namespace ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Cip;

/// <summary>How CIP requests reach the target's message router (review finding B3; the captures decide
/// each family's mode).</summary>
public enum CipRouting
{
    /// <summary>Forward Open a class-3 connection, then SendUnitData. Logix and Micro800 (empty route).</summary>
    Connected,

    /// <summary>SendRRData wrapping each request in Unconnected Send (0x52) carrying the route.</summary>
    UnconnectedSend,

    /// <summary>SendRRData carrying the request bare; any configured CIP path is ignored (PCCC families).</summary>
    Direct,
}

/// <summary>Per-device connection settings. Validated on assignment so an unusable value fails at the
/// configuration seam rather than on the wire.</summary>
public sealed record ConnectionOptions
{
    /// <summary>Press safety floor: no setting may let Forward Opens to one device start closer together.</summary>
    public static readonly TimeSpan MinimumForwardOpenInterval = TimeSpan.FromSeconds(1);

    /// <summary>Originator serial shared by every connection this process opens.</summary>
    private static readonly uint ProcessOriginatorSerial = (uint)Random.Shared.Next(1, int.MaxValue);

    private readonly TimeSpan _timeout = TimeSpan.FromSeconds(5);
    private readonly int _connectionSize = 4002;
    private readonly TimeSpan _minForwardOpenInterval = MinimumForwardOpenInterval;
    private readonly uint _rpiMicros = 2_000_000;
    private readonly byte _timeoutMultiplier = 1;
    private readonly TimeSpan? _keepAliveInterval;

    /// <summary>How requests reach the target's message router.</summary>
    public CipRouting Routing { get; init; } = CipRouting.Connected;

    /// <summary>Pack queued requests into Multiple Service Packets (the scheduler's switch).</summary>
    public bool AllowPacking { get; init; }

    /// <summary>Bound on each single exchange (TCP connect, RegisterSession, Forward Open, request).
    /// Must be finite and positive: an infinite timeout would let an abandoned exchange
    /// hold the session's single-flight gate forever.</summary>
    public TimeSpan Timeout
    {
        get => _timeout;
        init => _timeout = value > TimeSpan.Zero && value != System.Threading.Timeout.InfiniteTimeSpan
            ? value
            : throw new ArgumentOutOfRangeException(nameof(Timeout), value, "Timeout must be finite and positive.");
    }

    /// <summary>Requested connection size in bytes. Above 511 the open is a Large Forward Open (0x5B).</summary>
    public int ConnectionSize
    {
        get => _connectionSize;
        init => _connectionSize = value is >= 1 and <= ushort.MaxValue
            ? value
            : throw new ArgumentOutOfRangeException(nameof(ConnectionSize), value, "Connection size must be 1..65535.");
    }

    /// <summary>Minimum time between Forward Open attempt starts for one device (≥ 1 s, press safety).</summary>
    public TimeSpan MinForwardOpenInterval
    {
        get => _minForwardOpenInterval;
        init => _minForwardOpenInterval = value >= MinimumForwardOpenInterval && value != System.Threading.Timeout.InfiniteTimeSpan
            ? value
            : throw new ArgumentOutOfRangeException(nameof(MinForwardOpenInterval), value, "Must be finite and at least 1 s (press safety).");
    }

    /// <summary>Requested packet interval for both directions, in microseconds.</summary>
    public uint RpiMicros
    {
        get => _rpiMicros;
        init => _rpiMicros = value > 0 ? value : throw new ArgumentOutOfRangeException(nameof(RpiMicros), value, "RPI must be positive.");
    }

    /// <summary>Encoded connection timeout multiplier: the connection expires after RPI × (4 &lt;&lt; value).
    /// The default 1 means ×8, so 2 s × 8 = 16 s.</summary>
    public byte TimeoutMultiplier
    {
        get => _timeoutMultiplier;
        init => _timeoutMultiplier = value <= 7 ? value : throw new ArgumentOutOfRangeException(nameof(TimeoutMultiplier), value, "Multiplier must be 0..7.");
    }

    /// <summary>How long an idle connected session waits before the target would drop it.</summary>
    public TimeSpan ConnectionExpiry => TimeSpan.FromTicks(RpiMicros * 10L * (4L << TimeoutMultiplier));

    /// <summary>Idle time after which a keep-alive is sent (Connected only). Defaults to half the
    /// connection expiry: RPI × 8 / 2 = 8 s.</summary>
    public TimeSpan KeepAliveInterval
    {
        get => _keepAliveInterval ?? ConnectionExpiry / 2;
        init => _keepAliveInterval = value > TimeSpan.Zero && value != System.Threading.Timeout.InfiniteTimeSpan
            ? value
            : throw new ArgumentOutOfRangeException(nameof(KeepAliveInterval), value, "Keep-alive interval must be finite and positive.");
    }

    /// <summary>The vendor id sent in the Forward Open originator identity.</summary>
    public ushort VendorId { get; init; } = 0x1337;

    /// <summary>Random per process; together with the vendor id and connection serial it names a connection.</summary>
    public uint OriginatorSerial { get; init; } = ProcessOriginatorSerial;
}