Add filtering by tags

T120B165-ImgBoard/Controllers/PostController.cs

@@ -259,9 +259,9 @@ public class PostController(
     [HttpGet]
     [ProducesResponseType(StatusCodes.Status200OK)]
     [ProducesResponseType(StatusCodes.Status400BadRequest)]
-    public async Task<ActionResult<PagedList<PostDto>>> GetAll([Range(1, int.MaxValue)] int pageNumber = 1)
+    public async Task<ActionResult<PagedList<PostDto>>> GetAll(string? query, [Range(1, int.MaxValue)] int pageNumber = 1)
     {
-        var list = await postService.GetAll(pageNumber);
+        var list = await postService.FindAll(query, pageNumber);
         var newItems = list.Items.Select(i =>
         {
             var fileUrl = Url.Action(nameof(PatchFileContent), "Post",

T120B165-ImgBoard/Services/PostService.cs

@@ -1,3 +1,4 @@
+using System.Text.RegularExpressions;
 using Microsoft.EntityFrameworkCore;
 using T120B165_ImgBoard.Data;
 using T120B165_ImgBoard.Models;
@@ -13,6 +14,7 @@ public interface IPostService
         string fileName, string fileContentType, long fileSize);
     Task<Post?> GetById(int postId, bool includeUnfinished = false);
     Task<PagedList<Post>> GetAll(int pageNumber = 1);
+    public Task<PagedList<Post>> FindAll(string? query, int pageNumber = 1);
     Task<bool> Delete(Post post);
     Task<Post> Update(Post post);
 }
@@ -83,6 +85,70 @@ public class PostService(ImgBoardContext context): IPostService
             .ToListAsync();
         return new PagedList<Post>(items, pageNumber, PageSize, totalCount);
     }
+    
+    public async Task<PagedList<Post>> FindAll(string? query, int pageNumber = 1)
+    {
+        var postsQuery = context.Posts
+            .Where(p => p.File.FinishedDate != null);
+
+        // Apply query filtering if the query string is not null or empty
+        if (!string.IsNullOrWhiteSpace(query))
+        {
+            // Parse the query string into required and excluded tags
+            var (requiredTags, excludedTags) = ParseTagQuery(query);
+
+            // Filter for required tags (Post must have ALL of these tags)
+            foreach (var requiredTag in requiredTags)
+            {
+                // Where the post's Tags collection contains ANY tag whose name matches the requiredTag.
+                postsQuery = postsQuery.Where(p => p.Tags.Any(t => t.Name == requiredTag));
+            }
+
+            // Filter out excluded tags (Post must NOT have ANY of these tags)
+            foreach (var excludedTag in excludedTags)
+            {
+                // Where the post's Tags collection does NOT contain ANY tag whose name matches the excludedTag.
+                postsQuery = postsQuery.Where(p => p.Tags.All(t => t.Name != excludedTag));
+            }
+        }
+        
+        var totalCount = await postsQuery.CountAsync();
+        var items = await postsQuery
+            .Skip((pageNumber - 1) * PageSize)
+            .Take(PageSize)
+            .Include(b => b.Author)
+            .Include(b => b.Tags)
+            .Include(b => b.File)
+            .ToListAsync();
+        return new PagedList<Post>(items, pageNumber, PageSize, totalCount);
+    }
+    
+    private static (List<string> requiredTags, List<string> excludedTags) ParseTagQuery(string query)
+    {
+        var requiredTags = new List<string>();
+        var excludedTags = new List<string>();
+
+        // Regex to find all "+tag" or "-tag" segments
+        var matches = Regex.Matches(query, @"([+-])([\w-]+)");
+
+        foreach (Match match in matches)
+        {
+            var type = match.Groups[1].Value; // "+" or "-"
+            var tag = match.Groups[2].Value; // The tag name
+
+            switch (type)
+            {
+                case "+":
+                    requiredTags.Add(tag);
+                    break;
+                case "-":
+                    excludedTags.Add(tag);
+                    break;
+            }
+        }
+
+        return (requiredTags, excludedTags);
+    }
 
     public async Task<bool> Delete(Post post)
     {