namespace StellaOps.ElkSharp;

internal static partial class ElkEdgePostProcessor
{
    private static List<ElkPoint> ShiftSingleOrthogonalRun(
        IReadOnlyList<ElkPoint> path,
        int segmentIndex,
        double desiredCoordinate)
    {
        var candidate = path
            .Select(point => new ElkPoint { X = point.X, Y = point.Y })
            .ToList();
        if (segmentIndex < 0 || segmentIndex >= candidate.Count - 1)
        {
            return candidate;
        }

        var start = candidate[segmentIndex];
        var end = candidate[segmentIndex + 1];
        if (Math.Abs(start.Y - end.Y) <= 0.5d)
        {
            var original = start.Y;
            for (var i = 0; i < candidate.Count; i++)
            {
                if (Math.Abs(candidate[i].Y - original) <= 0.5d)
                {
                    candidate[i] = new ElkPoint { X = candidate[i].X, Y = desiredCoordinate };
                }
            }
        }
        else if (Math.Abs(start.X - end.X) <= 0.5d)
        {
            var original = start.X;
            for (var i = 0; i < candidate.Count; i++)
            {
                if (Math.Abs(candidate[i].X - original) <= 0.5d)
                {
                    candidate[i] = new ElkPoint { X = desiredCoordinate, Y = candidate[i].Y };
                }
            }
        }

        return NormalizePathPoints(candidate);
    }

    private static List<ElkPoint> ShiftStraightOrthogonalPath(
        IReadOnlyList<ElkPoint> path,
        double desiredCoordinate)
    {
        var candidate = path
            .Select(point => new ElkPoint { X = point.X, Y = point.Y })
            .ToList();
        if (candidate.Count != 2)
        {
            return candidate;
        }

        var start = candidate[0];
        var end = candidate[1];
        if (Math.Abs(start.Y - end.Y) <= 0.5d)
        {
            return NormalizePathPoints(
            [
                new ElkPoint { X = start.X, Y = start.Y },
                new ElkPoint { X = start.X, Y = desiredCoordinate },
                new ElkPoint { X = end.X, Y = desiredCoordinate },
                new ElkPoint { X = end.X, Y = end.Y },
            ]);
        }

        if (Math.Abs(start.X - end.X) <= 0.5d)
        {
            return NormalizePathPoints(
            [
                new ElkPoint { X = start.X, Y = start.Y },
                new ElkPoint { X = desiredCoordinate, Y = start.Y },
                new ElkPoint { X = desiredCoordinate, Y = end.Y },
                new ElkPoint { X = end.X, Y = end.Y },
            ]);
        }

        return candidate;
    }

    private static double[] ResolveLaneShiftCoordinates(
        ElkPoint start,
        ElkPoint end,
        ElkPoint otherStart,
        ElkPoint otherEnd,
        double minLineClearance)
    {
        var offset = minLineClearance + 4d;
        if (Math.Abs(start.Y - end.Y) <= 0.5d && Math.Abs(otherStart.Y - otherEnd.Y) <= 0.5d)
        {
            var lower = otherStart.Y - offset;
            var upper = otherStart.Y + offset;
            return start.Y <= otherStart.Y
                ? [lower, upper]
                : [upper, lower];
        }

        if (Math.Abs(start.X - end.X) <= 0.5d && Math.Abs(otherStart.X - otherEnd.X) <= 0.5d)
        {
            var lower = otherStart.X - offset;
            var upper = otherStart.X + offset;
            return start.X <= otherStart.X
                ? [lower, upper]
                : [upper, lower];
        }

        return [];
    }

    private static bool SegmentLeavesGraphBand(
        IReadOnlyList<ElkPoint> path,
        double graphMinY,
        double graphMaxY)
    {
        return path.Any(point => point.Y < graphMinY - 96d || point.Y > graphMaxY + 96d);
    }

    private static bool SegmentsShareLane(
        ElkPoint leftStart,
        ElkPoint leftEnd,
        ElkPoint rightStart,
        ElkPoint rightEnd,
        double minLineClearance)
    {
        var laneTolerance = Math.Max(4d, Math.Min(12d, minLineClearance * 0.2d));
        var minSharedLength = Math.Max(24d, minLineClearance * 0.4d);
        if (Math.Abs(leftStart.Y - leftEnd.Y) <= 0.5d
            && Math.Abs(rightStart.Y - rightEnd.Y) <= 0.5d
            && Math.Abs(leftStart.Y - rightStart.Y) <= laneTolerance)
        {
            var leftMinX = Math.Min(leftStart.X, leftEnd.X);
            var leftMaxX = Math.Max(leftStart.X, leftEnd.X);
            var rightMinX = Math.Min(rightStart.X, rightEnd.X);
            var rightMaxX = Math.Max(rightStart.X, rightEnd.X);
            return Math.Min(leftMaxX, rightMaxX) - Math.Max(leftMinX, rightMinX) >= minSharedLength;
        }

        if (Math.Abs(leftStart.X - leftEnd.X) <= 0.5d
            && Math.Abs(rightStart.X - rightEnd.X) <= 0.5d
            && Math.Abs(leftStart.X - rightStart.X) <= laneTolerance)
        {
            var leftMinY = Math.Min(leftStart.Y, leftEnd.Y);
            var leftMaxY = Math.Max(leftStart.Y, leftEnd.Y);
            var rightMinY = Math.Min(rightStart.Y, rightEnd.Y);
            var rightMaxY = Math.Max(rightStart.Y, rightEnd.Y);
            return Math.Min(leftMaxY, rightMaxY) - Math.Max(leftMinY, rightMinY) >= minSharedLength;
        }

        return false;
    }
}