Pass IDLE responses to caller.

Cargo.toml

@@ -31,6 +31,7 @@ lazy_static = "1.4"
 lettre = "0.9"
 lettre_email = "0.9"
 rustls-connector = "0.13.0"
+structopt = "0.3"
 
 [[example]]
 name = "basic"
@@ -40,6 +41,10 @@ required-features = ["default"]
 name = "gmail_oauth2"
 required-features = ["default"]
 
+[[example]]
+name = "idle"
+required-features = ["default"]
+
 [[test]]
 name = "imap_integration"
 required-features = ["default"]

examples/idle.rs

@@ -0,0 +1,84 @@
+use native_tls::TlsConnector;
+use structopt::StructOpt;
+
+#[derive(StructOpt, Debug)]
+#[structopt(name = "idle")]
+struct Opt {
+    // The server name to connect to
+    #[structopt(short, long)]
+    server: String,
+
+    // The port to use
+    #[structopt(short, long, default_value = "993")]
+    port: u16,
+
+    // The account username
+    #[structopt(short, long)]
+    username: String,
+
+    // The account password. In a production system passwords
+    // would normally be in a config or fetched at runtime from
+    // a password manager or user prompt and not passed on the
+    // command line.
+    #[structopt(short = "w", long)]
+    password: String,
+
+    // The mailbox to IDLE on
+    #[structopt(short, long, default_value = "INBOX")]
+    mailbox: String,
+
+    #[structopt(
+        short = "x",
+        long,
+        help = "The number of responses to receive before exiting",
+        default_value = "5"
+    )]
+    max_responses: usize,
+}
+
+fn main() {
+    let opt = Opt::from_args();
+
+    let ssl_conn = TlsConnector::builder().build().unwrap();
+    let client = imap::connect((opt.server.clone(), opt.port), opt.server, &ssl_conn)
+        .expect("Could not connect to imap server");
+    let mut imap = client
+        .login(opt.username, opt.password)
+        .expect("Could not authenticate");
+
+    // Turn on debug output so we can see the actual traffic coming
+    // from the server and how it is handled in our callback.
+    // This wouldn't be turned on in a production build, but is helpful
+    // in examples and for debugging.
+    imap.debug = true;
+
+    imap.select(opt.mailbox).expect("Could not select mailbox");
+
+    let idle = imap.idle().expect("Could not IDLE");
+
+    // Implement a trivial counter that causes the IDLE callback to end the IDLE
+    // after a fixed number of responses.
+    //
+    // A threaded client could use channels or shared data to interact with the
+    // rest of the program and update mailbox state, decide to exit the IDLE, etc.
+    let mut num_responses = 0;
+    let max_responses = opt.max_responses;
+    let idle_result = idle.wait_keepalive(|response| {
+        num_responses += 1;
+        println!("IDLE response #{}: {:?}", num_responses, response);
+        if num_responses >= max_responses {
+            // Stop IDLE
+            false
+        } else {
+            // Continue IDLE
+            true
+        }
+    });
+
+    match idle_result {
+        Ok(()) => println!("IDLE finished normally"),
+        Err(e) => println!("IDLE finished with error {:?}", e),
+    }
+
+    imap.logout().expect("Could not log out");
+}

