using System;
using System.Collections.Concurrent;
using System.Collections.Generic;

namespace AcDream.Core.Items;

/// <summary>
/// Ordered container snapshot entry from retail ContentProfile:
/// guid plus m_uContainerProperties.
/// </summary>
public readonly record struct ContainerContentEntry(uint Guid, uint ContainerType);

/// <summary>One login-time PlayerDescription equipment placement.</summary>
public readonly record struct EquipmentManifestEntry(
    uint Guid,
    EquipMask EquipLocation,
    uint Priority);

/// <summary>
/// Server rejection of an inventory move request. <paramref name="RolledBack"/>
/// is true when the table restored a locally optimistic move; false for
/// server-confirmed transactions which deliberately left the local projection
/// unchanged while waiting.
/// </summary>
public readonly record struct MoveRequestFailure(
    uint ItemId,
    uint WeenieError,
    bool RolledBack);

/// <summary>
/// One side of retail's <c>ServerSaysMoveItem_s</c> placement transition.
/// Container, slot, wielder, and equip location are captured before listeners
/// run so they never have to infer the old state from the already-mutated item.
/// </summary>
public readonly record struct ClientObjectPlacement(
    uint ContainerId,
    int ContainerSlot,
    uint WielderId,
    EquipMask EquipLocation)
{
    public static ClientObjectPlacement From(ClientObject item) => new(
        item.ContainerId,
        item.ContainerSlot,
        item.WielderId,
        item.CurrentlyEquippedLocation);
}

/// <summary>
/// Retail-shaped inventory placement notice. Named retail
/// <c>ACCWeenieObject::ServerSaysMoveItem @ 0x0058DBB0</c> snapshots and
/// publishes both complete placements after applying the new state.
/// </summary>
public readonly record struct ClientObjectMove(
    uint ItemId,
    ClientObject? Item,
    ClientObjectPlacement Previous,
    ClientObjectPlacement Current);

public enum ClientObjectRemovalReason
{
    Ordinary,
    LogicalDelete,
    GenerationReplacement,
}

public readonly record struct ClientObjectRemoval(
    ClientObject Object,
    ClientObjectRemovalReason Reason,
    ushort Generation);

/// <summary>
/// The client's table of every server object (retail <c>weenie_object_table</c> /
/// <c>CObjectMaint</c>). Resolve by guid via <c>Get</c>.
///
/// <para>
/// Retail semantics (r06):
/// <list type="bullet">
///   <item><description>
///     Every object is a <see cref="ClientObject"/> with a unique
///     <c>ObjectId</c>. CreateObject seeds it when the server tells us
///     the item exists (in our inventory, on the ground, in a
///     vendor's list, etc).
///   </description></item>
///   <item><description>
///     Moves happen via <see cref="GameEventType"/>-carrying messages:
///     <c>WieldObject</c>, <c>InventoryPutObjInContainer</c>,
///     <c>InventoryPutObjectIn3D</c>, <c>ViewContents</c>,
///     <c>CloseGroundContainer</c>.
///   </description></item>
///   <item><description>
///     <c>InventoryServerSaveFailed</c> reverts a speculative local
///     state change (e.g. when a drag-drop was rejected server-side).
///   </description></item>
/// </list>
/// </para>
///
/// <para>
/// Thread safety: designed for single-threaded use from the render
/// thread; the event delegates run synchronously on the caller's
/// thread. A <see cref="ConcurrentDictionary{TKey,TValue}"/> backs the
/// map so plugin code can look up items from any thread without
/// corrupting state.
/// </para>
/// </summary>
public sealed class ClientObjectTable
{
    private readonly ConcurrentDictionary<uint, ClientObject> _objects = new();
    private readonly ConcurrentDictionary<uint, Container> _containers = new();
    private readonly Dictionary<uint, List<uint>> _containerIndex = new();
    private readonly Dictionary<uint, List<uint>> _equipmentIndex = new();

    // B-Drag: pre-move snapshots for optimistic inventory moves. itemId → (container, slot, equip) BEFORE
    // the optimistic MoveItem; restored by RollbackMove on InventoryServerSaveFailed (0x00A0),
    // cleared by ConfirmMove on the InventoryPutObjInContainer (0x0022) echo.
    private readonly Dictionary<uint, (ClientObjectPlacement placement, int outstanding)> _pendingMoves = new();

    /// <summary>Fires when an object is first added to the session.</summary>
    public event Action<ClientObject>? ObjectAdded;

    /// <summary>
    /// Fires after a complete placement notice (moved between packs,
    /// equipped, unequipped, dropped on ground). <see cref="ClientObjectMove.Item"/>
    /// is null when retail publishes the notice before CreateObject resolves
    /// the GUID; the old/new placement remains authoritative notice data.
    /// </summary>
    public event Action<ClientObjectMove>? ObjectMoved;

    /// <summary>
    /// Fires after retail ViewContents replaces a container's ordered member
    /// lists. This is a list-projection change, not an item ownership move.
    /// </summary>
    public event Action<uint>? ContainerContentsReplaced;

    /// <summary>
    /// Fires after an optimistic inventory/equipment move is rejected and
    /// <see cref="RollbackMove"/> has restored the exact pre-move state.
    /// Consumers with projections outside the item grid (for example a
    /// parented 3-D weapon) can restore their prior projection without
    /// treating every ordinary equip as a rollback.
    /// </summary>
    public event Action<ClientObject>? MoveRolledBack;

    /// <summary>
    /// Fires for an authoritative WieldObject response after its object state
    /// has been applied. This is deliberately independent of optimistic-move
    /// rollback bookkeeping: retail clears IR_WIELD on the matching server
    /// response even when separate reconciliation state exists for the item.
    /// </summary>
    public event Action<uint>? WieldConfirmed;

    /// <summary>
    /// Fires for every InventoryServerSaveFailed response, including requests
    /// which did not mutate the table optimistically. Transaction coordinators
    /// use this to abandon server-confirmed multi-step moves without timers.
    /// </summary>
    public event Action<MoveRequestFailure>? MoveRequestFailed;

