1 files changed, 145 insertions, 0 deletions
diff --git a/src/session.rs b/src/session.rs
new file mode 100644
index 0000000..a3e4e24
--- /dev/null
+++ b/src/session.rs
@@ -0,0 +1,145 @@
+use std::sync::Arc;
+
+use boitalettres::errors::Error as BalError;
+use boitalettres::proto::{Request, Response};
+use futures::future::BoxFuture;
+use futures::future::FutureExt;
+use imap_codec::types::command::CommandBody;
+use tokio::sync::mpsc::error::TrySendError;
+use tokio::sync::{mpsc, oneshot};
+
+use crate::command;
+use crate::login::Credentials;
+use crate::mailbox::Mailbox;
+use crate::LoginProvider;
+
+/* 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<Result<Response, BalError>>,
+}
+
+pub struct Manager {
+    tx: mpsc::Sender<Message>,
+}
+
+//@FIXME we should garbage collect the Instance when the Manager is destroyed.
+impl Manager {
+    pub fn new(login_provider: Arc<dyn LoginProvider + Send + Sync>) -> Self {
+        let (tx, rx) = mpsc::channel(MAX_PIPELINED_COMMANDS);
+        tokio::spawn(async move {
+            let mut instance = Instance::new(login_provider, 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 {
+            match rx.await {
+                Ok(r) => r,
+                Err(e) => {
+                    tracing::warn!("Got error {:#?}", e);
+                    Response::bad("No response from the session handler")
+                }
+            }
+        }
+        .boxed()
+    }
+}
+
+pub struct User {
+    pub name: String,
+    pub creds: Credentials,
+}
+
+pub struct Instance {
+    rx: mpsc::Receiver<Message>,
+
+    pub login_provider: Arc<dyn LoginProvider + Send + Sync>,
+    pub selected: Option<Mailbox>,
+    pub user: Option<User>,
+}
+impl Instance {
+    fn new(login_provider: Arc<dyn LoginProvider + Send + Sync>, rx: mpsc::Receiver<Message>) -> Self {
+        Self {
+            login_provider,
+            rx,
+            selected: None,
+            user: 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 res = 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.")
+                    .map_err(anyhow::Error::new),
+            };
+
+            let wrapped_res = res.or_else(|e| match e.downcast::<BalError>() {
+                Ok(be) => Err(be),
+                Err(ae) => {
+                    tracing::warn!(error=%ae, "internal.error");
+                    Response::bad("Internal error")
+                }
+            });
+
+            //@FIXME I think we should quit this thread on error and having our manager watch it,
+            // and then abort the session as it is corrupted.
+            msg.tx.send(wrapped_res).unwrap_or_else(|e| {
+                tracing::warn!("failed to send imap response to manager: {:#?}", e)
+            });
+        }
+
+        //@FIXME add more info about the runner
+        tracing::debug!("exiting runner");
+    }
+}