Move select_folder to a separate submodule

src/imap/select_folder.rs

@@ -0,0 +1,90 @@
+use super::{Result, Error, Imap};
+use crate::context::Context;
+
+impl Imap {
+    /// select a folder, possibly update uid_validity and, if needed,
+    /// expunge the folder to remove delete-marked messages.
+    pub(super) async fn select_folder<S: AsRef<str>>(
+        &self,
+        context: &Context,
+        folder: Option<S>,
+    ) -> Result<()> {
+        if self.session.lock().await.is_none() {
+            let mut cfg = self.config.write().await;
+            cfg.selected_folder = None;
+            cfg.selected_folder_needs_expunge = false;
+            return Err(Error::NoSession);
+        }
+
+        // if there is a new folder and the new folder is equal to the selected one, there's nothing to do.
+        // if there is _no_ new folder, we continue as we might want to expunge below.
+        if let Some(ref folder) = folder {
+            if let Some(ref selected_folder) = self.config.read().await.selected_folder {
+                if folder.as_ref() == selected_folder {
+                    return Ok(());
+                }
+            }
+        }
+
+        // deselect existing folder, if needed (it's also done implicitly by SELECT, however, without EXPUNGE then)
+        let needs_expunge = { self.config.read().await.selected_folder_needs_expunge };
+        if needs_expunge {
+            if let Some(ref folder) = self.config.read().await.selected_folder {
+                info!(context, "Expunge messages in \"{}\".", folder);
+
+                // A CLOSE-SELECT is considerably faster than an EXPUNGE-SELECT, see
+                // https://tools.ietf.org/html/rfc3501#section-6.4.2
+                if let Some(ref mut session) = &mut *self.session.lock().await {
+                    match session.close().await {
+                        Ok(_) => {
+                            info!(context, "close/expunge succeeded");
+                        }
+                        Err(err) => {
+                            return Err(Error::CloseExpungeFailed(err));
+                        }
+                    }
+                } else {
+                    return Err(Error::NoSession);
+                }
+            }
+            self.config.write().await.selected_folder_needs_expunge = false;
+        }
+
+        // select new folder
+        if let Some(ref folder) = folder {
+            if let Some(ref mut session) = &mut *self.session.lock().await {
+                let res = session.select(folder).await;
+
+                // https://tools.ietf.org/html/rfc3501#section-6.3.1
+                // says that if the server reports select failure we are in
+                // authenticated (not-select) state.
+
+                match res {
+                    Ok(mailbox) => {
+                        let mut config = self.config.write().await;
+                        config.selected_folder = Some(folder.as_ref().to_string());
+                        config.selected_mailbox = Some(mailbox);
+                        Ok(())
+                    }
+                    Err(async_imap::error::Error::ConnectionLost) => {
+                        self.trigger_reconnect();
+                        self.config.write().await.selected_folder = None;
+                        Err(Error::ConnectionLost)
+                    }
+                    Err(async_imap::error::Error::Validate(_)) => {
+                        Err(Error::BadFolderName(folder.as_ref().to_string()))
+                    }
+                    Err(err) => {
+                        self.config.write().await.selected_folder = None;
+                        self.trigger_reconnect();
+                        Err(Error::Other(err.to_string()))
+                    }
+                }
+            } else {
+                Err(Error::NoSession)
+            }
+        } else {
+            Ok(())
+        }
+    }
+}