using MathNet.Numerics.Interpolation;
using System;
using System.Collections.Generic;
using System.Linq;

namespace ConductivityApp.GBStandard
{
    /// <summary>
    /// GB/T 32064-2015 标准计算器（严格遵循国标）
    /// 瞬态平面热源测试法计算导热系数和热扩散系数
    /// </summary>
    public class GB32064Calculator
    {
        #region 结构定义
        public struct BridgeConfig
        {
            public double Rs { get; set; }  // 串联电阻 (Ω)
            public double RL { get; set; }  // 引线电阻 (Ω)
        }

        public struct ProbeConfig
        {
            public double R0 { get; set; }       // 初始电阻 (Ω)
            public double Alpha { get; set; }    // 电阻温度系数 (1/K)
            public double RadiusMM { get; set; } // 探头半径 (mm)
            public int CoilCount { get; set; }   // 探头环数
        }

        public struct TestConfig
        {
            public double P0 { get; set; }            // 输出功率 (W)
            public double SampleDensity { get; set; } // 样品密度 (kg/m³)
        }

        public struct CalculationResult
        {
            public bool IsValid { get; set; }
            public double ThermalConductivity { get; set; } // λ - W/(m·K)
            public double ThermalDiffusivity { get; set; }  // α - m²/s
            public double SpecificHeatCapacity { get; set; } // Cp - J/(kg·K)
            public double CorrectionTime { get; set; }      // tc - s
            public double RSquared { get; set; }
            public string ValidationMessage { get; set; }
        }
        #endregion

        #region 常量定义（根据国标GB/T 32064-2015）
        private const double TAU_MAX_SQUARED_LOWER = 0.3; // τ_max²的最小值（国标5.3.4要求）
        private const double TAU_MAX_SQUARED_UPPER = 1.0; // τ_max²的最大值（国标5.3.4要求）
        private const double PROBING_DEPTH_RATIO_LOWER = 1.1; // 探测深度/探头半径最小值
        private const double PROBING_DEPTH_RATIO_UPPER = 2.0; // 探测深度/探头半径最大值
        private const double MIN_DATA_COUNT = 100; // 最小数据点数（国标5.3.3.3）
        private const double MIN_TIME_INTERVAL = 0.1; // 最小时间间隔(s)（国标5.3.3.3）
        private double PI_POW_1_5 = Math.Pow(Math.PI, 1.5); // π^(3/2)
        #endregion

        #region 私有字段
        private readonly BridgeConfig _bridge;
        private readonly ProbeConfig _probe;
        private readonly TestConfig _test;
        private IInterpolation _tauDInterpolation;
        #endregion

        #region 构造函数
        public GB32064Calculator(BridgeConfig bridge, ProbeConfig probe, TestConfig test)
        {
            _bridge = bridge;
            _probe = probe;
            _test = test;

            ValidateConfigurations();
            InitializeTauDTable();
        }
        #endregion

        #region 配置验证
        private void ValidateConfigurations()
        {
            var errors = new List<string>();

            if (_probe.R0 <= 0) errors.Add("探头初始电阻R0必须大于0");
            if (_probe.Alpha <= 0) errors.Add("探头温度系数α必须大于0");
            if (_probe.RadiusMM <= 0) errors.Add("探头半径必须大于0");
            if (_probe.CoilCount < 1) errors.Add("探头环数应大于0");

            if (_bridge.Rs <= 0) errors.Add("串联电阻Rs必须大于0");
            if (_bridge.RL < 0) errors.Add("引线电阻RL不能为负");

            if (_test.P0 <= 0) errors.Add("输出功率P0必须大于0");
            if (_test.SampleDensity <= 0) errors.Add("样品密度必须大于0");

            if (errors.Count > 0)
            {
                throw new ArgumentException($"配置验证失败:\n{string.Join("\n", errors)}");
            }
        }
        #endregion

        #region 核心计算方法

        public CalculationResult Calculate(double[] timeArray, double[] deltaUArray, double currentMA = 120.0)
        {
            try
            {
                // 1. 数据验证
                if (!ValidateInputData(timeArray, deltaUArray))
                {
                    return InvalidResult("输入数据验证失败");
                }

                double I0 = currentMA / 1000.0; // mA转A

                // 2. 计算ΔT(t) - 国标公式(3)
                double[] deltaT = CalculateTemperatureIncrements(deltaUArray, I0);