    /// <summary>Fires when an object is removed from the session.</summary>
    public event Action<ClientObject>? ObjectRemoved;

    /// <summary>
    /// Generation-aware removal stream for runtime owners. UI consumers keep
    /// using <see cref="ObjectRemoved"/>; runtime owners use the reason and
    /// generation to preserve only packets addressed to future incarnations.
    /// </summary>
    public event Action<ClientObjectRemoval>? ObjectRemovalClassified;

    /// <summary>Fires when an object's properties are updated (typically after Appraise).</summary>
    public event Action<ClientObject>? ObjectUpdated;

    /// <summary>Fires after all session object and pending-move state is flushed.</summary>
    public event Action? Cleared;

    /// <summary>PropertyInt.UiEffects (ACE enum value 18) — the icon effect bitfield;
    /// the typed mirror <see cref="UpdateIntProperty"/> maintains on
    /// <see cref="ClientObject.Effects"/>.</summary>
    public const uint UiEffectsPropertyId = 18u;
    public const uint CurrentWieldedLocationPropertyId = 10u;

    public int ObjectCount => _objects.Count;
    public int ContainerCount => _containers.Count;

    public IEnumerable<ClientObject> Objects => _objects.Values;
    public IEnumerable<Container> Containers => _containers.Values;

    /// <summary>
    /// Look up an object by its server-assigned <c>ObjectId</c>.
    /// </summary>
    public ClientObject? Get(uint objectId) =>
        _objects.TryGetValue(objectId, out var item) ? item : null;

    /// <summary>
    /// Look up a container by object id, creating a lightweight stub if
    /// the id doesn't match any known container (defensive — avoids losing
    /// references when the server announces a move into a container it
    /// hasn't described yet).
    /// </summary>
    public Container? GetContainer(uint objectId) =>
        _containers.TryGetValue(objectId, out var c) ? c : null;

    /// <summary>
    /// Register / refresh an object in the table. Called on
    /// CreateObject for item-typed weenies and on IdentifyObjectResponse
    /// to fill in detail properties.
    /// Does NOT update the container index — use Ingest for container-tracked objects.
    /// </summary>
    public void AddOrUpdate(ClientObject item)
    {
        ArgumentNullException.ThrowIfNull(item);
        bool existed = _objects.TryGetValue(item.ObjectId, out ClientObject? prior);
        ClientObjectPlacement previous = prior is null
            ? default
            : ClientObjectPlacement.From(prior);
        _objects[item.ObjectId] = item;
        UpdateEquipmentIndex(item.ObjectId, previous, ClientObjectPlacement.From(item));
        if (!existed) ObjectAdded?.Invoke(item);
        else ObjectUpdated?.Invoke(item);
    }

    /// <summary>
    /// Register a container. Idempotent.
    /// </summary>
    public void AddContainer(Container container)
    {
        ArgumentNullException.ThrowIfNull(container);
        _containers[container.ObjectId] = container;
    }

    /// <summary>
    /// Move the local projection of an item without changing authoritative
    /// WielderId. Optimistic inventory requests use this path because retail
    /// UIAttemptWield sends the request without rewriting public weenie fields.
    /// </summary>
    public bool MoveItem(uint itemId, uint newContainerId, int newSlot = -1,
        EquipMask newEquipLocation = EquipMask.None, uint? containerTypeHint = null)
    {
        if (!_objects.TryGetValue(itemId, out var item)) return false;
        return ApplyPlacement(
            item,
            new ClientObjectPlacement(
                newContainerId,
                newSlot,
                item.WielderId,
                newEquipLocation),
            containerTypeHint);
    }

    /// <summary>
    /// Apply an authoritative server move, including the item's wielder
    /// ownership. Retail <c>ACCWeenieObject::ServerSaysMoveItem @
    /// 0x0058DBB0</c> updates <c>_containerID</c>, <c>_wielderID</c>, and
    /// <c>_location</c> in one callback. Keeping the old wielder after an
    /// unwield makes <c>DetermineUseResult @ 0x00588460</c> classify a bow in
    /// the backpack as already wielded, so a later double click sends no
    /// request.
    /// </summary>
    public bool ApplyServerMove(
        uint itemId,
        uint newContainerId,
        uint newWielderId,
        int newSlot = -1,
        EquipMask newEquipLocation = EquipMask.None,
        uint? containerTypeHint = null)
    {
        if (!_objects.TryGetValue(itemId, out var item)) return false;
        return ApplyPlacement(
            item,
            new ClientObjectPlacement(
                newContainerId,
                newSlot,
                newWielderId,
                newEquipLocation),
            containerTypeHint);
    }

    private bool ApplyPlacement(
        ClientObject item,
        ClientObjectPlacement current,
        uint? containerTypeHint = null)
    {
        ClientObjectPlacement previous = ClientObjectPlacement.From(item);
        List<uint>? changedContainers = RemoveFromOtherContainerIndexes(
            item.ObjectId,
            current.ContainerId);
        item.ContainerId = current.ContainerId;
        item.ContainerSlot = current.ContainerSlot;
        item.WielderId = current.WielderId;
        item.CurrentlyEquippedLocation = current.EquipLocation;
        if (containerTypeHint is { } hint)
            item.ContainerTypeHint = hint;
        Reindex(item, previous.ContainerId);
        PublishPlacementChange(item, previous);
        PublishContainerContentsChanges(changedContainers);
        return true;
    }

    private void PublishPlacementChange(
        ClientObject item,
        ClientObjectPlacement previous)
    {
        ClientObjectPlacement current = ClientObjectPlacement.From(item);
        UpdateEquipmentIndex(item.ObjectId, previous, current);
        ObjectMoved?.Invoke(new ClientObjectMove(item.ObjectId, item, previous, current));
    }

