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

namespace BlueWest.WebApi.EF
{
    /// <summary>
    /// Country table database extensions
    /// </summary>
    public static class CountryDbExtensions
    {

        /// <summary>
        /// Add a new country 
        /// </summary>
        /// <param name="dbContext"></param>
        /// <param name="countryCreate"></param>
        /// <returns></returns>
        public static (bool, CountryUnique) AddCountry(this CountryDbContext dbContext, CountryCreate countryCreate)
        {
            Country newCountry = new Country(countryCreate);
            dbContext.Countries.Add(newCountry);
            bool success = dbContext.SaveChanges() >= 0;
            return (success, new CountryUnique(newCountry));
        } 
        /// <summary>
        /// Updates a country data.
        /// </summary>
        /// <param name="dbContext">DbContext.</param>
        /// <param name="countryUpdate">Country data to update.</param>
        /// <param name="countryId">Country Id.</param>
        /// <returns></returns>
        public static (bool, Country) UpdateCountry(
            this CountryDbContext dbContext, 
            CountryUpdate countryUpdate,
            int countryId)
        {
            var country = dbContext.Countries.FirstOrDefault(x => x.Id == countryId);
            if (country == null) return (false, null);
            country.Update(countryUpdate);
            dbContext.Countries.Update(country);
            var result = dbContext.SaveChanges() >= 0;
            return (result, country);

        }

        /// <summary>
        /// Adds a new Currency to the specified country
        /// </summary>
        /// <param name="dbContext"></param>
        /// <param name="countryId"></param>
        /// <param name="currencyCreate"></param>
        /// <returns></returns>
        public static (bool, string, Country) AddCurrency( 
            this CountryDbContext dbContext, 
            int countryId, 
            CurrencyCreate currencyCreate)
        {
            var country = dbContext.Countries.FirstOrDefault(d => d.Id == countryId);
            
            // Check if currency exists
            if (country == null) return (false, "Country Not found.", null);
            
            // Creates new currency
            var newCurrency = new Currency(currencyCreate);
            country.Currencies.Add(newCurrency);
            var success = dbContext.SaveChanges() >= 0;
            
            return !success ? (false, "Error saving the changes in the database.", null) : (true, string.Empty, country);
        }
        // country add (add currency) currency create, duplicatioon Validations
        
        /// <summary>
        /// Add Currency with optional duplication checks
        /// </summary>
        /// <param name="dbContext"></param>
        /// <param name="countryId">Country Id</param>
        /// <param name="currencyCreate">Data to create currency</param>
        /// <param name="duplicationValidations">List of expressions</param>
        /// <returns></returns>
        public static (bool, string, CurrencyUnique) AddCurrency( 
            this CountryDbContext dbContext, 
            int countryId, CurrencyCreate currencyCreate,  
            Expression<Func<Currency,bool>>[] duplicationValidations)
        {
            
            var countryQuery = from aCountry in dbContext.Countries
                where aCountry.Id == countryId
                let currencies = aCountry.Currencies
                select aCountry;
            
            var country = countryQuery.FirstOrDefault();
            
            if (country == null) return (false, $"{nameof(country)} Not found.", null);
            
            foreach (var duplicationValidation in duplicationValidations)
            {
                var currencyToGet = dbContext.Currencies.FirstOrDefault(duplicationValidation);
                if (currencyToGet != null)
                {
                    return (false, $"Duplication Validation failed: {nameof(duplicationValidation.Body.ToString)}", null);
                }
            }

            var newCurrency = new Currency(currencyCreate);
            country.Currencies.Add(newCurrency);
            var success = dbContext.SaveChanges() >= 0;
            return !success ? (false, "Error saving the changes in the database.", null) : (true, string.Empty, new CurrencyUnique(newCurrency));
        }
    }
}