src/imap/command/authenticated.rs

@@ -453,7 +453,7 @@ impl<'a> AuthenticatedContext<'a> {
                 .code(Code::ReadWrite)
                 .set_body(data)
                 .ok()?,
-            flow::Transition::Select(mb),
+            flow::Transition::Select(mb, flow::MailboxPerm::ReadWrite),
         ))
     }
 
@@ -491,7 +491,7 @@ impl<'a> AuthenticatedContext<'a> {
                 .code(Code::ReadOnly)
                 .set_body(data)
                 .ok()?,
-            flow::Transition::Examine(mb),
+            flow::Transition::Select(mb, flow::MailboxPerm::ReadOnly),
         ))
     }
 

src/imap/command/selected.rs

@@ -25,6 +25,7 @@ pub struct SelectedContext<'a> {
     pub mailbox: &'a mut MailboxView,
     pub server_capabilities: &'a ServerCapability,
     pub client_capabilities: &'a mut ClientCapability,
+    pub perm: &'a flow::MailboxPerm,
 }
 
 pub async fn dispatch<'a>(
@@ -39,7 +40,10 @@ pub async fn dispatch<'a>(
         CommandBody::Logout => anystate::logout(),
 
         // Specific to this state (7 commands + NOOP)
-        CommandBody::Close => ctx.close().await,
+        CommandBody::Close => match ctx.perm {
+            flow::MailboxPerm::ReadWrite => ctx.close().await,
+            flow::MailboxPerm::ReadOnly => ctx.examine_close().await,
+        },
         CommandBody::Noop | CommandBody::Check => ctx.noop().await,
         CommandBody::Fetch {
             sequence_set,
@@ -75,6 +79,11 @@ pub async fn dispatch<'a>(
         // UNSELECT extension (rfc3691)
         CommandBody::Unselect => ctx.unselect().await,
 
+        // IDLE extension (rfc2177)
+        CommandBody::Idle => {
+            unimplemented!()
+        }
+
         // In selected mode, we fallback to authenticated when needed
         _ => {
             authenticated::dispatch(authenticated::AuthenticatedContext {
@@ -102,6 +111,18 @@ impl<'a> SelectedContext<'a> {
         ))
     }
 
+    /// CLOSE in examined state is not the same as in selected state
+    /// (in selected state it also does an EXPUNGE, here it doesn't)
+    async fn examine_close(self) -> Result<(Response<'static>, flow::Transition)> {
+        Ok((
+            Response::build()
+                .to_req(self.req)
+                .message("CLOSE completed")
+                .ok()?,
+            flow::Transition::Unselect,
+        ))
+    }
+
     async fn unselect(self) -> Result<(Response<'static>, flow::Transition)> {
         Ok((
             Response::build()
@@ -189,6 +210,10 @@ impl<'a> SelectedContext<'a> {
     }
 
     async fn expunge(self) -> Result<(Response<'static>, flow::Transition)> {
+        if let Some(failed) = self.fail_read_only() {
+            return Ok((failed, flow::Transition::None))
+        }
+
         let tag = self.req.tag.clone();
         let data = self.mailbox.expunge().await?;
 
@@ -211,6 +236,10 @@ impl<'a> SelectedContext<'a> {
         modifiers: &[StoreModifier],
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
+        if let Some(failed) = self.fail_read_only() {
+            return Ok((failed, flow::Transition::None))
+        }
+
         let mut unchanged_since: Option<NonZeroU64> = None;
         modifiers.iter().for_each(|m| match m {
             StoreModifier::UnchangedSince(val) => {
@@ -251,6 +280,11 @@ impl<'a> SelectedContext<'a> {
         mailbox: &MailboxCodec<'a>,
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
+        //@FIXME Could copy be valid in EXAMINE mode?
+        if let Some(failed) = self.fail_read_only() {
+            return Ok((failed, flow::Transition::None))
+        }
+
         let name: &str = MailboxName(mailbox).try_into()?;
 
