w4c-workflows-api/Services/Nodes/NodeGraphRunner.Routing.cs

using System.Text.Json.Nodes;
using w4c_workflows.Models.Credentials;
using w4c_workflows.Models.Nodes;
using w4c_workflows.Services.Nodes.Interpolation;
using w4c_workflows.Services.Security;

namespace w4c_workflows.Services.Nodes;

// Routing half of the graph runner: forwarding produced items along outgoing
// edges (readiness accounting incl. loop-back edges), emitting listener events
// and shaping an error-port payload when a failure is routed.

public sealed partial class NodeGraphRunner
{
    // ------------------------------------------------------------------ routing

    private static void Propagate(
        NodeGraph graph,
        string nodeId,
        IReadOnlyList<IReadOnlyList<FlowItem>> ports,
        IReadOnlyDictionary<string, List<FlowItem>[]> inputs,
        IDictionary<string, int> arrived,
        IReadOnlyDictionary<string, int> incoming,
        Queue<string> ready,
        ISet<string> queued,
        ISet<string> exhausted,
        bool skipEmptyPorts)
    {
        for (var port = 0; port < ports.Count; port++)
        {
            var produced = ports[port];
            // On a loop node's final ("done") invocation the loop port is empty:
            // skip it so the body is not re-triggered for a no-op iteration.
            if (skipEmptyPorts && produced.Count == 0)
                continue;

            foreach (var edge in graph.EdgesFrom(nodeId, port))
            {
                // An exhausted loop node is not re-triggered by its loop-back edge.
                if (exhausted.Contains(edge.ToNodeId) && edge.IsLoopBack)
                    continue;

                var targetInputs = inputs[edge.ToNodeId];
                if (edge.ToInput >= 0 && edge.ToInput < targetInputs.Length)
                    targetInputs[edge.ToInput].AddRange(produced);

                arrived[edge.ToNodeId]++;
                // Max(incoming, 1): a node with no non-loop-back predecessor (an
                // entry loop node) must still be re-triggered by its loop-back
                // edge. The queued guard prevents a double enqueue when several
                // inputs arrive before the node next runs.
                if (arrived[edge.ToNodeId] >= Math.Max(incoming[edge.ToNodeId], 1)
                    && queued.Add(edge.ToNodeId))
                    ready.Enqueue(edge.ToNodeId);
            }
        }
    }

    // ------------------------------------------------------------------ listeners

    private static Task NotifyStarted(
        INodeRunListener? listener,
        NodeGraphNode node,
        IReadOnlyList<IReadOnlyList<FlowItem>> inputs,
        CancellationToken ct)
        => listener == null ? Task.CompletedTask : listener.NodeStartedAsync(node, inputs, ct);

    private static Task NotifyFinished(
        INodeRunListener? listener,
        NodeGraphNode node,
        IReadOnlyList<IReadOnlyList<FlowItem>> outputs,
        NodeFailure? failure,
        CancellationToken ct)
        => listener == null ? Task.CompletedTask : listener.NodeFinishedAsync(node, outputs, failure, ct);

    private List<IReadOnlyList<FlowItem>> BuildErrorOutputs(
        NodeGraphNode node,
        IReadOnlyList<IReadOnlyList<FlowItem>> inputs,
        NodeFailure failure,
        int errorPort)
    {
        var portCount = Math.Max(1, node.Blueprint.Outputs.Count);
        var ports = Enumerable.Range(0, portCount).Select(_ => (IReadOnlyList<FlowItem>)new List<FlowItem>()).ToList();
        if (errorPort < 0 || errorPort >= ports.Count)
            return ports;

        var errorJson = new JsonObject
        {
            ["message"] = failure.Message,
            ["code"] = failure.Code,
            ["description"] = failure.Description,
            ["httpStatus"] = failure.HttpStatus,
        };

        var source = inputs.FirstOrDefault(list => list.Count > 0);
        var items = new List<FlowItem>();

        if (source == null || source.Count == 0)
        {
            items.Add(new FlowItem { Json = new JsonObject { ["error"] = errorJson } });
        }
        else
        {
            foreach (var item in source)
            {
                var json = (JsonObject)item.Json.DeepClone();
                json["error"] = errorJson.DeepClone();
                items.Add(new FlowItem { Json = json, Binary = item.Binary, Origin = item.Origin });
            }
        }

        ports[errorPort] = items;
        return ports;
    }
}