refactor: standardise S3 URL generation (#362)

* refactor: replace presigned URL uploads with backend upload endpoints

* feat: update avatar upload to use new endpoint

* refactor: use createS3Client in auth hooks

* feat: generate presigned URLs for avatars

* fix: show avatar image in user menu

* fix: hide tooltip if content is empty

* fix: support external avatar URLs in generateAvatarUrl

* fix: remove content type restriction on attachments

apps/web/src/pages/api/upload/avatar.ts

@@ -0,0 +1,101 @@
+import type { NextApiRequest, NextApiResponse } from "next";
+import { PutObjectCommand } from "@aws-sdk/client-s3";
+
+import { createNextApiContext } from "@kan/api/trpc";
+import * as userRepo from "@kan/db/repository/user.repo";
+
+import { env } from "~/env";
+import { withRateLimit } from "@kan/api/utils/rateLimit";
+import { createS3Client } from "@kan/shared/utils";
+
+const MAX_SIZE_BYTES = 2 * 1024 * 1024; // 2MB
+const allowedContentTypes = ["image/jpeg", "image/png", "image/webp"];
+
+export const config = {
+  api: {
+    bodyParser: false,
+  },
+};
+
+export default withRateLimit(
+  { points: 100, duration: 60 },
+  async (req: NextApiRequest, res: NextApiResponse) => {
+    if (req.method !== "POST") {
+      return res.status(405).json({ error: "Method not allowed" });
+    }
+
+    try {
+      const { user, db } = await createNextApiContext(req);
+
+      if (!user) {
+        return res.status(401).json({ error: "Unauthorized" });
+      }
+
+      const bucket = env.NEXT_PUBLIC_AVATAR_BUCKET_NAME;
+      if (!bucket) {
+        return res.status(500).json({ error: "Avatar bucket not configured" });
+      }
+
+      const contentType = req.headers["content-type"];
+      const contentLengthHeader = req.headers["content-length"];
+      const contentLength = contentLengthHeader
+        ? Number.parseInt(contentLengthHeader, 10)
+        : NaN;
+
+      if (typeof contentType !== "string") {
+        return res.status(400).json({ error: "Missing content type" });
+      }
+
+      if (!allowedContentTypes.includes(contentType)) {
+        return res.status(400).json({ error: "Invalid content type" });
+      }
+
+      if (!Number.isFinite(contentLength) || contentLength <= 0) {
+        return res.status(400).json({ error: "Missing or invalid content length" });
+      }
+
+      if (contentLength > MAX_SIZE_BYTES) {
+        return res.status(400).json({ error: "File too large" });
+      }
+
+      const originalFilenameHeader =
+        (req.headers["x-original-filename"] as string | undefined) ?? "file";
+
+      const sanitizedFilename = originalFilenameHeader
+        .replace(/[^a-zA-Z0-9._-]/g, "_")
+        .substring(0, 200);
+
+      const s3Key = `${user.id}/${sanitizedFilename}`;
+
+      const client = createS3Client();
+
+      // Upload the file to S3
+      await client.send(
+        new PutObjectCommand({
+          Bucket: bucket,
+          Key: s3Key,
+          Body: req,
+          ContentType: contentType,
+          ContentLength: contentLength,
+        }),
+      );
+
+      // Update user image in database
+      const updatedUser = await userRepo.update(db, user.id, {
+        image: s3Key,
+      });
+
+      return res.status(200).json({
+        key: s3Key,
+        filename: sanitizedFilename,
+        contentType,
+        size: contentLength,
+        user: updatedUser,
+      });
+    } catch (error) {
+      console.error("Avatar upload failed", error);
+      return res.status(500).json({ error: "Internal server error" });
+    }
+  },
+);
+