using System;
using System.Collections.Generic;
using System.Linq;
using TabletTester2025.Models;

namespace TabletTester2025.Services
{
    public readonly record struct HardnessStatistics(
        double Average,
        double AverageDeviation,
        double RsdPercent,
        double Maximum,
        double Minimum,
        int Count,
        bool IsPass);

    public static class TestCalculationService
    {
        public static HardnessStatistics CalculateHardness(
            IReadOnlyCollection<double> values,
            double internalMin,
            double internalMax,
            int requiredCount)
        {
            var validValues = values
                .Where(value => double.IsFinite(value) && value > 0)
                .ToList();

            if (validValues.Count == 0)
                return new HardnessStatistics(0, 0, 0, 0, 0, 0, false);

            double average = validValues.Average();
            double averageDeviation = validValues.Average(value => Math.Abs(value - average));
            double standardDeviation = CalculateSampleStandardDeviation(validValues, average);
            double rsd = average == 0 ? 0 : standardDeviation / average * 100;
            bool countMet = validValues.Count >= Math.Max(1, requiredCount);
            bool inRange = validValues.All(value => value >= internalMin && value <= internalMax);

            return new HardnessStatistics(
                average,
                averageDeviation,
                rsd,
                validValues.Max(),
                validValues.Min(),
                validValues.Count,
                countMet && inRange);
        }

        public static double CalculateFriabilityLossPercent(double weightBefore, double weightAfter)
        {
            if (!double.IsFinite(weightBefore) || !double.IsFinite(weightAfter) || weightBefore <= 0)
                throw new InvalidOperationException("脆碎前重量必须大于0");

            if (weightAfter < 0)
                throw new InvalidOperationException("脆碎后重量数据异常");

            if (weightAfter > weightBefore)
                throw new InvalidOperationException("脆碎后重量不能大于初始重量");

            return (weightBefore - weightAfter) / weightBefore * 100;
        }

        public static bool TryGetDissolutionRateAt30Min(
            IReadOnlyList<double> times,
            IReadOnlyList<double> values,
            out double rate)
        {
            rate = 0;
            if (times.Count == 0 || times.Count != values.Count)
                return false;

            var points = times
                .Zip(values, (time, value) => new { Time = time, Value = value })
                .Where(point => double.IsFinite(point.Time)
                    && double.IsFinite(point.Value)
                    && point.Time >= 0
                    && point.Value >= 0
                    && point.Value <= 150)
                .OrderBy(point => point.Time)
                .ToList();

            if (points.Count == 0)
                return false;

            var exact = points.FirstOrDefault(point => Math.Abs(point.Time - 30) < 0.0001);
            if (exact != null)
            {
                rate = exact.Value;
                return true;
            }

            var before = points.LastOrDefault(point => point.Time < 30);
            var after = points.FirstOrDefault(point => point.Time > 30);
            if (before == null || after == null || after.Time <= before.Time)
                return false;

            double fraction = (30 - before.Time) / (after.Time - before.Time);
            rate = before.Value + (after.Value - before.Value) * fraction;
            return double.IsFinite(rate);
        }

        public static double CalculateRSquared(IReadOnlyList<double> timeMinutes, IReadOnlyList<double> concentration)
        {
            if (timeMinutes.Count < 2 || timeMinutes.Count != concentration.Count)
                return 0;

            int n = timeMinutes.Count;
            double sumX = timeMinutes.Sum();
            double sumY = concentration.Sum();
            double sumXY = timeMinutes.Zip(concentration, (x, y) => x * y).Sum();
            double sumX2 = timeMinutes.Select(x => x * x).Sum();
            double sumY2 = concentration.Select(y => y * y).Sum();

            double numerator = n * sumXY - sumX * sumY;
            double denominator = Math.Sqrt((n * sumX2 - sumX * sumX) * (n * sumY2 - sumY * sumY));
            if (denominator <= 0 || double.IsNaN(denominator))
                return 0;

            double r = numerator / denominator;
            double result = r * r;
            return double.IsFinite(result) ? result : 0;
        }

        public static bool ResolveCurrentTestQualified(
            TestType currentTest,
            bool hardnessPass,
            bool friabilityPass,
            bool disintegrationPass,
            bool dissolutionPass)
        {
            return currentTest switch
            {
                TestType.Hardness => hardnessPass,
                TestType.Friability => friabilityPass,
                TestType.Disintegration => disintegrationPass,
                TestType.Dissolution => dissolutionPass,
                _ => false
            };
        }

        private static double CalculateSampleStandardDeviation(IReadOnlyList<double> values, double average)
        {
            if (values.Count < 2)
                return 0;

            double sum = values.Sum(value => Math.Pow(value - average, 2));
            return Math.Sqrt(sum / (values.Count - 1));
        }
    }
}