using System;
using ActiveProtect.SimulationEnvironment;

namespace ActiveProtect.Models
{
    /// <summary>
    /// 毫米波导引头系统
    /// </summary>
    public class MillimeterWaveGuidanceSystem : BasicGuidanceSystem
    {
        private const double MAX_DETECTION_RANGE = 5000; // 最大探测范围(米)
        private const double FIELD_OF_VIEW = Math.PI / 4; // 视场角(弧度), 45度
        private const double TARGET_RECOGNITION_PROBABILITY = 0.95; // 目标识别概率
        private const double WAVE_FREQUENCY = 94e9; // 毫米波频率(Hz), 94GHz
        private const double PULSE_DURATION = 1e-6; // 脉冲持续时间(秒)
        private const double RECOGNITION_SNR_THRESHOLD = 6; // 识别目标信噪比阈值, 单位dB

        private readonly Random random = new();
        private Vector3D lastTargetPosition;

        public ISimulationManager SimulationManager { get; set; }

        /// <summary>
        /// 毫米波导引头系统构造函数
        /// </summary>
        public MillimeterWaveGuidanceSystem(double maxAcceleration, double guidanceCoefficient, ISimulationManager simulationManager) : base(maxAcceleration, guidanceCoefficient)
        {
            SimulationManager = simulationManager;
            lastTargetPosition = Vector3D.Zero;
        }

        /// <summary>
        /// 更新引导系统
        /// </summary>
        public override void Update(double deltaTime, Vector3D missilePosition, Vector3D missileVelocity)
        {
            base.Update(deltaTime, missilePosition, missileVelocity);

            if (TryDetectTank(missilePosition, missileVelocity, out Vector3D tankPosition))
            {
                //根据目标当前位置和上一次位置计算目标速度
                Vector3D targetVelocity = (tankPosition - lastTargetPosition) / deltaTime;
                lastTargetPosition = tankPosition;

                // 使用基类的比例控制算法
                GuidanceAcceleration = CalculateProportionalNavigation(ProportionalNavigationCoefficient, missilePosition, missileVelocity, tankPosition, targetVelocity);

                if (GuidanceAcceleration.Magnitude() > MaxAcceleration)
                {
                    GuidanceAcceleration = GuidanceAcceleration.Normalize() * MaxAcceleration;
                }

                HasGuidance = true;
            }
            else
            {
                HasGuidance = false;
            }
        }

        /// <summary>
        /// 尝试探测目标
        /// </summary>
        private bool TryDetectTank(Vector3D missilePosition, Vector3D missileVelocity, out Vector3D targetPosition)
        {
            targetPosition = Vector3D.Zero;

            foreach (var element in SimulationManager.GetElements())
            {
                if (element is Tank tank)
                {
                    Vector3D toTarget = tank.Position - missilePosition;
                    double distance = toTarget.Magnitude();

                    if (distance <= MAX_DETECTION_RANGE)
                    {
                        double angle = Math.Acos(Vector3D.DotProduct(toTarget.Normalize(), missileVelocity.Normalize()));

                        if (angle <= FIELD_OF_VIEW / 2)
                        {
                            // 模拟毫米波探测
                            double snr = CalculateSNR(distance, tank.RadarCrossSection);
                            Console.WriteLine($" 80信噪比 {snr}");

                            if(snr > RECOGNITION_SNR_THRESHOLD && random.NextDouble() < TARGET_RECOGNITION_PROBABILITY)
                            {
                                targetPosition = tank.Position;
                                return true;
                            }
                        }
                    }
                }
            }

            return false;
        }

        /// <summary>
        /// 获取导弹状态
        /// </summary>
        public override string GetStatus()
        {
            return base.GetStatus() + $", Target Position: {lastTargetPosition}";
        }

        /// <summary>
        /// 计算信噪比
        /// </summary>
       private static double CalculateSNR(double distance, double radarCrossSection)
        {
            // 雷达参数
            double transmitPower = 100; // 发射功率(W)
            double antennaGain = Math.Pow(10, 30/10); // 天线增益(线性值，从dB转换)
            double wavelength = 3e8 / WAVE_FREQUENCY; // 波长(m)
            double bandwidth = 1e6; // 接收机带宽(Hz)，假设为1MHz
            double noiseFigure = Math.Pow(10, 3/10); // 噪声系数(线性值，假设为3dB)

            // 常量
            double k = 1.38e-23; // 玻尔兹曼常数
            double T0 = 290; // 标准噪声温度(K)

            // 计算接收信号功率
            double signalPower = (transmitPower * Math.Pow(antennaGain, 2) * Math.Pow(wavelength, 2) * radarCrossSection) 
                                / (Math.Pow(4 * Math.PI, 3) * Math.Pow(distance, 4));

            // 计算噪声功率
            double noisePower = k * T0 * bandwidth * noiseFigure;

            // 计算信噪比
            double snr = signalPower / noisePower;

            // 转换为dB
            return 10 * Math.Log10(snr);
        }
    }
}