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

namespace Compliance.Services.ValidationRules
{
    public class EmergencyValidationRule : IValidationRule
    {
        private const string RULE_NAME = "Emergency Situation Validation";
        private const int MAX_EMERGENCY_PERIOD_DAYS = 180;
        private const decimal MIN_EMERGENCY_SUPPLY_PERCENTAGE = 10m;
        private const string MISSING_DECLARATION_ERROR = "Emergency declaration number is required for emergency situations";
        private const string PERIOD_EXCEEDED_ERROR = "Emergency period cannot exceed 180 days";
        private const string SUPPLY_BELOW_MINIMUM_ERROR = "Emergency supply must be at least 10% of normal load";
        private const string BILLING_EXCEEDED_ERROR = "Emergency billing cannot exceed normal load billing estimate";

        public int Priority => 1;  // High priority for emergency situations

        public Task<ValidationResult> ValidateAsync(
            BillComplianceRequest request,
            DistributorInformation distributorInfo,
            Client clientInfo)
        {
            if (!request.IsEmergencySituation)
                return Task.FromResult(ValidationResult.Success(RULE_NAME));

            var errors = ValidateEmergencyRequirements(request);

            return Task.FromResult(errors.Count == 0
                ? ValidationResult.Success(RULE_NAME)
                : ValidationResult.Failure(RULE_NAME, errors));
        }

        private static List<string> ValidateEmergencyRequirements(BillComplianceRequest request)
        {
            var errors = new List<string>();

            // Art. 350 - Emergency Declaration Validation
            ValidateDeclaration(request, errors);
            // Art. 351 - Emergency Period Validation
            ValidatePeriod(request, errors);
            // Art. 352 - Emergency Supply Percentage Validation
            ValidateSupplyPercentage(request, errors);
            // Art. 353 - Emergency Billing Amount Validation
            ValidateBillingAmount(request, errors);

            return errors;
        }

        private static void ValidateDeclaration(BillComplianceRequest request, List<string> errors)
        {
            if (string.IsNullOrEmpty(request.EmergencyDeclarationNumber))
                errors.Add(MISSING_DECLARATION_ERROR);
        }

        private static void ValidatePeriod(BillComplianceRequest request, List<string> errors)
        {
            if (request.EmergencyPeriodDays > MAX_EMERGENCY_PERIOD_DAYS)
                errors.Add(PERIOD_EXCEEDED_ERROR);
        }

        private static void ValidateSupplyPercentage(BillComplianceRequest request, List<string> errors)
        {
            if (request.EmergencySupplyPercentage < MIN_EMERGENCY_SUPPLY_PERCENTAGE)
                errors.Add(SUPPLY_BELOW_MINIMUM_ERROR);
        }

        private static void ValidateBillingAmount(BillComplianceRequest request, List<string> errors)
        {
            if (request.BillTotalBeforeLateCharges > request.NormalLoadBillEstimate)
                errors.Add(BILLING_EXCEEDED_ERROR);
        }
    }
}