                // 3. 迭代求解热扩散系数α和校正时间tc
                var (alpha, tc) = IterateThermalDiffusivity(timeArray, deltaT);

                // 4. 验证τ_max²是否符合国标要求
                double r = _probe.RadiusMM / 1000.0;
                double tmax = timeArray.Max();
                double tauMaxSquared = CalculateTauMaxSquared(tmax, tc, alpha, r);

                if (tauMaxSquared < TAU_MAX_SQUARED_LOWER || tauMaxSquared > TAU_MAX_SQUARED_UPPER)
                {
                    return InvalidResult($"τ_max²({tauMaxSquared:F3})不在国标要求范围[{TAU_MAX_SQUARED_LOWER}, {TAU_MAX_SQUARED_UPPER}]内，测试无效");
                }

                // 5. 计算导热系数λ - 国标公式(4)
                double lambda = CalculateThermalConductivity(timeArray, deltaT, alpha, tc);

                // 6. 计算比热容Cp - Cp = λ / (ρ × α)
                double cp = CalculateSpecificHeatCapacity(lambda, alpha);

                // 7. 验证测试结果有效性
                var validation = ValidateTestResults(timeArray, alpha, tc, tauMaxSquared);

                // 8. 计算R²
                double rSquared = CalculateRSquared(timeArray, deltaT, alpha, tc, lambda);

                return new CalculationResult
                {
                    IsValid = validation.IsValid,
                    ThermalConductivity = lambda,
                    ThermalDiffusivity = alpha,
                    SpecificHeatCapacity = cp,
                    CorrectionTime = tc,
                    RSquared = rSquared,
                    ValidationMessage = string.Join("\n", validation.Messages)
                };
            }
            catch (Exception ex)
            {
                return InvalidResult($"计算失败: {ex.Message}");
            }
        }

        /// <summary>
        /// 计算温度增量ΔT(t) - 国标公式(3)
        /// </summary>
        private double[] CalculateTemperatureIncrements(double[] deltaUArray, double I0)
        {
            double[] deltaT = new double[deltaUArray.Length];

            for (int i = 0; i < deltaUArray.Length; i++)
            {
                double deltaU = deltaUArray[i];

                // 国标公式(3): ΔT(t) = (Rs + RL + R0) × ΔU(t) / [(I0 × Rs - ΔU(t)) × α × R0]
                double numerator = (_bridge.Rs + _bridge.RL + _probe.R0) * deltaU;
                double denominator = (I0 * _bridge.Rs - deltaU) * _probe.Alpha * _probe.R0;

                if (Math.Abs(denominator) < 1e-12)
                {
                    throw new InvalidOperationException($"分母接近0，无法计算ΔT(t)");
                }

                deltaT[i] = numerator / denominator;
            }

            return deltaT;
        }

        /// <summary>
        /// 迭代求解热扩散系数α和校正时间tc
        /// </summary>
        private (double alpha, double tc) IterateThermalDiffusivity(double[] timeArray, double[] deltaT)
        {
            // 初始猜测值
            double bestAlpha = 1e-6;      // 常见建筑材料的热扩散系数
            //double bestAlpha = 3.58e-7;      // 常见建筑材料的热扩散系数
            double bestTc = timeArray.Max() * 0.01; // 测试时间的1%作为初始校正时间
            double bestError = double.MaxValue;

