ex-int-04-shipping-cost/ShippingCosts/Implementations/LPSShippingCostCalculator.cs

using ShippingCosts.Contracts;

namespace ShippingCosts.Implementations;

/// <summary>
///     Calculates the shipping costs for the Leonding Parcel Service carrier
/// </summary>
/// <inheritdoc cref="ShippingCostCalculatorBase" />
public sealed class LPSShippingCostCalculator(ICountryDistanceProvider countryDistanceProvider)
    : ShippingCostCalculatorBase(countryDistanceProvider)
{
    public override string CarrierName => "Leonding Parcel Service";

    public override decimal? CalculateShippingCosts(string targetCountry, IMeasuredBox box)
    {
        if (!CountryDistanceProvider.IsPossibleCountry(targetCountry))
        {
            return null;
        }
        
        decimal? weightCost = CalculateWeightCost(box.Weight);
        if (weightCost == null)
        {
            return null;
        }
        
        decimal? sizeCost = CalculateSizeCost(box);
        if (sizeCost == null)
        {
            return null;
        }
        
        decimal distanceCost = CalcDistanceCost(targetCountry);
        return weightCost + sizeCost + distanceCost;
    }

    private decimal? CalculateWeightCost(double weight)
    {
        if (weight <= 0)
        {
            return null;
        }
        
        if (weight < 1.5)
        {
            return 0;
        }
        if (weight < 2)
        {
            return 0.5M;
        }
        if (weight < 3)
        {
            return 1.5M;
        }
        
        return Math.Min(20M, (decimal)(weight * 0.55));
    }

    private decimal? CalculateSizeCost(IMeasuredBox box)
    {
        int sizeSum = SumOfLongestAndShortestSides(box);
        if (sizeSum <= 0)
        {
            return null;
        }
        
        if (sizeSum < 250)
        {
            return 0;
        }
        if (sizeSum < 400)
        {
            return 0.75M;
        }
        if (sizeSum < 650)
        {
            return 1.25M;
        }
        if (sizeSum < 900)
        {
            return 2.6M;
        }
        
        return 3.5M;
    }

    private decimal CalcDistanceCost(string targetCountry)
    {
        decimal baseCost = 2.99M;
        
        var distanceInfo = CountryDistanceProvider.GetDistanceTo(targetCountry);
        if (distanceInfo == null)
        {
            return baseCost;
        }
        
        if (!distanceInfo.Value.IsEuMember)
        {
            baseCost += 2.49M;
        }
        if (distanceInfo.Value.ApproxDistance == 0)
        {
            return baseCost;
        }
        
        int distanceUnits = Math.Max(1, (int)Math.Ceiling(distanceInfo.Value.ApproxDistance / 500.0));
        decimal perUnitCost = 1.1M;
        
        if (distanceInfo.Value.IsDirectNeighbor)
        {
            perUnitCost *= 0.75M;
        }
        
        return baseCost + (distanceUnits * perUnitCost);
    }
}