using System.Reflection;
using System.Text.Json;
using Nonemm.Core;

namespace Nonemm.App.Configuration;

/// What the program remembers between runs.
public sealed record Settings
{
    public string DatabasePath { get; init; } = "";

    public int ContestNumber { get; init; }

    public StoredStation Station { get; init; } = new();

    public string ClusterHost { get; init; } = "";

    public int ClusterPort { get; init; } = 7373;

    /// Only the few nodes that ask for one; most take the callsign alone.
    public string ClusterPassword { get; init; } = "";

    public IReadOnlyList<string> ClusterCommands { get; init; } = [];

    /// The nodes the operator keeps, listed on the telnet window's Clusters
    /// tab. Connecting to one copies it into `ClusterHost` and the rest.
    public IReadOnlyList<StoredClusterNode> ClusterNodes { get; init; } = [];

    /// Off for a node that wants the call typed in by hand.
    public bool ClusterAutoLogon { get; init; } = true;

    /// The call sent at login, or empty for the station callsign.
    public string ClusterLogonCall { get; init; } = "";

    /// How often to send an empty line to a node that has said nothing. Nodes
    /// drop a connection that has been quiet for a quarter of an hour.
    public int ClusterKeepAliveMinutes { get; init; } = 4;

    /// The buttons along the bottom of the telnet window. Empty means the ones
    /// in `StoredTelnetButton.Default`.
    public IReadOnlyList<StoredTelnetButton> TelnetButtons { get; init; } = [];

    /// Which cluster spots reach the bandmap.
    public StoredSpotFilter SpotFilter { get; init; } = new();

    /// How long a spot stays on the bandmap. N1MM's own default is 60.
    public int SpotTimeoutMinutes { get; init; } = 60;

    /// Moves each incoming CW spot by a few tens of hertz, so the operator has
    /// to find the station by ear. N1MM calls it randomising.
    public bool RandomizeSpots { get; init; }

    /// Enter sends the message the contact has got to, rather than only logging
    /// it. N1MM calls it ESM and most operators run with it on.
    public bool EsmEnabled { get; init; }

    /// N1MM's "big gun" switch: while searching, send the call once and be
    /// ready to copy the exchange rather than calling again.
    public bool EsmSendsCallOnce { get; init; }

    /// Work a station that calls in again while running, which is what N1MM
    /// recommends.
    public bool EsmWorksDupes { get; init; } = true;

    /// Send the call again in front of the message that ends the contact when
    /// it has changed since it went out.
    public bool EsmSendsCorrectedCall { get; init; } = true;

    /// How close to a spot the radio has to be for the entry window to say the
    /// station is there. N1MM asks for the same number, one per mode; this is
    /// one number for all of them.
    public int TuningToleranceHertz { get; init; } = 300;

    /// How far `{FREQUP}` and `{FREQDN}` move the radio. N1MM asks for the same
    /// number in its Configurer.
    public int FrequencyStepHertz { get; init; } = 100;

    /// How far `{PGUP}` and `{PGDN}` move the radio.
    public int PageStepHertz { get; init; } = 1_000;

    /// Sent with a spot the operator puts on the cluster with Alt+P.
    public string SpotComment { get; init; } = "";

    /// One entry per radio, in radio-number order. A second radio makes the
    /// station SO2R.
    public IReadOnlyList<StoredRadio> Radios { get; init; } = [];

    /// Written by versions that only knew one radio. Read once, to fill
    /// `Radios` in, and never written again.
    public string RigctldHost { get; init; } = "";

    public int RigctldPort { get; init; }

    public bool RadioEnabled { get; init; }

    public bool ClusterEnabled { get; init; }

    public string NetworkStationName { get; init; } = "";

    public int NetworkPort { get; init; } = 12060;

    public bool NetworkEnabled { get; init; }

    public IReadOnlyList<string> NetworkPeers { get; init; } = [];

    /// The call history file for this contest, or empty for none. They are
    /// published per contest, so this is not a fixed name.
    public string CallHistoryFile { get; init; } = "";

    /// The serial port of an SO2R box speaking OTRSP, or empty for none. The
    /// box routes the transmitter and the headphones between the two radios.
    public string So2rBoxPort { get; init; } = "";

