first attempt to implement decoding as 7or8bit through quopri, base64, and byte replacement

gpgmymail

@@ -34,12 +34,16 @@ import email.mime.application
 import email.mime.multipart
 import email.mime.message
 import typing
+# for decode_email:
+import quopri
+import base64
 
 # see: https://gnupg.readthedocs.io/en/latest/
 import gnupg
 
 # constants
 DEFAULT_ENCODING='utf-8'  # default is latin-1 which fails w some unicode chars
+CTES_TO_BE_DECODED = ("quoted-printable", "base64")
 
 def is_message_encrypted(message: email.message.Message) -> bool:
     """Determines whether or not an email message is encrypted.
@@ -55,19 +59,43 @@ def decode_email(message: email.message.Message) -> email.message.Message:
 
     :param message: email.message.Message to be decoded
     :return: decoded email.message.Message"""
-    if message.is_multipart():
+    # this is a kinda hacky way to do this by manipulating the message as a
-        payload = []
+    # string but i couldn't get it to work any other way
-        for part in message.walk():
-            if not part.is_multipart():
-                payload.append(part.get_payload(decode=True))
 
-        message.set_payload(payload)
+    msg_ctes = message.get_all("Content-Transfer-Encoding")
-    else:
+    
-        message.set_payload(message.get_payload(decode=True))
+    # this list will be populated with any encoding that needs to be decoded,
+    # e.g. base64
+    # empty if no decoding needed
+    # set used to avoid dupes
+    decodes_needed = set()
+    # check if any of the parts of the message need decoding
+    for cte in CTES_TO_BE_DECODED:
+        if cte in msg_ctes:
+            decodes_needed.add(cte)
+    # no decoding needed, go ahead with message
+    if not decodes_needed:
+        return message
 
-    message["Content-Transfer-Encoding"] = "7bit"
+    # decoding needed:
+    # as_string() gives us str, encode() gives us bytes
+    decoded_bytes = msg.as_string().encode()
+    if "quoted-printable" in decodes_needed:
+        decoded_bytes = quopri.decodestring(decoded_bytes)
+    if "base64" in decodes_needed:
+        decoded_bytes = base64.b64decode(decoded_bytes)
 
-    return message
+    # replace any instances of the Content-Transfer-Encoding header
+    decoded_bytes = decoded_bytes.replace(
+        b'Content-Transfer-Encoding: quoted-printable',
+        b'Content-Transfer-Encoding: 7bit'
+    )
+    decoded_bytes = decoded_bytes.replace(
+        b'Content-Transfer-Encoding: base64',
+        b'Content-Transfer-Encoding: 7bit'
+    )
+
+    return email.message_from_bytes(decoded_bytes)
 
 def encrypt(
         message: email.message.Message,