using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using gehGassi.Core.Interfaces;
using gehGassi.Domain.Shop;
using Microsoft.EntityFrameworkCore;

namespace gehGassi.Core.Services
{
    /// <summary>
    /// Service der die Verwaltung von Rechnungen ermöglicht
    /// </summary>
    public class InvoiceService : ServiceBase<Invoice>, IInvoiceService
    {
        /// <summary>
        /// Erstellt eine Instanz
        /// </summary>
        /// <param name="unitOfWork">Instanz eines IUnitOfWork</param>
        public InvoiceService(IUnitOfWork unitOfWork) : base(unitOfWork)
        {
        }

        /// <summary>
        /// Erstellen einer Rechnung
        /// </summary>
        /// <returns>Bestellung</returns>
        public Invoice Create()
        {
            var item = new Invoice()
            {
                UniqueId = Guid.NewGuid(),
                Created = DateTime.UtcNow
            };
            return item;
        }

        /// <summary>
        /// Erstellen einer Rechnung
        /// </summary>
        /// <param name="orderId">Id der Bestellung</param>
        /// <returns>Bestellung</returns>
        public async Task<Invoice> CreateAsync(long orderId)
        {
            var item = Create();
            item.OrderId = orderId;
            item.Number = await GetNextNumberAsync();
            item.Counter = await GetNextCounterAsync();

            return item;
        }

        /// <summary>
        /// Gibt eine Rechnung basierend auf der Bestellung zurück
        /// </summary>
        /// <param name="orderId">Id der Bestellung</param>
        /// <returns></returns>
        public async Task<Invoice> GetByOrderAsync(long orderId)
        {
            var item = await Repository.FirstOrDefaultAsync(c => c.OrderId == orderId).ConfigureAwait(false);
            return item;
        }

        /// <summary>
        /// Gibt den nächsten freien Rechnungs-spezifischen Zähler zurück
        /// </summary>
        /// <returns>Nächste freie Nummer</returns>
        public async Task<long> GetNextCounterAsync()
        {
            long number = 1;
            var last = await Repository.Query(c => c.Id > 0).OrderByDescending(c => c.Counter).FirstOrDefaultAsync().ConfigureAwait(false);
            if (last != null)
                number = last.Counter + 1;
            return number;
        }

        /// <summary>
        /// Gibt die nächste freie Nummer für eine Rechnung als Rechnungsnummer zurück
        /// </summary>
        /// <returns>EndKunden-Nummer</returns>
        public async Task<string> GetNextNumberAsync()
        {
            long number = 1;
            var last = await Repository.Query(c => c.Id > 0).OrderByDescending(c => c.Id).FirstOrDefaultAsync().ConfigureAwait(false);
            if (last != null)
                number = last.Counter + 1;
            return $"{DateTime.UtcNow.Year}{DateTime.UtcNow.Month}-{number:000000}";
        }
    }
}