using System;

namespace Footwear_Test_methodsfor_wholeshoe_Slipresistanceperformance.Models
{
    public sealed record SlipDeviceSnapshot(
        DateTime Timestamp,
        double VerticalLoadN,
        double HorizontalFrictionN,
        double DisplacementMm,
        bool IsTestRunning,
        bool IsResetting,
        bool IsConnected,
        string LastError)
    {
        // 低载荷段（加载/抬升阶段）垂直力很小，H/V 会放大成无意义尖峰（现场曲线冲到 1.4）。
        // GB/T 3903.6 初始压力为 50N，载荷低于该量级时摩擦系数无意义，置零以保证曲线干净。
        public const double MinimumLoadForCoefficientN = 30.0;

        public double FrictionCoefficient => Math.Abs(VerticalLoadN) >= MinimumLoadForCoefficientN
            ? HorizontalFrictionN / VerticalLoadN
            : 0;

        public static SlipDeviceSnapshot Offline(string error = "") =>
            new(DateTime.Now, 0, 0, 0, false, false, false, error);
    }
}