feat: add PATCH request support, expand PATCH /users/@me, serialize enums correctly

Foxnouns.Backend/Utils/ValidationUtils.cs

@@ -0,0 +1,76 @@
+using System.Text.RegularExpressions;
+
+namespace Foxnouns.Backend.Utils;
+
+/// <summary>
+/// Static methods for validating user input (mostly making sure it's not too short or too long)
+/// </summary>
+public static class ValidationUtils
+{
+    private static readonly Regex UsernameRegex = new("^[\\w-.]{2,40}$", RegexOptions.IgnoreCase);
+
+    private static readonly string[] InvalidUsernames =
+    [
+        "..",
+        "admin",
+        "administrator",
+        "mod",
+        "moderator",
+        "api",
+        "page",
+        "pronouns",
+        "settings",
+        "pronouns.cc",
+        "pronounscc"
+    ];
+
+    /// <summary>
+    /// Validates whether a username is valid. If it is not valid, throws <see cref="Foxnouns.Backend.ApiError" />.
+    /// This does not check if the username is already taken.
+    /// </summary>
+    public static void ValidateUsername(string username)
+    {
+        if (!UsernameRegex.IsMatch(username))
+            throw username.Length switch
+            {
+                < 2 => new ApiError.BadRequest("Username is too short", "username"),
+                > 40 => new ApiError.BadRequest("Username is too long", "username"),
+                _ => new ApiError.BadRequest(
+                    "Username is invalid, can only contain alphanumeric characters, dashes, underscores, and periods",
+                    "username")
+            };
+
+        if (InvalidUsernames.Any(u => string.Equals(u, username, StringComparison.InvariantCultureIgnoreCase)))
+            throw new ApiError.BadRequest("Username is not allowed", "username");
+    }
+
+    public static void ValidateDisplayName(string? displayName)
+    {
+        if (displayName == null) return;
+        switch (displayName.Length)
+        {
+            case 0:
+                throw new ApiError.BadRequest("Display name is too short", "display_name");
+            case > 100:
+                throw new ApiError.BadRequest("Display name is too long", "display_name");
+        }
+    }
+
+    public static void ValidateBio(string? bio)
+    {
+        if (bio == null) return;
+        switch (bio.Length)
+        {
+            case 0:
+                throw new ApiError.BadRequest("Bio is too short", "bio");
+            case > 1024:
+                throw new ApiError.BadRequest("Bio is too long", "bio");
+        }
+    }
+
+    public static void ValidateAvatar(string? avatar)
+    {
+        if (avatar == null) return;
+        if (avatar.Length > 1_500_000) throw new ApiError.BadRequest("Avatar is too big", "avatar");
+    }
+}