         let mb_opt = self.user.open_mailbox(&name).await?;
@@ -303,6 +337,10 @@ impl<'a> SelectedContext<'a> {
         mailbox: &MailboxCodec<'a>,
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
+        if let Some(failed) = self.fail_read_only() {
+            return Ok((failed, flow::Transition::None))
+        }
+
         let name: &str = MailboxName(mailbox).try_into()?;
 
         let mb_opt = self.user.open_mailbox(&name).await?;
@@ -350,4 +388,16 @@ impl<'a> SelectedContext<'a> {
             flow::Transition::None,
         ))
     }
+
+    fn fail_read_only(&self) -> Option<Response<'static>> {
+        match self.perm {
+            flow::MailboxPerm::ReadWrite => None,
+            flow::MailboxPerm::ReadOnly => {
+               Some(Response::build()
+                   .to_req(self.req)
+                   .message("Write command are forbidden while exmining mailbox")
+                   .no().unwrap())
+            },
+        }
+    }
 }

src/imap/flow.rs

@@ -19,17 +19,23 @@ impl StdError for Error {}
 pub enum State {
     NotAuthenticated,
     Authenticated(Arc<User>),
-    Selected(Arc<User>, MailboxView),
-    // Examined is like Selected, but indicates that the mailbox is read-only
-    Examined(Arc<User>, MailboxView),
+    Selected(Arc<User>, MailboxView, MailboxPerm),
+    Idle(Arc<User>, MailboxView, MailboxPerm),
     Logout,
 }
 
+#[derive(Clone)]
+pub enum MailboxPerm {
+    ReadOnly,
+    ReadWrite,
+}
+
 pub enum Transition {
     None,
     Authenticate(Arc<User>),
-    Examine(MailboxView),
-    Select(MailboxView),
+    Select(MailboxView, MailboxPerm),
+    Idle,
+    UnIdle,
     Unselect,
     Logout,
 }
@@ -38,20 +44,22 @@ pub enum Transition {
 // https://datatracker.ietf.org/doc/html/rfc3501#page-13
 impl State {
     pub fn apply(&mut self, tr: Transition) -> Result<(), Error> {
-        let new_state = match (&self, tr) {
+        let new_state = match (std::mem::replace(self, State::NotAuthenticated), tr) {
             (_s, Transition::None) => return Ok(()),
             (State::NotAuthenticated, Transition::Authenticate(u)) => State::Authenticated(u),
             (
-                State::Authenticated(u) | State::Selected(u, _) | State::Examined(u, _),
-                Transition::Select(m),
-            ) => State::Selected(u.clone(), m),
-            (
-                State::Authenticated(u) | State::Selected(u, _) | State::Examined(u, _),
-                Transition::Examine(m),
-            ) => State::Examined(u.clone(), m),
-            (State::Selected(u, _) | State::Examined(u, _), Transition::Unselect) => {
+                State::Authenticated(u) | State::Selected(u, _, _),
+                Transition::Select(m, p),
+            ) => State::Selected(u, m, p),
+            (State::Selected(u, _, _) , Transition::Unselect) => {
                 State::Authenticated(u.clone())
             }
+            (State::Selected(u, m, p), Transition::Idle) => {
+                State::Idle(u, m, p)
+            },
+            (State::Idle(u, m, p), Transition::UnIdle) => {
+                State::Selected(u, m, p)
+            },
             (_, Transition::Logout) => State::Logout,
             _ => return Err(Error::ForbiddenTransition),
         };

src/imap/mod.rs

@@ -8,22 +8,28 @@ mod index;
 mod mail_view;
 mod mailbox_view;
 mod mime_view;
+mod request;
 mod response;
 mod search;
 mod session;
 
 use std::net::SocketAddr;
 
