using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.Extensions.Logging;
using ZB.MOM.WW.OtOpcUa.Core.Hosting;

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

/// <summary>
///     Static factory registration helper for <see cref="ModbusDriver"/>. Server's Program.cs
///     calls <see cref="Register"/> once at startup; the bootstrapper (task #248) then
///     materialises Modbus DriverInstance rows from the central config DB into live driver
///     instances. Mirrors <c>GalaxyProxyDriverFactoryExtensions</c> / <c>FocasDriverFactoryExtensions</c>.
/// </summary>
public static class ModbusDriverFactoryExtensions
{
    public const string DriverTypeName = "Modbus";

    /// <summary>
    ///     Register the Modbus factory with the driver registry. The optional
    ///     <paramref name="loggerFactory"/> is captured at registration time and used to
    ///     construct an <see cref="ILogger{ModbusDriver}"/> per driver instance — without it,
    ///     the driver runs with the null logger (existing tests and standalone callers stay
    ///     unchanged).
    /// </summary>
    /// <param name="registry">The driver factory registry to register with.</param>
    /// <param name="loggerFactory">Optional logger factory for creating loggers per driver instance.</param>
    public static void Register(DriverFactoryRegistry registry, ILoggerFactory? loggerFactory = null)
    {
        ArgumentNullException.ThrowIfNull(registry);
        registry.Register(DriverTypeName, (id, json) => CreateInstance(id, json, loggerFactory));
    }

    /// <summary>Public for the Server-side bootstrapper + test consumers (Admin.Tests, etc.).</summary>
    /// <param name="driverInstanceId">The unique identifier for the driver instance.</param>
    /// <param name="driverConfigJson">The JSON configuration string for the driver.</param>
    public static ModbusDriver CreateInstance(string driverInstanceId, string driverConfigJson)
        => CreateInstance(driverInstanceId, driverConfigJson, loggerFactory: null);

    /// <summary>Logger-aware overload — used by <see cref="Register"/>'s closure when wired through DI.</summary>
    /// <param name="driverInstanceId">The unique identifier for the driver instance.</param>
    /// <param name="driverConfigJson">The JSON configuration string for the driver.</param>
    /// <param name="loggerFactory">Optional logger factory for creating loggers per driver instance.</param>
    public static ModbusDriver CreateInstance(string driverInstanceId, string driverConfigJson, ILoggerFactory? loggerFactory)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(driverInstanceId);
        ArgumentException.ThrowIfNullOrWhiteSpace(driverConfigJson);

        var dto = JsonSerializer.Deserialize<ModbusDriverConfigDto>(driverConfigJson, JsonOptions)
            ?? throw new InvalidOperationException(
                $"Modbus driver config for '{driverInstanceId}' deserialised to null");

        if (string.IsNullOrWhiteSpace(dto.Host))
            throw new InvalidOperationException(
                $"Modbus driver config for '{driverInstanceId}' missing required Host");

