using System;
using System.Threading.Tasks;
using System.Text;
using Compliance.Domain.Models;
using Compliance.DTOs;
using Compliance.Infrastructure.Repositories;

namespace Compliance.Services.ValidationRules
{
    public class SubsidyValidationRule(IDistributorRepository distributorRepository) : IValidationRule
    {
        private readonly IDistributorRepository _distributorRepository = distributorRepository;
        private const string RULE_NAME = "Subsidy and Discount Validation";
        private const string AMOUNT_ERROR = "Discount amount doesn't match the expected value";
        private const string ELIGIBILITY_ERROR = "Consumer not eligible for applied discount";
        private const string CONSUMPTION_ERROR = "Consumption outside eligible range for discount";
        private const decimal TOLERANCE = 0.01m;
        public int Priority => 6;  // Run after flag tariff validation

        public async Task<ValidationResult> ValidateAsync(
            BillComplianceRequest request,
            DistributorInformation distributorInfo,
            Client clientInfo)
        {
            var subsidyInfo = await _distributorRepository.GetSubsidyInformationAsync(
                request.DistributorName,
                request.ConsumerGroup,
                request.Month) ?? throw new InvalidOperationException("Subsidy information not found");

            var isValid = true;
            var message = new StringBuilder();

            // Check consumption eligibility
            if (request.ConsumptionAmount < subsidyInfo.Consumption.MinConsumption ||
                (subsidyInfo.Consumption.MaxConsumption > 0 && request.ConsumptionAmount > subsidyInfo.Consumption.MaxConsumption))
            {
                if (request.DiscountAmount != 0)
                {
                    isValid = false;
                    message.AppendLine($"{CONSUMPTION_ERROR}. Range: {subsidyInfo.Consumption.MinConsumption}-{subsidyInfo.Consumption.MaxConsumption} kWh");
                }
                return new ValidationResult
                {
                    IsValid = isValid,
                    RuleName = RULE_NAME,
                    Message = message.ToString().TrimEnd()
                };
            }

            // Get applicable discount rate
            var discountRate = subsidyInfo.GroupDiscounts.TryGetValue(request.ConsumerGroup.ToLower(), out var specialRate)
                ? specialRate
                : subsidyInfo.BaseDiscountPercentage;

            // Calculate expected discount
            var expectedDiscount = CalculateDiscount(request, subsidyInfo, discountRate);

            if (Math.Abs(request.DiscountAmount - expectedDiscount) > TOLERANCE)
            {
                isValid = false;
                message.AppendLine($"{AMOUNT_ERROR}. Expected: {expectedDiscount:F2}, Found: {request.DiscountAmount:F2}");
            }

            return new ValidationResult
            {
                IsValid = isValid,
                RuleName = RULE_NAME,
                Message = message.ToString().TrimEnd()
            };
        }

        private static decimal CalculateDiscount(
            BillComplianceRequest request,
            SubsidyInformation subsidyInfo,
            decimal discountRate)
        {
            var baseAmount = 0m;

            if (subsidyInfo.ApplyToTUSD)
            {
                baseAmount += request.TUSDAmount;
            }

            if (subsidyInfo.ApplyToTE)
            {
                baseAmount += request.TEAmount;
            }

            if (subsidyInfo.ApplyToFlags)
            {
                baseAmount += request.FlagAmount;
            }

            return baseAmount * (discountRate / 100m);
        }
    }
}