add: blog post service

Controllers/PostController.cs

@@ -0,0 +1,15 @@
+using backend.Services;
+using Microsoft.AspNetCore.Mvc;
+
+namespace backend.Controllers;
+[ApiController]
+[Route("blog/api[controller]")]
+public class PostController: ControllerBase
+{
+    private readonly PostService _postService;
+    
+    public PostController(PostService postService)
+    {
+        _postService = postService;
+    }
+}

Models/BlogPost.cs

@@ -15,7 +15,8 @@ public class BlogPost
 
     //Meta data
     [BsonRepresentation(BsonType.DateTime)]
-    public DateTime CreatedAt { get; set; }
+    public DateTime? CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
 
     [BsonRepresentation(BsonType.Array)] public List<string> Tags { get; set; }
 }

Services/PostService.cs

@@ -0,0 +1,57 @@
+using backend.Models;
+using Microsoft.Extensions.Options;
+using MongoDB.Driver;
+
+namespace backend.Services;
+
+public class PostService
+{
+    private readonly IMongoCollection<BlogPost> _posts;
+    
+    public PostService(IOptions<BlogDatabaseSettings> settings)
+    {
+        var client = new MongoClient(settings.Value.ConnectionString);
+        var database = client.GetDatabase(settings.Value.DatabaseName);
+
+        _posts = database.GetCollection<BlogPost>(settings.Value.PostsCollectionName);
+    }
+    
+    public async Task<BlogPost?> GetPostAsync(string id)
+    {
+        var post = await _posts.Find(p => p.Id == id).FirstOrDefaultAsync();
+        return post;
+    }
+
+    public async Task<List<BlogPost>> GetLastNPostsAsync(int n)
+    {
+        var posts = await _posts.Find(p => true).SortByDescending(p => p.CreatedAt).Limit(n).ToListAsync();
+        return posts;
+    }
+    
+    public async Task<List<BlogPost>> GetAllPostsAsync()
+    {
+        var posts = await _posts.Find(p => true).ToListAsync();
+        return posts;
+    }
+    
+    public async Task CreatePostAsync(BlogPost post)
+    {
+        post.CreatedAt = DateTime.UtcNow;
+        await _posts.InsertOneAsync(post);
+    }
+    
+    public async Task UpdatePostAsync(string id, BlogPost postIn)
+    {
+        var oldPost = await _posts.Find(p => p.Id == id).FirstOrDefaultAsync();
+        //Set timestamps
+        postIn.CreatedAt = oldPost.CreatedAt;
+        postIn.UpdatedAt = DateTime.UtcNow;
+        await _posts.ReplaceOneAsync(p => p.Id == id, postIn);
+    }
+    
+    public async Task DeletePostAsync(string id)
+    {
+        await _posts.DeleteOneAsync(p => p.Id == id);
+    }
+    
+}