-use anyhow::Result;
+use anyhow::{Result, bail};
 use futures::stream::{FuturesUnordered, StreamExt};
 
 use tokio::net::TcpListener;
 use tokio::sync::watch;
+use tokio::sync::mpsc;
 
 use imap_codec::imap_types::{core::Text, response::Greeting};
 use imap_flow::server::{ServerFlow, ServerFlowEvent, ServerFlowOptions};
 use imap_flow::stream::AnyStream;
+use imap_codec::imap_types::response::{Code, Response, CommandContinuationRequest, Status};
 
+use crate::imap::response::{Body, ResponseOrIdle};
+use crate::imap::session::Instance;
+use crate::imap::request::Request;
 use crate::config::ImapConfig;
 use crate::imap::capability::ServerCapability;
 use crate::login::ArcLoginProvider;
@@ -35,8 +41,8 @@ pub struct Server {
     capabilities: ServerCapability,
 }
 
+#[derive(Clone)]
 struct ClientContext {
-    stream: AnyStream,
     addr: SocketAddr,
     login_provider: ArcLoginProvider,
     must_exit: watch::Receiver<bool>,
@@ -74,13 +80,12 @@ impl Server {
             tracing::info!("IMAP: accepted connection from {}", remote_addr);
 
             let client = ClientContext {
-                stream: AnyStream::new(socket),
                 addr: remote_addr.clone(),
                 login_provider: self.login_provider.clone(),
                 must_exit: must_exit.clone(),
                 server_capabilities: self.capabilities.clone(),
             };
-            let conn = tokio::spawn(client_wrapper(client));
+            let conn = tokio::spawn(NetLoop::handler(client, AnyStream::new(socket)));
             connections.push(conn);
         }
         drop(tcp);
@@ -92,46 +97,74 @@ impl Server {
     }
 }
 
-async fn client_wrapper(ctx: ClientContext) {
-    let addr = ctx.addr.clone();
-    match client(ctx).await {
-        Ok(()) => {
-            tracing::debug!("closing successful session for {:?}", addr);
-        }
-        Err(e) => {
-            tracing::error!("closing errored session for {:?}: {}", addr, e);
-        }
-    }
+use  tokio::sync::mpsc::*;
+enum LoopMode {
+    Quit,
+    Interactive,
+    IdleUntil(tokio::sync::Notify),
 }
 
-async fn client(mut ctx: ClientContext) -> Result<()> {
-    // Send greeting
-    let (mut server, _) = ServerFlow::send_greeting(
-        ctx.stream,
-        ServerFlowOptions {
-            crlf_relaxed: false,
-            literal_accept_text: Text::unvalidated("OK"),
-            literal_reject_text: Text::unvalidated("Literal rejected"),
-            ..ServerFlowOptions::default()
-        },
-        Greeting::ok(
-            Some(Code::Capability(ctx.server_capabilities.to_vec())),
-            "Aerogramme",
-        )
-        .unwrap(),
-    )
-    .await?;
+struct NetLoop {
+    ctx: ClientContext,
+    server: ServerFlow,
+    cmd_tx: Sender<Request>,
+    resp_rx: UnboundedReceiver<ResponseOrIdle>,
+}
 
-    use crate::imap::response::{Body, Response as MyResponse};
-    use crate::imap::session::Instance;
-    use imap_codec::imap_types::command::Command;
-    use imap_codec::imap_types::response::{Code, Response, Status};
+impl NetLoop {
+    async fn handler(ctx: ClientContext, sock: AnyStream) {
+        let addr = ctx.addr.clone();
 
-    use tokio::sync::mpsc;
-    let (cmd_tx, mut cmd_rx) = mpsc::channel::<Command<'static>>(10);
-    let (resp_tx, mut resp_rx) = mpsc::unbounded_channel::<MyResponse<'static>>();
+        let nl = match Self::new(ctx, sock).await {
+            Ok(nl) => {
+                tracing::debug!(addr=?addr, "netloop successfully initialized");
+                nl
+            },
+            Err(e) => {
+                tracing::error!(addr=?addr, err=?e, "netloop can not be initialized, closing session");
+                return
+            }
+        };
 
