using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading.Tasks;
using BlueWest.Data;
using Microsoft.EntityFrameworkCore;

namespace BlueWest.WebApi.EF
{
    /// <summary>
    /// Currency table data extensions
    /// </summary>
    public static class CurrencyExtensions
    {
        
        /// <summary>
        /// Add new Currency
        /// </summary>
        /// <param name="dbContext"></param>
        /// <param name="currencyToCreate"></param>
        /// <returns></returns>
        public static (bool, Currency) AddCurrency(this CountryDbContext dbContext, CurrencyCreate currencyToCreate)
        {
            var newCurrency = new Currency(currencyToCreate);
            dbContext.Add(newCurrency);
            var resultOperation = dbContext.SaveChanges() >= 0;
            return (resultOperation, newCurrency);
        }
        
        
        /// <summary>
        /// Updates currency
        /// </summary>
        /// <param name="dbContext"></param>
        /// <param name="currencyId"></param>
        /// <param name="currencyToUpdate"></param>
        /// <returns></returns>
        public static (bool, Currency) UpdateCurrency(this CountryDbContext dbContext, int currencyId, CurrencyUpdate currencyToUpdate)
        {
            var currency =  dbContext.Currencies.SingleOrDefault(x => x.Id == currencyId);
            if (currency == null) return (false, null);
            currency.Update(currencyToUpdate);
            dbContext.Update(currency);
            var resultOperation = dbContext.SaveChanges() >= 0;
            return (resultOperation, currency);

        }
        
        /// <summary>
        /// Add Country associated with specified Currency.
        /// </summary>
        /// <param name="dbContext"></param>
        /// <param name="currencyId"></param>
        /// <param name="countryCreate"></param>
        /// <param name="duplicationValidations"></param>
        /// <returns></returns>
        public static (bool, string, CountryUnique) AddCountry( 
            this CountryDbContext dbContext, 
            int currencyId, CountryCreate countryCreate,  
            Expression<Func<Country,bool>>[] duplicationValidations)
        {
            
            var queryable = from aCurrency in dbContext.Currencies
                where aCurrency.Id == currencyId
                select aCurrency;
            
            queryable.Include(x => x.Countries);
            
            var currency = queryable.SingleOrDefault();
            
            // Check if currency exists
            if (currency == null) return (false, $"{nameof(Currency)}: {currencyId} - Not found.", null);

            // Check if there's currency with the same code
            foreach (var duplicationValidation in duplicationValidations)
            {
                var countryToCheck = dbContext.Countries.FirstOrDefault(duplicationValidation);
                
                if (countryToCheck != null)
                {
                    return (false, $"Duplication Validation failed: {duplicationValidation.Body}", null);
                }
            }
            
            // Creates new currency
            var newCountry = new Country(countryCreate);
            currency.Countries.Add(newCountry);
            var success = dbContext.SaveChanges() >= 0;
            return (success, string.Empty, new CountryUnique(newCountry));
        }
        
    }
}