    /// <summary>
    /// Applies a server-confirmed container/world move. The matching pending
    /// request is reconciled before <see cref="ObjectMoved"/> is published,
    /// matching retail <c>ServerSaysMoveItem</c>: a reentrant listener may start
    /// a new request without the old confirmation consuming it afterward.
    /// </summary>
    public bool ApplyConfirmedServerMove(
        uint itemId,
        uint newContainerId,
        uint newWielderId,
        int newSlot = -1,
        EquipMask newEquipLocation = EquipMask.None,
        uint? containerTypeHint = null)
    {
        ConfirmMove(itemId);
        if (ApplyServerMove(
            itemId,
            newContainerId,
            newWielderId,
            newSlot,
            newEquipLocation,
            containerTypeHint))
        {
            return true;
        }

        ObjectMoved?.Invoke(new ClientObjectMove(
            itemId,
            Item: null,
            Previous: default,
            Current: new ClientObjectPlacement(
                newContainerId,
                newSlot,
                newWielderId,
                newEquipLocation)));
        return false;
    }

    /// <summary>
    /// Applies retail WieldObject (0x0023). The packet has only item and
    /// location; the local player is the wielder, while ContainerId is zero.
    /// Pending reconciliation precedes notifications as in
    /// <c>ACCWeenieObject::ServerSaysMoveItem @ 0x0058DBB0</c>.
    /// </summary>
    public bool ApplyConfirmedServerWield(
        uint itemId,
        uint wielderId,
        EquipMask equipLocation)
    {
        ConfirmMove(itemId);
        var placement = new ClientObjectPlacement(
            ContainerId: 0u,
            ContainerSlot: 0,
            WielderId: wielderId,
            EquipLocation: equipLocation);
        if (!_objects.TryGetValue(itemId, out ClientObject? item))
        {
            ObjectMoved?.Invoke(new ClientObjectMove(
                itemId,
                Item: null,
                Previous: default,
                Current: placement));
            WieldConfirmed?.Invoke(itemId);
            return false;
        }

        if (!ApplyPlacement(
                item,
                placement))
        {
            return false;
        }

        WieldConfirmed?.Invoke(itemId);
        return true;
    }

    /// <summary>Snapshot the item's pre-move (container, slot, equip) the FIRST time it moves, and
    /// bump the OUTSTANDING count on subsequent in-flight moves of the same item (so an early confirm
    /// can't clear a still-pending later move — the I1 hardening). Shared by MoveItemOptimistic (unwield/
    /// move) and WieldItemOptimistic (wield).</summary>
    private void RecordPending(uint itemId, ClientObject item)
    {
        if (_pendingMoves.TryGetValue(itemId, out var p))
            _pendingMoves[itemId] = (p.placement, p.outstanding + 1);
        else
            _pendingMoves[itemId] = (ClientObjectPlacement.From(item), 1);
    }

    /// <summary>
    /// Optimistic (instant) move: snapshot the item's current (ContainerId, ContainerSlot) the FIRST
    /// time it moves, then <see cref="MoveItem"/> (immediate repaint via ObjectMoved). The wire
    /// PutItemInContainer is sent by the caller; <see cref="ConfirmMove"/>/<see cref="RollbackMove"/>
    /// reconcile against the server. Retail: local ItemList_InsertItem + ServerSaysMoveItem reconcile.
    /// </summary>
    public bool MoveItemOptimistic(uint itemId, uint newContainerId, int newSlot)
    {
        if (!_objects.TryGetValue(itemId, out var item)) return false;
        // Snapshot the ORIGINAL position once + count OUTSTANDING optimistic moves of this item. The
        // count stops an early confirm (0x0022) for the first of several in-flight moves of the SAME
        // item from clearing the snapshot while a later move is still unconfirmed — else a later
        // reject would find nothing pending and strand the item at the rejected position.
        RecordPending(itemId, item);

        // Gapless INSERT — treat newSlot as the insert INDEX, shift the other items, and renumber both
        // containers' slots 0..N-1. A raw MoveItem sets ONLY this item's slot, which then collides with
        // the item already at that slot; the sort-by-slot tie reshuffles the whole grid on every repaint
        // (the "items change position when I move one" bug). Retail's ItemList_InsertItem shifts the list.
        ClientObjectPlacement previous = ClientObjectPlacement.From(item);
        uint oldContainer = previous.ContainerId;
        item.ContainerId = newContainerId;
        item.CurrentlyEquippedLocation = EquipMask.None;
        List<uint>? changedContainers = RemoveFromOtherContainerIndexes(
            itemId,
            newContainerId);

        if (oldContainer != 0 && oldContainer != newContainerId
            && _containerIndex.TryGetValue(oldContainer, out var srcList))
        { srcList.Remove(itemId); RenumberContainer(srcList); }      // keep the source gapless too

        if (newContainerId != 0)
        {
            if (!_containerIndex.TryGetValue(newContainerId, out var dstList))
                _containerIndex[newContainerId] = dstList = new List<uint>();
            dstList.Remove(itemId);                                  // same-container move: pull out first
            int idx = (newSlot < 0 || newSlot > dstList.Count) ? dstList.Count : newSlot;
            dstList.Insert(idx, itemId);
            RenumberContainer(dstList);                              // sequential ContainerSlots → no ties
        }
        else item.ContainerSlot = newSlot;

        PublishPlacementChange(item, previous);
        PublishContainerContentsChanges(changedContainers);
        return true;
    }

    /// <summary>Optimistic (instant) wield: snapshot the pre-wield (container, slot, equip), then set
    /// ContainerId = wielderGuid and CurrentlyEquippedLocation = equipMask. WielderId remains unchanged
    /// until <see cref="ApplyConfirmedServerWield"/> receives the authoritative WieldObject, matching retail's
    /// UIAttemptWield request/confirmation split. The confirmation converts this temporary projection to
    /// ContainerId zero + authoritative WielderId. <see cref="RollbackMove"/> restores the local projection. Fires
    /// ObjectMoved for an immediate repaint. The caller sends GetAndWieldItem; ConfirmMove (on the 0x0023
    /// echo) / RollbackMove (on 0x00A0) reconcile.</summary>
    public bool WieldItemOptimistic(uint itemId, uint wielderGuid, EquipMask equipMask)
    {
        if (!_objects.TryGetValue(itemId, out var item)) return false;
        RecordPending(itemId, item);
        return MoveItem(itemId, wielderGuid, newSlot: -1, newEquipLocation: equipMask);
    }