src/extensions/idle.rs

@@ -3,6 +3,8 @@
 
 use crate::client::Session;
 use crate::error::{Error, Result};
+use crate::parse::parse_idle;
+use crate::types::UnsolicitedResponse;
 #[cfg(feature = "tls")]
 use native_tls::TlsStream;
 use std::io::{self, Read, Write};
@@ -13,8 +15,31 @@ use std::time::Duration;
 ///
 /// The handle blocks using the [`IDLE` command](https://tools.ietf.org/html/rfc2177#section-3)
 /// specificed in [RFC 2177](https://tools.ietf.org/html/rfc2177) until the underlying server state
-/// changes in some way. While idling does inform the client what changes happened on the server,
-/// this implementation will currently just block until _anything_ changes, and then notify the
+/// changes in some way.
+///
+/// Each of the `wait` functions takes a callback function which receives any responses
+/// that arrive on the channel while IDLE. The callback function implements whatever
+/// logic is needed to handle the IDLE response, and then returns a boolean
+/// to continue idling (`true`) or stop (`false`).
+/// For users that want the IDLE to exit on any change (the behavior proior to version 3.0),
+/// a convenience callback function [`stop_on_any`] is provided.
+///
+/// ```no_run
+/// # use native_tls::TlsConnector;
+/// use imap::extensions::idle;
+/// let ssl_conn = TlsConnector::builder().build().unwrap();
+/// let client = imap::connect(("example.com", 993), "example.com", &ssl_conn)
+///     .expect("Could not connect to imap server");
+/// let mut imap = client.login("user@example.com", "password")
+///     .expect("Could not authenticate");
+/// imap.select("INBOX")
+///     .expect("Could not select mailbox");
+///
+/// let idle = imap.idle().expect("Could not IDLE");
+///
+/// // Exit on any mailbox change
+/// let result = idle.wait_keepalive(idle::stop_on_any);
+/// ```
 ///
 /// Note that the server MAY consider a client inactive if it has an IDLE command running, and if
 /// such a server has an inactivity timeout it MAY log the client off implicitly at the end of its
@@ -40,6 +65,11 @@ pub enum WaitOutcome {
     MailboxChanged,
 }
 
+/// A convenience function to always cause the IDLE handler to exit on any change.
+pub fn stop_on_any(_response: UnsolicitedResponse) -> bool {
+    false
+}
+
 /// Must be implemented for a transport in order for a `Session` using that transport to support
 /// operations with timeouts.
 ///
@@ -100,37 +130,74 @@ impl<'a, T: Read + Write + 'a> Handle<'a, T> {
     /// Internal helper that doesn't consume self.
     ///
     /// This is necessary so that we can keep using the inner `Session` in `wait_keepalive`.
-    fn wait_inner(&mut self, reconnect: bool) -> Result<WaitOutcome> {
+    fn wait_inner<F>(&mut self, reconnect: bool, mut callback: F) -> Result<WaitOutcome>
+    where
+        F: FnMut(UnsolicitedResponse) -> bool,
+    {
         let mut v = Vec::new();
-        loop {
-            let result = match self.session.readline(&mut v).map(|_| ()) {
+        let result = loop {
+            let rest = match self.session.readline(&mut v) {
                 Err(Error::Io(ref e))
                     if e.kind() == io::ErrorKind::TimedOut
                         || e.kind() == io::ErrorKind::WouldBlock =>
                 {
-                    if reconnect {
-                        self.terminate()?;
-                        self.init()?;
-                        return self.wait_inner(reconnect);
+                    break Ok(WaitOutcome::TimedOut);
+                }
+                Ok(_len) => {
+                    //  Handle Dovecot's imap_idle_notify_interval message
+                    if v.eq_ignore_ascii_case(b"* OK Still here\r\n") {
+                        v.clear();
+                        continue;
+                    }
+                    match parse_idle(&v) {
+                        (_rest, Some(Err(r))) => break Err(r),
+                        (rest, Some(Ok(response))) => {
+                            if !callback(response) {
+                                break Ok(WaitOutcome::MailboxChanged);
+                            }
+                            rest
+                        }
+                        (rest, None) => rest,
                     }
-                    Ok(WaitOutcome::TimedOut)
                 }
-                Ok(()) => Ok(WaitOutcome::MailboxChanged),
-                Err(r) => Err(r),
-            }?;
+                Err(r) => break Err(r),
+            };
 
-            // Handle Dovecot's imap_idle_notify_interval message
-            if v.eq_ignore_ascii_case(b"* OK Still here\r\n") {
+            // Update remaining data with unparsed data if needed.
+            if rest.is_empty() {
                 v.clear();
             } else {
-                break Ok(result);
+                // Assert on partial parse in debug builds - we expect to always parse all
+                // or none of the input buffer. On release builds, we still do the right thing.
+                debug_assert!(
+                    rest.len() != v.len(),
+                    "Unexpected partial parse: input: {:?}, output: {:?}",
+                    v,
+                    rest
+                );
+                let used = v.len() - rest.len();
+                v.drain(0..used);
+            }
+        };
+
+        // Reconnect on timeout if needed
+        match (reconnect, result) {
+            (true, Ok(WaitOutcome::TimedOut)) => {
+                self.terminate()?;
+                self.init()?;
+                self.wait_inner(reconnect, callback)
             }
+            (_, result) => result,
         }
     }
 
