using System.Text.Json;
using ZB.MOM.WW.OtOpcUa.Core.Hosting;

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

/// <summary>
///     Static factory registration helper for <see cref="TwinCATDriver"/>. Server's Program.cs
///     calls <see cref="Register"/> once at startup; the bootstrapper materialises TwinCAT
///     DriverInstance rows from the central config DB into live driver instances. Mirrors
///     <c>S7DriverFactoryExtensions</c> / <c>AbCipDriverFactoryExtensions</c>.
/// </summary>
public static class TwinCATDriverFactoryExtensions
{
    public const string DriverTypeName = "TwinCAT";

    public static void Register(DriverFactoryRegistry registry)
    {
        ArgumentNullException.ThrowIfNull(registry);
        registry.Register(DriverTypeName, CreateInstance);
    }

    internal static TwinCATDriver CreateInstance(string driverInstanceId, string driverConfigJson)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(driverInstanceId);
        var options = ParseOptions(driverConfigJson, driverInstanceId);
        return new TwinCATDriver(options, driverInstanceId);
    }

    /// <summary>
    ///     Parse a TwinCAT driver-config JSON document into a <see cref="TwinCATDriverOptions"/>.
    ///     Shared by <see cref="CreateInstance"/> (constructor-time) and
    ///     <see cref="TwinCATDriver.InitializeAsync"/> / <see cref="TwinCATDriver.ReinitializeAsync"/>
    ///     so a config generation pushed via Reinitialize is actually applied (Driver.TwinCAT-001).
    /// </summary>
    internal static TwinCATDriverOptions ParseOptions(string driverConfigJson, string driverInstanceId)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(driverConfigJson);

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

        return new TwinCATDriverOptions
        {
            Devices = dto.Devices is { Count: > 0 }
                ? [.. dto.Devices.Select(d => new TwinCATDeviceOptions(
                    HostAddress: d.HostAddress ?? throw new InvalidOperationException(
                        $"TwinCAT config for '{driverInstanceId}' has a device missing HostAddress"),
                    DeviceName: d.DeviceName))]
                : [],
            Tags = dto.Tags is { Count: > 0 }
                ? [.. dto.Tags.Select(t => BuildTag(t, driverInstanceId))]
                : [],
            Probe = new TwinCATProbeOptions
            {
                Enabled = dto.Probe?.Enabled ?? true,
                Interval = TimeSpan.FromMilliseconds(dto.Probe?.IntervalMs ?? 5_000),
                Timeout = TimeSpan.FromMilliseconds(dto.Probe?.TimeoutMs ?? 2_000),
            },
            Timeout = TimeSpan.FromMilliseconds(dto.TimeoutMs ?? 2_000),
            UseNativeNotifications = dto.UseNativeNotifications ?? true,
            EnableControllerBrowse = dto.EnableControllerBrowse ?? false,
            NotificationMaxDelayMs = dto.NotificationMaxDelayMs ?? 0,
        };
    }

    /// <summary>
    ///     Test-visible wrapper around <see cref="ParseOptions"/> for the regression suite —
    ///     keeps the public driver surface unchanged while letting tests assert that JSON
    ///     fields like <c>NotificationMaxDelayMs</c> and <c>Structure</c>-tag rejection are
    ///     honored end-to-end.
    /// </summary>
    public static TwinCATDriverOptions ParseOptionsForTests(string driverConfigJson, string driverInstanceId)
        => ParseOptions(driverConfigJson, driverInstanceId);

    private static TwinCATTagDefinition BuildTag(TwinCATTagDto t, string driverInstanceId)
    {
        var dataType = ParseEnum<TwinCATDataType>(t.DataType, t.Name, driverInstanceId, "DataType");

        // Driver.TwinCAT-003: Structure-typed pre-declared tags are not supported. The driver's
        // atomic surface cannot read/write UDT blobs — MapToClrType falls through to typeof(int)
        // and ConvertForWrite throws NotSupportedException, producing garbage reads or late
        // runtime failures. BrowseSymbolsAsync already correctly yields DataType = null for
        // Structure symbols so they never appear in the discovered address space. Reject here
        // with a clear error so operators get a configuration-time failure, not a silent wrong value.
        if (dataType == TwinCATDataType.Structure)
            throw new InvalidOperationException(
                $"TwinCAT tag '{t.Name ?? "<unnamed>"}' in '{driverInstanceId}' specifies " +
                "DataType 'Structure'. The driver does not support UDT/FB-instance pre-declared tags. " +
                "Use EnableControllerBrowse to discover UDT members individually, or declare " +
                "individual atomic-typed tags for the fields you need.");

        return new TwinCATTagDefinition(
            Name: t.Name ?? throw new InvalidOperationException(
                $"TwinCAT config for '{driverInstanceId}' has a tag missing Name"),
            DeviceHostAddress: t.DeviceHostAddress ?? throw new InvalidOperationException(
                $"TwinCAT tag '{t.Name}' in '{driverInstanceId}' missing DeviceHostAddress"),
            SymbolPath: t.SymbolPath ?? throw new InvalidOperationException(
                $"TwinCAT tag '{t.Name}' in '{driverInstanceId}' missing SymbolPath"),
            DataType: dataType,
            Writable: t.Writable ?? true,
            WriteIdempotent: t.WriteIdempotent ?? false);
    }

    private static T ParseEnum<T>(string? raw, string? tagName, string driverInstanceId, string field)
        where T : struct, Enum
    {
        if (string.IsNullOrWhiteSpace(raw))
            throw new InvalidOperationException(
                $"TwinCAT tag '{tagName ?? "<unnamed>"}' in '{driverInstanceId}' missing {field}");
        return Enum.TryParse<T>(raw, ignoreCase: true, out var v)
            ? v
            : throw new InvalidOperationException(
                $"TwinCAT 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 TwinCATDriverConfigDto
    {
        public int? TimeoutMs { get; init; }
        public bool? UseNativeNotifications { get; init; }
        public bool? EnableControllerBrowse { get; init; }
        public int? NotificationMaxDelayMs { get; init; }
        public List<TwinCATDeviceDto>? Devices { get; init; }
        public List<TwinCATTagDto>? Tags { get; init; }
        public TwinCATProbeDto? Probe { get; init; }
    }

    internal sealed class TwinCATDeviceDto
    {
        public string? HostAddress { get; init; }
        public string? DeviceName { get; init; }
    }

    internal sealed class TwinCATTagDto
    {
        public string? Name { get; init; }
        public string? DeviceHostAddress { get; init; }
        public string? SymbolPath { get; init; }
        public string? DataType { get; init; }
        public bool? Writable { get; init; }
        public bool? WriteIdempotent { get; init; }
    }

    internal sealed class TwinCATProbeDto
    {
        public bool? Enabled { get; init; }
        public int? IntervalMs { get; init; }
        public int? TimeoutMs { get; init; }
    }
}