From 72925cf1d81e0812375ce7a09ccb99b401078298 Mon Sep 17 00:00:00 2001
From: Jon Gjengset <jon@thesquareplanet.com>
Date: Sat, 21 Jul 2018 12:29:43 -0400
Subject: [PATCH] Handle unilateral server responses

Fixes #81.
---
 src/client.rs | 23 ++++++++++++++++++++++-
 src/parse.rs  | 31 +++++++++++++++++++++++++++++--
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/src/client.rs b/src/client.rs
index 4384c42..7008735 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -298,6 +298,12 @@ impl<T: Read + Write> Client<T> {
     }
 
     /// Selects a mailbox
+    ///
+    /// Note that the server *is* allowed to unilaterally send things to the client for messages in
+    /// a selected mailbox whose status has changed. See the note on [unilateral server responses
+    /// in RFC 3501](https://tools.ietf.org/html/rfc3501#section-7). This means that if you use
+    /// [`Client::run_command_and_read_response`], you *may* see additional untagged `RECENT`,
+    /// `EXISTS`, `FETCH`, and `EXPUNGE` responses!
     pub fn select(&mut self, mailbox_name: &str) -> Result<Mailbox> {
         self.run_command_and_read_response(&format!("SELECT {}", validate_str(mailbox_name)?))
             .and_then(|lines| parse_mailbox(&lines[..]))
@@ -309,12 +315,21 @@ impl<T: Read + Write> Client<T> {
             .and_then(|lines| parse_mailbox(&lines[..]))
     }
 
-    /// Fetch retreives data associated with a message in the mailbox.
+    /// Fetch retreives data associated with a set of messages in the mailbox.
+    ///
+    /// Note that the server *is* allowed to unilaterally include `FETCH` responses for other
+    /// messages in the selected mailbox whose status has changed. See the note on [unilateral
+    /// server responses in RFC 3501](https://tools.ietf.org/html/rfc3501#section-7).
     pub fn fetch(&mut self, sequence_set: &str, query: &str) -> ZeroCopyResult<Vec<Fetch>> {
         self.run_command_and_read_response(&format!("FETCH {} {}", sequence_set, query))
             .and_then(|lines| parse_fetches(lines))
     }
 
+    /// Fetch retreives data associated with a set of messages by UID in the mailbox.
+    ///
+    /// Note that the server *is* allowed to unilaterally include `FETCH` responses for other
+    /// messages in the selected mailbox whose status has changed. See the note on [unilateral
+    /// server responses in RFC 3501](https://tools.ietf.org/html/rfc3501#section-7).
     pub fn uid_fetch(&mut self, uid_set: &str, query: &str) -> ZeroCopyResult<Vec<Fetch>> {
         self.run_command_and_read_response(&format!("UID FETCH {} {}", uid_set, query))
             .and_then(|lines| parse_fetches(lines))
@@ -472,6 +487,12 @@ impl<T: Read + Write> Client<T> {
         self.write_line(command.into_bytes().as_slice())
     }
 
+    /// Run a raw IMAP command and read back its response.
+    ///
+    /// Note that the server *is* allowed to unilaterally send things to the client for messages in
+    /// a selected mailbox whose status has changed. See the note on [unilateral server responses
+    /// in RFC 3501](https://tools.ietf.org/html/rfc3501#section-7). This means that you *may* see
+    /// additional untagged `RECENT`, `EXISTS`, `FETCH`, and `EXPUNGE` responses!
     pub fn run_command_and_read_response(&mut self, untagged_command: &str) -> Result<Vec<u8>> {
         self.run_command(untagged_command)?;
         self.read_response()
diff --git a/src/parse.rs b/src/parse.rs
index 7eb0ceb..8e68dce 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -1,4 +1,4 @@
-use imap_proto::{self, Response};
+use imap_proto::{self, MailboxDatum, Response};
 use nom::IResult;
 use regex::Regex;
 
@@ -19,6 +19,8 @@ pub fn parse_authenticate_response(line: String) -> Result<String> {
 enum MapOrNot<T> {
     Map(T),
     Not(Response<'static>),
+    #[allow(dead_code)]
+    Ignore,
 }
 
 unsafe fn parse_many<T, F>(lines: Vec<u8>, mut map: F) -> ZeroCopyResult<Vec<T>>
@@ -38,7 +40,20 @@ where
 
                     match map(resp) {
                         MapOrNot::Map(t) => things.push(t),
-                        MapOrNot::Not(resp) => break Err(resp.into()),
+                        MapOrNot::Not(resp) => {
+                            // check if this is simply a unilateral server response
+                            // (see Section 7 of RFC 3501):
+                            match resp {
+                                Response::MailboxData(MailboxDatum::Recent { .. })
+                                | Response::MailboxData(MailboxDatum::Exists { .. })
+                                | Response::Fetch(..)
+                                | Response::Expunge(..) => {
+                                    continue;
+                                }
+                                resp => break Err(resp.into()),
+                            }
+                        }
+                        MapOrNot::Ignore => continue,
                     }
                 }
                 _ => {
@@ -264,4 +279,16 @@ mod tests {
         assert_eq!(fetches[1].uid, None);
         assert_eq!(fetches[1].rfc822(), None);
     }
+
+    #[test]
+    fn parse_fetches_w_unilateral() {
+        // https://github.com/mattnenterprise/rust-imap/issues/81
+        let lines = b"\
+            * 37 FETCH (UID 74)\r\n\
+            * 1 RECENT\r\n";
+        let fetches = parse_fetches(lines.to_vec()).unwrap();
+        assert_eq!(fetches.len(), 1);
+        assert_eq!(fetches[0].message, 37);
+        assert_eq!(fetches[0].uid, Some(74));
+    }
 }