using System.Collections.Generic;
using System.Numerics;
using AcDream.Content;
using AcDream.Core.CharGen;
using AcDream.Core.Meshing;
using AcDream.Core.Physics;
using AcDream.Core.World;
using DatReaderWriter.DBObjs;

namespace AcDream.App.Rendering;

/// <summary>
/// One resolved drawable part of the chargen preview body — a Setup part
/// index (needed to sample <c>Animation.PartFrames[frame].Frames[index]</c>
/// and <c>Setup.DefaultScale[index]</c>) paired with its resolved GfxObj id,
/// default scale (captured once at build time — scale never changes across
/// an idle cycle), and surface overrides. <see cref="ChargenPreviewAnimator"/>
/// walks this list every tick without touching the dat source again.
/// </summary>
internal readonly record struct ChargenPreviewDrawablePart(
    int SetupPartIndex,
    uint GfxObjId,
    Vector3 DefaultScale,
    IReadOnlyDictionary<uint, uint>? SurfaceOverrides);

/// <summary>
/// The richer sibling of <see cref="ChargenPreviewEntityBuilder.TryBuild"/>'s
/// result: the built <see cref="WorldEntity"/> (seeded with retail's true
/// default pose — see <see cref="ChargenPreviewAnimator"/>) plus everything
/// needed to drive it frame-by-frame without re-touching the dat source —
/// the resolved drawable parts, the precomputed frozen rest pose, and the
/// resolved idle Animation + its frame range.
/// </summary>
internal sealed class ChargenPreviewAnimatedBuild
{
    public required WorldEntity Entity { get; init; }
    public required IReadOnlyList<ChargenPreviewDrawablePart> DrawableParts { get; init; }

    /// <summary>
    /// The held final-frame rest pose, precomputed once (retail:
    /// <c>gmCG3DView::StopAnimation</c>'s framerate-0
    /// <c>set_sequence_animation</c> call never advances, so there is
    /// nothing to recompute per tick while zoomed in). Falls back to each
    /// part's raw Setup-default transform (no-op) when the rest DID doesn't
    /// resolve, matching the pre-CC6b <c>ApplyHeldPose</c> no-op behavior.
    /// </summary>
    public required IReadOnlyList<MeshRef> RestMeshRefs { get; init; }

    /// <summary>Retail's live idle DID (<c>m_didAnimation</c>), or null if unresolved.</summary>
    public Animation? IdleAnimation { get; init; }
    public int IdleLowFrame { get; init; }
    public int IdleHighFrame { get; init; }
}

/// <summary>
/// Builds the chargen preview <see cref="WorldEntity"/> from a
/// <see cref="ChargenAppearanceResult"/> — the App-layer counterpart to
/// <see cref="DollEntityBuilder"/>, except this one resolves its OWN
/// MeshRefs from a Setup + the composed ObjDesc rather than receiving
/// already-resolved refs from a live entity (there is no live entity yet;
/// character creation hasn't happened). DAT-touching, unlike
/// <see cref="DollEntityBuilder"/>'s pure index-agnostic builder — the
/// closest existing precedent for the actual mesh-flatten/apply-changes/
/// resolve-surface-overrides steps is
/// <c>DatLiveEntityProjectionMaterializer.TryMaterialize</c>, trimmed to
/// what a private, non-collision preview scene needs.
///
/// <para>
/// <b>CC6b:</b> retail's chargen preview does NOT default to a frozen pose —
/// <c>gmCGAppearancePage::Update</c>'s own trailing gate
/// (~0x0047EF01-0x0047EF12) calls <c>gmCG3DView::StartAnimation</c> (idle
/// loop playing) whenever <c>m_bZoomedIn == 0</c>, and that default is
/// DIRECTLY ASSIGNED, not inherited:
/// <c>gmCGAppearancePage::InitializePage @0x0047FDD0</c> writes an
/// explicit <c>m_bZoomedIn = 0</c> at <c>0x004802C3</c> (right after
/// setting the camera to the zoomed-IN per-heritage eye at
/// <c>0x00480286-0x0048029E</c> — the null-tween quirk the zoom
/// controller's doc records). The earlier elided-ctor-byte argument was
/// unsound (heap-new members are indeterminate, not zero) and was
/// replaced by this citation at the CC6b-PRE re-review. So retail's
/// chargen preview plays its idle loop (<c>m_didAnimation</c>, 30fps) from
/// the very first frame; the REST pose (<c>m_didAnimationRest</c>, held
/// final frame, this class's pre-CC6b-only behavior) only appears once the
/// user presses Zoom In (<c>gmCGAppearancePage::ZoomIn</c> calls
/// <c>gmCG3DView::StopAnimation</c> immediately, before its camera tween
/// even starts). <see cref="TryBuild"/> keeps its ORIGINAL (rest-only)
/// behavior unchanged for its existing callers; <see cref="TryBuildAnimated"/>
/// plus <see cref="ChargenPreviewAnimator"/> are the new, retail-accurate
/// entry point a live preview (idle-playing by default, freezing on zoom-in)
/// should use.
/// </para>
/// </summary>
internal static class ChargenPreviewEntityBuilder
{
    /// <summary>Reserved synthetic guid for the chargen preview clone —
    /// same reserved family as <see cref="DollEntityBuilder.DollServerGuid"/>
    /// (0xDA11D0xx) and <c>CreatureAppraisalEntityBuilder</c> (0xDA11D02x).</summary>
    public const uint PreviewServerGuid = 0xDA11_D031u;

