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

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

/// <summary>
///     Static factory registration helper for <see cref="AbLegacyDriver"/>. Server's Program.cs
///     calls <see cref="Register"/> once at startup; the bootstrapper then
///     materialises AB Legacy DriverInstance rows from the central config DB into live
///     driver instances. Mirrors <c>GalaxyProxyDriverFactoryExtensions</c>.
/// </summary>
public static class AbLegacyDriverFactoryExtensions
{
    public const string DriverTypeName = "AbLegacy";

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

    /// <summary>
    /// Creates an instance of the AB Legacy driver from configuration.
    /// </summary>
    /// <param name="driverInstanceId">The unique identifier for this driver instance.</param>
    /// <param name="driverConfigJson">The driver configuration as a JSON string.</param>
    /// <returns>A configured <see cref="AbLegacyDriver"/> instance.</returns>
    internal static AbLegacyDriver CreateInstance(string driverInstanceId, string driverConfigJson)
        => CreateInstance(driverInstanceId, driverConfigJson, loggerFactory: null);

    /// <summary>
    /// Creates an instance of the AB Legacy driver with optional logger.
    /// </summary>
    /// <param name="driverInstanceId">The unique identifier for this driver instance.</param>
    /// <param name="driverConfigJson">The driver configuration as a JSON string.</param>
    /// <param name="loggerFactory">Optional logger factory for the driver instance.</param>
    /// <returns>A configured <see cref="AbLegacyDriver"/> instance.</returns>
    internal static AbLegacyDriver CreateInstance(string driverInstanceId, string driverConfigJson, ILoggerFactory? loggerFactory)
    {
        return new AbLegacyDriver(
            ParseOptions(driverInstanceId, driverConfigJson), driverInstanceId,
            tagFactory: null,
            logger: loggerFactory?.CreateLogger<AbLegacyDriver>());
    }

    /// <summary>
    ///     Parses an AB Legacy <c>DriverConfig</c> JSON document into typed options. Extracted so
    ///     <see cref="AbLegacyDriver.InitializeAsync"/> can re-parse a CHANGED config on reinitialize
    ///     (Gitea #516) instead of serving the options it was constructed with — which silently discarded
    ///     every operator edit while the deployment still sealed green.
    /// </summary>
    /// <param name="driverInstanceId">The unique driver instance identifier.</param>
    /// <param name="driverConfigJson">The driver configuration as a JSON string.</param>
    /// <returns>The parsed <see cref="AbLegacyDriverOptions"/>.</returns>
    internal static AbLegacyDriverOptions ParseOptions(string driverInstanceId, string driverConfigJson)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(driverInstanceId);
        ArgumentException.ThrowIfNullOrWhiteSpace(driverConfigJson);

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

        var options = new AbLegacyDriverOptions
        {
            Devices = dto.Devices is { Count: > 0 }
                ? [.. dto.Devices.Select(d => new AbLegacyDeviceOptions(
                    HostAddress: d.HostAddress ?? throw new InvalidOperationException(
                        $"AB Legacy config for '{driverInstanceId}' has a device missing HostAddress"),
                    PlcFamily: ParseEnum<AbLegacyPlcFamily>(d.PlcFamily, driverInstanceId, "PlcFamily",
                        fallback: AbLegacyPlcFamily.Slc500),
                    DeviceName: d.DeviceName))]
                : [],
            // v3: the deploy artifact (Wave C) populates rawTags with the cluster's authored raw AbLegacy
            // tags (RawPath + TagConfig blob + WriteIdempotent + owning DeviceName). The driver maps each
            // RawTagEntry's TagConfig blob through AbLegacyTagDefinitionFactory at Initialize and routes it
            // to its device by DeviceName; the legacy pre-declared DTO tag path is retired.
            RawTags = dto.RawTags is { Count: > 0 } ? [.. dto.RawTags] : [],
            Probe = new AbLegacyProbeOptions
            {
                Enabled = dto.Probe?.Enabled ?? true,
                Interval = TimeSpan.FromMilliseconds(dto.Probe?.IntervalMs ?? 5_000),
                Timeout = PositiveTimeoutOrDefault(dto.Probe?.TimeoutMs, 2_000),
                ProbeAddress = dto.Probe?.ProbeAddress ?? "S:0",
            },
            Timeout = PositiveTimeoutOrDefault(dto.TimeoutMs, 2_000),
        };

        return options;
    }

    /// <summary>
    ///     Maps an operator-supplied timeout (ms) to a positive <see cref="TimeSpan"/>, substituting
    ///     <paramref name="defaultMs"/> for a null / zero / negative value. libplctag's managed
    ///     <c>Tag.Timeout</c> setter throws <see cref="ArgumentOutOfRangeException"/> for a
    ///     non-positive value, which would otherwise fault tag creation on every read/write; clamping
    ///     here keeps a misconfigured <c>TimeoutMs: 0</c> running on the default bound instead. (Driver
    ///     timeout hardening, sibling of the S7 R2-01 read-leg fix.)
    /// </summary>
    /// <param name="ms">The operator-supplied timeout in milliseconds, or null.</param>
    /// <param name="defaultMs">The default applied when <paramref name="ms"/> is null or non-positive.</param>
    /// <returns>A strictly positive timeout.</returns>
    private static TimeSpan PositiveTimeoutOrDefault(int? ms, int defaultMs) =>
        TimeSpan.FromMilliseconds(ms is int v and > 0 ? v : defaultMs);

    private static T ParseEnum<T>(string? raw, string driverInstanceId, string field,
        string? tagName = null, T? fallback = null) where T : struct, Enum
    {
        if (string.IsNullOrWhiteSpace(raw))
        {
            if (fallback.HasValue) return fallback.Value;
            throw new InvalidOperationException(
                $"AB Legacy {(tagName is null ? "config" : $"tag '{tagName}'")} in '{driverInstanceId}' missing {field}");
        }
        return Enum.TryParse<T>(raw, ignoreCase: true, out var v)
            ? v
            : throw new InvalidOperationException(
                $"AB Legacy {(tagName is null ? "config" : $"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 AbLegacyDriverConfigDto
    {
        /// <summary>
        /// Gets or sets the timeout in milliseconds for operations.
        /// </summary>
        public int? TimeoutMs { get; init; }

        /// <summary>
        /// Gets or sets the list of devices to connect to.
        /// </summary>
        public List<AbLegacyDeviceDto>? Devices { get; init; }

        /// <summary>
        /// Gets or sets the authored raw tags (RawPath + TagConfig blob + WriteIdempotent + owning
        /// DeviceName) the deploy artifact delivers. The driver maps each through
        /// <see cref="AbLegacyTagDefinitionFactory.FromTagConfig"/> at Initialize.
        /// </summary>
        public List<RawTagEntry>? RawTags { get; init; }

        /// <summary>
        /// Gets or sets the probe configuration.
        /// </summary>
        public AbLegacyProbeDto? Probe { get; init; }
    }

    internal sealed class AbLegacyDeviceDto
    {
        /// <summary>
        /// Gets or sets the host address of the device.
        /// </summary>
        public string? HostAddress { get; init; }

        /// <summary>
        /// Gets or sets the PLC family.
        /// </summary>
        public string? PlcFamily { get; init; }

        /// <summary>
        /// Gets or sets the device name.
        /// </summary>
        public string? DeviceName { get; init; }
    }

    internal sealed class AbLegacyProbeDto
    {
        /// <summary>
        /// Gets or sets 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 address.
        /// </summary>
        public string? ProbeAddress { get; init; }
    }
}