    /// <summary>Assign each item in <paramref name="list"/> a sequential ContainerSlot (0..N-1) matching
    /// its list position — keeps a container gapless + collision-free so the grid order is stable.</summary>
    private void RenumberContainer(List<uint> list)
    {
        for (int i = 0; i < list.Count; i++)
            if (_objects.TryGetValue(list[i], out var o)) o.ContainerSlot = i;
    }

    /// <summary>The server confirmed a move (InventoryPutObjInContainer 0x0022 echo) — decrement the
    /// outstanding count; drop the snapshot only once no optimistic moves of this item remain. No-op
    /// for a server-initiated move we never tracked.</summary>
    public void ConfirmMove(uint itemId)
    {
        if (!_pendingMoves.TryGetValue(itemId, out var p)) return;
        if (p.outstanding <= 1)
        {
            _pendingMoves.Remove(itemId);
        }
        else
        {
            _pendingMoves[itemId] = (p.placement, p.outstanding - 1);
        }
    }

    /// <summary>The server rejected a move (InventoryServerSaveFailed 0x00A0) — restore the item to its
    /// pre-move (container, slot) and drop the snapshot entirely (the server's next snapshot reconciles
    /// any still-outstanding moves). False if nothing was pending.</summary>
    public bool RollbackMove(uint itemId)
    {
        if (!_pendingMoves.TryGetValue(itemId, out var pre)) return false;
        _pendingMoves.Remove(itemId);
        ClientObjectPlacement placement = pre.placement;
        if (!ApplyServerMove(
                itemId,
                placement.ContainerId,
                placement.WielderId,
                placement.ContainerSlot,
                placement.EquipLocation))
            return false;
        MoveRolledBack?.Invoke(_objects[itemId]);
        return true;
    }

    /// <summary>
    /// Reconcile an InventoryServerSaveFailed response and publish the failure
    /// even when no optimistic snapshot exists. Retail's blocked AutoWield path
    /// waits for the server before changing its local item lists, so failure is
    /// still a meaningful transaction event in that case.
    /// </summary>
    public bool RejectMove(uint itemId, uint weenieError)
    {
        bool rolledBack = RollbackMove(itemId);
        MoveRequestFailed?.Invoke(new MoveRequestFailure(itemId, weenieError, rolledBack));
        return rolledBack;
    }

    /// <summary>
    /// Handle a server-driven remove (destroyed item, dropped into 3D
    /// space, stolen, etc).
    /// </summary>
    public bool Remove(uint itemId)
        => RemoveCore(itemId, ClientObjectRemovalReason.Ordinary, 0, notifyObjectRemoved: true);

    /// <summary>Removes an exact accepted server object incarnation.</summary>
    public bool RemoveLogicalGeneration(uint itemId, ushort generation)
        => RemoveCore(
            itemId,
            ClientObjectRemovalReason.LogicalDelete,
            generation,
            notifyObjectRemoved: true);

    private bool RemoveCore(
        uint itemId,
        ClientObjectRemovalReason reason,
        ushort generation,
        bool notifyObjectRemoved)
    {
        if (!_objects.TryRemove(itemId, out var item)) return false;
        List<uint>? changedContainers = RemoveFromOtherContainerIndexes(
            itemId,
            exceptContainerId: 0u);
        UpdateEquipmentIndex(
            itemId,
            ClientObjectPlacement.From(item),
            default);
        _pendingMoves.Remove(itemId);   // a destroyed item must not leave a snapshot that mis-rolls-back a recycled guid
        if (notifyObjectRemoved)
            ObjectRemoved?.Invoke(item);
        ObjectRemovalClassified?.Invoke(new ClientObjectRemoval(item, reason, generation));
        PublishContainerContentsChanges(changedContainers);
        return true;
    }

    /// <summary>
    /// Atomically replaces the retained qualities for a newer server object
    /// incarnation while publishing a generation-specific teardown event.
    /// </summary>
    public ClientObject ReplaceGeneration(WeenieData data, ushort generation)
    {
        RemoveCore(
            data.Guid,
            ClientObjectRemovalReason.GenerationReplacement,
            generation,
            notifyObjectRemoved: true);

        return Ingest(data);
    }

    /// <summary>
    /// Apply a <see cref="PropertyBundle"/> patch (e.g. from an
    /// <c>IdentifyObjectResponse</c>) to an existing object. Individual
    /// keys in the incoming bundle overwrite existing values; keys not
    /// present are left untouched.
    /// </summary>
    public bool UpdateProperties(uint itemId, PropertyBundle incoming)
    {
        if (!_objects.TryGetValue(itemId, out var item)) return false;
        foreach (var kv in incoming.Ints)     item.Properties.Ints[kv.Key] = kv.Value;
        foreach (var kv in incoming.Int64s)   item.Properties.Int64s[kv.Key] = kv.Value;
        foreach (var kv in incoming.Bools)    item.Properties.Bools[kv.Key] = kv.Value;
        foreach (var kv in incoming.Floats)   item.Properties.Floats[kv.Key] = kv.Value;
        foreach (var kv in incoming.Strings)  item.Properties.Strings[kv.Key] = kv.Value;
        foreach (var kv in incoming.DataIds)  item.Properties.DataIds[kv.Key] = kv.Value;
        foreach (var kv in incoming.InstanceIds) item.Properties.InstanceIds[kv.Key] = kv.Value;
        ObjectUpdated?.Invoke(item);
        return true;
    }