        var options = new ModbusDriverOptions
        {
            Host = dto.Host!,
            Port = dto.Port ?? 502,
            UnitId = dto.UnitId ?? 1,
            Timeout = TimeSpan.FromMilliseconds(dto.TimeoutMs ?? 2_000),
            MaxRegistersPerRead = dto.MaxRegistersPerRead ?? 125,
            MaxRegistersPerWrite = dto.MaxRegistersPerWrite ?? 123,
            MaxCoilsPerRead = dto.MaxCoilsPerRead ?? 2000,
            UseFC15ForSingleCoilWrites = dto.UseFC15ForSingleCoilWrites ?? false,
            UseFC16ForSingleRegisterWrites = dto.UseFC16ForSingleRegisterWrites ?? false,
            DisableFC23 = dto.DisableFC23 ?? false,
            WriteOnChangeOnly = dto.WriteOnChangeOnly ?? false,
            MaxReadGap = dto.MaxReadGap ?? 0,
            Family = dto.Family is null ? ModbusFamily.Generic
                : ParseEnum<ModbusFamily>(dto.Family, "<driver-level>", driverInstanceId, "Family"),
            MelsecSubFamily = dto.MelsecSubFamily is null ? MelsecFamily.Q_L_iQR
                : ParseEnum<MelsecFamily>(dto.MelsecSubFamily, "<driver-level>", driverInstanceId, "MelsecSubFamily"),
            AutoProhibitReprobeInterval = dto.AutoProhibitReprobeMs is { } reprobeMs ? TimeSpan.FromMilliseconds(reprobeMs) : null,
            AutoReconnect = dto.AutoReconnect ?? true,
            Tags = dto.Tags is { Count: > 0 }
                ? [.. dto.Tags.Select(t => BuildTag(
                    t, driverInstanceId,
                    dto.Family is null ? ModbusFamily.Generic
                        : ParseEnum<ModbusFamily>(dto.Family, "<driver-level>", driverInstanceId, "Family"),
                    dto.MelsecSubFamily is null ? MelsecFamily.Q_L_iQR
                        : ParseEnum<MelsecFamily>(dto.MelsecSubFamily, "<driver-level>", driverInstanceId, "MelsecSubFamily")))]
                : [],
            Probe = new ModbusProbeOptions
            {
                Enabled = dto.Probe?.Enabled ?? true,
                Interval = TimeSpan.FromMilliseconds(dto.Probe?.IntervalMs ?? 5_000),
                Timeout = TimeSpan.FromMilliseconds(dto.Probe?.TimeoutMs ?? 2_000),
                ProbeAddress = dto.Probe?.ProbeAddress ?? 0,
            },
            KeepAlive = dto.KeepAlive is null ? new ModbusKeepAliveOptions() : new ModbusKeepAliveOptions
            {
                Enabled = dto.KeepAlive.Enabled ?? true,
                Time = TimeSpan.FromMilliseconds(dto.KeepAlive.TimeMs ?? 30_000),
                Interval = TimeSpan.FromMilliseconds(dto.KeepAlive.IntervalMs ?? 10_000),
                RetryCount = dto.KeepAlive.RetryCount ?? 3,
            },
            IdleDisconnectTimeout = dto.IdleDisconnectMs is { } ms ? TimeSpan.FromMilliseconds(ms) : null,
            Reconnect = dto.Reconnect is null ? new ModbusReconnectOptions() : new ModbusReconnectOptions
            {
                InitialDelay = TimeSpan.FromMilliseconds(dto.Reconnect.InitialDelayMs ?? 0),
                MaxDelay = TimeSpan.FromMilliseconds(dto.Reconnect.MaxDelayMs ?? 30_000),
                BackoffMultiplier = dto.Reconnect.BackoffMultiplier ?? 2.0,
            },
        };

        return new ModbusDriver(
            options, driverInstanceId,
            transportFactory: null,
            logger: loggerFactory?.CreateLogger<ModbusDriver>());
    }

    private static ModbusTagDefinition BuildTag(ModbusTagDto t, string driverInstanceId)
        => BuildTag(t, driverInstanceId, ModbusFamily.Generic, MelsecFamily.Q_L_iQR);

    private static ModbusTagDefinition BuildTag(ModbusTagDto t, string driverInstanceId, ModbusFamily family, MelsecFamily melsecSubFamily)
    {
        var name = t.Name ?? throw new InvalidOperationException(
            $"Modbus config for '{driverInstanceId}' has a tag missing Name");

        // Driver.Modbus-009: a String tag with StringLength = 0 yields RegisterCount = 0, which
        // turns into an FC03/FC04 with quantity 0 — a spec-illegal request the PLC rejects with
        // exception 03. Catch the misconfiguration at bind time with a clear diagnostic instead
        // of waiting for the cryptic Illegal Data Value to surface at runtime.

        // AddressString takes precedence over the structured fields (Region/Address/DataType/
        // ByteOrder/BitIndex/StringLength/ArrayCount). Tags can mix forms freely — newer pasted
        // rows use the grammar string, legacy rows keep the structured form. Fields not derivable
        // from the grammar (Writable, WriteIdempotent, StringByteOrder) always come from the DTO.
        ModbusTagDefinition tag;
        if (!string.IsNullOrWhiteSpace(t.AddressString))
        {
            if (!ModbusAddressParser.TryParse(t.AddressString, family, melsecSubFamily, out var parsed, out var parseError))
                throw new InvalidOperationException(
                    $"Modbus tag '{name}' in '{driverInstanceId}' has invalid AddressString '{t.AddressString}': {parseError}");
            tag = new ModbusTagDefinition(
                Name: name,
                Region: parsed!.Region,
                Address: parsed.Offset,
                DataType: parsed.DataType,
                Writable: t.Writable ?? true,
                ByteOrder: parsed.ByteOrder,
                BitIndex: parsed.Bit ?? 0,
                StringLength: parsed.StringLength,
                StringByteOrder: t.StringByteOrder is null
                    ? ModbusStringByteOrder.HighByteFirst
                    : ParseEnum<ModbusStringByteOrder>(t.StringByteOrder, name, driverInstanceId, "StringByteOrder"),
                WriteIdempotent: t.WriteIdempotent ?? false,
                ArrayCount: parsed.ArrayCount,
                Deadband: t.Deadband,
                UnitId: t.UnitId);
        }
        else
        {
            tag = new ModbusTagDefinition(
                Name: name,
                Region: ParseEnum<ModbusRegion>(t.Region, t.Name, driverInstanceId, "Region"),
                Address: t.Address ?? throw new InvalidOperationException(
                    $"Modbus tag '{t.Name}' in '{driverInstanceId}' missing Address"),
                DataType: ParseEnum<ModbusDataType>(t.DataType, t.Name, driverInstanceId, "DataType"),
                Writable: t.Writable ?? true,
                ByteOrder: t.ByteOrder is null
                    ? ModbusByteOrder.BigEndian
                    : ParseEnum<ModbusByteOrder>(t.ByteOrder, t.Name, driverInstanceId, "ByteOrder"),
                BitIndex: t.BitIndex ?? 0,
                StringLength: t.StringLength ?? 0,
                StringByteOrder: t.StringByteOrder is null
                    ? ModbusStringByteOrder.HighByteFirst
                    : ParseEnum<ModbusStringByteOrder>(t.StringByteOrder, t.Name, driverInstanceId, "StringByteOrder"),
                WriteIdempotent: t.WriteIdempotent ?? false,
                ArrayCount: t.ArrayCount,
                Deadband: t.Deadband,
                UnitId: t.UnitId);
        }

