feat(dcl): BrowseNext continuation paging + StubOpcUaClient canned browse (T15)

2026-06-18 02:21:59 -04:00
parent 3c9122bc07
commit 2cfe0de927
8 changed files with 258 additions and 37 deletions
@@ -132,15 +132,21 @@ public interface IOpcUaClient : IAsyncDisposable

    /// <summary>
    /// Enumerates the immediate children of <paramref name="parentNodeId"/>
-    /// (or the server's ObjectsFolder when null). Throws
+    /// (or the server's ObjectsFolder when null). Pageable via the OPC UA
+    /// continuation-point mechanism: when a prior call returned a non-null
+    /// <see cref="BrowseChildrenResult.ContinuationToken"/>, pass it back via
+    /// <paramref name="continuationToken"/> to fetch the next page (BrowseNext);
+    /// a null/empty token starts a fresh browse. Throws
    /// <see cref="ConnectionNotConnectedException"/> when the session is not
    /// currently up.
    /// </summary>
    /// <param name="parentNodeId">Node id whose children to browse, or null for the server root.</param>
+    /// <param name="continuationToken">Opaque token from a prior <see cref="BrowseChildrenResult.ContinuationToken"/> to fetch the next page via BrowseNext; null/empty starts a fresh browse.</param>
    /// <param name="cancellationToken">A cancellation token that can be used to cancel the operation.</param>
-    /// <returns>A task that completes with the immediate children of the requested node.</returns>
+    /// <returns>A task that completes with the immediate children of the requested node and a continuation token for the next page (null when exhausted).</returns>
    Task<BrowseChildrenResult> BrowseChildrenAsync(
        string? parentNodeId,
+        string? continuationToken = null,
        CancellationToken cancellationToken = default);
 }

@@ -235,8 +241,48 @@ internal class StubOpcUaClient : IOpcUaClient

    /// <inheritdoc />
    public Task<BrowseChildrenResult> BrowseChildrenAsync(
-        string? parentNodeId, CancellationToken cancellationToken = default)
-        => throw new NotImplementedException();
+        string? parentNodeId, string? continuationToken = null, CancellationToken cancellationToken = default)
+    {
+        // Canned address-space tree so DCL browse/paging flows can be exercised
+        // without a live OPC UA server (T15):
+        //   (root)
+        //   ├─ Folder1  (Object, HasChildren=true)
+        //   │   ├─ Tag1 (Variable)      ← page 1
+        //   │   └─ Tag2 (Variable)      ← page 2 (continuation token "STUB_PAGE2")
+        //   └─ Folder2  (Object, HasChildren=false, leaf)
+        // Folder1 fakes BrowseNext continuation paging so the continuation-token
+        // round-trip is testable; everything else is a single, exhausted page.
+        if (string.IsNullOrEmpty(parentNodeId))
+        {
+            return Task.FromResult(new BrowseChildrenResult(
+                new[]
+                {
+                    new BrowseNode("Folder1", "Folder1", BrowseNodeClass.Object, HasChildren: true),
+                    new BrowseNode("Folder2", "Folder2", BrowseNodeClass.Object, HasChildren: false),
+                },
+                Truncated: false));
+        }
+
+        if (parentNodeId == "Folder1")
+        {
+            // Page 2: the caller passed back the continuation token from page 1.
+            if (continuationToken == "STUB_PAGE2")
+            {
+                return Task.FromResult(new BrowseChildrenResult(
+                    new[] { new BrowseNode("Tag2", "Tag2", BrowseNodeClass.Variable, HasChildren: false) },
+                    Truncated: false));
+            }
+
+            // Page 1: return only Tag1 and a continuation token for the next page.
+            return Task.FromResult(new BrowseChildrenResult(
+                new[] { new BrowseNode("Tag1", "Tag1", BrowseNodeClass.Variable, HasChildren: false) },
+                Truncated: true,
+                ContinuationToken: "STUB_PAGE2"));
+        }
+
+        // Leaves (Folder2, Variable nodes, anything unknown) have no children.
+        return Task.FromResult(new BrowseChildrenResult(Array.Empty<BrowseNode>(), Truncated: false));
+    }

    /// <summary>Disposes this stub client and marks the connection as closed.</summary>
    /// <returns>A completed <see cref="ValueTask"/>.</returns>