printer discovery in print service

EpsonPrintService/PrinterDiscoveryBackgroundTask.cs

@@ -0,0 +1,94 @@
+using Inspectron.Epson;
+using Microsoft.Extensions.Logging;
+
+namespace EpsonPrintService;
+
+/// <summary>
+/// Background task that periodically discovers printers and notifies receivers when changes occur
+/// </summary>
+public class PrinterDiscoveryBackgroundTask
+{
+    private readonly IDiscoveryService _discoveryService;
+    private readonly IDiscoveredPrintersReceiver _receiver;
+    private readonly ILogger _logger;
+    private readonly TimeSpan _interval;
+    private readonly TimeSpan _discoveryTimeout;
+
+    private HashSet<string> _lastDiscoveredPrinterIps = new();
+    private List<DiscoveredPrinter> _lastDiscoveredPrinters = new();
+
+    public PrinterDiscoveryBackgroundTask(
+        IDiscoveryService discoveryService,
+        IDiscoveredPrintersReceiver receiver,
+        ILogger logger,
+        TimeSpan? interval = null,
+        TimeSpan? discoveryTimeout = null)
+    {
+        _discoveryService = discoveryService;
+        _receiver = receiver;
+        _logger = logger;
+        _interval = interval ?? TimeSpan.FromSeconds(30);
+        _discoveryTimeout = discoveryTimeout ?? TimeSpan.FromSeconds(3);
+    }
+
+    /// <summary>
+    /// Starts the background discovery task
+    /// </summary>
+    /// <param name="cancellationToken">Token to cancel the background task</param>
+    public async Task StartAsync(CancellationToken cancellationToken)
+    {
+        _logger.LogInformation("Starting printer discovery background task (interval: {Interval}s)", _interval.TotalSeconds);
+
+        // Run immediately on start
+        await DiscoverAndNotifyAsync();
+
+        // Then run periodically
+        while (!cancellationToken.IsCancellationRequested)
+        {
+            try
+            {
+                await Task.Delay(_interval, cancellationToken);
+                await DiscoverAndNotifyAsync();
+            }
+            catch (TaskCanceledException)
+            {
+                break;
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Error during printer discovery");
+            }
+        }
+
+        _logger.LogInformation("Printer discovery background task stopped");
+    }
+
+    private async Task DiscoverAndNotifyAsync()
+    {
+        try
+        {
+            var printers = await _discoveryService.DiscoverPrintersAsync(_discoveryTimeout);
+            var currentIps = printers.Select(p => p.IPAddress).ToHashSet();
+
+            if (HasConfigurationChanged(currentIps))
+            {
+                _logger.LogInformation("Discovered printer configuration changed: {Count} printer(s)", printers.Count);
+                _lastDiscoveredPrinterIps = currentIps;
+                _lastDiscoveredPrinters = printers;
+                await _receiver.OnPrintersDiscoveredAsync(printers.AsReadOnly());
+            }
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex, "Failed to discover printers");
+        }
+    }
+
+    private bool HasConfigurationChanged(HashSet<string> currentIps)
+    {
+        if (currentIps.Count != _lastDiscoveredPrinterIps.Count)
+            return true;
+
+        return !currentIps.SetEquals(_lastDiscoveredPrinterIps);
+    }
+}