-    let bckgrnd = tokio::spawn(async move {
+        match nl.core().await {
+            Ok(()) => {
+                tracing::debug!("closing successful netloop core for {:?}", addr);
+            }
+            Err(e) => {
+                tracing::error!("closing errored netloop core for {:?}: {}", addr, e);
+            }
+        }
+    }
+
+    async fn new(mut ctx: ClientContext, sock: AnyStream) -> Result<Self> {
+        // Send greeting
+        let (mut server, _) = ServerFlow::send_greeting(
+            sock,
+            ServerFlowOptions {
+                crlf_relaxed: false,
+                literal_accept_text: Text::unvalidated("OK"),
+                literal_reject_text: Text::unvalidated("Literal rejected"),
+                ..ServerFlowOptions::default()
+            },
+            Greeting::ok(
+                Some(Code::Capability(ctx.server_capabilities.to_vec())),
+                "Aerogramme",
+                )
+            .unwrap(),
+            )
+            .await?;
+
+        // Start a mailbox session in background
+        let (cmd_tx, mut cmd_rx) = mpsc::channel::<Request>(3);
+        let (resp_tx, mut resp_rx) = mpsc::unbounded_channel::<ResponseOrIdle>();
+        tokio::spawn(Self::session(ctx.clone(), cmd_rx, resp_tx));
+
+        // Return the object
+        Ok(NetLoop { ctx, server, cmd_tx, resp_rx })
+    }
+
+    /// Coms with the background session
+    async fn session(ctx: ClientContext, mut cmd_rx: Receiver<Request>, resp_tx: UnboundedSender<ResponseOrIdle>) -> () {
         let mut session = Instance::new(ctx.login_provider, ctx.server_capabilities);
         loop {
             let cmd = match cmd_rx.recv().await {
@@ -140,8 +173,8 @@ async fn client(mut ctx: ClientContext) -> Result<()> {
             };
 
             tracing::debug!(cmd=?cmd, sock=%ctx.addr, "command");
-            let maybe_response = session.command(cmd).await;
-            tracing::debug!(cmd=?maybe_response.completion, sock=%ctx.addr, "response");
+            let maybe_response = session.request(cmd).await;
+            tracing::debug!(cmd=?maybe_response, sock=%ctx.addr, "response");
 
             match resp_tx.send(maybe_response) {
                 Err(_) => break,
@@ -149,67 +182,81 @@ async fn client(mut ctx: ClientContext) -> Result<()> {
             };
         }
         tracing::info!("runner is quitting");
-    });
+    }
 
-    // Main loop
-    loop {
+    async fn core(mut self) -> Result<()> {
+        let mut mode = LoopMode::Interactive;
+        loop {
+            mode = match mode {
+                LoopMode::Interactive => self.interactive_mode().await?,
+                LoopMode::IdleUntil(notif) => self.idle_mode(notif).await?,
+                LoopMode::Quit => break,
+            }
+        }
+        Ok(())
+    }
+
+
+    async fn interactive_mode(&mut self) -> Result<LoopMode> {
         tokio::select! {
             // Managing imap_flow stuff
-            srv_evt = server.progress() =>  match srv_evt? {
+            srv_evt = self.server.progress() =>  match srv_evt? {
                 ServerFlowEvent::ResponseSent { handle: _handle, response } => {
                     match response {
-                        Response::Status(Status::Bye(_)) => break,
-                        _ => tracing::trace!("sent to {} content {:?}", ctx.addr, response),
+                        Response::Status(Status::Bye(_)) => return Ok(LoopMode::Quit),
+                        _ => tracing::trace!("sent to {} content {:?}", self.ctx.addr, response),
                     }
                 },
                 ServerFlowEvent::CommandReceived { command } => {
-                    match cmd_tx.try_send(command) {
+                    match self.cmd_tx.try_send(Request::ImapCommand(command)) {
                         Ok(_) => (),
                         Err(mpsc::error::TrySendError::Full(_)) => {
-                            server.enqueue_status(Status::bye(None, "Too fast").unwrap());
-                            tracing::error!("client {:?} is sending commands too fast, closing.", ctx.addr);
+                            self.server.enqueue_status(Status::bye(None, "Too fast").unwrap());
+                            tracing::error!("client {:?} is sending commands too fast, closing.", self.ctx.addr);
                         }
                         _ => {
-                            server.enqueue_status(Status::bye(None, "Internal session exited").unwrap());
-                            tracing::error!("session task exited for {:?}, quitting", ctx.addr);
+                            self.server.enqueue_status(Status::bye(None, "Internal session exited").unwrap());
+                            tracing::error!("session task exited for {:?}, quitting", self.ctx.addr);
                         }
                     }
                 },
                 flow => {
-                    server.enqueue_status(Status::bye(None, "Unsupported server flow event").unwrap());
-                    tracing::error!("session task exited for {:?} due to unsupported flow {:?}", ctx.addr, flow);
-
+                    self.server.enqueue_status(Status::bye(None, "Unsupported server flow event").unwrap());
+                    tracing::error!("session task exited for {:?} due to unsupported flow {:?}", self.ctx.addr, flow);
                 }
             },
 