            // 使用最小二乘法迭代优化
            int maxIterations = 200;
            double convergenceThreshold = 1e-8;

            for (int iteration = 0; iteration < maxIterations; iteration++)
            {
                double alphaStep = bestAlpha * 0.1 / (iteration + 1);
                double tcStep = 0.001 / (iteration + 1);

                var candidates = new List<(double alpha, double tc, double error)>
                {
                    (bestAlpha, bestTc, CalculateFitError(timeArray, deltaT, bestAlpha, bestTc)),
                    (bestAlpha + alphaStep, bestTc, CalculateFitError(timeArray, deltaT, bestAlpha + alphaStep, bestTc)),
                    (bestAlpha - alphaStep, bestTc, CalculateFitError(timeArray, deltaT, bestAlpha - alphaStep, bestTc)),
                    (bestAlpha, bestTc + tcStep, CalculateFitError(timeArray, deltaT, bestAlpha, bestTc + tcStep)),
                    (bestAlpha, bestTc - tcStep, CalculateFitError(timeArray, deltaT, bestAlpha, bestTc - tcStep))
                };

                var bestCandidate = candidates.OrderBy(c => c.error).First();

                double improvement = bestError - bestCandidate.error;
                if (improvement > 0)
                {
                    bestAlpha = bestCandidate.alpha;
                    bestTc = bestCandidate.tc;
                    bestError = bestCandidate.error;
                }

                // 收敛条件
                if (Math.Abs(improvement) < convergenceThreshold && iteration > 20)
                {
                    break;
                }
            }

            return (bestAlpha, bestTc);
        }

        /// <summary>
        /// 计算拟合误差
        /// </summary>
        private double CalculateFitError(double[] timeArray, double[] deltaT, double alpha, double tc)
        {
            double totalError = 0;
            int count = 0;
            double r = _probe.RadiusMM / 1000.0;

            for (int i = 0; i < timeArray.Length; i++)
            {
                if (timeArray[i] > tc)
                {
                    double tau = CalculateTau(timeArray[i], tc, alpha, r);

                    if (tau >= TAU_MAX_SQUARED_LOWER && tau <= TAU_MAX_SQUARED_UPPER)
                    {
                        try
                        {
                            double dTau = _tauDInterpolation.Interpolate(tau);
                            // 理论ΔT = [P0 / (π^(3/2) × r × λ)] × D(τ)
                            // 这里假设λ=1，因为我们只关心相对误差
                            double theoreticalDeltaT = _test.P0 * dTau / (PI_POW_1_5 * r);
                            double error = Math.Pow(deltaT[i] - theoreticalDeltaT, 2);
                            totalError += error;
                            count++;
                        }
                        catch
                        {
                            continue;
                        }
                    }
                }
            }

            return count > 0 ? Math.Sqrt(totalError / count) : double.MaxValue;
        }

        /// <summary>
        /// 计算导热系数λ - 国标公式(4)，使用国标范围内的数据
        /// </summary>
        private double CalculateThermalConductivity(double[] timeArray, double[] deltaT, double alpha, double tc)
        {
            double r = _probe.RadiusMM / 1000.0;
            var validPoints = new List<(double dTau, double deltaT)>();

            // 收集有效数据点（严格按国标τ范围筛选）
            int validCount = 0;
            int totalCount = 0;

            for (int i = 0; i < timeArray.Length; i++)
            {
                totalCount++;

                // 只使用校正后的数据（t > t_c）
                if (timeArray[i] > tc)
                {
                    double tau = CalculateTau(timeArray[i], tc, alpha, r);

                    // 只使用τ在国标要求范围内的数据点
                    if (tau >= TAU_MAX_SQUARED_LOWER && tau <= TAU_MAX_SQUARED_UPPER)
                    {
                        try
                        {
                            double dTau = _tauDInterpolation.Interpolate(tau);
                            validPoints.Add((dTau, deltaT[i]));
                            validCount++;
                        }
                        catch
                        {
                            continue;
                        }
                    }
                }
            }

            if (validPoints.Count < 10)
            {
                throw new InvalidOperationException(
                    $"有效数据点不足({validPoints.Count})，无法计算导热系数\n" +
                    $"国标要求：在τ范围[{TAU_MAX_SQUARED_LOWER}, {TAU_MAX_SQUARED_UPPER}]内应有足够数据点");
            }

            // 线性回归：ΔT(τ) = [P₀ / (π^(3/2) × r × λ)] × D(τ)
            double[] dTauArray = validPoints.Select(p => p.dTau).ToArray();
            double[] deltaTArray = validPoints.Select(p => p.deltaT).ToArray();

            var (slope, intercept) = LinearRegression(dTauArray, deltaTArray);