    /// `none`, `cwdaemon` or `winkeyer`.
    public string KeyerKind { get; init; } = "none";

    public string KeyerHost { get; init; } = "127.0.0.1";

    public int KeyerPort { get; init; } = 6789;

    public string KeyerSerialPort { get; init; } = "";

    public int KeyerSpeed { get; init; } = 28;

    /// How long alternating CQ leaves between one message ending and the other
    /// radio starting. N1MM asks for the same number and will not go below
    /// 100 ms, because an SO2R box works relays.
    public int AlternatingCqGapMs { get; init; } = 100;

    /// How the WAE QTC window behaves. The names and the defaults are N1MM's:
    /// it skips the confirm and ready steps out of the box, clears the header
    /// when the header is asked for again, and leaves a line alone when the
    /// line is.
    public int QtcLinesPerSeries { get; init; } = 10;

    public bool QtcSkipReady { get; init; } = true;

    public bool QtcSkipConfirm { get; init; } = true;

    public bool QtcHeaderAgainClears { get; init; } = true;

    public bool QtcAgainClearsLine { get; init; }

    /// Sub-band boundaries the operator has changed. Empty means the defaults
    /// in `BandPlan.Default`; an entry replaces one band's boundaries.
    public IReadOnlyList<StoredSubBand> SubBands { get; init; } = [];

    /// The function key messages as the text of an N1MM `.mc` file, which is
    /// what the editor edits and what import and export read and write. Empty
    /// means the built-in messages.
    public string CwMessageFile { get; init; } = "";

    public string PhoneMessageFile { get; init; } = "";

    /// Written by versions that kept twelve messages and no labels. Read once,
    /// to fill the file text in, and never written again.
    public IReadOnlyList<string> CwMessages { get; init; } = [];

    public IReadOnlyList<string> PhoneMessages { get; init; } = [];

    /// Reflection rather than a generated serializer: the generated one hands
    /// back null for every property the file leaves out instead of the value
    /// the property is declared with.
    private static readonly JsonSerializerOptions Json = new() { WriteIndented = true };

    public static Settings Load(string path)
    {
        if (!File.Exists(path))
        {
            return new Settings();
        }
        try
        {
            Settings read = JsonSerializer.Deserialize<Settings>(File.ReadAllText(path), Json) ?? new Settings();
            FillNulls(read);
            return Migrated(read);
        }
        catch (JsonException)
        {
            // a settings file that will not parse is replaced rather than
            // stopping the program before a contest
            return new Settings();
        }
    }

    /// The defaults with the operator's changes applied over them.
    public BandPlan ToBandPlan()
    {
        BandPlan plan = BandPlan.Default;
        foreach (StoredSubBand stored in SubBands)
        {
            if (stored.ToSegments() is { } segments)
            {
                plan = plan.With(segments);
            }
        }
        return plan;
    }

    public void Save(string path) =>
        File.WriteAllText(path, JsonSerializer.Serialize(this, Json));

    /// A settings file can hold a null where the property is not nullable: a
    /// file written before the property existed and then edited, or one an
    /// older version wrote. JSON puts the null in and the property's own
    /// default never runs, so the program reads a null it does not expect.
    /// Every null is put back to the default the property declares, top to
    /// bottom, so nothing downstream has to check.
    private static void FillNulls(object target)
    {
        Type type = target.GetType();
        object fresh = Activator.CreateInstance(type)!;
        foreach (PropertyInfo property in type.GetProperties(BindingFlags.Public | BindingFlags.Instance))
        {
            if (!property.CanWrite || property.GetIndexParameters().Length > 0)
            {
                continue;
            }
            object? value = property.GetValue(target);
            if (value is null)
            {
                property.SetValue(target, property.GetValue(fresh));
            }
            else if (value is System.Collections.IEnumerable items and not string)
            {
                foreach (object? item in items)
                {
                    FillOurOwn(item);
                }
            }
            else
            {
                FillOurOwn(value);
            }
        }
    }

    /// Only the types in this folder are walked into. A string, a number or a
    /// framework type has nothing to fill in.
    private static void FillOurOwn(object? value)
    {
        if (value is not null && value.GetType().Namespace == typeof(Settings).Namespace)
        {
            FillNulls(value);
        }
    }

