DH-4603 Decrypt file content if it is encrypted (#170)

dataherald/utils/s3.py

@@ -1,21 +1,33 @@
 import boto3
+from cryptography.fernet import InvalidToken
 
 from dataherald.config import Settings
+from dataherald.utils.encrypt import FernetEncrypt
 
 
 class S3:
     def __init__(self):
         self.settings = Settings()
 
     def download(self, path: str) -> str:
+        fernet_encrypt = FernetEncrypt()
         path = path.split("/")
         s3_client = boto3.client(
             "s3",
             aws_access_key_id=self.settings.s3_aws_access_key_id,
             aws_secret_access_key=self.settings.s3_aws_secret_access_key,
         )
-
+        file_location = f"tmp/{path[-1]}"
         s3_client.download_file(
-            Bucket=path[2], Key=f"{path[-1]}", Filename=f"tmp/{path[-1]}"
+            Bucket=path[2], Key=f"{path[-1]}", Filename=file_location
         )
-        return f"tmp/{path[-1]}"
+        # Decrypt file content if it is encrypted
+        try:
+            with open(file_location) as file_object:
+                decrypted_content = fernet_encrypt.decrypt(file_object.read())
+            with open(file_location, "w") as file_object:
+                file_object.write(decrypted_content)
+        except InvalidToken:
+            pass
+
+        return file_location