using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using Kreta.Core;
using Kreta.Core.Domain;
using Kreta.Core.Enum;
using Kreta.Core.Exceptions;

namespace Kreta.Ellenorzo.BL.VN.Logic
{
    /// <summary>
    /// Author: Kovács Kornél (DevKornél) Created On: 2019.06.
    /// Validates the models with "DataAnnotationAttributes" and gives You the option
    /// to create custom validation if model implements the "IValidatableObject" interface.
    /// </summary>
    internal class ValidatorLogic
    {
        private readonly List<ValidationResult> _errorList = new List<ValidationResult>();

        private readonly bool _isValid = true;

        internal ValidatorLogic(object instance)
        {
            var context = new ValidationContext(instance, serviceProvider: null, items: null);
            _isValid = Validator.TryValidateObject(instance, context, _errorList, true);
        }

        internal ValidatorLogic(IEnumerable<object> instance)
        {
            foreach (var item in instance)
            {
                var context = new ValidationContext(item, serviceProvider: null, items: null);
                if (!Validator.TryValidateObject(item, context, _errorList, true))
                {
                    _isValid = false;
                }
            }
        }

        public static implicit operator string(ValidatorLogic validator) => validator.GetFirstUserFriendlyError();

        internal BlException ConvertToValidationException()
        {
            var exception = new BlException(BlExceptionType.ModelValidacio);
            var count = 1;
            foreach (var error in _errorList)
            {
                var name = error.MemberNames.FirstOrDefault() ?? "custom_" + count;
                exception.ErrorList.Add(new DetailedErrorItem(name, error.ErrorMessage, BlExceptionType.ModelValidacio));
                count++;
            }

            return exception;
        }

        internal string GetFirstUserFriendlyError()
            => _errorList.Count > 0 ? _errorList[0].ErrorMessage : string.Empty;

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
        internal string GetUserFriendlyError()
            => string.Join(Constants.General.LineSeparator, _errorList.Select(x => x.ErrorMessage).ToArray());

        internal void ThrowExceptionIfModelIsNotvalid()
        {
            if (!_isValid)
            {
                throw ConvertToValidationException();
            }
        }
    }
}