Joseph Doherty
84 lines
3.0 KiB
C#
84 lines
3.0 KiB
C#
using ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxy;
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namespace ZB.MOM.WW.MxGateway.Client;
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/// <summary>
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/// One node in a lazy-loaded Galaxy browse tree. Holds the underlying
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/// <see cref="GalaxyObject"/> and exposes <see cref="ExpandAsync"/> to fetch
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/// its direct children on demand. Expansion is one-shot: a second call is a
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/// no-op. Pagination of large sibling sets is handled internally.
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/// </summary>
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public sealed class LazyBrowseNode
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{
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private readonly GalaxyRepositoryClient _client;
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private readonly BrowseChildrenOptions _options;
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private readonly List<LazyBrowseNode> _children = [];
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private bool _isExpanded;
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internal LazyBrowseNode(
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GalaxyRepositoryClient client,
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GalaxyObject @object,
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bool hasChildrenHint,
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BrowseChildrenOptions options)
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{
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_client = client;
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Object = @object;
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HasChildrenHint = hasChildrenHint;
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_options = options;
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}
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/// <summary>The underlying Galaxy object for this node.</summary>
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public GalaxyObject Object { get; }
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/// <summary>True when the server reports this node has at least one matching descendant.</summary>
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public bool HasChildrenHint { get; }
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/// <summary>Direct children loaded by <see cref="ExpandAsync"/>; empty until then.</summary>
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public IReadOnlyList<LazyBrowseNode> Children => _children;
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/// <summary>True after the first <see cref="ExpandAsync"/> call completes.</summary>
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public bool IsExpanded => _isExpanded;
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/// <summary>
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/// Fetches direct children from the gateway and populates <see cref="Children"/>.
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/// Idempotent: subsequent calls are no-ops.
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/// </summary>
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/// <param name="cancellationToken">Token to observe for cancellation.</param>
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public async Task ExpandAsync(CancellationToken cancellationToken = default)
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{
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if (_isExpanded)
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{
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return;
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}
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string pageToken = string.Empty;
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HashSet<string> seenPageTokens = new(StringComparer.Ordinal);
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do
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{
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BrowseChildrenRequest request = GalaxyRepositoryClient.BuildBrowseChildrenRequest(_options);
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request.ParentGobjectId = Object.GobjectId;
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request.PageToken = pageToken;
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BrowseChildrenReply reply = await _client
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.BrowseChildrenRawAsync(request, cancellationToken)
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.ConfigureAwait(false);
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for (int i = 0; i < reply.Children.Count; i++)
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{
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bool hint = i < reply.ChildHasChildren.Count && reply.ChildHasChildren[i];
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_children.Add(new LazyBrowseNode(_client, reply.Children[i], hint, _options));
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}
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pageToken = reply.NextPageToken;
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if (!string.IsNullOrWhiteSpace(pageToken) && !seenPageTokens.Add(pageToken))
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{
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throw new MxGatewayException(
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$"Galaxy BrowseChildren returned a repeated page token '{pageToken}'.");
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}
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}
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while (!string.IsNullOrWhiteSpace(pageToken));
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_isExpanded = true;
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}
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}
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