-    /// Block until the selected mailbox changes.
-    pub fn wait(mut self) -> Result<()> {
-        self.wait_inner(true).map(|_| ())
+    /// Block until the given callback returns `false`, or until a response
+    /// arrives that is not explicitly handled by [`UnsolicitedResponse`].
+    pub fn wait<F>(mut self, callback: F) -> Result<()>
+    where
+        F: FnMut(UnsolicitedResponse) -> bool,
+    {
+        self.wait_inner(true, callback).map(|_| ())
     }
 }
 
@@ -142,15 +209,19 @@ impl<'a, T: SetReadTimeout + Read + Write + 'a> Handle<'a, T> {
         self.keepalive = interval;
     }
 
-    /// Block until the selected mailbox changes.
+    /// Block until the given callback returns `false`, or until a response
+    /// arrives that is not explicitly handled by [`UnsolicitedResponse`].
     ///
     /// This method differs from [`Handle::wait`] in that it will periodically refresh the IDLE
     /// connection, to prevent the server from timing out our connection. The keepalive interval is
     /// set to 29 minutes by default, as dictated by RFC 2177, but can be changed using
     /// [`Handle::set_keepalive`].
     ///
     /// This is the recommended method to use for waiting.
-    pub fn wait_keepalive(self) -> Result<()> {
+    pub fn wait_keepalive<F>(self, callback: F) -> Result<()>
+    where
+        F: FnMut(UnsolicitedResponse) -> bool,
+    {
         // The server MAY consider a client inactive if it has an IDLE command
         // running, and if such a server has an inactivity timeout it MAY log
         // the client off implicitly at the end of its timeout period.  Because
@@ -159,26 +230,33 @@ impl<'a, T: SetReadTimeout + Read + Write + 'a> Handle<'a, T> {
         // This still allows a client to receive immediate mailbox updates even
         // though it need only "poll" at half hour intervals.
         let keepalive = self.keepalive;
-        self.timed_wait(keepalive, true).map(|_| ())
-    }
-
-    /// Block until the selected mailbox changes, or until the given amount of time has expired.
-    #[deprecated(note = "use wait_with_timeout instead")]
-    pub fn wait_timeout(self, timeout: Duration) -> Result<()> {
-        self.wait_with_timeout(timeout).map(|_| ())
+        self.timed_wait(keepalive, true, callback).map(|_| ())
     }
 
-    /// Block until the selected mailbox changes, or until the given amount of time has expired.
-    pub fn wait_with_timeout(self, timeout: Duration) -> Result<WaitOutcome> {
-        self.timed_wait(timeout, false)
+    /// Block until the given given amount of time has elapsed, the given callback
+    /// returns `false`, or until a response arrives that is not explicitly handled
+    /// by [`UnsolicitedResponse`].
+    pub fn wait_with_timeout<F>(self, timeout: Duration, callback: F) -> Result<WaitOutcome>
+    where
+        F: FnMut(UnsolicitedResponse) -> bool,
+    {
+        self.timed_wait(timeout, false, callback)
     }
 
-    fn timed_wait(mut self, timeout: Duration, reconnect: bool) -> Result<WaitOutcome> {
+    fn timed_wait<F>(
+        mut self,
+        timeout: Duration,
+        reconnect: bool,
+        callback: F,
+    ) -> Result<WaitOutcome>
+    where
+        F: FnMut(UnsolicitedResponse) -> bool,
+    {
         self.session
             .stream
             .get_mut()
             .set_read_timeout(Some(timeout))?;
-        let res = self.wait_inner(reconnect);
+        let res = self.wait_inner(reconnect, callback);
         let _ = self.session.stream.get_mut().set_read_timeout(None).is_ok();
         res
     }