    /// <summary>Reserved render-local entity id — passed in
    /// <c>animatedEntityIds</c> by the renderer so a re-dress (a new
    /// selection) bypasses <c>WbDrawDispatcher</c>'s Tier-1 classification
    /// cache, mirroring <see cref="DollEntityBuilder.DollRenderId"/>'s own
    /// doc comment.</summary>
    public const uint PreviewRenderId = 0xDA11_D032u;

    /// <summary>Reserved synthetic guid for the chargen preview's ENVIRONMENT
    /// backdrop (GF-7/GF-14 fix) — next slot in the same 0xDA11D03x chargen
    /// family as <see cref="PreviewServerGuid"/>.</summary>
    public const uint PreviewBackdropServerGuid = 0xDA11_D033u;

    /// <summary>Reserved render-local entity id for the backdrop object,
    /// passed in <c>animatedEntityIds</c> alongside <see cref="PreviewRenderId"/>
    /// so a heritage switch's new environment Setup also bypasses the
    /// classification cache — same reasoning as <see cref="PreviewRenderId"/>'s
    /// own doc comment, applied to retail's SECOND <c>creature_mode_objects</c>
    /// member (<c>gmCG3DView::m_pbgObject</c>).</summary>
    public const uint PreviewBackdropRenderId = 0xDA11_D034u;

    /// <summary>
    /// F16 (Campaign CC gate round 1 closeout, 2026-08-16): the Summary
    /// page's OWN preview render-local id — DISTINCT from
    /// <see cref="PreviewRenderId"/>. Both the Appearance and Summary pages
    /// construct their own <c>ChargenPreviewRenderer</c>, but they share
    /// ONE process-wide <c>TextureCache</c> (<c>Wb.IEntityTextureLifetime</c>)
    /// via <c>LivePresentationComposition</c>'s <c>foundation.TextureCache</c>
    /// — confirmed by tracing <c>FixedEntityTextureOwnerLease.Replace</c> →
    /// <c>TextureCache.ReleaseOwner</c> → <c>CompositeTextureArrayCache.ReleaseOwner</c>
    /// → its own <c>_owners</c> tracker, keyed ONLY by the raw
    /// <c>ownerLocalId</c> uint with no per-renderer namespace. Both pages
    /// are mounted as PERMANENT siblings (register AP-229) and can be
    /// simultaneously live, so two <c>PrivateEntityViewportRenderer</c>
    /// instances sharing <see cref="PreviewRenderId"/> would share this
    /// SAME owner bucket: either page re-dressing its own entity (a
    /// <c>FixedEntityTextureOwnerLease.Replace</c> call) or being disposed
    /// would call <c>ReleaseOwner(PreviewRenderId)</c> and release textures
    /// the OTHER page's preview is still actively drawing with — a real
    /// cross-page texture-corruption path, not a theoretical one. Reserved
    /// in the SAME 0xDA11D0xx synthetic family, next free slot after the
    /// Appearance page's own pair.
    /// </summary>
    public const uint SummaryPreviewRenderId = 0xDA11_D035u;

