using System;

using System.Linq;

using System.Collections.Generic;

using Newtonsoft.Json;

​

public class Program

{

    private static readonly IDictionary<string, PlanPricingModel> _planPricingModels;

    private static readonly decimal _taxRate; // as a %

    private static readonly PricingModel _pricingModel;

    public static void Main()

    {

        // Change these

        // regular, regular_plus, elite, elite_plus

        string plan = "regular";

        int members = 30;

        int supporters = 0;

        bool yearlyPayment = false;

        bool includeTax = true;

        bool includeSignupFee = false;

        var price = CalculatePrice(plan, members, supporters, yearlyPayment, includeTax, includeSignupFee);

        Console.WriteLine("The price is: {0:0,#}円", price);

    }

    static Program()

    {

        var pricingModel = JsonConvert.DeserializeObject<PricingModel>(GetPricingJson());

        _pricingModel = pricingModel;

        _taxRate = pricingModel.TaxRate;

        _planPricingModels = (pricingModel?.Plans ?? new Dictionary<string, PlanPricingModel>()).ToDictionary(p => p.Key, p => p.Value, StringComparer.OrdinalIgnoreCase);

    }

    public static decimal? CalculatePrice(string plan, int memberCount, int supporterCount, bool yearlyPayment, bool includeTax, bool includeSignupFee = false)

    {

        if (!_planPricingModels.TryGetValue(plan, out var model))

        {

            Console.WriteLine("plan not found");

            return null;

        }

​

        PlanPricingUnitCosts pricingData;

        int defaultMembers;

        if (model.Tiers is not null && model.Tiers.Any())

        {

            var tier = model.Tiers

                .OrderByDescending(t => t.MemberThreshold)

                .FirstOrDefault(t => memberCount >= t.MemberThreshold);

​

            // If we can't find the desired threshold

            tier ??= model.Tiers.OrderBy(t => t.MemberThreshold).First();

​

            pricingData = yearlyPayment ? tier.YearlyUnitCosts : tier.MonthlyUnitCosts;

            defaultMembers = tier.DefaultMembers ?? model.DefaultMembers;

        }

        else

        {

            pricingData = yearlyPayment ? model.YearlyUnitCosts : model.MonthlyUnitCosts;

            defaultMembers = model.DefaultMembers;

        }

​

        if (pricingData == null)

        {

            return null;

        }

​

        var supportersForMembers = model.SupportersPerUser * Math.Max(defaultMembers, memberCount);

        var extraMemberCount = Math.Max(defaultMembers, memberCount) - defaultMembers;

        var extraSupporterCount = Math.Max(0, Math.Max(model.DefaultSupporters, supporterCount) - (model.DefaultSupporters + supportersForMembers));

        var memberCost = (defaultMembers * pricingData.DefaultMemberUnitCost) + (extraMemberCount * pricingData.ExtraMemberUnitCost)

            + (model.DefaultSupporters * pricingData.DefaultSupporterUnitCost) + (extraSupporterCount * pricingData.ExtraSupporterUnitCost);

​

        var planCostSubtotal = model.BasePrice + memberCost;

​

        var periodSubtotal = yearlyPayment ? (planCostSubtotal * model.YearlyMultiplier) : planCostSubtotal;

        decimal finalPrice = periodSubtotal;

​

        if (finalPrice <= 0)

        {

            return null;

        }

​

        if (includeSignupFee)

        {

            finalPrice += CalculateInitialFee(plan, includeTax: true) ?? 0;

        }

​

        if (!includeTax)

        {

            finalPrice = RemoveTax(finalPrice);

        }

​

        return finalPrice;

    }

    private static string GetPricingJson()

    {

        return """

