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

namespace Compliance.Services.ValidationRules
{
    public class ConsumptionValidationRule : IValidationRule
    {
        private const string RULE_NAME = "Consumption Validation";
        private const string TOTAL_ERROR = "Total amount doesn't match the sum of TUSD and TE amounts";
        private const string READING_PERIOD_ERROR = "Invalid reading period";
        private const string CONSUMPTION_ERROR = "Consumption amount doesn't match readings difference";
        private const string PEAK_OFFPEAK_ERROR = "Total consumption doesn't match sum of peak and off-peak consumption";
        private const decimal TOLERANCE = 0.01m;
        private const int MAX_BILLING_DAYS = 33;  // According to ANEEL Resolution
        public int Priority => 2;  // Run after basic validation

        public async Task<ValidationResult> ValidateAsync(
            BillComplianceRequest request,
            DistributorInformation distributorInfo,
            Client clientInfo)
        {
            var isValid = true;
            var message = new StringBuilder();

            // Validate reading period
            var billingDays = (request.CurrentReadingDate - request.PreviousReadingDate).Days;
            if (billingDays <= 0 || billingDays > MAX_BILLING_DAYS)
            {
                isValid = false;
                message.AppendLine(READING_PERIOD_ERROR);
            }

            // Validate consumption calculation
            var calculatedConsumption = request.CurrentReading - request.PreviousReading;
            if (Math.Abs(calculatedConsumption - request.ConsumptionAmount) > TOLERANCE)
            {
                isValid = false;
                message.AppendLine(CONSUMPTION_ERROR);
            }

            // Validate peak/off-peak total
            if (Math.Abs(request.ConsumptionAmount - (request.PeakConsumption + request.OffPeakConsumption)) > TOLERANCE)
            {
                isValid = false;
                message.AppendLine(PEAK_OFFPEAK_ERROR);
            }

            // Validate total amount matches sum of components
            var expectedTotal = request.TUSDAmount + request.TEAmount + 
                request.PowerFactorAdjustment + request.PublicLightingAmount + 
                request.FlagAmount;
            if (Math.Abs(request.TotalAmount - expectedTotal) > TOLERANCE)
            {
                isValid = false;
                message.AppendLine(TOTAL_ERROR);
            }

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