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

namespace Compliance.Services.ValidationRules
{
    public class MeterReadingValidationRule : IValidationRule
    {
        private const string RULE_NAME = "Meter Reading Validation";
        private const string READING_ERROR = "Invalid meter reading value";
        private const string SEQUENCE_ERROR = "Current reading must be greater than previous reading";
        private const string RESET_ERROR = "Meter reset not properly documented";
        private const string ESTIMATION_ERROR = "Estimated reading without proper justification";
        
        public int Priority => 1; // High priority as other validations depend on readings

        public Task<ValidationResult> ValidateAsync(
            BillComplianceRequest request,
            DistributorInformation distributorInfo,
            Client clientInfo)
        {
            var errors = new List<string>();

            ValidateReadingValues(request, errors);
            ValidateReadingSequence(request, errors);
            ValidateEstimatedReadings(request, errors);
            ValidateMeterReset(request, errors);

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

        private static void ValidateReadingValues(BillComplianceRequest request, List<string> errors)
        {
            if (request.CurrentReading < 0 || request.PreviousReading < 0)
                errors.Add($"{READING_ERROR}: Negative readings are not allowed");
        }

        private static void ValidateReadingSequence(BillComplianceRequest request, List<string> errors)
        {
            if (!request.IsMeterReset && request.CurrentReading < request.PreviousReading)
                errors.Add(SEQUENCE_ERROR);
        }

        private static void ValidateEstimatedReadings(BillComplianceRequest request, List<string> errors)
        {
            if (request.IsEstimatedReading && string.IsNullOrEmpty(request.EstimationJustification))
                errors.Add(ESTIMATION_ERROR);
        }

        private static void ValidateMeterReset(BillComplianceRequest request, List<string> errors)
        {
            if (request.IsMeterReset && 
                (string.IsNullOrEmpty(request.MeterResetJustification) || 
                 request.MeterResetDate == default))
            {
                errors.Add(RESET_ERROR);
            }
        }
    }
}