using AcDream.Core.Net.Messages;
using AcDream.Core.Physics;
using DatReaderWriter.DBObjs;

namespace AcDream.App.Rendering;

/// <summary>
/// Builds the initial motion-table state for a server CreateObject using the
/// same description-then-enter-world lifecycle as retail.
/// </summary>
/// <remarks>
/// Retail oracle: <c>ACCObjectMaint::CreateObject</c> (0x00558870) calls
/// <c>CPhysicsObj::set_description</c> (0x00514F40), which applies the wire
/// MovementData. <c>SmartBox::HandleCreateObject</c> (0x00454C80) then calls
/// <c>CPhysicsObj::enter_world</c> (0x00516170), reaching
/// <c>CPartArray::HandleEnterWorld</c> (0x00517D70) and
/// <c>MotionTableManager::HandleEnterWorld</c> (0x0051BDD0).
/// </remarks>
internal static class SpawnMotionInitializer
{
    internal readonly record struct Plan(uint Style, uint Motion);

    public static AnimationSequencer Create(
        Setup setup,
        MotionTable motionTable,
        IAnimationLoader loader,
        CreateObject.ServerMotionState? wireState)
    {
        var sequencer = new AnimationSequencer(setup, motionTable, loader);
        Plan plan = ResolvePlan(motionTable, wireState);

        // set_description: install the table default, then apply MovementData.
        sequencer.InitializeState();
        sequencer.SetCycle(plan.Style, plan.Motion);

        // enter_world: discard description-time transition links so the first
        // rendered pose is the server-authored persistent cycle. A corpse's
        // NonCombat+Dead therefore starts fallen; a door's NonCombat+On/Off
        // comes from the same wire path with no object-type special case.
        sequencer.Manager.HandleEnterWorld();
        return sequencer;
    }

    /// <summary>
    /// Replays description-time MovementData into the same retained PartArray
    /// sequencer. This is used only when a fresher same-incarnation CreateObject
    /// interrupted initial hydration before the object crossed its ready edge;
    /// completed objects consume the packet through SetObjectMovement instead.
    /// </summary>
    public static void Reinitialize(
        AnimationSequencer sequencer,
        MotionTable motionTable,
        CreateObject.ServerMotionState? wireState)
    {
        ArgumentNullException.ThrowIfNull(sequencer);
        ArgumentNullException.ThrowIfNull(motionTable);
        Plan plan = ResolvePlan(motionTable, wireState);
        sequencer.Reset();
        sequencer.InitializeState();
        sequencer.SetCycle(plan.Style, plan.Motion);
        sequencer.Manager.HandleEnterWorld();
    }

    internal static Plan ResolvePlan(
        MotionTable motionTable,
        CreateObject.ServerMotionState? wireState)
    {
        uint style = wireState is { Stance: > 0 } state
            ? 0x80000000u | state.Stance
            : (uint)motionTable.DefaultStyle;

        uint motion = MotionCommand.Ready;
        if (wireState?.ForwardCommand is ushort command && command > 0)
        {
            uint resolved = MotionCommandResolver.ReconstructFullCommand(command);
            motion = resolved != 0
                ? resolved
                : 0x40000000u | command;
        }

        return new Plan(style, motion);
    }
}