neon-sprawl/server/NeonSprawl.Server/Game/Npc/NpcRuntimeOperations.cs

namespace NeonSprawl.Server.Game.Npc;

/// <summary>Deterministic prototype NPC behavior state machine + lazy tick advance (NEO-93).</summary>
public static class NpcRuntimeOperations
{
    /// <summary>Default per-advance simulation cap (seconds) for lazy poll ticks.</summary>
    public const double DefaultMaxDeltaSeconds = 5.0;

    /// <summary>
    /// Advances all prototype NPC runtime rows by up to <paramref name="maxDeltaSeconds"/> since the last call.
    /// </summary>
    public static void AdvanceAll(
        DateTimeOffset nowUtc,
        INpcRuntimeStateStore runtimeStore,
        IThreatStateStore threatStore,
        INpcBehaviorDefinitionRegistry behaviorRegistry,
        double maxDeltaSeconds = DefaultMaxDeltaSeconds)
    {
        if (maxDeltaSeconds <= 0)
        {
            return;
        }

        var lastAdvanced = runtimeStore.LastAdvancedUtc;
        if (lastAdvanced == DateTimeOffset.MinValue)
        {
            foreach (var npcInstanceId in PrototypeNpcRegistry.GetInstanceIdsInOrder())
            {
                AdvanceOne(
                    npcInstanceId,
                    nowUtc,
                    nowUtc,
                    runtimeStore,
                    threatStore,
                    behaviorRegistry);
            }

            runtimeStore.LastAdvancedUtc = nowUtc;
            return;
        }

        var rawDeltaSeconds = (nowUtc - lastAdvanced).TotalSeconds;
        if (rawDeltaSeconds <= 0)
        {
            foreach (var npcInstanceId in PrototypeNpcRegistry.GetInstanceIdsInOrder())
            {
                AdvanceOne(
                    npcInstanceId,
                    nowUtc,
                    nowUtc,
                    runtimeStore,
                    threatStore,
                    behaviorRegistry);
            }

            runtimeStore.LastAdvancedUtc = nowUtc;
            return;
        }

        var deltaSeconds = Math.Min(rawDeltaSeconds, maxDeltaSeconds);
        var windowStart = lastAdvanced;
        var windowEnd = windowStart.AddSeconds(deltaSeconds);

        foreach (var npcInstanceId in PrototypeNpcRegistry.GetInstanceIdsInOrder())
        {
            AdvanceOne(
                npcInstanceId,
                windowStart,
                windowEnd,
                runtimeStore,
                threatStore,
                behaviorRegistry);
        }

        runtimeStore.LastAdvancedUtc = nowUtc;
    }

    /// <summary>Resets all prototype NPC runtime rows to idle (dev fixture).</summary>
    public static void ResetAllPrototypeRows(INpcRuntimeStateStore runtimeStore) =>
        runtimeStore.ResetAllPrototypeRows();

    private static void AdvanceOne(
        string npcInstanceId,
        DateTimeOffset windowStart,
        DateTimeOffset windowEnd,
        INpcRuntimeStateStore runtimeStore,
        IThreatStateStore threatStore,
        INpcBehaviorDefinitionRegistry behaviorRegistry)
    {
        if (!PrototypeNpcRegistry.TryGet(npcInstanceId, out var entry) ||
            !behaviorRegistry.TryGetDefinition(entry.BehaviorDefId, out var behavior))
        {
            return;
        }

        if (!runtimeStore.TryGet(npcInstanceId, out var snapshot))
        {
            return;
        }

        if (!TryHasAggroHolder(npcInstanceId, threatStore, out _))
        {
            if (snapshot.BehaviorState != NpcBehaviorState.Idle || snapshot.ActiveTelegraph is not null)
            {
                WriteIdle(runtimeStore, npcInstanceId);
            }

            return;
        }

        if (snapshot.BehaviorState == NpcBehaviorState.Idle)
        {
            WriteState(
                runtimeStore,
                npcInstanceId,
                NpcBehaviorState.Aggro,
                windowStart,
                activeTelegraph: null);
            // telemetry: npc_state_transition (NEO-96)
            if (!runtimeStore.TryGet(npcInstanceId, out snapshot))
            {
                return;
            }
        }