            {"taxRate":10,"defaultSignupFeeInclTax":22000,"supportPlanFeeMonthly":36300,"supportPlanFeeYearly":33000,"plans":{"start":{"defaultMembers":15,"defaultSupporters":0,"monthlyUnitCosts":{"defaultMemberUnitCost":320,"extraMemberUnitCost":320,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":160},"yearlyUnitCosts":{"defaultMemberUnitCost":320,"extraMemberUnitCost":320,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":160},"yearlyMultiplier":10},"standard":{"defaultMembers":40,"defaultSupporters":0,"monthlyUnitCosts":{"defaultMemberUnitCost":270,"extraMemberUnitCost":270,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":160},"yearlyUnitCosts":{"defaultMemberUnitCost":270,"extraMemberUnitCost":270,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":160},"yearlyMultiplier":10},"premium":{"defaultMembers":100,"defaultSupporters":0,"monthlyUnitCosts":{"defaultMemberUnitCost":220,"extraMemberUnitCost":220,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":160},"yearlyUnitCosts":{"defaultMemberUnitCost":220,"extraMemberUnitCost":220,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":160},"yearlyMultiplier":10},"lite":{"defaultMembers":10,"defaultSupporters":0,"monthlyUnitCosts":{"defaultMemberUnitCost":390,"extraMemberUnitCost":390,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":330,"extraMemberUnitCost":330,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290},"yearlyMultiplier":12},"basic":{"defaultMembers":10,"defaultSupporters":0,"monthlyUnitCosts":{"defaultMemberUnitCost":690,"extraMemberUnitCost":690,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":580,"extraMemberUnitCost":580,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290},"yearlyMultiplier":12},"basic_plus":{"defaultMembers":10,"defaultSupporters":0,"supportersPerUser":1,"monthlyUnitCosts":{"defaultMemberUnitCost":690,"extraMemberUnitCost":690,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":580,"extraMemberUnitCost":580,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290},"yearlyMultiplier":12},"advanced":{"defaultMembers":10,"defaultSupporters":0,"monthlyUnitCosts":{"defaultMemberUnitCost":890,"extraMemberUnitCost":890,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":750,"extraMemberUnitCost":750,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290},"yearlyMultiplier":12},"regular":{"defaultMembers":15,"defaultSupporters":0,"yearlyMultiplier":12,"tiers":[{"memberThreshold":15,"defaultMembers":15,"monthlyUnitCosts":{"defaultMemberUnitCost":1320,"extraMemberUnitCost":690,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":1100,"extraMemberUnitCost":580,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}},{"memberThreshold":30,"defaultMembers":30,"monthlyUnitCosts":{"defaultMemberUnitCost":954,"extraMemberUnitCost":690,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":795,"extraMemberUnitCost":580,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}},{"memberThreshold":50,"defaultMembers":50,"monthlyUnitCosts":{"defaultMemberUnitCost":792,"extraMemberUnitCost":690,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":660,"extraMemberUnitCost":580,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}}]},"regular_plus":{"defaultMembers":15,"defaultSupporters":0,"supportersPerUser":1,"yearlyMultiplier":12,"tiers":[{"memberThreshold":15,"defaultMembers":15,"monthlyUnitCosts":{"defaultMemberUnitCost":1320,"extraMemberUnitCost":690,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":1100,"extraMemberUnitCost":580,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}},{"memberThreshold":30,"defaultMembers":30,"monthlyUnitCosts":{"defaultMemberUnitCost":954,"extraMemberUnitCost":690,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":795,"extraMemberUnitCost":580,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}},{"memberThreshold":50,"defaultMembers":50,"monthlyUnitCosts":{"defaultMemberUnitCost":792,"extraMemberUnitCost":690,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":660,"extraMemberUnitCost":580,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}}]},"elite":{"defaultMembers":15,"defaultSupporters":0,"yearlyMultiplier":12,"tiers":[{"memberThreshold":15,"defaultMembers":15,"monthlyUnitCosts":{"defaultMemberUnitCost":1704,"extraMemberUnitCost":890,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":1420,"extraMemberUnitCost":750,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}},{"memberThreshold":30,"defaultMembers":30,"monthlyUnitCosts":{"defaultMemberUnitCost":1236,"extraMemberUnitCost":890,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":1030,"extraMemberUnitCost":750,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}},{"memberThreshold":50,"defaultMembers":50,"monthlyUnitCosts":{"defaultMemberUnitCost":1020,"extraMemberUnitCost":890,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":850,"extraMemberUnitCost":750,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}}]},"elite_plus":{"defaultMembers":15,"defaultSupporters":0,"supportersPerUser":1,"yearlyMultiplier":12,"tiers":[{"memberThreshold":15,"defaultMembers":15,"monthlyUnitCosts":{"defaultMemberUnitCost":1704,"extraMemberUnitCost":890,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":1420,"extraMemberUnitCost":750,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}},{"memberThreshold":30,"defaultMembers":30,"monthlyUnitCosts":{"defaultMemberUnitCost":1236,"extraMemberUnitCost":890,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":1030,"extraMemberUnitCost":750,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}},{"memberThreshold":50,"defaultMembers":50,"monthlyUnitCosts":{"defaultMemberUnitCost":1020,"extraMemberUnitCost":890,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":350},"yearlyUnitCosts":{"defaultMemberUnitCost":850,"extraMemberUnitCost":750,"defaultSupporterUnitCost":0,"extraSupporterUnitCost":290}}]}}}