             // Managing response generated by Aerogramme
-            maybe_msg = resp_rx.recv() => {
-                let response = match maybe_msg {
-                    None => {
-                        server.enqueue_status(Status::bye(None, "Internal session exited").unwrap());
-                        tracing::error!("session task exited for {:?}, quitting", ctx.addr);
-                        continue
-                    },
-                    Some(r) => r,
-                };
-
-                for body_elem in response.body.into_iter() {
-                    let _handle = match body_elem {
-                        Body::Data(d) => server.enqueue_data(d),
-                        Body::Status(s) => server.enqueue_status(s),
-                    };
-                }
-                server.enqueue_status(response.completion);
+            maybe_msg = self.resp_rx.recv() => match maybe_msg {
+                Some(ResponseOrIdle::Response(response)) => {
+                    for body_elem in response.body.into_iter() {
+                        let _handle = match body_elem {
+                            Body::Data(d) => self.server.enqueue_data(d),
+                            Body::Status(s) => self.server.enqueue_status(s),
+                        };
+                    }
+                    self.server.enqueue_status(response.completion);
+                },
+                Some(ResponseOrIdle::Idle) => {
+                    let cr = CommandContinuationRequest::basic(None, "idling")?;
+                    self.server.enqueue_continuation(cr);
+                    return Ok(LoopMode::IdleUntil(tokio::sync::Notify::new()))
+                },
+                None => {
+                    self.server.enqueue_status(Status::bye(None, "Internal session exited").unwrap());
+                    tracing::error!("session task exited for {:?}, quitting", self.ctx.addr);
+                },
             },
 
             // When receiving a CTRL+C
-            _ = ctx.must_exit.changed() => {
-                server.enqueue_status(Status::bye(None, "Server is being shutdown").unwrap());
+            _ = self.ctx.must_exit.changed() => {
+                self.server.enqueue_status(Status::bye(None, "Server is being shutdown").unwrap());
             },
         };
+        Ok(LoopMode::Interactive)
     }
 
-    drop(cmd_tx);
-    bckgrnd.await?;
-    Ok(())
+    async fn idle_mode(&mut self, notif: tokio::sync::Notify) -> Result<LoopMode> {
+        Ok(LoopMode::IdleUntil(notif))
+    }
 }

src/imap/request.rs

@@ -0,0 +1,8 @@
+use imap_codec::imap_types::command::Command;
+use tokio::sync::Notify;
+
+#[derive(Debug)]
+pub enum Request {
+    ImapCommand(Command<'static>),
+    IdleUntil(Notify),
+}

src/imap/response.rs

@@ -3,6 +3,7 @@ use imap_codec::imap_types::command::Command;
 use imap_codec::imap_types::core::Tag;
 use imap_codec::imap_types::response::{Code, Data, Status};
 