    /// <summary>F16: the Summary page's own backdrop render-local id,
    /// paired with <see cref="SummaryPreviewRenderId"/> exactly as
    /// <see cref="PreviewBackdropRenderId"/> pairs with
    /// <see cref="PreviewRenderId"/> — see that constant's own doc for why a
    /// distinct id is required, not merely tidy.</summary>
    public const uint SummaryPreviewBackdropRenderId = 0xDA11_D036u;

    /// <summary>
    /// Retail's held-pose (REST) animation DID enum key, resolved through
    /// master map slot 7 exactly like <c>RetailPaperdollPoseApplicator.ResolvePoseDid</c>
    /// — 0x10000005 for every standard heritage (the SAME enum id the
    /// paperdoll's own held pose reads), matching
    /// <c>gmCG3DView</c>'s ctor / <c>::Update</c> per-heritage
    /// <c>m_didAnimationRest</c> assignment (pseudo-C ~0x004EE948,
    /// ~0x004EEC43). Olthoi and OlthoiAcid each get their OWN distinct rest
    /// DID — the one divergence from the paperdoll, which never needs an
    /// Olthoi branch because a live player can't be one.
    /// </summary>
    private static uint ResolveRestPoseEnum(uint heritageId) => heritageId switch
    {
        (uint)ChargenHeritageGroup.Olthoi => 0x10000011u,
        (uint)ChargenHeritageGroup.OlthoiAcid => 0x10000013u,
        _ => 0x10000005u,
    };

    /// <summary>
    /// Retail's LIVE idle-loop animation DID enum key (<c>m_didAnimation</c>,
    /// the one <c>gmCG3DView::StartAnimation</c> plays at 30fps) — 0x10000006
    /// for every standard heritage, matching <c>gmCG3DView</c>'s ctor /
    /// <c>::Update</c> per-heritage assignment (pseudo-C ~0x004ee6cc,
    /// ~0x004eec2d). <b>Olthoi and OlthoiAcid use the SAME did for BOTH idle
    /// and rest</b> (0x10000011 / 0x10000013 respectively, pseudo-C
    /// ~0x004ee7e9/0x004ee7ff and ~0x004ee892/0x004ee8a8) — a genuine retail
    /// quirk, not a porting shortcut: those two heritages show no visible
    /// difference between "idle playing" and "zoomed in and frozen" in the
    /// chargen preview.
    /// </summary>
    private static uint ResolveIdleAnimEnum(uint heritageId) => heritageId switch
    {
        (uint)ChargenHeritageGroup.Olthoi => 0x10000011u,
        (uint)ChargenHeritageGroup.OlthoiAcid => 0x10000013u,
        _ => 0x10000006u,
    };

    /// <summary>
    /// Builds the STATIC (held rest-pose) preview entity, or null when the
    /// resolved body Setup isn't in the dat source (a corrupted/incomplete
    /// install — the same failure shape
    /// <see cref="DatLiveEntityProjectionMaterializer"/> treats as "drop this
    /// spawn"). Unchanged since CC6a for its RESULT — a thin wrapper over
    /// <see cref="TryBuildAnimated"/> that returns exactly the same
    /// <c>WorldEntity</c> (rest-posed) this method's existing callers already
    /// expect; ALL 3 of those callers' tests still pass unmodified. Not
    /// byte-identical internally any more — <see cref="TryBuildAnimated"/>
    /// also resolves the idle DID and loads the idle Animation before this
    /// wrapper discards them, extra dat work the pre-CC6b method never did.
    /// New code that wants retail's true default (idle loop playing) should call
    /// <see cref="TryBuildAnimated"/> and wrap the result in a
    /// <see cref="ChargenPreviewAnimator"/> instead.
    /// </summary>
    /// <param name="datLock">
    /// Shared exclusion object for every dat read this method performs.
    /// <c>DatCollection</c> is NOT thread-safe (see
    /// <c>claude-memory/feedback_phase_a1_hotfix_saga.md</c>) — every other
    /// dat-touching renderer/resolver in this layer
    /// (<c>RetailPaperdollPoseApplicator</c>, <c>PlayerModeController</c>,
    /// <c>DatProjectileSetupResolver</c>, <c>EquippedChildRenderController</c>)
    /// takes the SAME <c>object datLock</c> the composition root threads
    /// through as <c>RuntimeOptions</c>/<c>d.DatLock</c>; callers MUST pass
    /// that same shared instance, not a private lock, or this method's reads
    /// race every other consumer's.
    /// </param>
    public static WorldEntity? TryBuild(
        IDatReaderWriter dats,
        IAnimationLoader animations,
        ChargenAppearanceResult appearance,
        uint heritageId,
        Quaternion heading,
        object datLock,
        uint renderId = PreviewRenderId)
    {
        ChargenPreviewAnimatedBuild? build = TryBuildAnimated(
            dats, animations, appearance, heritageId, heading, datLock, renderId);
        if (build is null)
            return null;

