using NeonSprawl.Server.Game.Combat;

namespace NeonSprawl.Server.Game.Npc;

/// <summary>
/// Deterministic prototype NPC behavior state machine + lazy tick advance (NEO-93).
/// NEO-96 telemetry hook sites: state transition commits and telegraph starts in <see cref="AdvanceAll"/>
/// (<c>telegraph_fired</c>, <c>npc_state_transition</c>).
/// </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,
        IPlayerCombatHealthStore playerHealthStore,
        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,
                    playerHealthStore);
            }

            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,
                    playerHealthStore);
            }

            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,
                playerHealthStore);
        }

        runtimeStore.LastAdvancedUtc = windowEnd;
    }

    /// <summary>Resets all prototype NPC runtime rows to idle (dev fixture).</summary>
    public static void ResetAllPrototypeRows(INpcRuntimeStateStore runtimeStore)
    {
        // NEO-96: dev fixture reset writes idle directly — bypasses AdvanceOne npc_state_transition hooks.
        // TODO(E9.M1): optional catalog emit anchor here if fixture reset transitions must be tracked.
        runtimeStore.ResetAllPrototypeRows();
    }

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

        if (!HasPositiveTimingDurations(behavior))
        {
            return;
        }

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

        if (!TryHasAggroHolder(npcInstanceId, threatStore, out var aggroHolderPlayerId))
        {
            if (snapshot.BehaviorState != NpcBehaviorState.Idle || snapshot.ActiveTelegraph is not null)
            {
                WriteIdle(runtimeStore, npcInstanceId);
                // --- Telemetry hook site (NEO-96): future E9.M1 catalog event `npc_state_transition` ---
                // TODO(E9.M1): catalog emit — holder cleared during AdvanceAll (any → idle).
                // Planned payload fields: npcInstanceId, behaviorDefId, fromState, toState (idle),
                // phaseStartedUtc, optional aggroHolderPlayerId (previous holder when known).
            }

            return;
        }

        if (snapshot.BehaviorState == NpcBehaviorState.Idle)
        {
            WriteState(
                runtimeStore,
                npcInstanceId,
                NpcBehaviorState.Aggro,
                windowStart,
                activeTelegraph: null);
            // --- Telemetry hook site (NEO-96): future E9.M1 catalog event `npc_state_transition` ---
            // TODO(E9.M1): catalog emit — idle → aggro when aggro holder is set.
            // Planned payload fields: npcInstanceId, behaviorDefId, fromState (idle), toState (aggro),
            // phaseStartedUtc, aggroHolderPlayerId.
            if (!runtimeStore.TryGet(npcInstanceId, out snapshot))
            {
                return;
            }
        }

        var cursor = windowStart;
        while (cursor < windowEnd)
        {
            if (!TryHasAggroHolder(npcInstanceId, threatStore, out aggroHolderPlayerId))
            {
                WriteIdle(runtimeStore, npcInstanceId);
                // --- Telemetry hook site (NEO-96): future E9.M1 catalog event `npc_state_transition` ---
                // TODO(E9.M1): catalog emit — holder cleared mid-cycle during AdvanceAll (any → idle).
                // Planned payload fields: npcInstanceId, behaviorDefId, fromState, toState (idle),
                // phaseStartedUtc, optional aggroHolderPlayerId (previous holder).
                return;
            }

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

            var loopCursorBefore = cursor;
            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 hook site (NEO-96): future E9.M1 catalog event `npc_state_transition` ---
                    // TODO(E9.M1): catalog emit — aggro → telegraph_windup.
                    // Planned payload fields: npcInstanceId, behaviorDefId, fromState (aggro),
                    // toState (telegraph_windup), phaseStartedUtc, aggroHolderPlayerId, telegraphId.
                    // --- Telemetry hook site (NEO-96): future E9.M1 catalog event `telegraph_fired` ---
                    // TODO(E9.M1): catalog emit — once per telegraph start (each windup cycle).
                    // Planned payload fields: npcInstanceId, telegraphId, behaviorDefId, archetypeKind,
                    // aggroHolderPlayerId, windupStartedUtc, telegraphWindupSeconds.
                    break;
                }

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

                    cursor = phaseEnd;
                    NpcAttackOperations.TryResolveTelegraphComplete(
                        npcInstanceId,
                        aggroHolderPlayerId,
                        behavior.AttackDamage,
                        playerHealthStore,
                        threatStore);
                    WriteState(
                        runtimeStore,
                        npcInstanceId,
                        NpcBehaviorState.Recover,
                        cursor,
                        activeTelegraph: null);
                    // --- Telemetry hook site (NEO-96): future E9.M1 catalog event `npc_state_transition` ---
                    // TODO(E9.M1): catalog emit — telegraph_windup → recover (logical attack_execute instant).
                    // Planned payload fields: npcInstanceId, behaviorDefId, fromState (telegraph_windup),
                    // toState (recover), phaseStartedUtc, aggroHolderPlayerId, telegraphId (completed windup).
                    break;
                }

                case NpcBehaviorState.AttackExecute:
                    // Unreachable in normal windup→recover flow (NEO-93); defensive if execute becomes a visible phase.
                    NpcAttackOperations.TryResolveTelegraphComplete(
                        npcInstanceId,
                        aggroHolderPlayerId,
                        behavior.AttackDamage,
                        playerHealthStore,
                        threatStore);
                    WriteState(
                        runtimeStore,
                        npcInstanceId,
                        NpcBehaviorState.Recover,
                        cursor,
                        activeTelegraph: null);
                    // --- Telemetry hook site (NEO-96): future E9.M1 catalog event `npc_state_transition` ---
                    // TODO(E9.M1): catalog emit — attack_execute → recover (defensive visible phase).
                    // Planned payload fields: npcInstanceId, behaviorDefId, fromState (attack_execute),
                    // toState (recover), phaseStartedUtc, aggroHolderPlayerId.
                    break;

                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 hook site (NEO-96): future E9.M1 catalog event `npc_state_transition` ---
                    // TODO(E9.M1): catalog emit — recover → telegraph_windup.
                    // Planned payload fields: npcInstanceId, behaviorDefId, fromState (recover),
                    // toState (telegraph_windup), phaseStartedUtc, aggroHolderPlayerId, telegraphId.
                    // --- Telemetry hook site (NEO-96): future E9.M1 catalog event `telegraph_fired` ---
                    // TODO(E9.M1): catalog emit — once per telegraph start (each windup cycle).
                    // Planned payload fields: npcInstanceId, telegraphId, behaviorDefId, archetypeKind,
                    // aggroHolderPlayerId, windupStartedUtc, telegraphWindupSeconds.
                    break;
                }

                default:
                    return;
            }

            if (cursor <= loopCursorBefore)
            {
                return;
            }
        }
    }

    /// <summary>Catalog timings must be positive; CI/content gate enforces for prototype defs.</summary>
    internal static bool HasPositiveTimingDurations(NpcBehaviorDefRow behavior) =>
        behavior.AttackCooldownSeconds > 0 && behavior.TelegraphWindupSeconds > 0;

    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));
    }
}