#1090: Notification to the consumer when the product is back in stock

src/Modules/SimplCommerce.Module.Catalog/Areas/Catalog/Views/Product/ProductDetail.cshtml

@@ -199,6 +199,31 @@
                     <div class="out-of-stock">
                         <span class="label label-danger">@Localizer["Out of stock"]</span>
                     </div>
+
+                    <div class="back-in-stock-subscribe">
+                        <form action="api/stocks/back-in-stock">
+                            <div>
+                                @if (SignInManager.IsSignedIn(User))
+                                {
+                                    <p>Subscribe and we'll notify you when the product is back in stock.</p>
+                                    <div class="d-flex">
+                                        <input type="hidden" name="productId" value="@Model.Id" />
+                                        <input type="hidden" class="form-control mr-2" name="customerEmail" value="@User.Claims.First(c => c.Type == "email").Value"/>
+                                        <button type="button" class="btn btn-primary btn-back-in-stock-subscribe" id="subscribeBackInStock">Subscribe</button>
+                                    </div>
+                                }
+                                else
+                                {
+                                    <p>Leave your email and we'll notify you when the product is in stock</p>
+                                    <div class="d-flex">
+                                        <input type="hidden" name="productId" value="@Model.Id" />
+                                        <input type="text" class="form-control mr-2" name="customerEmail" />
+                                        <button type="button" class="btn btn-primary btn-back-in-stock-subscribe" id="subscribeBackInStock">Send</button>
+                                    </div>
+                                }
+                            </div>
+                        </form>
+                    </div>
                 }
                 <div class="add-to-cart">
                     <form class="inline">

src/Modules/SimplCommerce.Module.Catalog/wwwroot/product-detail.js

@@ -71,4 +71,22 @@ $(document).ready(function () {
                 });
         }
     });
+
+    $("#subscribeBackInStock").on('click', function (e) {
+        e.preventDefault();
+        var $form = $(this).closest("form"),
+            productId = $(this).closest("form").find('input[name=productId]').val(),
+            customerEmail = $(this).closest("form").find('input[name=customerEmail]').val();
+
+        var that = this;
+        $.post($form.attr('action'), $form.serializeArray())
+            .done(function (result) {
+                $(that).closest('.back-in-stock-subscribe').html('<b>Thank you. We\'ll notify you.</b>');
+            })
+            .fail(function (result) {
+                if (result.status === 409) {
+                    $(that).closest('.back-in-stock-subscribe').html('<b>You\'ve already subscribed.</b>');
+                } 
+            });
+    });
 });

src/Modules/SimplCommerce.Module.Core/Extensions/IWorkContext.cs

@@ -5,6 +5,8 @@ namespace SimplCommerce.Module.Core.Extensions
 {
     public interface IWorkContext
     {
+        string GetCurrentHostName();
+
         Task<User> GetCurrentUser();
     }
 }

src/Modules/SimplCommerce.Module.Core/Extensions/WorkContext.cs

@@ -33,6 +33,11 @@ public class WorkContext : IWorkContext
             _configuration = configuration;
         }
 
+        public string GetCurrentHostName()
+        {
+            return _httpContext.Request.Host.Value;
+        }
+
         public async Task<User> GetCurrentUser()
         {
             if (_currentUser != null)

src/Modules/SimplCommerce.Module.Inventory/Areas/Inventory/Controllers/StockApiController.cs

@@ -20,17 +20,21 @@ public class StockApiController : Controller
     {
         private readonly IRepository<Stock> _stockRepository;
         private readonly IStockService _stockService;
+        private readonly IStockSubscriptionService _stockSubscriptionService;
         private readonly IWorkContext _workContext;
         private readonly IRepository<Warehouse> _warehouseRepository;
         private readonly IRepository<StockHistory> _stockHistoryRepository;
+        private readonly IRepository<BackInStockSubscription> _backInStockSubscriptionRepository;
 
-        public StockApiController(IRepository<Stock> stockRepository, IStockService stockService, IWorkContext workContext, IRepository<Warehouse> warehouseRepository, IRepository<StockHistory> stockHistoryRepository)
+        public StockApiController(IRepository<Stock> stockRepository, IStockService stockService, IWorkContext workContext, IRepository<Warehouse> warehouseRepository, IRepository<StockHistory> stockHistoryRepository, IRepository<BackInStockSubscription> backInStockSubscriptionRepository, IStockSubscriptionService stockSubscriptionService)
         {
             _stockRepository = stockRepository;
             _stockService = stockService;
             _workContext = workContext;
             _warehouseRepository = warehouseRepository;
             _stockHistoryRepository = stockHistoryRepository;
+            _backInStockSubscriptionRepository = backInStockSubscriptionRepository;
+            _stockSubscriptionService = stockSubscriptionService;
         }
 