        build.Entity.MeshRefs = build.RestMeshRefs;
        return build.Entity;
    }

    /// <summary>
    /// Builds the preview entity PLUS everything a <see cref="ChargenPreviewAnimator"/>
    /// needs to drive retail's idle-loop ↔ rest-pose swap without re-touching
    /// the dat source. The returned <see cref="ChargenPreviewAnimatedBuild.Entity"/>
    /// is initially posed with <see cref="ChargenPreviewAnimatedBuild.RestMeshRefs"/>
    /// (cheap, always available) — <see cref="ChargenPreviewAnimator"/>'s
    /// constructor immediately reposes it to the true retail default (idle
    /// frame 0) when an idle Animation resolved.
    /// </summary>
    public static ChargenPreviewAnimatedBuild? TryBuildAnimated(
        IDatReaderWriter dats,
        IAnimationLoader animations,
        ChargenAppearanceResult appearance,
        uint heritageId,
        Quaternion heading,
        object datLock,
        // F16 (Campaign CC gate round 1 closeout): the Appearance and
        // Summary pages both call this method through their own
        // ChargenPreviewController, but must NOT stamp the same Id on
        // both entities — see SummaryPreviewRenderId's own doc for the
        // full TextureCache collision trace this id also feeds.
        uint renderId = PreviewRenderId)
    {
        ArgumentNullException.ThrowIfNull(dats);
        ArgumentNullException.ThrowIfNull(animations);
        ArgumentNullException.ThrowIfNull(appearance);
        ArgumentNullException.ThrowIfNull(datLock);

        uint setupId = appearance.SetupId;
        List<ChargenPreviewDrawablePart> drawableParts;
        List<MeshRef> restMeshRefs;
        Animation? idleAnimation;
        int idleLowFrame = 0, idleHighFrame = -1;

        // Every dat read this method performs — the Setup fetch, both pose
        // DID resolutions, the per-part GfxObj drawable checks, and the
        // texture-change surface resolution — happens inside this one lock,
        // mirroring RetailPaperdollPoseApplicator.Apply's "resolve
        // everything under lock, then do pure processing" shape.
        lock (datLock)
        {
            Setup? setup = dats.Get<Setup>(setupId);
            if (setup is null)
                return null;

            var flattened = new List<MeshRef>(SetupMesh.Flatten(setup));

            foreach (ChargenAnimPartChange change in appearance.ObjDesc.AnimPartChanges)
            {
                if (change.PartIndex < flattened.Count)
                    flattened[change.PartIndex] = new MeshRef(change.PartId, flattened[change.PartIndex].PartTransform);
            }

            // Rest pose: overwrite flattened's transforms with the held
            // final frame (no-op — keeps Setup-default transforms — if the
            // rest DID or its Animation don't resolve).
            ApplyHeldPoseTransforms(dats, animations, setup, ResolveRestPoseEnum(heritageId), flattened);

            Dictionary<int, Dictionary<uint, uint>>? surfaceOverrides =
                ResolveSurfaceOverrides(dats, flattened, appearance.ObjDesc.TextureChanges);

            drawableParts = new List<ChargenPreviewDrawablePart>(flattened.Count);
            restMeshRefs = new List<MeshRef>(flattened.Count);
            for (int partIndex = 0; partIndex < flattened.Count; partIndex++)
            {
                MeshRef part = flattened[partIndex];
                if (dats.Get<GfxObj>(part.GfxObjId) is null)
                    continue; // matches DatLiveEntityProjectionMaterializer's drawable filter.

