feat: add S3 utility functions for file upload and presigned URL generation

app/utilities/s3.py

@@ -0,0 +1,60 @@
+import mimetypes
+
+import boto3
+from botocore.config import Config
+from flask import current_app
+from flask_login import current_user
+
+
+def get_s3_client():
+    s3_config = Config(
+        retries={"max_attempts": 3, "mode": "standard"},
+        request_checksum_calculation="when_required",
+        response_checksum_validation="when_required",
+        s3={"addressing_style": "path"},
+        signature_version="s3v4",
+    )
+
+    return boto3.client(
+        "s3",
+        endpoint_url=current_app.config["S3_ENDPOINT_URL"],
+        aws_access_key_id=current_app.config["S3_ACCESS_KEY_ID"],
+        aws_secret_access_key=current_app.config["S3_SECRET_KEY"],
+        region_name="us-east-1",
+        config=s3_config,
+    )
+
+
+def generate_presigned_url(key, expiration=3600):
+    s3_client = get_s3_client()
+    bucket = current_app.config["S3_BUCKET_NAME"]
+
+    presigned_url = s3_client.generate_presigned_url(
+        "get_object",
+        Params={"Bucket": bucket, "Key": key},
+        ExpiresIn=expiration,
+    )
+
+    return presigned_url
+
+
+def upload_to_s3(file, filename, content_type=None):
+    s3 = get_s3_client()
+    bucket = current_app.config["S3_BUCKET_NAME"]
+
+    if content_type is None:
+        guessed, _ = mimetypes.guess_type(filename)
+        content_type = guessed or "application/octet-stream"
+
+    file_content = file.read()
+    file.seek(0)
+
+    key = f"notes/{current_user.id}/{filename}"
+    s3.put_object(
+        Bucket=bucket,
+        Key=key,
+        Body=file_content,
+        ContentType=content_type,
+    )
+
+    return key