using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Webshop.Application;
using Webshop.Application.DTOs.Shipping;
using Webshop.Domain.Entities;
using Webshop.Domain.Interfaces;
using Webshop.Infrastructure.Data;

namespace Webshop.Application.Services.Admin
{
    public class AdminShippingMethodService : IAdminShippingMethodService
    {
        private readonly IShippingMethodRepository _shippingMethodRepository;
        private readonly ApplicationDbContext _context;

        public AdminShippingMethodService(IShippingMethodRepository shippingMethodRepository, ApplicationDbContext context)
        {
            _shippingMethodRepository = shippingMethodRepository;
            _context = context;
        }

        public async Task<ServiceResult<IEnumerable<ShippingMethodDto>>> GetAllAsync()
        {
            var methods = await _shippingMethodRepository.GetAllAsync();
            var dtos = methods.Select(MapToDto).ToList();
            return ServiceResult.Ok<IEnumerable<ShippingMethodDto>>(dtos);
        }

        public async Task<ServiceResult<ShippingMethodDto>> GetByIdAsync(Guid id)
        {
            var sm = await _shippingMethodRepository.GetByIdAsync(id);
            if (sm == null)
            {
                return ServiceResult.Fail<ShippingMethodDto>(ServiceResultType.NotFound, $"Versandmethode mit ID '{id}' nicht gefunden.");
            }
            return ServiceResult.Ok(MapToDto(sm));
        }

        public async Task<ServiceResult<ShippingMethodDto>> CreateAsync(ShippingMethodDto shippingMethodDto)
        {
            var allMethods = await _shippingMethodRepository.GetAllAsync();
            if (allMethods.Any(sm => sm.Name.Equals(shippingMethodDto.Name, StringComparison.OrdinalIgnoreCase)))
            {
                return ServiceResult.Fail<ShippingMethodDto>(ServiceResultType.Conflict, $"Eine Versandmethode mit dem Namen '{shippingMethodDto.Name}' existiert bereits.");
            }

            var newMethod = new ShippingMethod
            {
                Id = Guid.NewGuid(),
                Name = shippingMethodDto.Name,
                Description = shippingMethodDto.Description,
                BaseCost = shippingMethodDto.Cost,
                IsActive = shippingMethodDto.IsActive,
                MinDeliveryDays = shippingMethodDto.MinDeliveryDays,
                MaxDeliveryDays = shippingMethodDto.MaxDeliveryDays,
                // NEU: Gewichte mappen
                MinWeight = shippingMethodDto.MinWeight,
                MaxWeight = shippingMethodDto.MaxWeight
            };

            await _shippingMethodRepository.AddAsync(newMethod);

            return ServiceResult.Ok(MapToDto(newMethod));
        }

        public async Task<ServiceResult> UpdateAsync(ShippingMethodDto shippingMethodDto)
        {
            var existingMethod = await _shippingMethodRepository.GetByIdAsync(shippingMethodDto.Id);
            if (existingMethod == null)
            {
                return ServiceResult.Fail(ServiceResultType.NotFound, $"Versandmethode mit ID '{shippingMethodDto.Id}' nicht gefunden.");
            }

            var allMethods = await _shippingMethodRepository.GetAllAsync();
            // Prüfen, ob der Name von einer ANDEREN Methode bereits verwendet wird
            if (allMethods.Any(sm => sm.Name.Equals(shippingMethodDto.Name, StringComparison.OrdinalIgnoreCase) && sm.Id != shippingMethodDto.Id))
            {
                return ServiceResult.Fail(ServiceResultType.Conflict, $"Eine andere Versandmethode mit dem Namen '{shippingMethodDto.Name}' existiert bereits.");
            }

            existingMethod.Name = shippingMethodDto.Name;
            existingMethod.Description = shippingMethodDto.Description;
            existingMethod.BaseCost = shippingMethodDto.Cost;
            existingMethod.IsActive = shippingMethodDto.IsActive;
            existingMethod.MinDeliveryDays = shippingMethodDto.MinDeliveryDays;
            existingMethod.MaxDeliveryDays = shippingMethodDto.MaxDeliveryDays;
            // NEU: Gewichte aktualisieren
            existingMethod.MinWeight = shippingMethodDto.MinWeight;
            existingMethod.MaxWeight = shippingMethodDto.MaxWeight;

            await _shippingMethodRepository.UpdateAsync(existingMethod);
            return ServiceResult.Ok();
        }

        public async Task<ServiceResult> DeleteAsync(Guid id)
        {
            var method = await _shippingMethodRepository.GetByIdAsync(id);
            if (method == null)
            {
                return ServiceResult.Fail(ServiceResultType.NotFound, $"Versandmethode mit ID '{id}' nicht gefunden.");
            }

            var isUsedInOrders = await _context.Orders.AnyAsync(o => o.ShippingMethodId == id);
            if (isUsedInOrders)
            {
                return ServiceResult.Fail(ServiceResultType.Conflict, "Diese Versandmethode kann nicht gelöscht werden, da sie noch in bestehenden Bestellungen verwendet wird.");
            }

            await _shippingMethodRepository.DeleteAsync(id);
            return ServiceResult.Ok();
        }

        private ShippingMethodDto MapToDto(ShippingMethod sm)
        {
            return new ShippingMethodDto
            {
                Id = sm.Id,
                Name = sm.Name,
                Description = sm.Description,
                Cost = sm.BaseCost,
                IsActive = sm.IsActive,
                MinDeliveryDays = sm.MinDeliveryDays,
                MaxDeliveryDays = sm.MaxDeliveryDays,
                // NEU: Gewichte ins DTO übertragen
                MinWeight = sm.MinWeight,
                MaxWeight = sm.MaxWeight
            };
        }
    }
}