                IReadOnlyDictionary<uint, uint>? overrides = null;
                if (surfaceOverrides is not null && surfaceOverrides.TryGetValue(partIndex, out var perPart))
                    overrides = perPart;

                restMeshRefs.Add(new MeshRef(part.GfxObjId, part.PartTransform) { SurfaceOverrides = overrides });

                Vector3 defaultScale = partIndex < setup.DefaultScale.Count
                    ? setup.DefaultScale[partIndex]
                    : Vector3.One;
                drawableParts.Add(new ChargenPreviewDrawablePart(partIndex, part.GfxObjId, defaultScale, overrides));
            }
            if (drawableParts.Count == 0)
                return null;

            // Idle DID: independent lookup, no mutation of flattened.
            uint idleDid = RetailHeldPose.ResolvePoseDid(dats, ResolveIdleAnimEnum(heritageId));
            idleAnimation = (idleDid >> 24) == 0x03u ? animations.LoadAnimation(idleDid) : null;
            if (idleAnimation is not null && idleAnimation.PartFrames.Count > 0)
            {
                idleLowFrame = 0;
                idleHighFrame = idleAnimation.PartFrames.Count - 1;
            }
            else
            {
                idleAnimation = null;
            }
        }

        var entity = new WorldEntity
        {
            Id = renderId,
            ServerGuid = PreviewServerGuid,
            SourceGfxObjOrSetupId = setupId,
            Position = Vector3.Zero,
            Rotation = heading,
            MeshRefs = restMeshRefs,
            PaletteOverride = BuildPaletteOverride(appearance),
            PartOverrides = BuildPartOverrides(appearance),
            ParentCellId = null,
        };

        return new ChargenPreviewAnimatedBuild
        {
            Entity = entity,
            DrawableParts = drawableParts,
            RestMeshRefs = restMeshRefs,
            IdleAnimation = idleAnimation,
            IdleLowFrame = idleLowFrame,
            IdleHighFrame = idleHighFrame,
        };
    }