+#[derive(Debug)]
 pub enum Body<'a> {
     Data(Data<'a>),
     Status(Status<'a>),
@@ -88,6 +89,7 @@ impl<'a> ResponseBuilder<'a> {
     }
 }
 
+#[derive(Debug)]
 pub struct Response<'a> {
     pub body: Vec<Body<'a>>,
     pub completion: Status<'a>,
@@ -110,3 +112,9 @@ impl<'a> Response<'a> {
         })
     }
 }
+
+#[derive(Debug)]
+pub enum ResponseOrIdle {
+    Response(Response<'static>),
+    Idle,
+}

src/imap/session.rs

@@ -1,7 +1,9 @@
+use anyhow::anyhow;
 use crate::imap::capability::{ClientCapability, ServerCapability};
 use crate::imap::command::{anonymous, authenticated, examined, selected};
 use crate::imap::flow;
-use crate::imap::response::Response;
+use crate::imap::request::Request;
+use crate::imap::response::{Response, ResponseOrIdle};
 use crate::login::ArcLoginProvider;
 use imap_codec::imap_types::command::Command;
 
@@ -23,7 +25,24 @@ impl Instance {
         }
     }
 
-    pub async fn command(&mut self, cmd: Command<'static>) -> Response<'static> {
+    pub async fn request(&mut self, req: Request) -> ResponseOrIdle {
+        match req {
+            Request::IdleUntil(stop) => ResponseOrIdle::Response(self.idle(stop).await),
+            Request::ImapCommand(cmd) => self.command(cmd).await,
+        }
+    }
+
+    pub async fn idle(&mut self, stop: tokio::sync::Notify) -> Response<'static> {
+        let (user, mbx) = match &mut self.state {
+            flow::State::Idle(ref user, ref mut mailbox, ref perm) => (user, mailbox),
+            _ => unreachable!(),
+        };
+
+        unimplemented!();
+    }
+
+
+    pub async fn command(&mut self, cmd: Command<'static>) -> ResponseOrIdle {
         // Command behavior is modulated by the state.
         // To prevent state error, we handle the same command in separate code paths.
         let (resp, tr) = match &mut self.state {
@@ -44,26 +63,18 @@ impl Instance {
                 };
                 authenticated::dispatch(ctx).await
             }
-            flow::State::Selected(ref user, ref mut mailbox) => {
+            flow::State::Selected(ref user, ref mut mailbox, ref perm) => {
                 let ctx = selected::SelectedContext {
                     req: &cmd,
                     server_capabilities: &self.server_capabilities,
                     client_capabilities: &mut self.client_capabilities,
                     user,
                     mailbox,
+                    perm,
                 };
                 selected::dispatch(ctx).await
             }
-            flow::State::Examined(ref user, ref mut mailbox) => {
-                let ctx = examined::ExaminedContext {
-                    req: &cmd,
-                    server_capabilities: &self.server_capabilities,
-                    client_capabilities: &mut self.client_capabilities,
-                    user,
-                    mailbox,
-                };
-                examined::dispatch(ctx).await
-            }
+            flow::State::Idle(..) => Err(anyhow!("can not receive command while idling")),
             flow::State::Logout => Response::build()
                 .tag(cmd.tag.clone())
                 .message("No commands are allowed in the LOGOUT state.")
@@ -88,15 +99,18 @@ impl Instance {
                 e,
                 cmd
             );
-            return Response::build()
+            return ResponseOrIdle::Response(Response::build()
                 .to_req(&cmd)
                 .message(
                     "Internal error, processing command triggered an illegal IMAP state transition",
                 )
                 .bad()
-                .unwrap();
+                .unwrap());
         }
 
-        resp
+        match self.state {
+            flow::State::Idle(..) => ResponseOrIdle::Idle,
+            _ => ResponseOrIdle::Response(resp),
+        }
     }
 }