using System;
using System.Collections.Generic;
using System.Numerics;
using AcDream.Core.World;

namespace AcDream.App.Rendering;

/// <summary>
/// Builds the dedicated paperdoll WorldEntity — retail's <c>makeObject(player)</c>
/// clone: the player's Setup id + current ObjDesc (base palette + subpalette overlays
/// + part overrides), posed at the scene origin facing the viewer.
///
/// <para>
/// The palette / part-override mapping mirrors the inline construction in
/// <c>GameWindow.cs</c> around lines 3390–3431. Extracted here so it is
/// unit-testable without dats and so the paperdoll renderer owns a clean
/// seam: it calls <see cref="Build"/> with fresh player state each time the
/// ObjDesc changes, and the renderer only has to swap the entity into its
/// dedicated mini-scene.
/// </para>
///
/// <para>
/// The <see cref="DollServerGuid"/> is a reserved synthetic guid that is:
/// (a) non-zero (so <c>EntitySpawnAdapter.OnCreate</c>'s <c>ServerGuid != 0</c>
/// guard accepts it), and (b) high enough that it never collides with a real
/// server-assigned guid.
/// </para>
/// </summary>
public static class DollEntityBuilder
{
    /// <summary>
    /// Reserved synthetic guid for the paperdoll clone. High, deliberately
    /// outside the server's assignable range, and non-zero.
    /// </summary>
    public const uint DollServerGuid = 0xDA11_D011u;

    /// <summary>
    /// Reserved render-local entity id for the doll. FIXED (the doll is a singleton)
    /// and high enough never to collide with <c>_liveEntityIdCounter</c> ids. The
    /// renderer passes this in <c>animatedEntityIds</c> so the dispatcher treats the
    /// doll as animated — which BYPASSES the Tier-1 classification cache
    /// (WbDrawDispatcher.cs:1142). That matters because a re-dress builds a NEW
    /// WorldEntity with this SAME id; without the cache bypass the dispatcher would
    /// serve the previous doll's cached batches and the new gear wouldn't appear.
    /// </summary>
    public const uint DollRenderId = 0xDA11_D012u;

    // retail RedressCreature: CPhysicsObj::set_heading(191.367905°) (decomp 0x004a3c0a). Frame::set_heading(h)
    // (decomp 0x00535e40) builds the facing vector as (sin h°, cos h°, 0): at h=0 the creature faces +Y (AC
    // North), the heading increasing CLOCKWISE toward +X. We rotate the doll's default +Y-forward body about
    // +Z; System.Numerics rotates +Y → (−sin θ, cos θ), so to land on retail's (sin h, cos h) the angle is
    // NEGATED (θ = −h). Using +h mirrors the X-lean (~22° off → the face reads as turned away from the viewer).
    private const float _headingDegrees = 191.367905f;
    private static readonly float _headingRad = -_headingDegrees * (MathF.PI / 180f);
    private static readonly Quaternion _dollRotation =
        Quaternion.CreateFromAxisAngle(new Vector3(0f, 0f, 1f), _headingRad);

    /// <summary>
    /// Builds a synthetic <see cref="WorldEntity"/> for the paperdoll mini-scene.
    /// </summary>
    /// <param name="setupId">The player's Setup dat id (0x02xxxxxx).</param>
    /// <param name="meshRefs">Pre-resolved mesh refs (may be empty; caller fills them in).</param>
    /// <param name="basePaletteId">
    /// ObjDesc base palette id (0x04xxxxxx). Passed only when subpalettes are
    /// also present — mirrors GameWindow which only builds a PaletteOverride
    /// when <c>SubPalettes.Count &gt; 0</c>.
    /// </param>
    /// <param name="subPalettes">
    /// Subpalette overlays from the server ObjDesc. Each tuple carries the
    /// subpalette dat id, byte offset into the base palette, and byte length.
    /// Null or empty → <c>PaletteOverride</c> on the returned entity is null.
    /// </param>
    /// <param name="partOverrides">
    /// AnimPartChange swaps from the server ObjDesc. Each tuple is a
    /// (PartIndex, replacement GfxObj id) pair. Null or empty → empty array.
    /// </param>
    public static WorldEntity Build(
        uint setupId,
        IReadOnlyList<MeshRef> meshRefs,
        uint? basePaletteId = null,
        IReadOnlyList<(uint SubPaletteId, byte Offset, byte Length)>? subPalettes = null,
        IReadOnlyList<(byte PartIndex, uint GfxObjId)>? partOverrides = null)
    {
        // --- palette override (mirrors GameWindow:3395-3405) ---
        // Only build when there are sub-palette overlays — same gate as GameWindow.
        PaletteOverride? paletteOverride = null;
        if (subPalettes is { Count: > 0 } spList)
        {
            var ranges = new PaletteOverride.SubPaletteRange[spList.Count];
            for (int i = 0; i < spList.Count; i++)
                ranges[i] = new PaletteOverride.SubPaletteRange(
                    spList[i].SubPaletteId,
                    spList[i].Offset,
                    spList[i].Length);
            paletteOverride = new PaletteOverride(
                BasePaletteId: basePaletteId ?? 0u,
                SubPalettes: ranges);
        }

        // --- part overrides (mirrors GameWindow:3407-3418) ---
        PartOverride[] entityPartOverrides;
        if (partOverrides is null or { Count: 0 })
        {
            entityPartOverrides = Array.Empty<PartOverride>();
        }
        else
        {
            entityPartOverrides = new PartOverride[partOverrides.Count];
            for (int i = 0; i < partOverrides.Count; i++)
                entityPartOverrides[i] = new PartOverride(
                    partOverrides[i].PartIndex,
                    partOverrides[i].GfxObjId);
        }

        // --- assemble entity (mirrors GameWindow:3420-3431) ---
        // Id=0: the paperdoll renderer assigns its own render-local id when it
        // registers this entity with the mini-scene GpuWorldState. We set zero
        // here so the builder stays pure (no static counter). The caller may
        // replace it before registration.
        return new WorldEntity
        {
            Id = DollRenderId,
            ServerGuid = DollServerGuid,
            SourceGfxObjOrSetupId = setupId,
            Position = Vector3.Zero,
            Rotation = _dollRotation,
            MeshRefs = meshRefs,
            PaletteOverride = paletteOverride,
            PartOverrides = entityPartOverrides,
            ParentCellId = null,  // paperdoll mini-scene has no parent cell
        };
    }
}