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

namespace StellaOps.ElkSharp;

internal static partial class ElkEdgePostProcessor
{
    private static List<ElkPoint> FixGatewaySourcePreferredFace(
        IReadOnlyList<ElkPoint> sourcePath,
        ElkPositionedNode sourceNode)
    {
        if (!HasGatewaySourcePreferredFaceMismatch(sourcePath, sourceNode))
        {
            return sourcePath.Select(point => new ElkPoint { X = point.X, Y = point.Y }).ToList();
        }

        var path = sourcePath
            .Select(point => new ElkPoint { X = point.X, Y = point.Y })
            .ToList();
        var firstExteriorIndex = FindFirstGatewayExteriorPointIndex(path, sourceNode);
        var continuationIndex = FindGatewaySourceCurlRecoveryIndex(path, firstExteriorIndex)
            ?? FindPreferredGatewayExitContinuationIndex(path, sourceNode, firstExteriorIndex);
        var continuationPoint = path[continuationIndex];
        if (!TryResolvePreferredGatewaySourceBoundary(sourceNode, continuationPoint, path[^1], out var preferredBoundary))
        {
            return path;
        }

        return BuildGatewaySourceRepairPath(
            path,
            sourceNode,
            preferredBoundary,
            continuationPoint,
            continuationIndex,
            path[^1]);
    }

    private static bool HasGatewaySourcePreferredFaceMismatch(
        IReadOnlyList<ElkPoint> path,
        ElkPositionedNode sourceNode)
    {
        if (!ElkShapeBoundaries.IsGatewayShape(sourceNode) || path.Count < 2)
        {
            return false;
        }

        var centerX = sourceNode.X + (sourceNode.Width / 2d);
        var centerY = sourceNode.Y + (sourceNode.Height / 2d);
        var desiredDx = path[^1].X - centerX;
        var desiredDy = path[^1].Y - centerY;
        var boundaryDx = path[0].X - centerX;
        var boundaryDy = path[0].Y - centerY;

        if (Math.Abs(desiredDx) >= Math.Abs(desiredDy) * 1.25d)
        {
            return Math.Sign(boundaryDx) != Math.Sign(desiredDx)
                || Math.Abs(boundaryDy) > sourceNode.Height * 0.28d;
        }

        if (Math.Abs(desiredDy) >= Math.Abs(desiredDx) * 1.25d)
        {
            return Math.Sign(boundaryDy) != Math.Sign(desiredDy)
                || Math.Abs(boundaryDx) > sourceNode.Width * 0.28d;
        }

        return false;
    }

    private static List<ElkPoint> FixGatewaySourceExitCurl(
        IReadOnlyList<ElkPoint> sourcePath,
        ElkPositionedNode sourceNode)
    {
        if (!ElkShapeBoundaries.IsGatewayShape(sourceNode) || sourcePath.Count < 3)
        {
            return sourcePath.Select(point => new ElkPoint { X = point.X, Y = point.Y }).ToList();
        }

        var sample = sourcePath
            .Take(Math.Min(sourcePath.Count, 6))
            .ToArray();
        var desiredDx = sourcePath[^1].X - sourcePath[0].X;
        var desiredDy = sourcePath[^1].Y - sourcePath[0].Y;
        if (!HasGatewaySourceExitCurl(sample))
        {
            return sourcePath.Select(point => new ElkPoint { X = point.X, Y = point.Y }).ToList();
        }