    /// <summary>
    /// Apply a <see cref="PropertyBundle"/> patch, creating the object if it does not
    /// exist yet. Used for the local player's own properties from PlayerDescription
    /// (0x0013), which may arrive BEFORE the player's CreateObject — unlike
    /// <see cref="UpdateProperties"/>, which no-ops on an unknown object. Fires
    /// ObjectAdded on create, else ObjectUpdated.
    /// </summary>
    public void UpsertProperties(uint guid, PropertyBundle incoming)
    {
        ArgumentNullException.ThrowIfNull(incoming);
        bool existed = _objects.TryGetValue(guid, out var item);
        if (!existed || item is null)
        {
            item = new ClientObject { ObjectId = guid };
            _objects[guid] = item;
        }
        foreach (var kv in incoming.Ints)        item.Properties.Ints[kv.Key] = kv.Value;
        foreach (var kv in incoming.Int64s)      item.Properties.Int64s[kv.Key] = kv.Value;
        foreach (var kv in incoming.Bools)       item.Properties.Bools[kv.Key] = kv.Value;
        foreach (var kv in incoming.Floats)      item.Properties.Floats[kv.Key] = kv.Value;
        foreach (var kv in incoming.Strings)     item.Properties.Strings[kv.Key] = kv.Value;
        foreach (var kv in incoming.DataIds)     item.Properties.DataIds[kv.Key] = kv.Value;
        foreach (var kv in incoming.InstanceIds) item.Properties.InstanceIds[kv.Key] = kv.Value;
        if (!existed) ObjectAdded?.Invoke(item); else ObjectUpdated?.Invoke(item);
    }

    /// <summary>
    /// Apply a single PropertyInt update (from PublicUpdatePropertyInt 0x02CE) to an
    /// object: store it in the bundle and, for known typed ints, mirror to the typed
    /// field. Today: UiEffects (18) → <see cref="ClientObject.Effects"/>. Fires
    /// ObjectUpdated so bound widgets re-composite. Extensible hook for future
    /// typed PropertyInts (StackSize, Structure, …). False if the object is unknown.
    /// </summary>
    public bool UpdateIntProperty(uint itemId, uint propertyId, int value)
    {
        if (!_objects.TryGetValue(itemId, out var item)) return false;
        ClientObjectPlacement previous = ClientObjectPlacement.From(item);
        item.Properties.Ints[propertyId] = value;
        if (propertyId == UiEffectsPropertyId) item.Effects = (uint)value;
        if (propertyId == CurrentWieldedLocationPropertyId)
            item.CurrentlyEquippedLocation = (EquipMask)(uint)value;
        if (propertyId == CurrentWieldedLocationPropertyId)
            UpdateEquipmentIndex(itemId, previous, ClientObjectPlacement.From(item));
        ObjectUpdated?.Invoke(item);
        return true;
    }

    /// <summary>
    /// Apply a single PropertyInt64 update to an object's bundle and fire
    /// ObjectUpdated so bound widgets refresh. Int64 counterpart of
    /// <see cref="UpdateIntProperty"/> (used by the character sheet's
    /// optimistic unassigned-XP debit; also the hook for future
    /// PrivateUpdatePropertyInt64 parsing). False if the object is unknown.
    /// </summary>
    public bool UpdateInt64Property(uint itemId, uint propertyId, long value)
    {
        if (!_objects.TryGetValue(itemId, out var item)) return false;
        item.Properties.Int64s[propertyId] = value;
        ObjectUpdated?.Invoke(item);
        return true;
    }

    /// <summary>
    /// Apply a SetStackSize (0x0197) update: set the object's StackSize + Value and
    /// fire ObjectUpdated so bound widgets refresh the quantity overlay. False if the
    /// object is unknown. Retail: ACCWeenieObject::ServerSaysSetStackSize (0x0058...).
    /// </summary>
    public bool UpdateStackSize(uint guid, int stackSize, int value)
    {
        if (!_objects.TryGetValue(guid, out var item)) return false;
        item.StackSize = stackSize;
        item.Value = value;
        ObjectUpdated?.Invoke(item);
        return true;
    }

    /// <summary>
    /// Canonical CreateObject ingestion: create-if-absent, else patch the
    /// wire-carried fields in place (retail SetWeenieDesc). Preserves the
    /// PropertyBundle (appraise) and any field the wire didn't carry.
    /// Effects is assigned unconditionally (0 clears) — the D.5.2 icon contract.
    /// </summary>
    public ClientObject Ingest(WeenieData d)
    {
        bool existed = _objects.TryGetValue(d.Guid, out var obj);
        if (!existed || obj is null) // keep: satisfies nullable flow analysis
        {
            obj = new ClientObject { ObjectId = d.Guid };
            _objects[d.Guid] = obj;
        }
        uint oldContainer = obj.ContainerId;
        ClientObjectPlacement previous = ClientObjectPlacement.From(obj);

        if (!string.IsNullOrEmpty(d.Name)) obj.Name = d.Name!;
        if (!string.IsNullOrEmpty(d.PluralName)) obj.PluralName = d.PluralName!;
        if (d.Type is { } t) obj.Type = t;
        // WeenieClassId arrives on every CreateObject (fixed prefix) and is never
        // legitimately 0 for a real weenie; the != 0 guard avoids clobbering a known
        // class id with a spurious 0 (and leaves a PD stub's 0 until CreateObject fills it).
        if (d.WeenieClassId != 0) obj.WeenieClassId = d.WeenieClassId;
        if (d.IconId != 0) obj.IconId = d.IconId;
        if (d.IconOverlayId != 0) obj.IconOverlayId = d.IconOverlayId;
        if (d.IconUnderlayId != 0) obj.IconUnderlayId = d.IconUnderlayId;
        obj.Effects = d.Effects;                                   // D.5.2 contract
        if (d.Value is { } v) obj.Value = v;
        if (d.StackSize is { } s) obj.StackSize = s;
        if (d.StackSizeMax is { } sm) obj.StackSizeMax = sm;
        if (d.Burden is { } b) obj.Burden = b;
        if (d.ContainerId is { } c) obj.ContainerId = c;
        if (d.WielderId is { } w) obj.WielderId = w;
        if (d.ValidLocations is { } vl) obj.ValidLocations = (EquipMask)vl;
        if (d.CurrentWieldedLocation is { } cwl) obj.CurrentlyEquippedLocation = (EquipMask)cwl;
        if (d.Priority is { } pr) obj.Priority = pr;
        if (d.Useability is { } use) obj.Useability = use;
        if (d.TargetType is { } targetType) obj.TargetType = targetType;
        if (d.PublicWeenieBitfield is { } bitfield) obj.PublicWeenieBitfield = bitfield;
        if (d.PetOwnerId is { } petOwnerId) obj.PetOwnerId = petOwnerId;
        if (d.CombatUse is { } combatUse) obj.CombatUse = combatUse;
        if (d.AmmoType is { } ammoType) obj.AmmoType = ammoType;
        if (d.SpellId is { } spellId) obj.SpellId = spellId;
        if (d.RadarBlipColor is { } radarBlipColor) obj.RadarBlipColor = radarBlipColor;
        if (d.RadarBehavior is { } radarBehavior) obj.RadarBehavior = radarBehavior;
        if (d.ItemsCapacity is { } ic) obj.ItemsCapacity = ic;
        if (d.ContainersCapacity is { } cc) obj.ContainersCapacity = cc;
        if (d.Structure is { } st) obj.Structure = st;
        if (d.MaxStructure is { } ms) obj.MaxStructure = ms;
        if (d.Workmanship is { } wm) obj.Workmanship = wm;