            // 检查斜率是否合理
            if (Math.Abs(slope) < 1e-12)
            {
                throw new InvalidOperationException("回归斜率接近0，计算结果不可靠");
            }

            // 计算导热系数 λ = P₀ / (π^(3/2) × r × slope) - 国标公式(4)
            double lambda = _test.P0 / (PI_POW_1_5 * r * slope);

            return lambda;
        }

        /// <summary>
        /// 计算无量纲时间τ - 国标公式(5)
        /// τ = √[(t - t_c) / (r²/a)]
        /// 等价于：τ = √[(t - t_c) * a / r²]
        /// </summary>
        private double CalculateTau(double time, double tc, double alpha, double r)
        {
            if (time <= tc)
            {
                return 0;
            }

            // 国标公式(5): τ = √[(t - t_c) / (r²/a)]
            double theta = (r * r) / alpha; // 特征时间 θ = r²/a
            double tau = Math.Sqrt((time - tc) / theta);

            return tau;
        }

        /// <summary>
        /// 计算比热容Cp - Cp = λ / (ρ × α)
        /// </summary>
        private double CalculateSpecificHeatCapacity(double lambda, double alpha)
        {
            if (alpha <= 0 || _test.SampleDensity <= 0)
            {
                throw new InvalidOperationException("热扩散系数或密度无效，无法计算比热容");
            }

            double cp = lambda / (_test.SampleDensity * alpha);
            return cp;
        }

        /// <summary>
        /// 验证测试结果 - 严格遵循国标5.3.4节要求
        /// </summary>
        private ValidationResult ValidateTestResults(double[] timeArray, double alpha, double tc, double tauMaxSquared)
        {
            var result = new ValidationResult { IsValid = true };
            double r = _probe.RadiusMM / 1000.0; // 转换为米
            double tmax = timeArray.Max();

            // 1. 验证τ_max²是否满足国标要求
            if (tauMaxSquared < TAU_MAX_SQUARED_LOWER)
            {
                result.IsValid = false;
                result.Messages.Add($"τ_max²({tauMaxSquared:F3}) < {TAU_MAX_SQUARED_LOWER}，测试时间不足，结果无效");
            }
            else if (tauMaxSquared > TAU_MAX_SQUARED_UPPER)
            {
                result.IsValid = false;
                result.Messages.Add($"τ_max²({tauMaxSquared:F3}) > {TAU_MAX_SQUARED_UPPER}，测试时间过长，结果无效");
            }
            else
            {
                result.Messages.Add($"τ_max²({tauMaxSquared:F3})满足国标要求[{TAU_MAX_SQUARED_LOWER}, {TAU_MAX_SQUARED_UPPER}]");
            }

            // 2. 计算探测深度 ΔP_probe = 2√(a·t_max) （国标5.3.4）
            double probingDepth = 2 * Math.Sqrt(alpha * tmax);
            double probingDepthRatio = probingDepth / r;

            // 3. 验证探测深度是否满足国标要求
            if (probingDepthRatio < PROBING_DEPTH_RATIO_LOWER)
            {
                result.IsValid = false;
                result.Messages.Add($"探测深度/探头半径({probingDepthRatio:F2}) < {PROBING_DEPTH_RATIO_LOWER}，样品厚度可能不足");
            }
            else if (probingDepthRatio > PROBING_DEPTH_RATIO_UPPER)
            {
                result.IsValid = false;
                result.Messages.Add($"探测深度/探头半径({probingDepthRatio:F2}) > {PROBING_DEPTH_RATIO_UPPER}，可能超出测试范围");
            }
            else
            {
                result.Messages.Add($"探测深度/探头半径({probingDepthRatio:F2})满足国标要求[{PROBING_DEPTH_RATIO_LOWER}, {PROBING_DEPTH_RATIO_UPPER}]");
            }

            // 4. 验证数据点数量（国标5.3.3.3要求采集次数大于100次）
            if (timeArray.Length < MIN_DATA_COUNT)
            {
                result.Messages.Add($"警告：采集次数({timeArray.Length})少于国标要求的{MIN_DATA_COUNT}次");
            }
            else
            {
                result.Messages.Add($"采集次数({timeArray.Length})满足国标要求(≥{MIN_DATA_COUNT}次)");
            }

