using System.Diagnostics;
using System.Net.Sockets;
using System.Text.Json;
using System.Text.Json.Serialization;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

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

/// <summary>
///     Cheap TCP-connect probe for the <see cref="FocasDriverOptions"/>-shaped driver config.
///     Opens a socket to the first device's FOCAS Ethernet address + port and closes
///     immediately. Surfaces a green tick + latency on success; red chip + SocketError on
///     failure; "timed out" on the caller's cancellation. Does NOT exchange any FOCAS/2 bytes —
///     a richer FOCAS handshake (cnc_allclibhndl3) probe is a documented follow-up.
/// </summary>
public sealed class FocasDriverProbe : IDriverProbe
{
    private static readonly JsonSerializerOptions _opts = new()
    {
        PropertyNameCaseInsensitive = true,
        UnmappedMemberHandling = JsonUnmappedMemberHandling.Skip,
    };

    /// <inheritdoc />
    public string DriverType => "FOCAS";

    /// <inheritdoc />
    public async Task<DriverProbeResult> ProbeAsync(string configJson, TimeSpan timeout, CancellationToken ct)
    {
        FocasDriverOptions? opts;
        try { opts = JsonSerializer.Deserialize<FocasDriverOptions>(configJson, _opts); }
        catch (Exception ex) { return new(false, $"Config JSON is invalid: {ex.Message}", null); }
        if (opts is null) return new(false, "Config JSON deserialized to null.", null);

        var (host, port) = ExtractTarget(opts);
        if (string.IsNullOrWhiteSpace(host) || port <= 0)
            return new(false, "Config has no host/port to probe.", null);

        var sw = Stopwatch.StartNew();
        try
        {
            using var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            await socket.ConnectAsync(host, port, ct);
            sw.Stop();
            return new(true, null, sw.Elapsed);
        }
        catch (SocketException ex)
        {
            return new(false, $"Connect failed: {ex.SocketErrorCode}", null);
        }
        catch (OperationCanceledException)
        {
            return new(false, $"Probe timed out after {timeout.TotalSeconds:F0}s.", null);
        }
        catch (Exception ex)
        {
            return new(false, ex.Message, null);
        }
    }

    private static (string host, int port) ExtractTarget(FocasDriverOptions opts)
    {
        // Parse the first device's focas:// address to extract host + port.
        var firstDevice = opts.Devices.FirstOrDefault();
        if (firstDevice is null) return (string.Empty, 0);

        var parsed = FocasHostAddress.TryParse(firstDevice.HostAddress);
        if (parsed is null) return (string.Empty, 0);

        return (parsed.Host, parsed.Port);
    }
}