        var path = sourcePath
            .Select(point => new ElkPoint { X = point.X, Y = point.Y })
            .ToList();
        var firstExteriorIndex = FindFirstGatewayExteriorPointIndex(path, sourceNode);
        var continuationIndex = FindGatewaySourceCurlRecoveryIndex(path, firstExteriorIndex)
            ?? FindPreferredGatewayExitContinuationIndex(path, sourceNode, firstExteriorIndex);
        var continuationPoint = path[continuationIndex];
        var boundary = sourceNode.Kind == "Decision"
            ? ResolveDecisionSourceExitBoundary(sourceNode, continuationPoint, continuationPoint)
            : PreferGatewaySourceExitBoundary(
                sourceNode,
                ElkShapeBoundaries.ProjectOntoShapeBoundary(sourceNode, continuationPoint),
                continuationPoint);
        var continuationAligned = BuildGatewaySourceRepairPath(
            path,
            sourceNode,
            boundary,
            continuationPoint,
            continuationIndex,
            continuationPoint);
        if (PathChanged(path, continuationAligned)
            && !HasGatewaySourceExitBacktracking(continuationAligned)
            && !HasGatewaySourceExitCurl(continuationAligned))
        {
            return continuationAligned;
        }

        var collapsedCurl = TryBuildGatewaySourceDominantAxisShortcut(path, sourceNode, path[0]);
        if (collapsedCurl is not null
            && PathChanged(path, collapsedCurl)
            && !HasGatewaySourceExitBacktracking(collapsedCurl)
            && !HasGatewaySourceExitCurl(collapsedCurl))
        {
            return collapsedCurl;
        }

        const double axisTolerance = 4d;
        var rebuilt = path;
        var dominantHorizontal = Math.Abs(desiredDx) >= Math.Abs(desiredDy) * 1.15d && Math.Sign(desiredDx) != 0;
        var dominantVertical = Math.Abs(desiredDy) >= Math.Abs(desiredDx) * 1.15d && Math.Sign(desiredDy) != 0;

        if (dominantHorizontal && Math.Abs(rebuilt[1].Y - rebuilt[0].Y) <= axisTolerance)
        {
            rebuilt[1] = new ElkPoint
            {
                X = rebuilt[1].X,
                Y = rebuilt[0].Y,
            };
        }
        else if (dominantVertical && Math.Abs(rebuilt[1].X - rebuilt[0].X) <= axisTolerance)
        {
            rebuilt[1] = new ElkPoint
            {
                X = rebuilt[0].X,
                Y = rebuilt[1].Y,
            };
        }

        return NormalizePathPoints(rebuilt);
    }

    private static List<ElkPoint> FixGatewaySourceDominantAxisDetour(
        IReadOnlyList<ElkPoint> sourcePath,
        ElkPositionedNode sourceNode)
    {
        var path = sourcePath
            .Select(point => new ElkPoint { X = point.X, Y = point.Y })
            .ToList();
        if (!HasGatewaySourceDominantAxisDetour(path, sourceNode))
        {
            return path;
        }

        var boundary = path[0];
        var desiredDx = path[^1].X - boundary.X;
        var desiredDy = path[^1].Y - boundary.Y;
        var dominantHorizontal = Math.Abs(desiredDx) >= Math.Abs(desiredDy) * 1.15d && Math.Sign(desiredDx) != 0;
        var dominantVertical = Math.Abs(desiredDy) >= Math.Abs(desiredDx) * 1.15d && Math.Sign(desiredDy) != 0;
        var firstExteriorIndex = FindFirstGatewayExteriorPointIndex(path, sourceNode);
        var boundaryReferencePoint = path[firstExteriorIndex];
        if (!TryResolvePreferredGatewaySourceBoundary(sourceNode, boundaryReferencePoint, path[^1], out var preferredBoundary))
        {
            return path;
        }

        var localContinuationPoint = path[firstExteriorIndex];
        var localRepair = new List<ElkPoint> { preferredBoundary };
        if (!ElkEdgeRoutingGeometry.PointsEqual(localRepair[^1], localContinuationPoint))
        {
            AppendGatewayOrthogonalCorner(
                localRepair,
                localRepair[^1],
                localContinuationPoint,
                firstExteriorIndex + 1 < path.Count ? path[firstExteriorIndex + 1] : null,
                preferHorizontalFromReference: ShouldPreferHorizontalGatewayExit(localRepair[^1], localContinuationPoint));
            if (!ElkEdgeRoutingGeometry.PointsEqual(localRepair[^1], localContinuationPoint))
            {
                localRepair.Add(localContinuationPoint);
            }
        }