            // 5. 验证数据采集间隔（国标5.3.3.3要求不小于0.1s）
            if (timeArray.Length > 1)
            {
                double minInterval = timeArray[1] - timeArray[0];
                for (int i = 2; i < timeArray.Length; i++)
                {
                    double interval = timeArray[i] - timeArray[i - 1];
                    if (interval < minInterval) minInterval = interval;
                }

                if (minInterval < MIN_TIME_INTERVAL)
                {
                    result.Messages.Add($"警告：数据采集间隔({minInterval:F3}s)小于国标要求的{MIN_TIME_INTERVAL}s");
                }
                else
                {
                    result.Messages.Add($"数据采集间隔({minInterval:F3}s)满足国标要求(≥{MIN_TIME_INTERVAL}s)");
                }
            }

            // 6. 生成详细验证报告
            result.Messages.Insert(0, $"【国标GB/T 32064-2015测试结果有效性验证】");
            result.Messages.Insert(1, $"测试总时间: {tmax:F2}s，校正时间: {tc:F4}s");
            result.Messages.Insert(2, $"热扩散系数α: {alpha:E6} m²/s");
            result.Messages.Insert(3, $"探头半径r: {r * 1000:F2}mm，探测深度: {probingDepth * 1000:F2}mm");
            result.Messages.Insert(4, $"验证依据：5.3.4节 测试结果有效性验证");

            return result;
        }

        /// <summary>
        /// 计算τ_max²
        /// </summary>
        private double CalculateTauMaxSquared(double tmax, double tc, double alpha, double r)
        {
            // 国标公式：τ_max² = (t_max - t_c) × a / r²
            if (r <= 0) throw new ArgumentException("探头半径必须大于0");
            if (tmax <= tc) return 0;

            double tauMaxSquared = (tmax - tc) * alpha / (r * r);
            return tauMaxSquared;
        }

        /// <summary>
        /// 计算R²拟合优度
        /// </summary>
        private double CalculateRSquared(double[] timeArray, double[] deltaT, double alpha, double tc, double lambda)
        {
            var observed = new List<double>();
            var predicted = new List<double>();
            double r = _probe.RadiusMM / 1000.0;

            for (int i = 0; i < timeArray.Length; i++)
            {
                if (timeArray[i] > tc)
                {
                    double tau = CalculateTau(timeArray[i], tc, alpha, r);
                    if (tau >= TAU_MAX_SQUARED_LOWER && tau <= TAU_MAX_SQUARED_UPPER)
                    {
                        try
                        {
                            double dTau = _tauDInterpolation.Interpolate(tau);
                            double theoretical = _test.P0 * dTau / (PI_POW_1_5 * r * lambda);

                            observed.Add(deltaT[i]);
                            predicted.Add(theoretical);
                        }
                        catch
                        {
                            continue;
                        }
                    }
                }
            }

            if (observed.Count < 2) return 0;

            double meanObserved = observed.Average();
            double ssTotal = observed.Sum(o => Math.Pow(o - meanObserved, 2));
            double ssResidual = observed.Zip(predicted, (o, p) => Math.Pow(o - p, 2)).Sum();

            if (Math.Abs(ssTotal) < 1e-12) return 0;

            double rSquared = 1 - (ssResidual / ssTotal);
            return rSquared;
        }
        #endregion

        #region 辅助方法
        private CalculationResult InvalidResult(string message)
        {
            return new CalculationResult
            {
                IsValid = false,
                ValidationMessage = message,
                ThermalConductivity = 0,
                ThermalDiffusivity = 0,
                SpecificHeatCapacity = 0,
                CorrectionTime = 0,
                RSquared = 0
            };
        }

        private bool ValidateInputData(double[] timeArray, double[] deltaUArray)
        {
            if (timeArray == null || deltaUArray == null)
            {
                throw new ArgumentNullException("时间和电压数据不能为空");
            }

            if (timeArray.Length != deltaUArray.Length)
            {
                throw new ArgumentException("时间和电压数据长度不一致");
            }

            if (timeArray.Length < 20)
            {
                throw new ArgumentException($"数据点数量({timeArray.Length})不足，至少需要20个点");
            }

