1 files changed, 102 insertions, 0 deletions
diff --git a/src/session.rs b/src/session.rs
new file mode 100644
index 0000000..7553caf
--- /dev/null
+++ b/src/session.rs
@@ -0,0 +1,102 @@
+use std::sync::Arc;
+
+use boitalettres::proto::{Request, Response};
+use boitalettres::errors::Error as BalError;
+use imap_codec::types::command::CommandBody;
+use tokio::sync::{oneshot,mpsc};
+use tokio::sync::mpsc::error::TrySendError;
+use futures::future::BoxFuture;
+use futures::future::FutureExt;
+
+use crate::command;
+use crate::login::Credentials;
+use crate::mailstore::Mailstore;
+use crate::mailbox::Mailbox;
+
+/* This constant configures backpressure in the system,
+ * or more specifically, how many pipelined messages are allowed
+ * before refusing them 
+ */
+const MAX_PIPELINED_COMMANDS: usize = 10;
+
+struct Message {
+    req: Request,
+    tx: oneshot::Sender<Response>,
+}
+
+pub struct Manager {
+    tx: mpsc::Sender<Message>,
+}
+
+//@FIXME we should garbage collect the Instance when the Manager is destroyed.
+impl Manager {
+    pub fn new(mailstore: Arc<Mailstore>) -> Self {
+        let (tx, mut rx) = mpsc::channel(MAX_PIPELINED_COMMANDS);
+        tokio::spawn(async move { 
+            let mut instance = Instance::new(mailstore, rx);
+            instance.start().await;
+        });
+        Self { tx }
+    }
+
+    pub fn process(&self, req: Request) -> BoxFuture<'static, Result<Response, BalError>> {
+        let (tx, rx) = oneshot::channel();
+        let msg = Message { req, tx };
+
+        // We use try_send on a bounded channel to protect the daemons from DoS.
+        // Pipelining requests in IMAP are a special case: they should not occure often
+        // and in a limited number (like 3 requests). Someone filling the channel
+        // will probably be malicious so we "rate limit" them.
+        match self.tx.try_send(msg) {
+            Ok(()) => (),
+            Err(TrySendError::Full(_)) => return async { Response::bad("Too fast! Send less pipelined requests!") }.boxed(),
+            Err(TrySendError::Closed(_)) => return async { Response::bad("The session task has exited") }.boxed(),
+        };
+
+        // @FIXME add a timeout, handle a session that fails.
+        async {
+            rx.await.or_else(|e| {
+                tracing::warn!("Got error {:#?}", e);
+                Response::bad("No response from the session handler")
+            })
+        }.boxed()
+    }
+}
+
+pub struct Instance {
+    rx: mpsc::Receiver<Message>,
+
+    pub mailstore: Arc<Mailstore>, 
+    pub creds: Option<Credentials>,
+    pub selected: Option<Mailbox>,
+}
+impl Instance {
+    fn new(mailstore: Arc<Mailstore>, rx: mpsc::Receiver<Message>) -> Self {
+        Self { mailstore, rx, creds: None, selected: None, }
+    }
+
+    //@FIXME add a function that compute the runner's name from its local info
+    // to ease debug
+    // fn name(&self) -> String { }
+
+    async fn start(&mut self) {
+        //@FIXME add more info about the runner
+        tracing::debug!("starting runner");
+
+        while let Some(msg) = self.rx.recv().await {
+            let mut cmd = command::Command::new(msg.req.tag, self);
+            let _ = match msg.req.body {
+                CommandBody::Capability => cmd.capability().await,
+                CommandBody::Login { username, password } => cmd.login(username, password).await,
+                CommandBody::Lsub { reference, mailbox_wildcard } => cmd.lsub(reference, mailbox_wildcard).await,
+                CommandBody::List { reference, mailbox_wildcard } => cmd.list(reference, mailbox_wildcard).await,
+                CommandBody::Select { mailbox } => cmd.select(mailbox).await,
+                CommandBody::Fetch { sequence_set, attributes, uid } => cmd.fetch(sequence_set, attributes, uid).await,
+                _ => Response::bad("Error in IMAP command received by server."),
+            };
+        }
+
+        //@FIXME add more info about the runner
+        tracing::debug!("exiting runner");
+    }
+}