        for (var i = firstExteriorIndex + 1; i < path.Count; i++)
        {
            localRepair.Add(path[i]);
        }

        localRepair = NormalizePathPoints(localRepair);
        if (PathChanged(path, localRepair)
            && !HasGatewaySourceExitBacktracking(localRepair)
            && !HasGatewaySourceExitCurl(localRepair)
            && !HasGatewaySourceDominantAxisDetour(localRepair, sourceNode)
            && !HasGatewaySourcePreferredFaceMismatch(localRepair, sourceNode))
        {
            return localRepair;
        }

        var dominantAxisShortcut = TryBuildGatewaySourceDominantAxisShortcut(path, sourceNode, preferredBoundary);
        if (dominantAxisShortcut is not null
            && PathChanged(path, dominantAxisShortcut)
            && !HasGatewaySourceExitBacktracking(dominantAxisShortcut)
            && !HasGatewaySourceExitCurl(dominantAxisShortcut)
            && !HasGatewaySourceDominantAxisDetour(dominantAxisShortcut, sourceNode)
            && !HasGatewaySourcePreferredFaceMismatch(dominantAxisShortcut, sourceNode))
        {
            return dominantAxisShortcut;
        }

        var preferredContinuationIndex = FindPreferredGatewayExitContinuationIndex(path, sourceNode, firstExteriorIndex);
        var candidateContinuationIndices = new[]
        {
            firstExteriorIndex,
            Math.Min(path.Count - 1, firstExteriorIndex + 1),
            Math.Min(path.Count - 1, firstExteriorIndex + 2),
            preferredContinuationIndex,
        }
            .Distinct()
            .Where(index => index >= firstExteriorIndex && index < path.Count)
            .ToArray();

        List<ElkPoint>? bestCandidate = null;
        var bestScore = double.PositiveInfinity;
        foreach (var continuationIndex in candidateContinuationIndices)
        {
            var continuationCandidates = new List<ElkPoint>
            {
                path[continuationIndex],
            };
            if (dominantHorizontal)
            {
                AddUniquePoint(
                    continuationCandidates,
                    new ElkPoint
                    {
                        X = path[continuationIndex].X,
                        Y = preferredBoundary.Y,
                    });
            }
            else if (dominantVertical)
            {
                AddUniquePoint(
                    continuationCandidates,
                    new ElkPoint
                    {
                        X = preferredBoundary.X,
                        Y = path[continuationIndex].Y,
                    });
            }

            foreach (var continuationPoint in continuationCandidates)
            {
                var candidate = BuildGatewaySourceRepairPath(
                    path,
                    sourceNode,
                    preferredBoundary,
                    continuationPoint,
                    continuationIndex,
                    continuationPoint);
                if (!PathChanged(path, candidate))
                {
                    continue;
                }

                var score = ComputePathLength(candidate);
                if (!ElkEdgeRoutingGeometry.PointsEqual(continuationPoint, path[continuationIndex]))
                {
                    score -= 18d;
                }

                if (HasGatewaySourceExitBacktracking(candidate)
                    || HasGatewaySourceExitCurl(candidate))
                {
                    score += 100_000d;
                }

                if (HasGatewaySourceDominantAxisDetour(candidate, sourceNode))
                {
                    score += 50_000d;
                }

                if (HasGatewaySourcePreferredFaceMismatch(candidate, sourceNode))
                {
                    score += 25_000d;
                }

                if (score >= bestScore)
                {
                    continue;
                }

                bestScore = score;
                bestCandidate = candidate;
            }
        }

        if (bestCandidate is null
            || HasGatewaySourceExitBacktracking(bestCandidate)
            || HasGatewaySourceExitCurl(bestCandidate)
            || HasGatewaySourceDominantAxisDetour(bestCandidate, sourceNode)
            || HasGatewaySourcePreferredFaceMismatch(bestCandidate, sourceNode))
        {
            return path;
        }

        return bestCandidate;
    }

}