        ValidateStringLength(tag, driverInstanceId);
        return tag;
    }

    /// <summary>
    ///     Driver.Modbus-009: reject <c>StringLength = 0</c> for <c>String</c>-typed tags. The
    ///     driver computes <c>RegisterCount = (StringLength + 1) / 2</c> which would emit an
    ///     FC03/FC04 with <c>quantity = 0</c>, a spec-illegal request the PLC rejects with
    ///     exception 03 (Illegal Data Value). Surface as a clear bind-time error.
    /// </summary>
    private static void ValidateStringLength(ModbusTagDefinition tag, string driverInstanceId)
    {
        if (tag.DataType == ModbusDataType.String && tag.StringLength < 1)
            throw new InvalidOperationException(
                $"Modbus tag '{tag.Name}' in '{driverInstanceId}' has DataType=String but StringLength={tag.StringLength}. " +
                $"String tags must declare StringLength >= 1 (the number of ASCII characters, packed 2 per register).");
    }

    private static T ParseEnum<T>(string? raw, string? tagName, string driverInstanceId, string field) where T : struct, Enum
    {
        if (string.IsNullOrWhiteSpace(raw))
            throw new InvalidOperationException(
                $"Modbus tag '{tagName ?? "<unnamed>"}' in '{driverInstanceId}' missing {field}");
        return Enum.TryParse<T>(raw, ignoreCase: true, out var v)
            ? v
            : throw new InvalidOperationException(
                $"Modbus tag '{tagName}' has unknown {field} '{raw}'. " +
                $"Expected one of {string.Join(", ", Enum.GetNames<T>())}");
    }

    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNameCaseInsensitive = true,
        ReadCommentHandling = JsonCommentHandling.Skip,
        AllowTrailingCommas = true,
    };

    internal sealed class ModbusDriverConfigDto
    {
        /// <summary>Gets or sets the host address.</summary>
        public string? Host { get; init; }
        /// <summary>Gets or sets the port number.</summary>
        public int? Port { get; init; }
        /// <summary>Gets or sets the unit identifier.</summary>
        public byte? UnitId { get; init; }
        /// <summary>Gets or sets the timeout in milliseconds.</summary>
        public int? TimeoutMs { get; init; }
        /// <summary>Gets or sets the maximum number of registers per read operation.</summary>
        public ushort? MaxRegistersPerRead { get; init; }
        /// <summary>Gets or sets the maximum number of registers per write operation.</summary>
        public ushort? MaxRegistersPerWrite { get; init; }
        /// <summary>Gets or sets the maximum number of coils per read operation.</summary>
        public ushort? MaxCoilsPerRead { get; init; }
        /// <summary>Gets or sets a value indicating whether to use function code 15 for single coil writes.</summary>
        public bool? UseFC15ForSingleCoilWrites { get; init; }
        /// <summary>Gets or sets a value indicating whether to use function code 16 for single register writes.</summary>
        public bool? UseFC16ForSingleRegisterWrites { get; init; }
        /// <summary>Gets or sets a value indicating whether to disable function code 23.</summary>
        public bool? DisableFC23 { get; init; }
        /// <summary>Gets or sets a value indicating whether to write only on change.</summary>
        public bool? WriteOnChangeOnly { get; init; }
        /// <summary>Gets or sets the maximum gap between register addresses for coalescing.</summary>
        public ushort? MaxReadGap { get; init; }
        /// <summary>Gets or sets the Modbus family type.</summary>
        public string? Family { get; init; }
        /// <summary>Gets or sets the Melsec subfamily.</summary>
        public string? MelsecSubFamily { get; init; }
        /// <summary>Gets or sets the automatic prohibition reprobei interval in milliseconds.</summary>
        public int? AutoProhibitReprobeMs { get; init; }
        /// <summary>Gets or sets a value indicating whether automatic reconnection is enabled.</summary>
        public bool? AutoReconnect { get; init; }
        /// <summary>Gets or sets the collection of tag definitions.</summary>
        public List<ModbusTagDto>? Tags { get; init; }
        /// <summary>Gets or sets the probe configuration.</summary>
        public ModbusProbeDto? Probe { get; init; }