        List<uint>? changedContainers = RemoveFromOtherContainerIndexes(
            obj.ObjectId,
            obj.ContainerId);
        Reindex(obj, oldContainer);
        UpdateEquipmentIndex(obj.ObjectId, previous, ClientObjectPlacement.From(obj));
        if (!existed) ObjectAdded?.Invoke(obj); else ObjectUpdated?.Invoke(obj);
        PublishContainerContentsChanges(changedContainers);
        return obj;
    }

    /// <summary>
    /// PlayerDescription manifest: record that this guid is the player's
    /// (in inventory or equipped at <paramref name="equip"/>), creating an
    /// empty entry if CreateObject hasn't arrived yet. PlayerDescription may
    /// use the player as <paramref name="containerId"/> for its login-time
    /// placement projection; live WieldObject confirmation later establishes
    /// canonical ContainerId zero plus WielderId player.
    /// Never touches icon/name/type/effects — that data comes from CreateObject.
    /// </summary>
    public ClientObject RecordMembership(uint guid, uint containerId = 0,
        EquipMask equip = EquipMask.None, uint? containerTypeHint = null,
        uint? priority = null)
    {
        bool existed = _objects.TryGetValue(guid, out var obj);
        if (!existed || obj is null) // keep: satisfies nullable flow analysis
        {
            obj = new ClientObject { ObjectId = guid };
            _objects[guid] = obj;
        }
        uint oldContainer = obj.ContainerId;
        ClientObjectPlacement previous = ClientObjectPlacement.From(obj);
        if (containerId != 0)
            obj.ContainerId = containerId;
        obj.CurrentlyEquippedLocation = equip;
        if (equip != EquipMask.None)
            obj.ContainerSlot = -1;
        if (containerTypeHint is { } hint) obj.ContainerTypeHint = hint;
        if (priority is { } p) obj.Priority = p;
        List<uint>? changedContainers = RemoveFromOtherContainerIndexes(
            obj.ObjectId,
            obj.ContainerId);
        Reindex(obj, oldContainer);
        UpdateEquipmentIndex(obj.ObjectId, previous, ClientObjectPlacement.From(obj));
        if (!existed) ObjectAdded?.Invoke(obj); else ObjectUpdated?.Invoke(obj);
        PublishContainerContentsChanges(changedContainers);
        return obj;
    }

    /// <summary>
    /// Initialize PlayerDescription equipment in canonical retail form while
    /// preserving the packed InventoryPlacement list order exactly. Retail
    /// <c>UpdateObjectInventory @ 0x00559550</c> assigns the complete list; it
    /// does not replay live head-insertion for each login entry.
    /// </summary>
    public void InitializeEquipmentManifest(
        uint wielderId,
        IReadOnlyList<EquipmentManifestEntry> entries)
    {
        ArgumentNullException.ThrowIfNull(entries);
        if (wielderId == 0u) return;

        var ordered = new List<uint>(entries.Count);
        var notifications = new List<(ClientObject Item, bool Existed)>(entries.Count);
        var changedContainers = new List<uint>();
        var incoming = new HashSet<uint>();
        for (int i = 0; i < entries.Count; i++)
            incoming.Add(entries[i].Guid);

        // UpdateObjectInventory assigns a complete authoritative list. Clear
        // canonical placement on members omitted by a replay/replacement
        // manifest before installing the new order; replacing only the index
        // leaves ghost equipment visible to AutoWield and burden queries.
        if (_equipmentIndex.TryGetValue(wielderId, out List<uint>? priorEquipment))
        {
            foreach (uint priorId in priorEquipment.ToArray())
            {
                if (incoming.Contains(priorId)
                    || !_objects.TryGetValue(priorId, out ClientObject? prior)
                    || prior is null
                    || (prior.WielderId != wielderId
                        && !(prior.ContainerId == wielderId
                             && prior.CurrentlyEquippedLocation != EquipMask.None)))
                    continue;

                prior.ContainerId = 0u;
                prior.ContainerSlot = -1;
                prior.WielderId = 0u;
                prior.CurrentlyEquippedLocation = EquipMask.None;
                prior.Priority = 0u;
                if (RemoveFromOtherContainerIndexes(priorId, exceptContainerId: 0u)
                    is { } removedFrom)
                {
                    changedContainers.AddRange(removedFrom);
                }
                notifications.Add((prior, true));
            }
        }

        for (int i = 0; i < entries.Count; i++)
        {
            EquipmentManifestEntry entry = entries[i];
            ordered.Add(entry.Guid);
            bool existed = _objects.TryGetValue(entry.Guid, out ClientObject? obj);
            if (!existed || obj is null)
            {
                obj = new ClientObject { ObjectId = entry.Guid };
                _objects[entry.Guid] = obj;
            }

            ClientObjectPlacement previous = ClientObjectPlacement.From(obj);
            obj.ContainerId = 0u;
            obj.ContainerSlot = -1;
            obj.WielderId = wielderId;
            obj.CurrentlyEquippedLocation = entry.EquipLocation;
            obj.Priority = entry.Priority;
            if (RemoveFromOtherContainerIndexes(entry.Guid, exceptContainerId: 0u)
                is { } changed)
            {
                changedContainers.AddRange(changed);
            }
            Reindex(obj, previous.ContainerId);
            RemoveEquipmentIndexMembership(entry.Guid);
            notifications.Add((obj, existed));
        }

