using System.Collections.Concurrent;
using System.Threading.Channels;
using CliFx.Attributes;
using CliFx.Exceptions;
using CliFx.Infrastructure;
using Opc.Ua;
using ZB.MOM.WW.OtOpcUa.Client.CLI.Helpers;
using ZB.MOM.WW.OtOpcUa.Client.Shared;
using ZB.MOM.WW.OtOpcUa.Client.Shared.Models;

namespace ZB.MOM.WW.OtOpcUa.Client.CLI.Commands;

[Command("subscribe", Description = "Monitor a node for value changes")]
public class SubscribeCommand : CommandBase
{
    /// <summary>
    /// Creates the subscribe command used to monitor a node (or a subtree of nodes) for data-change
    /// notifications.
    /// </summary>
    /// <param name="factory">The factory that creates the shared client service for the command run.</param>
    public SubscribeCommand(IOpcUaClientServiceFactory factory) : base(factory)
    {
    }

    /// <summary>
    /// Gets the node ID to monitor. When <see cref="Recursive" /> is set, this node is the browse root
    /// and every <c>Variable</c> child it reaches is subscribed.
    /// </summary>
    [CommandOption("node", 'n', Description = "Node ID to monitor", IsRequired = true)]
    public string NodeId { get; init; } = default!;

    /// <summary>
    /// Gets the sampling interval, in milliseconds, requested for every monitored item.
    /// </summary>
    [CommandOption("interval", 'i', Description = "Sampling interval in milliseconds")]
    public int Interval { get; init; } = 1000;

    /// <summary>
    /// Gets a value indicating whether the command should browse from <see cref="NodeId" />
    /// and subscribe to every <c>Variable</c> in the subtree.
    /// </summary>
    [CommandOption("recursive", 'r', Description = "Browse recursively from --node and subscribe to every Variable found")]
    public bool Recursive { get; init; }

    /// <summary>
    /// Gets the maximum recursion depth applied while collecting variables when <see cref="Recursive" /> is set.
    /// </summary>
    [CommandOption("max-depth", Description = "Maximum recursion depth when --recursive is set")]
    public int MaxDepth { get; init; } = 10;

    /// <summary>
    /// Gets a value indicating whether per-update lines should be suppressed in favour of the final summary only.
    /// </summary>
    [CommandOption("quiet", 'q', Description = "Suppress per-update output; only print a final summary on Ctrl+C")]
    public bool Quiet { get; init; }

    /// <summary>
    /// Gets the duration, in seconds, before the command auto-exits and prints its summary.
    /// A value of <c>0</c> means the command runs until Ctrl+C.
    /// </summary>
    [CommandOption("duration", Description = "Auto-exit after N seconds and print summary (0 = run until Ctrl+C)")]
    public int DurationSeconds { get; init; } = 0;

    /// <summary>
    /// Gets the optional path that the command should write the final summary to on exit, in addition to stdout.
    /// </summary>
    [CommandOption("summary-file", Description = "Write summary to this file path on exit (in addition to stdout)")]
    public string? SummaryFile { get; init; }

    /// <inheritdoc />
    public override async ValueTask ExecuteAsync(IConsole console)
    {
        ConfigureLogging();

        if (Interval <= 0)
            throw new CommandException($"--interval must be greater than 0 (was {Interval}).");
        if (Recursive && MaxDepth <= 0)
            throw new CommandException($"--max-depth must be greater than 0 (was {MaxDepth}).");
        if (DurationSeconds < 0)
            throw new CommandException($"--duration must be 0 or a positive number (was {DurationSeconds}).");

        NodeId rootNodeId;
        try
        {
            rootNodeId = NodeIdParser.ParseRequired(NodeId);
        }
        catch (Exception ex) when (ex is FormatException or ArgumentException)
        {
            throw new CommandException($"Invalid --node value: {ex.Message}");
        }

        IOpcUaClientService? service = null;
        try
        {
            var ct = console.RegisterCancellationHandler();
            (service, _) = await CreateServiceAndConnectAsync(ct);

            var targets = new List<(NodeId nodeId, string displayPath)>();
            if (Recursive)
            {
                await console.Output.WriteLineAsync($"Browsing subtree of {NodeId} (max depth {MaxDepth})...");
                await CollectVariablesAsync(service, rootNodeId, NodeId, MaxDepth, 0, targets, ct);
                await console.Output.WriteLineAsync($"Found {targets.Count} variable nodes.");
            }
            else
            {
                targets.Add((rootNodeId, NodeId));
            }

            var lastStatus = new ConcurrentDictionary<string, (StatusCode Status, DateTime LastUpdate, object? Value)>();
            var updateCount = new ConcurrentDictionary<string, int>();
            var everBad = new ConcurrentDictionary<string, byte>();
            var displayNameByNodeId = targets.ToDictionary(t => t.nodeId.ToString(), t => t.displayPath);

