add command and handler to vote for links

Application/VoteForLink/VoteForLinkCommand.cs

@@ -0,0 +1,22 @@
+using System;
+using System.ComponentModel.DataAnnotations;
+using HN.Domain;
+using MediatR;
+
+namespace HN.Application
+{
+  public sealed class VoteForLinkCommand : IRequest
+  {
+    [Required]
+    public Guid LinkId { get; set; }
+
+    [Required]
+    public VoteType Type { get; set; }
+
+    public VoteForLinkCommand(Guid linkId, VoteType type)
+    {
+      LinkId = linkId;
+      Type = type;
+    }
+  }
+}

Application/VoteForLink/VoteForLinkCommandHandler.cs

@@ -0,0 +1,36 @@
+using System.Threading;
+using System.Threading.Tasks;
+using HN.Domain;
+using MediatR;
+
+namespace HN.Application
+{
+  public sealed class VoteForLinkCommandHandler : IRequestHandler<VoteForLinkCommand>
+  {
+    private readonly ILinkRepository _linkRepository;
+
+    public VoteForLinkCommandHandler(ILinkRepository linkRepository)
+    {
+      _linkRepository = linkRepository;
+    }
+
+    public async Task<Unit> Handle(VoteForLinkCommand request, CancellationToken cancellationToken)
+    {
+      var link = await _linkRepository.GetByIdAsync(request.LinkId);
+
+      switch (request.Type)
+      {
+        case VoteType.Up:
+          link.Upvote();
+          break;
+        case VoteType.Down:
+          link.Downvote();
+          break;
+      }
+
+      await _linkRepository.UpdateAsync(link);
+
+      return Unit.Value;
+    }
+  }
+}

Apps/Website/Controllers/LinksController.cs

@@ -3,6 +3,7 @@ using HN.Application;
 using MediatR;
 using System.Threading.Tasks;
 using System;
+using HN.Domain;
 
 namespace Website.Controllers
 {
@@ -32,6 +33,16 @@ namespace Website.Controllers
       return View(new AddLinkCommand());
     }
 
+    [HttpPost("{controller}/{id:guid}/vote")]
+    [ValidateAntiForgeryToken]
+    public async Task<IActionResult> Vote(Guid id, string url, VoteType type)
+    {
+      await _bus.Send(new VoteForLinkCommand(id, type));
+
+      SetFlash($"Successfuly {type} for {url}!");
+      return RedirectToAction(nameof(Index));
+    }
+
     [HttpPost]
     [ValidateAntiForgeryToken]
     public async Task<IActionResult> Create(AddLinkCommand command)

Apps/Website/Views/Links/_LinkItem.cshtml

@@ -1,3 +1,8 @@
 @model HN.Application.LinkDto
 
-<a asp-action="Show" asp-controller="Links" asp-route-id="@Model.Id">@Model.Url - created at @Model.CreatedAt.ToLocalTime() (👍: @Model.UpVotes / 👎: @Model.DownVotes)</a>
+<a asp-action="Show" asp-controller="Links" asp-route-id="@Model.Id">@Model.Url - created at @Model.CreatedAt.ToLocalTime() (👍: @Model.UpVotes / 👎: @Model.DownVotes)</a>
+
+<form asp-controller="Links" asp-action="Vote" asp-route-id="@Model.Id" asp-route-url="@Model.Url" method="post">
+  <input type="submit" name="type" value="up">👍</button>
+  <input type="submit" name="type" value="down">👎</button>
+</form>

Domain/ILinkRepository.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Threading.Tasks;
 
 namespace HN.Domain
@@ -5,5 +6,7 @@ namespace HN.Domain
   public interface ILinkRepository
   {
     Task AddAsync(Link link);
+    Task UpdateAsync(Link link);
+    Task<Link> GetByIdAsync(Guid id);
   }
 }

Domain/Link.cs

@@ -23,5 +23,15 @@ namespace HN.Domain
     {
       return new Link(url);
     }
+
+    public void Upvote()
+    {
+      _votes.Add(new Vote(VoteType.Up));
+    }
+
+    public void Downvote()
+    {
+      _votes.Add(new Vote(VoteType.Down));
+    }
   }
 }

Infrastructure/LinkRepository.cs

@@ -1,5 +1,7 @@
+using System;
 using System.Threading.Tasks;
 using HN.Domain;
+using Microsoft.EntityFrameworkCore;
 
 namespace HN.Infrastructure
 {
@@ -13,5 +15,15 @@ namespace HN.Infrastructure
     {
       await base.AddAsync(link);
     }
+
+    public Task<Link> GetByIdAsync(Guid id)
+    {
+      return Entries.SingleOrDefaultAsync(o => o.Id == id);
+    }
+
+    public async Task UpdateAsync(Link link)
+    {
+      await base.UpdateAsync(link);
+    }
   }
 }

Infrastructure/Repository.cs

@@ -20,5 +20,10 @@ namespace HN.Infrastructure
       await Entries.AddRangeAsync(entities);
       await _context.SaveChangesAsync();
     }
+
+    protected async Task UpdateAsync(params TEntity[] entities)
+    {
+      await _context.SaveChangesAsync();
+    }
   }
 }