        var cursor = windowStart;
        while (cursor < windowEnd)
        {
            if (!TryHasAggroHolder(npcInstanceId, threatStore, out _))
            {
                WriteIdle(runtimeStore, npcInstanceId);
                return;
            }

            if (!runtimeStore.TryGet(npcInstanceId, out snapshot))
            {
                return;
            }

            switch (snapshot.BehaviorState)
            {
                case NpcBehaviorState.Idle:
                    return;

                case NpcBehaviorState.Aggro:
                {
                    var phaseEnd = snapshot.PhaseStartedUtc.AddSeconds(behavior.AttackCooldownSeconds);
                    if (windowEnd < phaseEnd)
                    {
                        return;
                    }

                    cursor = phaseEnd;
                    var telegraph = CreateTelegraph(npcInstanceId, cursor);
                    WriteState(
                        runtimeStore,
                        npcInstanceId,
                        NpcBehaviorState.TelegraphWindup,
                        cursor,
                        telegraph);
                    // telemetry: npc_state_transition (NEO-96)
                    continue;
                }

                case NpcBehaviorState.TelegraphWindup:
                {
                    var phaseEnd = snapshot.PhaseStartedUtc.AddSeconds(behavior.TelegraphWindupSeconds);
                    if (windowEnd < phaseEnd)
                    {
                        return;
                    }

                    cursor = phaseEnd;
                    WriteState(
                        runtimeStore,
                        npcInstanceId,
                        NpcBehaviorState.Recover,
                        cursor,
                        activeTelegraph: null);
                    // telemetry: telegraph_fired / npc_state_transition (NEO-96); logical attack_execute → recover (NEO-95 applies attackDamage)
                    continue;
                }

                case NpcBehaviorState.AttackExecute:
                    WriteState(
                        runtimeStore,
                        npcInstanceId,
                        NpcBehaviorState.Recover,
                        cursor,
                        activeTelegraph: null);
                    // telemetry: npc_state_transition (NEO-96); NEO-95 applies attackDamage here
                    continue;

                case NpcBehaviorState.Recover:
                {
                    var phaseEnd = snapshot.PhaseStartedUtc.AddSeconds(behavior.AttackCooldownSeconds);
                    if (windowEnd < phaseEnd)
                    {
                        return;
                    }

                    cursor = phaseEnd;
                    var telegraph = CreateTelegraph(npcInstanceId, cursor);
                    WriteState(
                        runtimeStore,
                        npcInstanceId,
                        NpcBehaviorState.TelegraphWindup,
                        cursor,
                        telegraph);
                    // telemetry: npc_state_transition (NEO-96)
                    continue;
                }

                default:
                    return;
            }
        }
    }

    private static bool TryHasAggroHolder(
        string npcInstanceId,
        IThreatStateStore threatStore,
        out string holderPlayerId)
    {
        holderPlayerId = string.Empty;
        if (!threatStore.TryGet(npcInstanceId, out var threat) ||
            string.IsNullOrEmpty(threat.AggroHolderPlayerId))
        {
            return false;
        }

        holderPlayerId = threat.AggroHolderPlayerId;
        return true;
    }

    private static ActiveTelegraphSnapshot CreateTelegraph(string npcInstanceId, DateTimeOffset windupStartedUtc)
    {
        var telegraphId = $"{npcInstanceId}:{windupStartedUtc.UtcTicks}";
        return new ActiveTelegraphSnapshot(telegraphId, windupStartedUtc);
    }

    private static void WriteIdle(INpcRuntimeStateStore runtimeStore, string npcInstanceId) =>
        WriteState(runtimeStore, npcInstanceId, NpcBehaviorState.Idle, DateTimeOffset.MinValue, activeTelegraph: null);

    private static void WriteState(
        INpcRuntimeStateStore runtimeStore,
        string npcInstanceId,
        NpcBehaviorState behaviorState,
        DateTimeOffset phaseStartedUtc,
        ActiveTelegraphSnapshot? activeTelegraph)
    {
        _ = runtimeStore.TryWrite(
            npcInstanceId,
            new NpcRuntimeStateSnapshot(npcInstanceId, behaviorState, phaseStartedUtc, activeTelegraph));
    }
}