        _equipmentIndex[wielderId] = ordered;
        foreach ((ClientObject item, bool existed) in notifications)
        {
            if (!existed) ObjectAdded?.Invoke(item);
            else ObjectUpdated?.Invoke(item);
        }
        PublishContainerContentsChanges(changedContainers);
    }

    private List<uint>? RemoveFromOtherContainerIndexes(
        uint itemId,
        uint exceptContainerId)
    {
        List<uint>? changed = null;
        foreach ((uint containerId, List<uint> members) in _containerIndex)
        {
            if (containerId == exceptContainerId || !members.Remove(itemId))
                continue;
            (changed ??= new List<uint>()).Add(containerId);
        }

        return changed;
    }

    private void PublishContainerContentsChanges(List<uint>? changed)
    {
        if (changed is null || changed.Count == 0)
            return;
        var published = new HashSet<uint>();
        foreach (uint containerId in changed)
        {
            if (!published.Add(containerId))
                continue;
            ContainerContentsReplaced?.Invoke(containerId);
        }
    }

    private void Reindex(ClientObject obj, uint oldContainerId)
    {
        if (oldContainerId != obj.ContainerId && oldContainerId != 0
            && _containerIndex.TryGetValue(oldContainerId, out var oldList))
            oldList.Remove(obj.ObjectId);

        if (obj.ContainerId != 0)
        {
            if (!_containerIndex.TryGetValue(obj.ContainerId, out var list))
                _containerIndex[obj.ContainerId] = list = new List<uint>();
            if (!list.Contains(obj.ObjectId)) list.Add(obj.ObjectId);
            var priorOrder = new Dictionary<uint, int>(list.Count);
            for (int i = 0; i < list.Count; i++)
                priorOrder[list[i]] = i;
            list.Sort((a, b) =>
            {
                int c = SlotOf(a).CompareTo(SlotOf(b));
                return c != 0 ? c : priorOrder[a].CompareTo(priorOrder[b]);
            });
        }
    }

    private static uint EquipmentOwner(ClientObjectPlacement placement)
    {
        if (placement.EquipLocation == EquipMask.None)
            return 0u;
        return placement.WielderId != 0u
            ? placement.WielderId
            : placement.ContainerId;
    }

    private void RemoveEquipmentIndexMembership(uint itemId)
    {
        List<uint>? emptyOwners = null;
        foreach ((uint ownerId, List<uint> placements) in _equipmentIndex)
        {
            placements.Remove(itemId);
            if (placements.Count == 0)
                (emptyOwners ??= new List<uint>()).Add(ownerId);
        }

        if (emptyOwners is null)
            return;
        foreach (uint ownerId in emptyOwners)
            _equipmentIndex.Remove(ownerId);
    }

    /// <summary>
    /// Maintain retail's <c>_invPlacement</c> order. Named retail
    /// <c>SetPlayerWieldLocation @ 0x0058D8C0</c> inserts a placement at the
    /// head; <c>GetObjectAtLocation @ 0x0058CE00</c> scans head-to-tail.
    /// </summary>
    private void UpdateEquipmentIndex(
        uint itemId,
        ClientObjectPlacement previous,
        ClientObjectPlacement current)
    {
        if (previous == current)
            return;

        uint previousOwner = EquipmentOwner(previous);
        if (previousOwner != 0u
            && _equipmentIndex.TryGetValue(previousOwner, out List<uint>? oldList))
        {
            oldList.Remove(itemId);
            if (oldList.Count == 0)
                _equipmentIndex.Remove(previousOwner);
        }

        uint currentOwner = EquipmentOwner(current);
        if (currentOwner == 0u)
            return;
        if (!_equipmentIndex.TryGetValue(currentOwner, out List<uint>? currentList))
            _equipmentIndex[currentOwner] = currentList = new List<uint>();
        currentList.Remove(itemId);
        currentList.Insert(0, itemId);
    }

    private int SlotOf(uint guid) =>
        _objects.TryGetValue(guid, out var o) && o.ContainerSlot >= 0
            ? o.ContainerSlot
            : int.MaxValue;

    /// <summary>
    /// Ordered item guids in a container (retail object_inventory_table), by ContainerSlot.
    /// Returns a SNAPSHOT (safe to hold / read off-thread); empty for an unknown container.
    /// </summary>
    public IReadOnlyList<uint> GetContents(uint containerId) =>
        _containerIndex.TryGetValue(containerId, out var l)
            ? l.ToArray() : System.Array.Empty<uint>();

    /// <summary>
    /// Snapshot of items equipped by <paramref name="wielderId"/>. Confirmed
    /// retail equipment has ContainerId zero and WielderId set; the
    /// ContainerId arm keeps the optimistic pre-confirm projection visible.
    /// </summary>
    public IReadOnlyList<ClientObject> GetEquippedBy(uint wielderId) =>
        _equipmentIndex.TryGetValue(wielderId, out List<uint>? placements)
            ? placements
                .Select(Get)
                .Where(item => item is not null
                    && item.CurrentlyEquippedLocation != EquipMask.None
                    && (item.WielderId == wielderId || item.ContainerId == wielderId))
                .Cast<ClientObject>()
                .ToArray()
            : Array.Empty<ClientObject>();

    /// <summary>
    /// Replace only a viewed container's ordered membership projection.
    /// Retail <c>ACCObjectMaint::ViewObjectContents @ 0x00558A70</c> rebuilds
    /// the container lists without mutating child ownership or equip state.
    /// </summary>
    public void ReplaceContents(uint containerId, IReadOnlyList<uint> guids)
    {
        ArgumentNullException.ThrowIfNull(guids);
        if (containerId == 0) return;

        var entries = new ContainerContentEntry[guids.Count];
        for (int i = 0; i < guids.Count; i++)
            entries[i] = new ContainerContentEntry(guids[i], 0u);
        ReplaceContents(containerId, entries);
    }

