1 files changed, 95 insertions, 1 deletions
diff --git a/alot/mail/reply.py b/alot/mail/reply.py
index 0e7d897e..4a69ecee 100644
--- a/alot/mail/reply.py
+++ b/alot/mail/reply.py
@@ -2,7 +2,8 @@
 # For further details see the COPYING file
 
 import email.policy
-from   email.utils import getaddresses
+from   email.utils import getaddresses, parseaddr
+from   enum        import Enum, auto
 import logging
 
 from .                      import headers as HDR
@@ -69,6 +70,99 @@ def determine_account(headers, action = ACT_REPLY):
     from_value = formataddr((realname, str(address)))
     return from_value, account
 
+class ReplyMode(Enum):
+    AUTHOR = auto()
+    GROUP  = auto()
+    LIST   = auto()
+
+def _ensure_unique_address(recipients):
+    """
+    clean up a list of name,address pairs so that
+    no address appears multiple times.
+    """
+    res = dict()
+    for name, address in getaddresses(recipients):
+        res[address] = name
+    logging.debug(res)
+    urecipients = [formataddr((n, a)) for a, n in res.items()]
+    return sorted(urecipients)
+
+def _clear_my_address(my_account, value):
+    """return recipient header without the addresses in my_account
+
+    :param my_account: my account
+    :type my_account: :class:`Account`
+    :param value: a list of recipient or sender strings (with or without
+        real names as taken from email headers)
+    :type value: list(str)
+    :returns: a new, potentially shortend list
+    :rtype: list(str)
+    """
+    new_value = []
+    for name, address in getaddresses(value):
+        if not my_account.matches_address(address):
+            new_value.append(formataddr((name, address)))
+    return new_value
+
+def determine_recipients(message, account, mode):
+    # set To
+    sender = (message.headers.get(HDR.REPLY_TO) or
+              message.headers.get(HDR.FROM) or '')
+    sender_address = parseaddr(sender)[1]
+    cc = []
+
+    # check if reply is to self sent message
+    if account.matches_address(sender_address):
+        recipients = message.headers.get_all(HDR.TO)
+        emsg = 'Replying to own message, set recipients to: %s' \
+            % recipients
+        logging.debug(emsg)
+    else:
+        recipients = [sender]
+
+    if mode == ReplyMode.GROUP:
+        # make sure that our own address is not included
+        # if the message was self-sent, then our address is not included
+        MFT = message.headers.get_all(HDR.MAIL_FOLLOWUP_TO)
+        followupto = _clear_my_address(account, MFT)
+        if followupto and settings.get('honor_followup_to'):
+            logging.debug('honor followup to: %s', ', '.join(followupto))
+            recipients = followupto
+            # since Mail-Followup-To was set, ignore the Cc header
+        else:
+            if sender != message.headers.get(HDR.FROM):
+                recipients.append(message.headers.get(HDR.FROM))
+
+            # append To addresses if not replying to self sent message
+            if not account.matches_address(sender_address):
+                cleared = _clear_my_address(account,
+                                           message.headers.get_all(HDR.TO))
+                recipients.extend(cleared)
+
+            # copy cc for group-replies
+            if HDR.CC in message.headers:
+                cc = _clear_my_address(account, message.headers.get_all(HDR.CC))
+
+    to = ', '.join(_ensure_unique_address(recipients))
+    cc = ', '.join(cc)
+    logging.debug('reply to: %s', to)
+
+    if mode == ReplyMode.LIST:
+        # To choose the target of the reply --list
+        # Reply-To is standart reply target RFC 2822:, RFC 1036: 2.2.1
+        # X-BeenThere is needed by sourceforge ML also winehq
+        # X-Mailing-List is also standart and is used by git-send-mail
+        to = (message.headers.get(HDR.REPLY_TO)     or
+              message.headers.get(HDR.X_BEEN_THERE) or
+              message.headers.get(HDR.X_MAILING_LIST))
+
+        # Some mail server (gmail) will not resend you own mail, so you
+        # have to deal with the one in sent
+        if to is None:
+            to = message.headers[HDR.TO]
+        logging.debug('mail list reply to: %s', to)
+
+    return to, cc
 
 def subject(message):
     subject = message.headers.get(HDR.SUBJECT) or ''