feat: expand compressed IPv6 Host

Author: abishekve

ThingConnect.Pulse.Server/Services/Monitoring/DiscoveryService.cs

@@ -150,7 +150,48 @@ public IEnumerable<string> ExpandWildcard(string wildcard, int startRange = 1, i
         }
     }
 
-    public async Task<IEnumerable<string>> ResolveHostnameAsync(string hostname, CancellationToken cancellationToken = default)
+    /// <summary>
+    /// Expands a single IPv6 host into compressed (::) and full (0000:0000:...) forms.
+    /// Handles optional zone index.
+    /// </summary>
+    private IEnumerable<string> ExpandIPv6Host(string host)
+    {
+        string hostPart = host;
+        string? zoneIndex = null;
+
+        if (host.Contains('%'))
+        {
+            var split = host.Split('%');
+            hostPart = split[0];
+            zoneIndex = split[1];
+        }
+
+        if (!IPAddress.TryParse(hostPart, out var ip)) yield break;
+        if (ip.AddressFamily != AddressFamily.InterNetworkV6) yield break;
+
+        // Compressed form
+        string compressed = ip.ToString();
+
+        // Full form
+        string full = string.Join(":", ip.GetAddressBytes()
+            .Select((b, i) => i % 2 == 0 ? $"{b:X2}" : $"{b:X2}")
+            .Select((s, i) => i % 2 == 1 ? s : s) // ensure proper grouping
+        );
+
+        if (zoneIndex != null)
+        {
+            yield return $"{compressed}%{zoneIndex}";
+            yield return $"{full}%{zoneIndex}";
+        }
+        else
+        {
+            yield return compressed;
+            yield return full;
+        }
+    }
+
+
+   public async Task<IEnumerable<string>> ResolveHostnameAsync(string hostname, CancellationToken cancellationToken = default)
     {
         try
         {
@@ -159,9 +200,10 @@ public async Task<IEnumerable<string>> ResolveHostnameAsync(string hostname, Can
                 .Where(addr => addr.AddressFamily == AddressFamily.InterNetwork || addr.AddressFamily == AddressFamily.InterNetworkV6)
                 .Select(addr =>
                 {
-                    // Include zone index for IPv6 link-local if needed
-                    if (addr.IsIPv6LinkLocal && addr.ScopeId != 0)
+                    // Include zone index for IPv6 link-local
+                    if (addr.AddressFamily == AddressFamily.InterNetworkV6 && addr.IsIPv6LinkLocal && addr.ScopeId != 0)
                         return addr + "%" + addr.ScopeId;
+
                     return addr.ToString();
                 })
                 .ToList();
@@ -209,15 +251,28 @@ public async Task<IEnumerable<string>> ResolveHostnameAsync(string hostname, Can
         {
             string host = (string)target.host;
 
-            // Check if it's an IP address or hostname
-            if (IPAddress.TryParse(host, out _))
+            if (IPAddress.TryParse(host, out var ip))
             {
-                hosts.Add(host);
+                if (ip.AddressFamily == AddressFamily.InterNetworkV6)
+                {
+                    // Expand IPv6 host into compressed and full forms
+                    hosts.AddRange(ExpandIPv6Host(host));
+                }
+                else
+                {
+                    hosts.Add(host); // IPv4
+                }
             }
             else
             {
                 IEnumerable<string> resolvedHosts = await ResolveHostnameAsync(host, cancellationToken);
-                hosts.AddRange(resolvedHosts);
+                foreach (var resolvedHost in resolvedHosts)
+                {
+                    if (IPAddress.TryParse(resolvedHost, out var resolvedIp) && resolvedIp.AddressFamily == AddressFamily.InterNetworkV6)
+                        hosts.AddRange(ExpandIPv6Host(resolvedHost));
+                    else
+                        hosts.Add(resolvedHost);
+                }
             }
         }
         else if (target.cidr != null)
@@ -231,7 +286,6 @@ public async Task<IEnumerable<string>> ResolveHostnameAsync(string hostname, Can
             hosts.AddRange(ExpandWildcard(wildcard));
         }
 
-        // Create endpoint for each expanded host
         foreach (string host in hosts)
         {
             dynamic endpoint = CreateEndpointFromTarget(target, host);