    /// <summary>
    /// Builds the chargen preview's ENVIRONMENT BACKDROP entity — the fix for
    /// GF-7/GF-14 (preview backdrop black on Appearance and Summary).
    ///
    /// <para>
    /// Decomp-cited: <c>gmCG3DView::Update @0x004EE9D0</c>
    /// (~0x004eecd3-0x004eed44) constructs a SECOND <c>CPhysicsObj</c> from
    /// <c>m_bgSetupID</c> and adds it to the SAME viewport's
    /// <c>creature_mode_objects</c> the player object lives in — <b>BEFORE</b>
    /// the player is re-added (the player's own re-<c>AddObject</c> happens
    /// much later, at ~0x004ef199, after the full clothing ObjDesc is
    /// composed), so retail's own draw-list order is backdrop first, player
    /// second. <c>m_bgSetupID</c> is compared against a freshly-read value the
    /// decompiler elides (<c>var_b8</c>/<c>eax_32</c>, an unresolved-call
    /// artifact — see <c>claude-memory/feedback_bn_decomp_field_names.md</c>)
    /// immediately after <c>ACCharGenData::GetHG(charGenData, mHeritageGroup)</c>
    /// (0x004eea1a) resolves the current heritage's <c>HeritageGroup_CG</c>;
    /// <c>acclient.h</c>'s verbatim struct layout
    /// (<c>HeritageGroup_CG.environmentSetupID</c>, right after
    /// <c>setupID</c>) confirms the elided value IS that field — i.e. THE
    /// SAME id this codebase already parses as
    /// <see cref="AcDream.Core.CharGen.ChargenHeritageOptions.EnvironmentSetupId"/>
    /// (<c>ChargenTableReader.cs</c>) but never consumed. The backdrop object
    /// gets NO explicit position/orientation/scale anywhere in the function —
    /// <c>CPhysicsObj::makeObject(eax_32, 0, 1)</c> (0x004eed2f) leaves it at
    /// its physics-object default (origin, identity), exactly like the player
    /// object's own placement in this same private scene. This method mirrors
    /// that: a plain, unposed, unpalette-overridden Setup mesh at the origin.
    /// </para>
    ///
    /// <para>
    /// Both the Appearance page (<c>gmCGAppearancePage</c>) and the Summary
    /// page (<c>gmCGSummaryPage</c>) call this SAME <c>gmCG3DView::Update</c>
    /// function on their own <c>gmCG3DView</c> instance (confirmed at
    /// pseudo-C ~0x0047bbf0/~0x0047c92c for Summary and ~0x0047c840/
    /// ~0x0047eee1 for Appearance) — so the backdrop mechanism is identical
    /// for both viewports, not page-specific.
    /// </para>
    /// </summary>
    /// <param name="environmentSetupId">
    /// <see cref="AcDream.Core.CharGen.ChargenHeritageOptions.EnvironmentSetupId"/>.
    /// Zero (unset/no environment authored for this heritage) returns null —
    /// matches retail's own <c>if (eax_32 != INVALID_DID.id)</c> gate at
    /// 0x004eed29, which skips <c>makeObject</c>/<c>AddObject</c> entirely
    /// when the heritage has no environment Setup.
    /// </param>
    public static WorldEntity? TryBuildBackdrop(
        IDatReaderWriter dats,
        uint environmentSetupId,
        object datLock,
        // F16 (Campaign CC gate round 1 closeout): see TryBuildAnimated's
        // own renderId parameter doc — same Appearance-vs-Summary
        // distinction, applied to the backdrop entity.
        uint renderId = PreviewBackdropRenderId)
    {
        ArgumentNullException.ThrowIfNull(dats);
        ArgumentNullException.ThrowIfNull(datLock);

        if (environmentSetupId == 0u)
            return null;

        lock (datLock)
        {
            Setup? setup = dats.Get<Setup>(environmentSetupId);
            if (setup is null)
                return null;

            var flattened = SetupMesh.Flatten(setup);
            var drawable = new List<MeshRef>(flattened.Count);
            foreach (MeshRef part in flattened)
            {
                if (dats.Get<GfxObj>(part.GfxObjId) is not null)
                    drawable.Add(part);
            }
            if (drawable.Count == 0)
                return null;

            return new WorldEntity
            {
                Id = renderId,
                ServerGuid = PreviewBackdropServerGuid,
                SourceGfxObjOrSetupId = environmentSetupId,
                Position = Vector3.Zero,
                Rotation = Quaternion.Identity,
                MeshRefs = drawable,
                ParentCellId = null,
            };
        }
    }

    /// <summary>No dat access — pure projection of the already-composed
    /// ObjDesc's subpalettes, safe to call outside <c>datLock</c>.</summary>
    private static PaletteOverride? BuildPaletteOverride(ChargenAppearanceResult appearance)
    {
        if (appearance.ObjDesc.SubPalettes.Count == 0)
            return null;

        var ranges = new PaletteOverride.SubPaletteRange[appearance.ObjDesc.SubPalettes.Count];
        for (int i = 0; i < appearance.ObjDesc.SubPalettes.Count; i++)
        {
            ChargenSubPalette sub = appearance.ObjDesc.SubPalettes[i];
            ranges[i] = new PaletteOverride.SubPaletteRange(sub.SubPaletteId, sub.Offset, sub.NumColors);
        }
        return new PaletteOverride(appearance.BasePaletteId, ranges);
    }

    /// <summary>No dat access — pure projection, safe to call outside
    /// <c>datLock</c>.</summary>
    private static PartOverride[] BuildPartOverrides(ChargenAppearanceResult appearance)
    {
        var partOverrides = new PartOverride[appearance.ObjDesc.AnimPartChanges.Count];
        for (int i = 0; i < appearance.ObjDesc.AnimPartChanges.Count; i++)
        {
            ChargenAnimPartChange change = appearance.ObjDesc.AnimPartChanges[i];
            partOverrides[i] = new PartOverride(change.PartIndex, change.PartId);
        }
        return partOverrides;
    }