        /// <summary>Gets or sets the keep-alive configuration (connection-layer knob #139).</summary>
        public ModbusKeepAliveDto? KeepAlive { get; init; }
        /// <summary>Gets or sets the idle disconnect timeout in milliseconds.</summary>
        public int? IdleDisconnectMs { get; init; }
        /// <summary>Gets or sets the reconnect configuration.</summary>
        public ModbusReconnectDto? Reconnect { get; init; }
    }

    internal sealed class ModbusKeepAliveDto
    {
        /// <summary>Gets or sets a value indicating whether keep-alive is enabled.</summary>
        public bool? Enabled { get; init; }
        /// <summary>Gets or sets the keep-alive time in milliseconds.</summary>
        public int? TimeMs { get; init; }
        /// <summary>Gets or sets the keep-alive interval in milliseconds.</summary>
        public int? IntervalMs { get; init; }
        /// <summary>Gets or sets the retry count.</summary>
        public int? RetryCount { get; init; }
    }

    internal sealed class ModbusReconnectDto
    {
        /// <summary>Gets or sets the initial reconnect delay in milliseconds.</summary>
        public int? InitialDelayMs { get; init; }
        /// <summary>Gets or sets the maximum reconnect delay in milliseconds.</summary>
        public int? MaxDelayMs { get; init; }
        /// <summary>Gets or sets the backoff multiplier for exponential reconnect delays.</summary>
        public double? BackoffMultiplier { get; init; }
    }

    internal sealed class ModbusTagDto
    {
        /// <summary>Gets or sets the tag name.</summary>
        public string? Name { get; init; }

        /// <summary>
        ///     Address grammar string per <c>ModbusAddressParser</c> — when present, takes
        ///     precedence over the structured Region/Address/DataType/ByteOrder/BitIndex/
        ///     StringLength/ArrayCount fields. Examples: <c>"40001"</c>, <c>"40001:F"</c>,
        ///     <c>"40001:F:CDAB:5"</c>, <c>"HR1:I"</c>, <c>"C100"</c>.
        /// </summary>
        public string? AddressString { get; init; }

        /// <summary>Gets or sets the register region.</summary>
        public string? Region { get; init; }
        /// <summary>Gets or sets the starting address.</summary>
        public ushort? Address { get; init; }
        /// <summary>Gets or sets the data type.</summary>
        public string? DataType { get; init; }
        /// <summary>Gets or sets a value indicating whether the tag is writable.</summary>
        public bool? Writable { get; init; }
        /// <summary>Gets or sets the byte order.</summary>
        public string? ByteOrder { get; init; }
        /// <summary>Gets or sets the bit index for bit-level tags.</summary>
        public byte? BitIndex { get; init; }
        /// <summary>Gets or sets the string length for string-typed tags.</summary>
        public ushort? StringLength { get; init; }
        /// <summary>Gets or sets the byte order for string values.</summary>
        public string? StringByteOrder { get; init; }
        /// <summary>Gets or sets a value indicating whether writes are idempotent.</summary>
        public bool? WriteIdempotent { get; init; }
        /// <summary>Gets or sets the array count for array-typed tags.</summary>
        public int? ArrayCount { get; init; }
        /// <summary>Gets or sets the deadband for change detection.</summary>
        public double? Deadband { get; init; }
        /// <summary>Gets or sets the unit identifier for this tag.</summary>
        public byte? UnitId { get; init; }
    }

    internal sealed class ModbusProbeDto
    {
        /// <summary>Gets or sets a value indicating whether probing is enabled.</summary>
        public bool? Enabled { get; init; }
        /// <summary>Gets or sets the probe interval in milliseconds.</summary>
        public int? IntervalMs { get; init; }
        /// <summary>Gets or sets the probe timeout in milliseconds.</summary>
        public int? TimeoutMs { get; init; }
        /// <summary>Gets or sets the probe register address.</summary>
        public ushort? ProbeAddress { get; init; }
    }
}