using System.Numerics;
using AcDream.Content;
using DatReaderWriter;
using DatReaderWriter.DBObjs;

namespace AcDream.App.Rendering;

/// <summary>
/// Shared primitives behind retail's "resolve a rest-pose DID via master-map
/// slot 7, load its Animation, hold the final frame" algorithm — the
/// mechanism <see cref="RetailPaperdollPoseApplicator"/> (paperdoll,
/// <c>gmPaperDollUI::RedressCreature @ 0x004A3C22</c>) and
/// <see cref="ChargenPreviewEntityBuilder"/> (chargen preview,
/// <c>gmCG3DView::StopAnimation @ 0x004EE640</c>) both implement. Extracted
/// per the CC6a review's F11/F12 note ("before adding a FOURTH consumer... a
/// shared <c>RetailHeldPose</c> helper is worth extracting before a fourth
/// held-pose consumer exists") — CC6b's own idle-loop work makes chargen's
/// implementation grow enough that mechanically sharing the two primitives
/// BOTH sites already had byte-identical (DID resolution, final-frame
/// transform composition) is a clean win without forcing the two sites'
/// slightly different per-index LOOP shapes (paperdoll walks an
/// already-built, already-filtered <c>WorldEntity.MeshRefs</c>; chargen
/// walks the pre-filter, Setup-part-indexed scratch list) into one method
/// they don't actually share.
/// </summary>
internal static class RetailHeldPose
{
    /// <summary>
    /// <c>DBCache::GetDIDFromEnumStatic(poseEnum, 7)</c> equivalent: master
    /// map → slot 7's sub-map → <paramref name="poseEnum"/>'s Animation DID.
    /// Returns 0 if any link in the chain is missing. MUST be called under
    /// the caller's dat lock (see <see cref="ChargenPreviewEntityBuilder.TryBuild"/>'s
    /// <c>datLock</c> doc — <c>DatCollection</c> is not thread-safe).
    /// </summary>
    public static uint ResolvePoseDid(IDatReaderWriter dats, uint poseEnum)
    {
        uint masterDid = (uint)dats.Portal.Db.Header.MasterMapId;
        if (masterDid == 0
            || !dats.Portal.TryGet<EnumIDMap>(masterDid, out var master)
            || !master.ClientEnumToID.TryGetValue(7u, out uint subDid)
            || !dats.Portal.TryGet<EnumIDMap>(subDid, out var sub))
        {
            return 0u;
        }

        return sub.ClientEnumToID.TryGetValue(poseEnum, out uint did) ? did : 0u;
    }

    /// <summary>
    /// Retail's per-part pose transform: <c>Scale(defaultScale) *
    /// Rotate(orientation) * Translate(origin)</c> — the SAME composition
    /// both <c>RetailPaperdollPoseApplicator.Apply</c> and
    /// <see cref="ChargenPreviewEntityBuilder"/>'s pose steps use, whether
    /// the (origin, orientation) pair comes from a held final frame or an
    /// interpolated idle-cycle frame.
    /// </summary>
    public static Matrix4x4 ComposePartTransform(Vector3 defaultScale, Vector3 origin, Quaternion orientation) =>
        Matrix4x4.CreateScale(defaultScale)
        * Matrix4x4.CreateFromQuaternion(orientation)
        * Matrix4x4.CreateTranslation(origin);
}