        """;

    }

​

        public static decimal AddTax(decimal value)

        {

            value = Math.Round((value * (_taxRate + 100)) / 100m, 2, MidpointRounding.AwayFromZero);

            return value;

        }

​

        public static decimal RemoveTax(decimal value)

        {

            value = Math.Round((value * 100) / (_taxRate + 100m), 2, MidpointRounding.ToZero);

            return value;

        }

​

        public static decimal? CalculateInitialFee(string plan, bool includeTax)

        {

            if (!_planPricingModels.TryGetValue(plan, out var model))

            {

                return null;

            }

​

            decimal initialFee = 0;

            if (model.SignupFeeInclTax.HasValue)

            {

                initialFee += model.SignupFeeInclTax.Value;

            }

            else if (_pricingModel.DefaultSignupFeeInclTax.HasValue)

            {

                initialFee += _pricingModel.DefaultSignupFeeInclTax.Value;

            }

​

            if (!includeTax)

            {

                initialFee = RemoveTax(initialFee);

            }

​

            return initialFee;

        }

​

        public static decimal CalculateSupportFee(bool yearlyPayment, bool includeTax)

        {

            decimal supportFee = yearlyPayment ? _pricingModel.SupportPlanFeeYearly : _pricingModel.SupportPlanFeeMonthly;

​

            if (!includeTax)

            {

                supportFee = RemoveTax(supportFee);

            }

​

            return supportFee;

        }

​

    public class PricingModel

    {

        public IDictionary<string, PlanPricingModel> Plans { get; set; }

        public decimal TaxRate { get; set; }

        public decimal? DefaultSignupFeeInclTax { get; set; }

        public decimal SupportPlanFeeMonthly { get; set; }

        public decimal SupportPlanFeeYearly { get; set; }

    }

    public class PlanPricingModel

    {

        public decimal BasePrice { get; set; }

        public int DefaultMembers { get; set; }

        public int DefaultSupporters { get; set; }

        public int SupportersPerUser { get; set; }

        public PlanPricingUnitCosts MonthlyUnitCosts { get; set; }

        public PlanPricingUnitCosts YearlyUnitCosts { get; set; }

        public PlanPricingTiers[] Tiers { get; set; }

        public decimal YearlyMultiplier { get; set; }

        public decimal? SignupFeeInclTax { get; set; }

    }

​

    public class PlanPricingUnitCosts

    {

        public decimal DefaultMemberUnitCost { get; set; }

        public decimal ExtraMemberUnitCost { get; set; }

        public decimal DefaultSupporterUnitCost { get; set; }

        public decimal ExtraSupporterUnitCost { get; set; }

    }

​

    public class PlanPricingTiers

    {

        public int MemberThreshold { get; set; }

        public int? DefaultMembers { get; set; }

        public PlanPricingUnitCosts MonthlyUnitCosts { get; set; }

        public PlanPricingUnitCosts YearlyUnitCosts { get; set; }

    }

}