    /// The twelve messages an older settings file holds, written out as the
    /// text of a function key file with the labels this program used then.
    private static string FileFrom(IReadOnlyList<string> messages)
    {
        IReadOnlyList<(string Key, string Label)> keys =
        [
            ("F1", "CQ"), ("F2", "Exch"), ("F3", "TU"), ("F4", "MyCall"),
            ("F5", "HisCall"), ("F6", "QSO B4"), ("F7", "?"), ("F8", "Agn"),
            ("F9", "Nr?"), ("F10", "Call?"), ("F11", "Spot"), ("F12", "Wipe"),
        ];
        return string.Join(
            '\n',
            messages.Select((message, at) => at < keys.Count
                ? $"{keys[at].Key} {keys[at].Label},{message}"
                : $",{message}"));
    }

    /// Carries what older settings files hold into the shape this one uses: the
    /// single radio into the list of radios, and the twelve messages into the
    /// text of a function key file.
    private static Settings Migrated(Settings settings)
    {
        if (settings.RigctldHost.Length > 0 && settings.Radios.Count == 0)
        {
            settings = settings with
            {
                Radios = [new StoredRadio
                {
                    Host = settings.RigctldHost,
                    Port = settings.RigctldPort,
                    IsEnabled = settings.RadioEnabled,
                }],
                RigctldHost = "",
                RigctldPort = 0,
                RadioEnabled = false,
            };
        }
        if (settings.CwMessages.Count > 0 && settings.CwMessageFile.Length == 0)
        {
            settings = settings with { CwMessageFile = FileFrom(settings.CwMessages), CwMessages = [] };
        }
        if (settings.PhoneMessages.Count > 0 && settings.PhoneMessageFile.Length == 0)
        {
            settings = settings with
            {
                PhoneMessageFile = FileFrom(settings.PhoneMessages),
                PhoneMessages = [],
            };
        }
        return settings;
    }
}

/// One band's sub-band boundaries as they are stored. Kilohertz, because that
/// is what the operator types into the editor.
public sealed record StoredSubBand
{
    public string Band { get; init; } = "";

    public double CwHigh { get; init; }

    public double DigitalLow { get; init; }

    public double DigitalHigh { get; init; }

    /// Null when the band name is not one we know, or the CW boundary is
    /// missing: an entry that cannot be read leaves the default in place.
    public BandSegments? ToSegments() =>
        Bands.Named(Band) is { } band && CwHigh > 0
            ? new BandSegments(
                band,
                Frequency.FromKilohertz(CwHigh),
                Frequency.FromKilohertz(DigitalLow),
                Frequency.FromKilohertz(DigitalHigh))
            : null;

    public static StoredSubBand From(BandSegments segments) => new()
    {
        Band = segments.Band.Name,
        CwHigh = segments.CwHigh.Kilohertz,
        DigitalLow = segments.DigitalLow.Kilohertz,
        DigitalHigh = segments.DigitalHigh.Kilohertz,
    };
}

/// One radio's `rigctld`.
public sealed record StoredRadio
{
    public string Host { get; init; } = "127.0.0.1";

    public int Port { get; init; } = 4532;

    public bool IsEnabled { get; init; }
}

/// The operator's station as it is stored, kept separate from `StationInfo` so
/// the file format does not follow every change to the domain type.
public sealed record StoredStation
{
    public string Callsign { get; init; } = "";

    public int CqZone { get; init; }

    public int ItuZone { get; init; }

    public string Continent { get; init; } = "";

    public string CountryPrefix { get; init; } = "";

    public string State { get; init; } = "";

    public string Province { get; init; } = "";

    public string ArrlSection { get; init; } = "";

    public string GridSquare { get; init; } = "";

    public string County { get; init; } = "";

    public string Name { get; init; } = "";

    public string Power { get; init; } = "";

    public string Club { get; init; } = "";

    public int Check { get; init; }

    public string Precedence { get; init; } = "A";

    public StationInfo ToStationInfo() => new()
    {
        Callsign = Callsign,
        CqZone = CqZone,
        ItuZone = ItuZone,
        Continent = Continent,
        CountryPrefix = CountryPrefix,
        State = State,
        Province = Province,
        ArrlSection = ArrlSection,
        GridSquare = GridSquare,
        County = County,
        Name = Name,
        Power = Power,
        Club = Club,
        Check = Check,
        Precedence = Precedence,
    };
}