using System.Collections.Concurrent;
using System.Diagnostics;
using System.Globalization;

namespace StellaOps.ElkSharp;

internal static partial class ElkEdgeRouterIterative
{
    private static string[] ExpandRepeatCollectorRepairSet(
        IReadOnlyCollection<string> selectedEdgeIds,
        IReadOnlyCollection<ElkRoutedEdge> edges,
        IReadOnlyCollection<ElkPositionedNode> nodes)
    {
        var selected = selectedEdgeIds.ToHashSet(StringComparer.Ordinal);
        foreach (var group in ElkRepeatCollectorCorridors.DetectSharedLaneGroups(edges, nodes))
        {
            if (!group.EdgeIds.Any(selected.Contains))
            {
                continue;
            }

            foreach (var edgeId in group.EdgeIds)
            {
                selected.Add(edgeId);
            }
        }

        return selected
            .OrderBy(edgeId => edgeId, StringComparer.Ordinal)
            .ToArray();
    }

    private static string[] ExpandTargetApproachJoinRepairSet(
        IReadOnlyCollection<string> selectedEdgeIds,
        IReadOnlyCollection<ElkRoutedEdge> edges,
        IReadOnlyCollection<ElkPositionedNode> nodes,
        double minLineClearance)
    {
        var selected = selectedEdgeIds.ToHashSet(StringComparer.Ordinal);
        var nodesById = nodes.ToDictionary(node => node.Id, StringComparer.Ordinal);
        var edgeArray = edges.ToArray();

        foreach (var group in edgeArray.GroupBy(edge => edge.TargetNodeId ?? string.Empty, StringComparer.Ordinal))
        {
            if (string.IsNullOrWhiteSpace(group.Key)
                || !nodesById.TryGetValue(group.Key, out var targetNode))
            {
                continue;
            }

            var targetEdges = group.ToArray();
            for (var i = 0; i < targetEdges.Length; i++)
            {
                var leftEdge = targetEdges[i];
                var leftPath = ExtractPath(leftEdge);
                if (leftPath.Count < 2)
                {
                    continue;
                }

                var leftSide = ElkEdgeRoutingGeometry.ResolveBoundaryApproachSide(leftPath[^1], leftPath[^2], targetNode);
                for (var j = i + 1; j < targetEdges.Length; j++)
                {
                    var rightEdge = targetEdges[j];
                    var rightPath = ExtractPath(rightEdge);
                    if (rightPath.Count < 2)
                    {
                        continue;
                    }

                    var rightSide = ElkEdgeRoutingGeometry.ResolveBoundaryApproachSide(rightPath[^1], rightPath[^2], targetNode);
                    if (!string.Equals(leftSide, rightSide, StringComparison.Ordinal))
                    {
                        continue;
                    }

                    if (!HasTargetApproachJoinPair(leftPath, rightPath, minLineClearance))
                    {
                        continue;
                    }

                    selected.Add(leftEdge.Id);
                    selected.Add(rightEdge.Id);
                }
            }
        }

        return selected
            .OrderBy(edgeId => edgeId, StringComparer.Ordinal)
            .ToArray();
    }

    private static string[] ExpandSharedLaneRepairSet(
        IReadOnlyCollection<string> selectedEdgeIds,
        IReadOnlyCollection<ElkRoutedEdge> edges,
        IReadOnlyCollection<ElkPositionedNode> nodes)
    {
        var selected = selectedEdgeIds.ToHashSet(StringComparer.Ordinal);
        foreach (var (leftEdgeId, rightEdgeId) in ElkEdgeRoutingScoring.DetectSharedLaneConflicts(edges, nodes))
        {
            if (!selected.Contains(leftEdgeId) && !selected.Contains(rightEdgeId))
            {
                continue;
            }

            selected.Add(leftEdgeId);
            selected.Add(rightEdgeId);
        }

        return selected
            .OrderBy(edgeId => edgeId, StringComparer.Ordinal)
            .ToArray();
    }

    private static string[] ExpandUnderNodeRepairSet(
        IReadOnlyCollection<string> selectedEdgeIds,
        IReadOnlyCollection<ElkRoutedEdge> edges,
        IReadOnlyCollection<ElkPositionedNode> nodes)
    {
        var selected = selectedEdgeIds.ToHashSet(StringComparer.Ordinal);
        foreach (var edge in edges)
        {
            if (ElkEdgeRoutingScoring.CountUnderNodeViolations([edge], nodes) > 0)
            {
                selected.Add(edge.Id);
            }
        }

        return selected
            .OrderBy(edgeId => edgeId, StringComparer.Ordinal)
            .ToArray();
    }

    private static List<ElkPoint> ExtractPath(ElkRoutedEdge edge)
    {
        var path = new List<ElkPoint>();
        foreach (var section in edge.Sections)
        {
            if (path.Count == 0)
            {
                path.Add(section.StartPoint);
            }

            path.AddRange(section.BendPoints);
            path.Add(section.EndPoint);
        }

        return path;
    }

    private static bool HasTargetApproachJoinPair(
        IReadOnlyList<ElkPoint> leftPath,
        IReadOnlyList<ElkPoint> rightPath,
        double minLineClearance,
        int maxSegmentsFromEnd = 3)
    {
        var leftSegments = FlattenSegmentsNearEnd(leftPath, maxSegmentsFromEnd);
        var rightSegments = FlattenSegmentsNearEnd(rightPath, maxSegmentsFromEnd);

        foreach (var leftSegment in leftSegments)
        {
            foreach (var rightSegment in rightSegments)
            {
                if (!ElkEdgeRoutingGeometry.AreParallelAndClose(
                        leftSegment.Start,
                        leftSegment.End,
                        rightSegment.Start,
                        rightSegment.End,
                        minLineClearance))
                {
                    continue;
                }

                var overlap = ElkEdgeRoutingGeometry.ComputeSharedSegmentLength(
                    leftSegment.Start,
                    leftSegment.End,
                    rightSegment.Start,
                    rightSegment.End);
                if (overlap > 8d)
                {
                    return true;
                }

                var leftLength = ElkEdgeRoutingGeometry.ComputeSegmentLength(leftSegment.Start, leftSegment.End);
                var rightLength = ElkEdgeRoutingGeometry.ComputeSegmentLength(rightSegment.Start, rightSegment.End);
                if (Math.Min(leftLength, rightLength) > 8d)
                {
                    return true;
                }
            }
        }

        return false;
    }

    private static IReadOnlyList<RoutedEdgeSegment> FlattenSegmentsNearEnd(
        IReadOnlyList<ElkPoint> path,
        int maxSegmentsFromEnd)
    {
        if (path.Count < 2 || maxSegmentsFromEnd <= 0)
        {
            return [];
        }

        var startIndex = Math.Max(0, path.Count - (maxSegmentsFromEnd + 1));
        var segments = new List<RoutedEdgeSegment>();
        for (var i = startIndex; i < path.Count - 1; i++)
        {
            segments.Add(new RoutedEdgeSegment(string.Empty, path[i], path[i + 1]));
        }

        return segments;
    }

}