         [HttpPost("grid")]
@@ -135,5 +139,21 @@ public async Task<IActionResult> GetStockHistory(int warehouseId, int productId)
 
             return Ok(stockHistory);
         }
+
+        [AllowAnonymous]
+        [HttpPost("back-in-stock")]
+        public async Task<IActionResult> BackInStockSubscribe(long productId, string customerEmail)
+        {
+            if (await _backInStockSubscriptionRepository.Query()
+                .Where(o => o.ProductId == productId && o.CustomerEmail == customerEmail)
+                .AnyAsync())
+            {
+                return Conflict();
+            }
+
+            await _stockSubscriptionService.BackInStockSubscribeAsync(productId, customerEmail);
+
+            return Ok();
+        }
     }
 }

src/Modules/SimplCommerce.Module.Inventory/Areas/Inventory/Views/EmailTemplates/BackInStockEmail.cshtml

@@ -0,0 +1,30 @@
+@using SimplCommerce.Module.Catalog.Models
+@using SimplCommerce.Module.Core.Extensions
+@using SimplCommerce.Module.Core.Services
+
+@inject IWorkContext _workContext
+@inject IMediaService _mediaService
+
+@{
+    Layout = null;
+
+    var hostName = _workContext.GetCurrentHostName();
+    var thumbnailUrl = _mediaService.GetThumbnailUrl(Model.ThumbnailImage);
+}
+
+@model SimplCommerce.Module.Catalog.Models.Product
+
+<div style="border: 1px solid #ebebeb; width: 50%; padding: 16px 24px; margin: 0 auto;">
+    Hi, <b>@Model.Name</b> in now available.
+    Get in now before it out of stock again.
+    <br />
+    <br />
+    <div>
+        <img src="https://@hostName@thumbnailUrl" />
+        <h2>@Model.Name</h2>
+        <h4 style="color:red;">$1000</h4>
+    </div>
+    <a href="https://@hostName/@Model.Slug">
+        View product
+    </a>
+</div>

src/Modules/SimplCommerce.Module.Inventory/Event/BackInStock.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using MediatR;
+
+namespace SimplCommerce.Module.Inventory.Event
+{
+    public class BackInStock : INotification
+    {
+        public long ProductId { get; set; }
+    }
+}

src/Modules/SimplCommerce.Module.Inventory/Event/BackInStockSendEmailHandler.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using MediatR;
+using SimplCommerce.Module.Inventory.Services;
+
+namespace SimplCommerce.Module.Inventory.Event
+{
+    public class BackInStockSendEmailHandler : INotificationHandler<BackInStock>
+    {
+        public readonly IStockSubscriptionService _stockSubscriptionService;
+
+        public BackInStockSendEmailHandler(IStockSubscriptionService stockSubscriptionService)
+        {
+            _stockSubscriptionService = stockSubscriptionService;
+        }
+
+        public async Task Handle(BackInStock notification, CancellationToken cancellationToken)
+        {
+            await _stockSubscriptionService.BackInStockSendNotificationsAsync(notification.ProductId);
+        }
+    }
+}

src/Modules/SimplCommerce.Module.Inventory/Models/BackInStockSubscription.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using SimplCommerce.Infrastructure.Models;
+
+namespace SimplCommerce.Module.Inventory.Models
+{
+    public class BackInStockSubscription : EntityBase
+    {
+        public long ProductId { get; set; }
+        public string CustomerEmail { get; set; }
+    }
+}

src/Modules/SimplCommerce.Module.Inventory/ModuleInitializer.cs

@@ -4,6 +4,10 @@
 using SimplCommerce.Infrastructure.Modules;
 using SimplCommerce.Module.Inventory.Services;
 using SimplCommerce.Infrastructure;
+using MediatR;
+using SimplCommerce.Module.Catalog.Events;
+using SimplCommerce.Module.Core.Events;
+using SimplCommerce.Module.Inventory.Event;
 
 namespace SimplCommerce.Module.Inventory
 {
@@ -12,6 +16,9 @@ public class ModuleInitializer : IModuleInitializer
         public void ConfigureServices(IServiceCollection serviceCollection)
         {
             serviceCollection.AddTransient<IStockService, StockService>();
+            serviceCollection.AddTransient<IStockSubscriptionService, StockSubscriptionService>();
+            serviceCollection.AddTransient<INotificationHandler<BackInStock>, BackInStockSendEmailHandler>();
+
 
             GlobalConfiguration.RegisterAngularModule("simplAdmin.inventory");
         }

src/Modules/SimplCommerce.Module.Inventory/Services/IStockSubscriptionService.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace SimplCommerce.Module.Inventory.Services
+{
+    public interface IStockSubscriptionService
+    {
+        Task BackInStockSubscribeAsync(long productId, string customerEmail);
+
+        Task BackInStockSendNotificationsAsync(long productId);
+    }
+}

src/Modules/SimplCommerce.Module.Inventory/Services/StockService.cs

@@ -1,9 +1,11 @@
 using System;
 using System.Linq;
 using System.Threading.Tasks;
+using MediatR;
 using Microsoft.EntityFrameworkCore;
 using SimplCommerce.Infrastructure.Data;
 using SimplCommerce.Module.Catalog.Models;
+using SimplCommerce.Module.Inventory.Event;
 using SimplCommerce.Module.Inventory.Models;
 
 namespace SimplCommerce.Module.Inventory.Services
@@ -13,12 +15,14 @@ public class StockService : IStockService
         private readonly IRepository<Stock> _stockRepository;
         private readonly IRepository<Product> _productRepository;
         private readonly IRepository<StockHistory> _stockHistoryRepository;
+        private readonly IMediator _mediator;
 