            // 检查时间单调递增
            for (int i = 1; i < timeArray.Length; i++)
            {
                if (timeArray[i] <= timeArray[i - 1])
                {
                    throw new ArgumentException($"时间数据必须严格单调递增，第{i}点不符合要求");
                }
            }

            return true;
        }

        private (double slope, double intercept) LinearRegression(double[] x, double[] y)
        {
            if (x.Length != y.Length || x.Length < 2)
                throw new ArgumentException("线性回归需要至少2个数据点且x、y长度相等");

            double xAvg = x.Average();
            double yAvg = y.Average();

            double numerator = 0;
            double denominator = 0;

            for (int i = 0; i < x.Length; i++)
            {
                numerator += (x[i] - xAvg) * (y[i] - yAvg);
                denominator += (x[i] - xAvg) * (x[i] - xAvg);
            }

            if (Math.Abs(denominator) < 1e-12)
                throw new InvalidOperationException("数据方差太小，无法进行线性回归");

            double slope = numerator / denominator;
            double intercept = yAvg - slope * xAvg;

            return (slope, intercept);
        }
        #endregion

        #region τ-D(τ)插值表初始化
        private void InitializeTauDTable()
        {
            // 使用国标理论公式计算 D(τ) = (√(τ²+1) - 1) / τ
            var tauList = new List<double>();
            var dList = new List<double>();

            // 根据国标要求，τ范围通常为0.01-3.0
            for (double tau = 0.01; tau <= 3.0; tau += 0.01)
            {
                tauList.Add(tau);
                double d = (Math.Sqrt(tau * tau + 1.0) - 1.0) / tau;
                dList.Add(d);
            }

            double[] tauValues = tauList.ToArray();
            double[] dValues = dList.ToArray();

            _tauDInterpolation = CubicSpline.InterpolateAkimaSorted(tauValues, dValues);
        }
        #endregion

        #region 内部类 
        private class ValidationResult
        {
            public bool IsValid { get; set; }
            public List<string> Messages { get; } = new List<string>();
        }
        #endregion

        #region 土壤测试辅助方法（但不影响核心计算）
        /// <summary>
        /// 用于土壤测试的参数设置建议（仅建议，不影响计算）
        /// </summary>
        public static class SoilTestRecommendations
        {
            /// <summary>
            /// 根据土壤类型获取建议的测试参数
            /// </summary>
            /// <param name="soilType">土壤类型（干土、湿土、冻土等）</param>
            /// <returns>建议的测试时间范围</returns>
            public static (double minTime, double maxTime) GetRecommendedTestTime(string soilType)
            {
                // 土壤热扩散系数典型范围：1e-7 到 1e-6 m²/s
                // 使用典型探头半径6.4mm计算
                double r = 0.0064; // 米

                // 根据τ_max² = (t * a) / r²，反推时间
                // t = τ_max² * r² / a

                // 对于导热系数较低的土壤（干土、冻土）
                if (soilType.Contains("冻土") || soilType.Contains("干土"))
                {
                    double alpha = 0.5e-6; // 较低的热扩散系数
                    double t_min = TAU_MAX_SQUARED_LOWER * r * r / alpha;
                    double t_max = TAU_MAX_SQUARED_UPPER * r * r / alpha;
                    return (t_min, t_max);
                }
                // 对于导热系数较高的土壤（湿土）
                else if (soilType.Contains("湿土"))
                {
                    double alpha = 1.2e-6; // 较高的热扩散系数
                    double t_min = TAU_MAX_SQUARED_LOWER * r * r / alpha;
                    double t_max = TAU_MAX_SQUARED_UPPER * r * r / alpha;
                    return (t_min, t_max);
                }
                // 默认值
                else
                {
                    double alpha = 1e-6; // 典型热扩散系数
                    double t_min = TAU_MAX_SQUARED_LOWER * r * r / alpha;
                    double t_max = TAU_MAX_SQUARED_UPPER * r * r / alpha;
                    return (t_min, t_max);
                }
            }
        }
        #endregion
    }
}