using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;

/// <summary>
///     Modbus TCP driver configuration. Bound from the driver's <c>DriverConfig</c> JSON at
///     <c>DriverHost.RegisterAsync</c>. Every register the driver exposes appears in
///     <see cref="Tags"/>; names become the OPC UA browse name + full reference.
/// </summary>
public sealed class ModbusDriverOptions
{
    public string Host { get; init; } = "127.0.0.1";
    public int Port { get; init; } = 502;
    public byte UnitId { get; init; } = 1;
    public TimeSpan Timeout { get; init; } = TimeSpan.FromSeconds(2);

    /// <summary>Pre-declared tag map. Modbus has no discovery protocol — the driver returns exactly these.</summary>
    public IReadOnlyList<ModbusTagDefinition> Tags { get; init; } = [];

    /// <summary>
    ///     Background connectivity-probe settings. When <see cref="ModbusProbeOptions.Enabled"/>
    ///     is true the driver runs a tick loop that issues a cheap FC03 at register 0 every
    ///     <see cref="ModbusProbeOptions.Interval"/> and raises <c>OnHostStatusChanged</c> on
    ///     Running ↔ Stopped transitions. The Admin UI / OPC UA clients see the state through
    ///     <see cref="IHostConnectivityProbe"/>.
    /// </summary>
    public ModbusProbeOptions Probe { get; init; } = new();
}

public sealed class ModbusProbeOptions
{
    public bool Enabled { get; init; } = true;
    public TimeSpan Interval { get; init; } = TimeSpan.FromSeconds(5);
    public TimeSpan Timeout { get; init; } = TimeSpan.FromSeconds(2);
    /// <summary>Register to read for the probe. Zero is usually safe; override for PLCs that lock register 0.</summary>
    public ushort ProbeAddress { get; init; } = 0;
}

/// <summary>
///     One Modbus-backed OPC UA variable. Address is zero-based (Modbus spec numbering, not
///     the documentation's 1-based coil/register conventions). Multi-register types
///     (Int32/UInt32/Float32 = 2 regs; Int64/UInt64/Float64 = 4 regs) respect the
///     <see cref="ByteOrder"/> field — real-world PLCs disagree on word ordering.
/// </summary>
/// <param name="Name">
///     Tag name, used for both the OPC UA browse name and the driver's full reference. Must be
///     unique within the driver.
/// </param>
/// <param name="Region">Coils / DiscreteInputs / InputRegisters / HoldingRegisters.</param>
/// <param name="Address">Zero-based address within the region.</param>
/// <param name="DataType">
///     Logical data type. See <see cref="ModbusDataType"/> for the register count each encodes.
/// </param>
/// <param name="Writable">When true and Region supports writes (Coils / HoldingRegisters), IWritable routes writes here.</param>
/// <param name="ByteOrder">Word ordering for multi-register types. Ignored for Bool / Int16 / UInt16 / BitInRegister / String.</param>
/// <param name="BitIndex">For <c>DataType = BitInRegister</c>: which bit of the holding register (0-15, LSB-first).</param>
/// <param name="StringLength">For <c>DataType = String</c>: number of ASCII characters (2 per register, rounded up).</param>
public sealed record ModbusTagDefinition(
    string Name,
    ModbusRegion Region,
    ushort Address,
    ModbusDataType DataType,
    bool Writable = true,
    ModbusByteOrder ByteOrder = ModbusByteOrder.BigEndian,
    byte BitIndex = 0,
    ushort StringLength = 0);

public enum ModbusRegion { Coils, DiscreteInputs, InputRegisters, HoldingRegisters }

public enum ModbusDataType
{
    Bool,
    Int16,
    UInt16,
    Int32,
    UInt32,
    Int64,
    UInt64,
    Float32,
    Float64,
    /// <summary>Single bit within a holding register. <see cref="ModbusTagDefinition.BitIndex"/> selects 0-15 LSB-first.</summary>
    BitInRegister,
    /// <summary>ASCII string packed 2 chars per register, <see cref="ModbusTagDefinition.StringLength"/> characters long.</summary>
    String,
}

/// <summary>
///     Word ordering for multi-register types. Modbus TCP standard is <see cref="BigEndian"/>
///     (ABCD for 32-bit: high word at the lower address). Many PLCs — Siemens S7, several
///     Allen-Bradley series, some Modicon families — use <see cref="WordSwap"/> (CDAB), which
///     keeps bytes big-endian within each register but reverses the word pair(s).
/// </summary>
public enum ModbusByteOrder
{
    BigEndian,
    WordSwap,
}