using Unity.Mathematics;

namespace ProjectM.Simulation
{
    /// <summary>
    /// Pure mapping from authoritative planar velocity + facing to client animation blend params.
    /// Forward (along facing) -> MoveZ+, right of facing -> MoveX+ (matches the slim controller's 2D
    /// strafe tree: +X=right, +Z=forward). EditMode-tested, no World needed. Burst-safe (no enums/strings).
    /// </summary>
    public static class AnimParamMath
    {
        /// <param name="planarVelocity">World velocity (KinematicCharacterBody.RelativeVelocity for the owner,
        /// or LocalTransform position-delta/dt for remotes). Y is ignored.</param>
        /// <param name="facing">Normalized world planar facing (PlayerFacing.Direction, world XZ as x,y). May be zero.</param>
        /// <param name="maxSpeed">EffectiveCharacterStats.MoveSpeed (normalizer; guarded > 0).</param>
        /// <returns>x = MoveX (strafe, -1..1), y = MoveZ (fwd/back, -1..1), z = Speed (0..1).</returns>
        public static float3 LocomotionParams(float3 planarVelocity, float2 facing, float maxSpeed)
        {
            float2 vWorld = planarVelocity.xz;
            float safeMax = math.max(maxSpeed, 1e-4f);
            float speed = math.saturate(math.length(vWorld) / safeMax);

            // Degenerate facing -> default to world +Z so the basis is well-defined.
            float2 fwd = math.lengthsq(facing) > 1e-6f ? math.normalize(facing) : new float2(0f, 1f);
            float2 right = new float2(fwd.y, -fwd.x); // 90deg clockwise in XZ (right-hand of forward)

            float2 local = new float2(math.dot(vWorld, right), math.dot(vWorld, fwd)) / safeMax;
            local = math.clamp(local, -1f, 1f);
            return new float3(local.x, local.y, speed);
        }
    }
}