    /// <summary>
    /// Replace only a viewed container's ordered membership projection.
    /// ContentProfile order is retained in <see cref="GetContents"/> while the
    /// child weenie's canonical placement remains owned by move/wield events.
    /// </summary>
    public void ReplaceContents(uint containerId, IReadOnlyList<ContainerContentEntry> entries)
    {
        ArgumentNullException.ThrowIfNull(entries);
        if (containerId == 0) return;

        var ordered = new List<uint>(entries.Count);
        var added = new List<ClientObject>();
        for (int i = 0; i < entries.Count; i++)
        {
            var entry = entries[i];
            ordered.Add(entry.Guid);
            bool existed = _objects.TryGetValue(entry.Guid, out var obj);
            if (!existed || obj is null)
            {
                obj = new ClientObject { ObjectId = entry.Guid };
                _objects[entry.Guid] = obj;
            }
            obj.ContainerTypeHint = entry.ContainerType;
            if (!existed) added.Add(obj);
        }

        _containerIndex[containerId] = ordered;
        foreach (ClientObject item in added)
            ObjectAdded?.Invoke(item);
        ContainerContentsReplaced?.Invoke(containerId);
    }

    /// <summary>
    /// Initialize canonical inventory ownership from PlayerDescription. This
    /// login manifest is object-state initialization, not a move transition.
    /// </summary>
    public void InitializeInventoryManifest(
        uint ownerId,
        IReadOnlyList<ContainerContentEntry> entries)
    {
        ArgumentNullException.ThrowIfNull(entries);
        if (ownerId == 0u) return;

        var ordered = new List<uint>(entries.Count);
        var changedContainers = new List<uint>();
        var notifications = new List<(ClientObject Item, bool Existed)>(entries.Count);
        var incoming = new HashSet<uint>();
        for (int i = 0; i < entries.Count; i++)
            incoming.Add(entries[i].Guid);

        if (_containerIndex.TryGetValue(ownerId, out List<uint>? priorInventory))
        {
            foreach (uint priorId in priorInventory.ToArray())
            {
                if (incoming.Contains(priorId)
                    || !_objects.TryGetValue(priorId, out ClientObject? prior)
                    || prior is null
                    || prior.ContainerId != ownerId)
                    continue;

                ClientObjectPlacement previous = ClientObjectPlacement.From(prior);
                prior.ContainerId = 0u;
                prior.ContainerSlot = -1;
                prior.WielderId = 0u;
                prior.CurrentlyEquippedLocation = EquipMask.None;
                prior.Priority = 0u;
                UpdateEquipmentIndex(
                    prior.ObjectId,
                    previous,
                    ClientObjectPlacement.From(prior));
                notifications.Add((prior, true));
            }
        }

        for (int i = 0; i < entries.Count; i++)
        {
            ContainerContentEntry entry = entries[i];
            ordered.Add(entry.Guid);
            bool existed = _objects.TryGetValue(entry.Guid, out ClientObject? obj);
            if (!existed || obj is null)
            {
                obj = new ClientObject { ObjectId = entry.Guid };
                _objects[entry.Guid] = obj;
            }

            ClientObjectPlacement previous = ClientObjectPlacement.From(obj);
            obj.ContainerId = ownerId;
            obj.ContainerSlot = i;
            obj.WielderId = 0u;
            obj.CurrentlyEquippedLocation = EquipMask.None;
            obj.ContainerTypeHint = entry.ContainerType;
            if (RemoveFromOtherContainerIndexes(entry.Guid, ownerId) is { } changed)
                changedContainers.AddRange(changed);
            UpdateEquipmentIndex(entry.Guid, previous, ClientObjectPlacement.From(obj));
            notifications.Add((obj, existed));
        }

        _containerIndex[ownerId] = ordered;
        foreach ((ClientObject item, bool existed) in notifications)
        {
            if (!existed) ObjectAdded?.Invoke(item);
            else ObjectUpdated?.Invoke(item);
        }
        ContainerContentsReplaced?.Invoke(ownerId);
        PublishContainerContentsChanges(changedContainers);
    }

    /// <summary>
    /// Σ Burden over every object carried by <paramref name="ownerGuid"/>: items
    /// whose container chain roots at the owner (pack + side-bag contents, retail
    /// hierarchy is 2-deep) plus items wielded by the owner. The client-side
    /// equivalent of the server's <c>EncumbranceVal</c> (PropertyInt 5) — used by
    /// the inventory burden bar until the wire value is parsed (B-Wire). The hop
    /// cap (8) is a cycle guard; real chains are ≤2.
    /// </summary>
    public int SumCarriedBurden(uint ownerGuid)
    {
        int total = 0;
        foreach (var o in _objects.Values)
            if (IsCarriedBy(o, ownerGuid))
                total += o.Burden;
        return total;
    }

    // NOTE: WielderId is populated from authoritative wire data only (CreateObject →
    // Ingest or ApplyServerMove). An
    // optimistically-wielded item (WieldItemOptimistic, before the server confirm) has
    // WielderId == 0 and is detected via the ContainerId walk below (ContainerId == wielder).
    // Equipment queries must therefore accept authoritative WielderId OR the optimistic ContainerId.
    private bool IsCarriedBy(ClientObject o, uint ownerGuid)
    {
        if (o.WielderId == ownerGuid) return true;
        uint c = o.ContainerId;
        for (int hops = 0; c != 0 && hops < 8; hops++)
        {
            if (c == ownerGuid) return true;
            c = _objects.TryGetValue(c, out var parent) ? parent.ContainerId : 0u;
        }
        return false;
    }

    /// <summary>
    /// Flush the table — typically called on logoff or teleport
    /// that drops the session's object state.
    /// </summary>
    public void Clear()
    {
        _objects.Clear();
        _containers.Clear();
        _containerIndex.Clear();
        _equipmentIndex.Clear();
        _pendingMoves.Clear();   // B-Drag: drop in-flight optimistic snapshots (a recycled guid must not mis-rollback)
        Cleared?.Invoke();
    }
}