Add decode_text()

app/email_utils.py

@@ -746,6 +746,17 @@ def encode_text(text: str, encoding: EmailEncoding = EmailEncoding.NO) -> str:
         return text
 
 
+def decode_text(text: str, encoding: EmailEncoding = EmailEncoding.NO) -> str:
+    if encoding == EmailEncoding.QUOTED:
+        decoded = quopri.decodestring(text.encode("utf-8"))
+        return str(decoded, "utf-8")
+    elif encoding == EmailEncoding.BASE64:
+        decoded = base64.b64decode(text.encode("utf-8"))
+        return str(decoded, "utf-8")
+    else:  # 7bit - no encoding
+        return text
+
+
 def add_header(msg: Message, text_header, html_header) -> Message:
     if msg.get_content_type() == "text/plain":
         encoding = get_encoding(msg)

tests/test_email_utils.py

@@ -23,6 +23,7 @@ from app.email_utils import (
     EmailEncoding,
     replace,
     should_disable,
+    decode_text,
 )
 from app.extensions import db
 from app.models import User, CustomDomain, Alias, Contact, EmailLog
@@ -554,6 +555,33 @@ def test_encode_text():
     assert encode_text("mèo méo", EmailEncoding.QUOTED) == "m=C3=A8o m=C3=A9o"
 
 
+def test_decode_text():
+    assert decode_text("") == ""
+    assert decode_text("ascii") == "ascii"
+
+    assert (
+        decode_text(encode_text("ascii", EmailEncoding.BASE64), EmailEncoding.BASE64)
+        == "ascii"
+    )
+    assert (
+        decode_text(
+            encode_text("mèo méo 🇪🇺", EmailEncoding.BASE64), EmailEncoding.BASE64
+        )
+        == "mèo méo 🇪🇺"
+    )
+
+    assert (
+        decode_text(encode_text("ascii", EmailEncoding.QUOTED), EmailEncoding.QUOTED)
+        == "ascii"
+    )
+    assert (
+        decode_text(
+            encode_text("mèo méo 🇪🇺", EmailEncoding.QUOTED), EmailEncoding.QUOTED
+        )
+        == "mèo méo 🇪🇺"
+    )
+
+
 def test_should_disable(flask_client):
     user = User.create(
         email="a@b.c",