    /// <summary>
    /// Overwrites every part's transform from the resolved pose DID's FINAL
    /// frame — same "hold the settled last frame at zero frame rate"
    /// approach as <c>RetailPaperdollPoseApplicator.Apply</c>
    /// (<c>RedressCreature @ 0x004A3C22</c>), applied to the FULL
    /// setup-part-indexed array (before drawable filtering) so the index
    /// alignment holds even if a later part turns out to have a missing
    /// GfxObj. No-ops (keeps the default placement frame) when the pose
    /// DID or its animation can't be resolved.
    /// </summary>
    private static void ApplyHeldPoseTransforms(
        IDatReaderWriter dats,
        IAnimationLoader animations,
        Setup setup,
        uint poseEnum,
        List<MeshRef> flattened)
    {
        uint poseDid = RetailHeldPose.ResolvePoseDid(dats, poseEnum);
        if ((poseDid >> 24) != 0x03u)
            return;

        Animation? animation = animations.LoadAnimation(poseDid);
        if (animation is null || animation.PartFrames.Count == 0)
            return;

        var frame = animation.PartFrames[^1];
        for (int index = 0; index < flattened.Count; index++)
        {
            Vector3 scale = index < setup.DefaultScale.Count ? setup.DefaultScale[index] : Vector3.One;
            Vector3 origin = Vector3.Zero;
            Quaternion orientation = Quaternion.Identity;
            if (index < frame.Frames.Count)
            {
                origin = frame.Frames[index].Origin;
                orientation = frame.Frames[index].Orientation;
            }

            flattened[index] = new MeshRef(
                flattened[index].GfxObjId,
                RetailHeldPose.ComposePartTransform(scale, origin, orientation));
        }
    }

    /// <summary>
    /// Part-index → (old texture id → new texture id) resolution, verbatim
    /// port of <c>DatLiveEntityProjectionMaterializer.ResolveSurfaceOverrides</c>'s
    /// algorithm against <see cref="ChargenTextureChange"/> instead of the
    /// wire's <c>CreateObject.TextureChange</c>.
    /// </summary>
    private static Dictionary<int, Dictionary<uint, uint>>? ResolveSurfaceOverrides(
        IDatReaderWriter dats,
        IReadOnlyList<MeshRef> parts,
        IReadOnlyList<ChargenTextureChange> textureChanges)
    {
        if (textureChanges.Count == 0)
            return null;

        var oldToNewByPart = new Dictionary<int, Dictionary<uint, uint>>();
        foreach (ChargenTextureChange change in textureChanges)
        {
            if (!oldToNewByPart.TryGetValue(change.PartIndex, out var oldToNew))
            {
                oldToNew = [];
                oldToNewByPart.Add(change.PartIndex, oldToNew);
            }
            oldToNew[change.OldTextureId] = change.NewTextureId;
        }

        var result = new Dictionary<int, Dictionary<uint, uint>>();
        for (int partIndex = 0; partIndex < parts.Count; partIndex++)
        {
            if (!oldToNewByPart.TryGetValue(partIndex, out var oldToNew))
                continue;

            GfxObj? gfx = dats.Get<GfxObj>(parts[partIndex].GfxObjId);
            if (gfx is null)
                continue;

            Dictionary<uint, uint>? resolved = null;
            foreach (var surfaceQid in gfx.Surfaces)
            {
                uint surfaceId = (uint)surfaceQid;
                Surface? surface = dats.Get<Surface>(surfaceId);
                if (surface is null)
                    continue;
                uint originalTexture = (uint)surface.OrigTextureId;
                if (originalTexture == 0 || !oldToNew.TryGetValue(originalTexture, out uint newTexture))
                    continue;

                (resolved ??= [])[surfaceId] = newTexture;
            }

            if (resolved is not null)
                result[partIndex] = resolved;
        }

        return result.Count == 0 ? null : result;
    }
}