using System.Numerics;

namespace AcDream.Core.World;

public sealed class WorldEntity
{
    public required uint Id { get; init; }
    /// <summary>
    /// Server-assigned GUID (from CreateObject). Zero for dat-hydrated
    /// scenery/static entities that don't come from the server.
    /// Used by GpuWorldState for persistent-entity rescue on landblock unload.
    /// </summary>
    public uint ServerGuid { get; init; }
    public required uint SourceGfxObjOrSetupId { get; init; }
    /// <summary>
    /// World-space position. Settable so Phase 6.7 position-update events
    /// can reseat an existing entity without rebuilding its meshes.
    /// </summary>
    public required Vector3 Position { get; set; }
    /// <summary>Settable for the same reason as <see cref="Position"/>.</summary>
    public required Quaternion Rotation { get; set; }
    /// <summary>
    /// Per-part mesh references with their root-relative transforms.
    /// Mutable so the animation tick can replace it each frame for
    /// entities that play a cycle (Phase 6.4); static entities set it
    /// once at hydration and never touch it again.
    /// </summary>
    public required IReadOnlyList<MeshRef> MeshRefs { get; set; }

    /// <summary>
    /// Optional per-entity palette override (server-specified base +
    /// subpalette overlays). When non-null, applies to every palette-
    /// indexed texture on this entity. Used for character skin/hair
    /// colors, creature recolors (e.g. stone-colored drudge statue),
    /// and team colors. Non-palette-indexed textures ignore this field.
    /// </summary>
    public PaletteOverride? PaletteOverride { get; init; }

    /// <summary>
    /// EnvCell ID that owns this entity (room geometry or static object inside
    /// the cell). Used by portal visibility to filter interior entities — only
    /// entities whose ParentCellId appears in the visible set are rendered.
    /// Null for outdoor entities (stabs, scenery, live server spawns).
    /// </summary>
    public uint? ParentCellId { get; init; }

    /// <summary>
    /// Uniform scale applied to this entity's mesh by the scenery pipeline.
    /// For scenery objects this is spawn.Scale (typically 0.8–1.3). For stabs
    /// and interior static objects this is 1.0 (no scaling).
    ///
    /// Used by the collision registration path to scale CylSphere / Sphere /
    /// Setup.Radius shapes so they match the visually-scaled mesh. Without
    /// this, scaled scenery has a collision cylinder that's smaller than the
    /// visible trunk, producing "partial passthrough" bugs.
    /// </summary>
    public float Scale { get; init; } = 1.0f;

    /// <summary>
    /// Server-sent part-swap overrides from <c>AnimPartChange</c>. Each entry
    /// replaces a Setup part's GfxObj with an alternate model (clothing, weapons,
    /// helmets). Carried on the entity so <c>EntitySpawnAdapter</c> can populate
    /// <c>AnimatedEntityState</c>'s override map at spawn time. Empty for atlas-
    /// tier entities.
    /// </summary>
    public IReadOnlyList<PartOverride> PartOverrides { get; init; } = Array.Empty<PartOverride>();

    /// <summary>
    /// Bitmask of hidden Setup parts. Bit <c>i</c> set hides part <c>i</c> at
    /// draw time. Sourced from the server's <c>CreateObject</c> record when
    /// present. Zero (no parts hidden) is the default.
    /// </summary>
    public ulong HiddenPartsMask { get; init; }

    // Per Phase A.5 spec §4.6 Change #2 — cache per-entity AABB so the
    // dispatcher's frustum cull is a memory read, not a per-frame recompute.
    // AabbDirty starts true so the dispatcher calls RefreshAabb on first read
    // (AabbMin/AabbMax are Vector3.Zero until refreshed).
    public Vector3 AabbMin { get; private set; }
    public Vector3 AabbMax { get; private set; }
    public bool AabbDirty { get; private set; } = true;

    private const float DefaultAabbRadius = 5.0f;

    public void RefreshAabb()
    {
        var p = Position;
        AabbMin = new Vector3(p.X - DefaultAabbRadius, p.Y - DefaultAabbRadius, p.Z - DefaultAabbRadius);
        AabbMax = new Vector3(p.X + DefaultAabbRadius, p.Y + DefaultAabbRadius, p.Z + DefaultAabbRadius);
        AabbDirty = false;
    }

    public void SetPosition(Vector3 pos)
    {
        Position = pos;
        AabbDirty = true;
    }
}

/// <summary>
/// Lightweight value type for a server-sent <c>AnimPartChange</c> (part index
/// → replacement GfxObj id). Decouples <c>WorldEntity</c> (Core) from the
/// network-layer <c>CreateObject.AnimPartChange</c> type.
/// </summary>
public readonly record struct PartOverride(byte PartIndex, uint GfxObjId);