git.stella-ops.org/src/__Libraries/StellaOps.ElkSharp/ElkEdgePostProcessor.BoundaryShortcuts.cs

namespace StellaOps.ElkSharp;

internal static partial class ElkEdgePostProcessor
{
    internal static ElkRoutedEdge[] PreferShortestBoundaryShortcuts(
        ElkRoutedEdge[] edges,
        ElkPositionedNode[] nodes,
        IReadOnlyCollection<string>? restrictedEdgeIds = null)
    {
        if (edges.Length == 0 || nodes.Length == 0)
        {
            return edges;
        }

        var restrictedSet = restrictedEdgeIds is null
            ? null
            : restrictedEdgeIds.ToHashSet(StringComparer.Ordinal);
        var nodesById = nodes.ToDictionary(node => node.Id, StringComparer.Ordinal);
        var graphMinY = nodes.Min(node => node.Y);
        var graphMaxY = nodes.Max(node => node.Y + node.Height);
        var minLineClearance = ResolveMinLineClearance(nodes);
        var result = edges.ToArray();

        for (var i = 0; i < result.Length; i++)
        {
            var edge = result[i];
            if (restrictedSet is not null && !restrictedSet.Contains(edge.Id))
            {
                continue;
            }

            if (!string.IsNullOrWhiteSpace(edge.SourcePortId)
                || !string.IsNullOrWhiteSpace(edge.TargetPortId)
                || !nodesById.TryGetValue(edge.SourceNodeId ?? string.Empty, out var sourceNode)
                || !nodesById.TryGetValue(edge.TargetNodeId ?? string.Empty, out var targetNode))
            {
                continue;
            }

            if (!string.IsNullOrWhiteSpace(edge.Kind)
                && edge.Kind.StartsWith("backward|", StringComparison.OrdinalIgnoreCase))
            {
                continue;
            }

            if (HasProtectedUnderNodeGeometry(edge)
                && ElkEdgeRoutingScoring.CountUnderNodeViolations([edge], nodes) > 0)
            {
                continue;
            }

            if (IsRepeatCollectorLabel(edge.Label)
                && HasCorridorBendPoints(edge, graphMinY, graphMaxY))
            {
                continue;
            }

            var path = ExtractFullPath(edge);
            if (path.Count < 2)
            {
                continue;
            }

            List<ElkPoint>? bestShortcut = null;
            var currentLength = ComputePathLength(path);

            bool IsAcceptableShortcutCandidate(IReadOnlyList<ElkPoint> candidate)
            {
                if (candidate.Count < 2
                    || HasNodeObstacleCrossing(candidate, nodes, edge.SourceNodeId, edge.TargetNodeId))
                {
                    return false;
                }

                if (ElkShapeBoundaries.IsGatewayShape(sourceNode))
                {
                    if (!HasAcceptableGatewayBoundaryPath(
                            candidate,
                            nodes,
                            edge.SourceNodeId,
                            edge.TargetNodeId,
                            sourceNode,
                            fromStart: true))
                    {
                        return false;
                    }
                }
                else if (!HasValidBoundaryAngle(candidate[0], candidate[1], sourceNode))
                {
                    return false;
                }

                if (ElkShapeBoundaries.IsGatewayShape(targetNode))
                {
                    return CanAcceptGatewayTargetRepair(candidate, targetNode)
                        && HasAcceptableGatewayBoundaryPath(
                            candidate,
                            nodes,
                            edge.SourceNodeId,
                            edge.TargetNodeId,
                            targetNode,
                            fromStart: false);
                }

                return !HasTargetApproachBacktracking(candidate, targetNode)
                    && HasValidBoundaryAngle(candidate[^1], candidate[^2], targetNode);
            }

            void ConsiderShortcutCandidate(List<ElkPoint>? candidate)
            {
                if (candidate is null
                    || ComputePathLength(candidate) + 16d >= currentLength
                    || !IsAcceptableShortcutCandidate(candidate))
                {
                    return;
                }

                if (bestShortcut is not null
                    && ComputePathLength(candidate) + 0.5d >= ComputePathLength(bestShortcut))
                {
                    return;
                }

                bestShortcut = candidate;
            }

            if (TryBuildDominantPreferredBoundaryShortcutPath(
                    sourceNode,
                    targetNode,
                    nodes,
                    edge.SourceNodeId,
                    edge.TargetNodeId,
                    out var dominantShortcut))
            {
                ConsiderShortcutCandidate(dominantShortcut);
            }

            if (TryBuildPreferredBoundaryShortcutPath(
                    sourceNode,
                    targetNode,
                    nodes,
                    edge.SourceNodeId,
                    edge.TargetNodeId,
                    out var preferredShortcut))
            {
                ConsiderShortcutCandidate(preferredShortcut);
            }

            var localSkirtShortcut = TryBuildLocalObstacleSkirtBoundaryShortcut(
                path,
                path[0],
                path[^1],
                nodes,
                edge.SourceNodeId,
                edge.TargetNodeId,
                targetNode,
                minLineClearance);
            ConsiderShortcutCandidate(localSkirtShortcut);

            if (bestShortcut is null)
            {
                continue;
            }

            result[i] = BuildSingleSectionEdge(edge, bestShortcut);
        }

        return result;
    }
}