            // Channel serialises notification-thread writes to the main async loop so that
            // concurrent SDK callbacks and main-thread summary output never interleave on
            // the shared TextWriter.
            var outputChannel = Channel.CreateUnbounded<string>(
                new UnboundedChannelOptions { SingleReader = true });

            void DataChangedHandler(object? sender, DataChangedEventArgs e)
            {
                try
                {
                    var key = e.NodeId.ToString();
                    lastStatus[key] = (e.Value.StatusCode, DateTime.UtcNow, e.Value.Value);
                    updateCount.AddOrUpdate(key, 1, (_, v) => v + 1);
                    if (!StatusCode.IsGood(e.Value.StatusCode))
                        everBad.TryAdd(key, 0);
                    if (!Quiet)
                    {
                        var line =
                            $"[{e.Value.SourceTimestamp:O}] {displayNameByNodeId.GetValueOrDefault(key, key)} = {e.Value.Value} ({e.Value.StatusCode})";
                        outputChannel.Writer.TryWrite(line);
                    }
                }
                catch
                {
                    // Never let handler exceptions escape into the SDK callback.
                }
            }

            service.DataChanged += DataChangedHandler;

            var subscribed = 0;
            foreach (var (nodeId, _) in targets)
            {
                try
                {
                    await service.SubscribeAsync(nodeId, Interval, ct);
                    subscribed++;
                }
                catch (Exception ex)
                {
                    await console.Output.WriteLineAsync($"  FAILED to subscribe {nodeId}: {ex.Message}");
                }
            }

            await console.Output.WriteLineAsync(
                $"Subscribed to {subscribed}/{targets.Count} nodes (interval: {Interval}ms). Press Ctrl+C to stop and print summary.");

            // Drain the output channel on the main thread until cancellation fires.
            using var drainCts = CancellationTokenSource.CreateLinkedTokenSource(ct);
            var drainTask = Task.Run(async () =>
            {
                await foreach (var line in outputChannel.Reader.ReadAllAsync(drainCts.Token))
                    await console.Output.WriteLineAsync(line);
            }, CancellationToken.None);

            try
            {
                if (DurationSeconds > 0)
                    await Task.Delay(TimeSpan.FromSeconds(DurationSeconds), ct);
                else
                    await Task.Delay(Timeout.Infinite, ct);
            }
            catch (OperationCanceledException)
            {
            }

            // Stop accepting new notifications before writing the summary.
            service.DataChanged -= DataChangedHandler;
            outputChannel.Writer.Complete();
            await drainCts.CancelAsync();
            try { await drainTask; } catch (OperationCanceledException) { }

            // Summary
            var summary = new List<string>();
            summary.Add("");
            summary.Add("==================== SUMMARY ====================");
            var good = new List<string>();
            var bad = new List<string>();
            var never = new List<string>();
            foreach (var (nodeId, display) in targets)
            {
                var key = nodeId.ToString();
                if (!lastStatus.TryGetValue(key, out var entry))
                {
                    never.Add(display);
                    continue;
                }
                if (StatusCode.IsGood(entry.Status))
                    good.Add($"{display} = {entry.Value} ({entry.Status})");
                else
                    bad.Add($"{display} = {entry.Value} ({entry.Status})");
            }

            var neverWentBad = targets
                .Where(t => lastStatus.ContainsKey(t.nodeId.ToString()) && !everBad.ContainsKey(t.nodeId.ToString()))
                .Select(t => t.displayPath)
                .ToList();
            var didGoBad = targets.Count(t => everBad.ContainsKey(t.nodeId.ToString()));

            summary.Add($"Total subscribed: {targets.Count}");
            summary.Add($"  Ever went BAD during window:    {didGoBad}");
            summary.Add($"  NEVER went bad (suspect):       {neverWentBad.Count}");
            summary.Add($"  Last status GOOD:               {good.Count}");
            summary.Add($"  Last status NOT-GOOD:           {bad.Count}");
            summary.Add($"  No update received at all:      {never.Count}");

            if (neverWentBad.Count > 0 && neverWentBad.Count < targets.Count)
            {
                summary.Add("");
                summary.Add("--- Nodes that NEVER received a bad-quality update (suspect) ---");
                foreach (var line in neverWentBad) summary.Add($"  {line}");
            }
            if (never.Count > 0)
            {
                summary.Add("");
                summary.Add("--- Nodes that never received an update at all ---");
                foreach (var line in never) summary.Add($"  {line}");
            }

            foreach (var line in summary) await console.Output.WriteLineAsync(line);
            if (!string.IsNullOrEmpty(SummaryFile))
            {
                try { await File.WriteAllLinesAsync(SummaryFile, summary); }
                catch (Exception ex) { await console.Output.WriteLineAsync($"Failed to write summary file: {ex.Message}"); }
            }

            foreach (var (nodeId, _) in targets)
            {
                try { await service.UnsubscribeAsync(nodeId); } catch { /* ignore */ }
            }
        }
        finally
        {
            if (service != null)
            {
                await service.DisconnectAsync();
                service.Dispose();
            }
        }
    }

    private static async Task CollectVariablesAsync(
        IOpcUaClientService service,
        NodeId? parent,
        string parentPath,
        int maxDepth,
        int currentDepth,
        List<(NodeId nodeId, string displayPath)> into,
        CancellationToken ct)
    {
        if (currentDepth >= maxDepth) return;
        var children = await service.BrowseAsync(parent, ct);
        foreach (var child in children)
        {
            var nodeId = NodeIdParser.Parse(child.NodeId);
            if (nodeId is null) continue;
            var childPath = $"{parentPath}/{child.DisplayName}";
            if (child.NodeClass == "Variable")
            {
                into.Add((nodeId, childPath));
            }
            if (child.HasChildren)
            {
                await CollectVariablesAsync(service, nodeId, childPath, maxDepth, currentDepth + 1, into, ct);
            }
        }
    }
}