station] = trafficWith.GetValueOrDefault(station) + 1;
            return;
        }
        workedKeys[DupeKey(qso)] = qso.TimestampUtc;
        foreach (Multiplier multiplier in verdict.NewMultipliers)
        {
            claimedMultipliers.Add(MultiplierKey(multiplier, qso));
            if (counts)
            {
                tally.AddMultiplier(multiplier);
                row.AddMultiplier(multiplier);
            }
        }
    }

    /// Scores the whole log again. Nothing here needs it — every change
    /// rescores what it touches — but the stored points and multiplier flags
    /// are written from this, and a caller that is about to write them asks for
    /// a pass first.
    public void Rescore() => Rebuild();

    /// Rescores the whole log. A removed or edited contact can hand its
    /// multiplier to a later one, which only a full pass gets right.
    private ScoreTally RowFor(Qso qso)
    {
        ScoreKey key = new(qso.Band?.Name ?? "", contest.RowKindFor(qso));
        if (!rows.TryGetValue(key, out ScoreTally? row))
        {
            row = new ScoreTally();
            rows[key] = row;
        }
        return row;
    }

    private void Rebuild()
    {
        workedKeys.Clear();
        trafficWith.Clear();
        claimedMultipliers.Clear();
        rows.Clear();
        tally = new ScoreTally();
        List<Qso> ordered = qsos.OrderBy(q => q.TimestampUtc).ToList();
        qsos.Clear();
        foreach (Qso qso in ordered)
        {
            Verdict verdict = Judge(qso);
            Qso scored = ApplyVerdict(qso, verdict);
            qsos.Add(scored);
            Index(scored, verdict);
        }
    }

    private string DupeKey(Qso qso)
    {
        string call = qso.Call.Text.ToUpperInvariant();
        string extra = contest.ExtraDupeKey(qso);
        string key = contest.DupeScope switch
        {
            DupeScope.Once => call,
            DupeScope.PerBand => $"{call}|{qso.Band?.Name}",
            DupeScope.PerMode => $"{call}|{qso.Mode.Category}",
            DupeScope.PerBandAndMode => $"{call}|{qso.Band?.Name}|{qso.Mode.Category}",
            _ => call,
        };
        // a station worked in an earlier session may be worked again
        key = $"{key}|{contest.SessionOf(qso.TimestampUtc)}";
        return extra.Length == 0 ? key : $"{key}|{extra}";
    }

    private string MultiplierKey(Multiplier multiplier, Qso qso) =>
        contest.ResetsMultipliersEachSession
            ? $"{multiplier.Index}|{multiplier.Value}|{multiplier.Scope}|{contest.SessionOf(qso.TimestampUtc)}"
            : $"{multiplier.Index}|{multiplier.Value}|{multiplier.Scope}";
}