-        public StockService(IRepository<Stock> stockRepository, IRepository<Product> productRepository, IRepository<StockHistory> stockHistoryRepository)
+        public StockService(IRepository<Stock> stockRepository, IRepository<Product> productRepository, IRepository<StockHistory> stockHistoryRepository, IMediator mediator)
         {
             _stockRepository = stockRepository;
             _productRepository = productRepository;
             _stockHistoryRepository = stockHistoryRepository;
+            _mediator = mediator;
         }
 
         public async Task AddAllProduct(Warehouse warehouse)
@@ -44,6 +48,8 @@ public async Task UpdateStock(StockUpdateRequest stockUpdateRequest)
             var product = await _productRepository.Query().FirstOrDefaultAsync(x => x.Id == stockUpdateRequest.ProductId);
             var stock = await _stockRepository.Query().FirstOrDefaultAsync(x => x.ProductId == stockUpdateRequest.ProductId && x.WarehouseId == stockUpdateRequest.WarehouseId);
 
+            var prevStockQuantity = product.StockQuantity;
+
             stock.Quantity = stock.Quantity + stockUpdateRequest.AdjustedQuantity;
             product.StockQuantity = product.StockQuantity + stockUpdateRequest.AdjustedQuantity;
             var stockHistory = new StockHistory
@@ -58,6 +64,11 @@ public async Task UpdateStock(StockUpdateRequest stockUpdateRequest)
 
             _stockHistoryRepository.Add(stockHistory);
             await _stockHistoryRepository.SaveChangesAsync();
+
+            if (prevStockQuantity <= 0 && product.StockQuantity > 0)
+            {
+                await _mediator.Publish(new BackInStock { ProductId = product.Id });
+            }
         }
     }
 }

src/Modules/SimplCommerce.Module.Inventory/Services/StockSubscriptionService.cs

@@ -0,0 +1,70 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc.Routing;
+using Microsoft.EntityFrameworkCore;
+using SimplCommerce.Infrastructure.Data;
+using SimplCommerce.Infrastructure.Web;
+using SimplCommerce.Module.Catalog.Models;
+using SimplCommerce.Module.Core.Models;
+using SimplCommerce.Module.Core.Services;
+using SimplCommerce.Module.Inventory.Models;
+
+namespace SimplCommerce.Module.Inventory.Services
+{
+    public class StockSubscriptionService : IStockSubscriptionService
+    {
+        private readonly IRepository<BackInStockSubscription> _backInStockSubscriptionRepository;
+        private readonly IRepository<Product> _productRepository;
+        private readonly IEmailSender _emailSender;
+        private readonly IRazorViewRenderer _viewRender;
+
+        public StockSubscriptionService(IRepository<BackInStockSubscription> backInStockSubscriptionRepository, IEmailSender emailSender, IRazorViewRenderer viewRender, IRepository<Product> productRepository)
+        {
+            _backInStockSubscriptionRepository = backInStockSubscriptionRepository;
+            _emailSender = emailSender;
+            _viewRender = viewRender;
+            _productRepository = productRepository;
+        }
+
+        public async Task BackInStockSendNotificationsAsync(long productId)
+        {
+            var subscriptions = await _backInStockSubscriptionRepository
+                .Query()
+                .Where(o => o.ProductId == productId)
+                .ToListAsync();
+
+            var product = await _productRepository
+                .Query()
+                .Where(o => o.Id == productId)
+                .Include(o => o.ThumbnailImage)
+                .FirstOrDefaultAsync();
+
+            var emailBody = await _viewRender.RenderViewToStringAsync("/Areas/Inventory/Views/EmailTemplates/BackInStockEmail.cshtml", product);
+            var emailSubject = $"Back in stock";
+
+            foreach (var subscription in subscriptions)
+            {
+                await _emailSender.SendEmailAsync(subscription.CustomerEmail, emailSubject, emailBody, true);
+
+                _backInStockSubscriptionRepository.Remove(subscription);
+            }
+
+            await _backInStockSubscriptionRepository.SaveChangesAsync();
+        }
+
+        public async Task BackInStockSubscribeAsync(long productId, string customerEmail)
+        {
+            var subscription = new BackInStockSubscription
+            {
+                ProductId = productId,
+                CustomerEmail = customerEmail
+            };
+
+            _backInStockSubscriptionRepository.Add(subscription);
+            await _backInStockSubscriptionRepository.SaveChangesAsync();
+        }
+    }
+}