using System.Diagnostics;

namespace StellaOps.ElkSharp;

internal static partial class ElkEdgeRouterIterative
{
    /// <summary>
    /// Creates a worst-case retry state used as the initial "best" baseline
    /// in the strategy evaluation loop.
    /// </summary>
    private static RoutingRetryState BuildMaxRetryState()
    {
        return new RoutingRetryState(
            RemainingShortHighways: int.MaxValue,
            RepeatCollectorCorridorViolations: int.MaxValue,
            RepeatCollectorNodeClearanceViolations: int.MaxValue,
            TargetApproachJoinViolations: int.MaxValue,
            TargetApproachBacktrackingViolations: int.MaxValue,
            ExcessiveDetourViolations: int.MaxValue,
            SharedLaneViolations: int.MaxValue,
            BoundarySlotViolations: int.MaxValue,
            BelowGraphViolations: int.MaxValue,
            UnderNodeViolations: int.MaxValue,
            LongDiagonalViolations: int.MaxValue,
            ProximityViolations: int.MaxValue,
            EntryAngleViolations: int.MaxValue,
            GatewaySourceExitViolations: int.MaxValue,
            LabelProximityViolations: int.MaxValue,
            EdgeCrossings: int.MaxValue);
    }

    /// <summary>
    /// Checks stagnation conditions: repeated repair focus, repeated plateau
    /// fingerprints, and blocking cycle detection. Returns the stagnation
    /// outcome reason or null if the attempt should continue.
    /// </summary>
    private static string? DetectStrategyStagnation(
        RepairPlan? repairPlan,
        RoutingRetryState retryState,
        RoutingRetryState bestAttemptRetryState,
        int attempt,
        ref string? lastRepairFocusFingerprint,
        ref int repeatedRepairFocusCount,
        ref string? lastPlateauFingerprint,
        ref int repeatedPlateauFingerprintCount,
        List<string> recentBlockingCycleFingerprints)
    {
        var repairFocusFingerprint = BuildRepairFocusFingerprint(repairPlan);
        if (!string.IsNullOrEmpty(repairFocusFingerprint))
        {
            if (string.Equals(repairFocusFingerprint, lastRepairFocusFingerprint, StringComparison.Ordinal))
            {
                repeatedRepairFocusCount++;
            }
            else
            {
                lastRepairFocusFingerprint = repairFocusFingerprint;
                repeatedRepairFocusCount = 0;
            }

            if (repeatedRepairFocusCount >= 1 && attempt >= 3)
            {
                return $"stalled-same-focus({DescribeRetryState(retryState)})@attempt{attempt + 1}";
            }
        }
        else
        {
            lastRepairFocusFingerprint = null;
            repeatedRepairFocusCount = 0;
        }

        var plateauFingerprint = BuildPlateauFingerprint(retryState, repairPlan);
        if (string.Equals(plateauFingerprint, lastPlateauFingerprint, StringComparison.Ordinal))
        {
            repeatedPlateauFingerprintCount++;
        }
        else
        {
            lastPlateauFingerprint = plateauFingerprint;
            repeatedPlateauFingerprintCount = 0;
        }

        if (repeatedPlateauFingerprintCount >= 2 && attempt >= 3)
        {
            return $"stalled-repeat({DescribeRetryState(retryState)})@attempt{attempt + 1}";
        }

        var blockingCycleFingerprint = BuildBlockingCycleFingerprint(retryState, repairPlan);
        if (ShouldStopForBlockingCycle(
                recentBlockingCycleFingerprints,
                blockingCycleFingerprint,
                retryState,
                bestAttemptRetryState,
                attempt))
        {
            return $"stalled-cycle({DescribeRetryState(retryState)})@attempt{attempt + 1}";
        }

        AppendRecentFingerprint(recentBlockingCycleFingerprints, blockingCycleFingerprint, 4);
        return null;
    }

    /// <summary>
    /// Determines the retry/accept decision for a strategy attempt based on
    /// violation categories. Returns the attempt outcome string and whether
    /// the loop should continue, break, or accept.
    /// </summary>
    private static (string Outcome, bool ShouldContinue, bool IsValid) DecideStrategyAttemptOutcome(
        EdgeRoutingScore score,
        RoutingRetryState retryState,
        int maxAllowedNodeCrossings,
        int attempt,
        int maxAttempts,
        StrategyWorkItem workItem,
        RoutingStrategy strategy)
    {
        if (score.NodeCrossings > maxAllowedNodeCrossings)
        {
            strategy.AdaptForViolations(score, attempt, retryState);
            return ($"hard-violation(nc={score.NodeCrossings}>{maxAllowedNodeCrossings})@attempt{attempt + 1}", true, false);
        }

        if (retryState.RemainingShortHighways > 0
            || retryState.RepeatCollectorCorridorViolations > 0
            || retryState.RepeatCollectorNodeClearanceViolations > 0
            || retryState.TargetApproachJoinViolations > 0
            || retryState.TargetApproachBacktrackingViolations > 0
            || retryState.SharedLaneViolations > 0
            || retryState.BelowGraphViolations > 0
            || retryState.UnderNodeViolations > 0
            || retryState.LongDiagonalViolations > 0
            || retryState.EntryAngleViolations > 0
            || retryState.GatewaySourceExitViolations > 0)
        {
            if (ShouldRetryForPrimaryViolations(retryState, attempt, maxAttempts))
            {
                strategy.AdaptForViolations(score, attempt, retryState);
                return ($"retry({DescribeRetryState(retryState)})@attempt{attempt + 1}", true, false);
            }

            return ($"invalid({DescribeRetryState(retryState)})@attempt{attempt + 1}", false, false);
        }

        if (retryState.RequiresLengthRetry)
        {
            if (ShouldRetryForPrimaryViolations(retryState, attempt, maxAttempts))
            {
                strategy.AdaptForViolations(score, attempt, retryState);
                return ($"retry({DescribeRetryState(retryState)})@attempt{attempt + 1}", true, false);
            }

            return ($"invalid({DescribeRetryState(retryState)})@attempt{attempt + 1}", false, false);
        }

        if (retryState.RequiresQualityRetry
            && ShouldRetryForPrimaryViolations(retryState, attempt, maxAttempts))
        {
            strategy.AdaptForViolations(score, attempt, retryState);
            return ($"retry({DescribeRetryState(retryState)})@attempt{attempt + 1}", true, false);
        }

        if (ShouldRetryForEdgeCrossings(retryState, attempt, maxAttempts))
        {
            strategy.AdaptForViolations(score, attempt, retryState);
            return ($"retry(edge-crossings={retryState.EdgeCrossings})@attempt{attempt + 1}", true, false);
        }

        var residualSoftViolations = retryState.RequiresQualityRetry || retryState.EdgeCrossings > 0;
        var validOutcome = residualSoftViolations
            ? $"valid-soft({DescribeRetryState(retryState)})@attempt{attempt + 1}"
            : $"valid@attempt{attempt + 1}";
        return (validOutcome, false, true);
    }
}