namespace StellaOps.ElkSharp;

internal static partial class ElkEdgeRouterIterative
{
    private static bool TryPromoteFastTerminalCandidates(
        CandidateSolution current,
        ElkPositionedNode[] nodes,
        ElkLayoutDirection direction,
        double minLineClearance,
        IReadOnlyList<string> orderedEdgeIds,
        out CandidateSolution promoted)
    {
        promoted = current;
        if (orderedEdgeIds.Count == 0)
        {
            return false;
        }

        var candidatePromotions = new CandidateSolution?[orderedEdgeIds.Count];
        var parallelOptions = new ParallelOptions
        {
            MaxDegreeOfParallelism = Math.Min(
                orderedEdgeIds.Count,
                Math.Max(1, Environment.ProcessorCount)),
        };

        Parallel.For(
            0,
            orderedEdgeIds.Count,
            parallelOptions,
            index =>
            {
                var candidateEdges = BuildFastTerminalOnlyHardRuleCandidate(
                    current.Edges,
                    nodes,
                    direction,
                    minLineClearance,
                    [orderedEdgeIds[index]]);
                if (TryPromoteFinalHardRuleCandidate(current, candidateEdges, nodes, out var candidatePromoted))
                {
                    candidatePromotions[index] = candidatePromoted;
                }
            });

        for (var index = 0; index < candidatePromotions.Length; index++)
        {
            if (candidatePromotions[index] is not { } candidatePromoted)
            {
                continue;
            }

            promoted = candidatePromoted;
            return true;
        }

        return false;
    }
}