chore: users can leave federations with zero balance

src/fedimint.rs

@@ -175,7 +175,7 @@ impl Wallet {
 
     pub async fn connect_to_joined_federations(&self) -> anyhow::Result<()> {
         // Note: We're intentionally locking the clients mutex earlier than
-        // necessary so that the lock is held while we're reading the data directory.
+        // necessary so that the lock is held while we're accessing the data directory.
         let mut clients = self.clients.lock().await;
 
         // List all files in the data directory.
@@ -217,7 +217,7 @@ impl Wallet {
 
     pub async fn join_federation(&self, invite_code: InviteCode) -> anyhow::Result<()> {
         // Note: We're intentionally locking the clients mutex earlier than
-        // necessary so that the lock is held while we're reading the data directory.
+        // necessary so that the lock is held while we're accessing the data directory.
         let mut clients = self.clients.lock().await;
 
         let federation_id = invite_code.federation_id();
@@ -242,6 +242,42 @@ impl Wallet {
         Ok(())
     }
 
+    // TODO: Call `ClientModule::leave()` for every module.
+    // https://docs.rs/fedimint-client/0.4.2/fedimint_client/module/trait.ClientModule.html#method.leave
+    // Currently it isn't implemented for the `LightningClientModule`, so for now we're just checking
+    // that the client has a zero balance.
+    pub async fn leave_federation(&self, federation_id: FederationId) -> anyhow::Result<()> {
+        // Note: We're intentionally locking the clients mutex earlier than
+        // necessary so that the lock is held while we're accessing the data directory.
+        let mut clients = self.clients.lock().await;
+
+        if let Some(client) = clients.remove(&federation_id) {
+            if client.get_balance().await.msats != 0 {
+                // Re-insert the client back into the clients map.
+                clients.insert(federation_id, client);
+
+                return Err(anyhow::anyhow!(
+                    "Cannot leave federation with non-zero balance: {}",
+                    federation_id
+                ));
+            }
+
+            client.shutdown().await;
+
+            let federation_data_dir = self
+                .fedimint_clients_data_dir
+                .join(federation_id.to_string());
+
+            if federation_data_dir.is_dir() {
+                std::fs::remove_dir_all(federation_data_dir)?;
+            }
+        }
+
+        self.force_update_view(clients).await;
+
+        Ok(())
+    }
+
     /// Constructs the current view of the wallet.
     /// SHOULD ONLY BE CALLED FROM THE `view_update_task`.
     /// This way, `view_update_task` can only yield values

src/routes/bitcoin_wallet.rs

@@ -1,7 +1,7 @@
 use std::str::FromStr;
 
 use fedimint_core::{
-    config::{ClientConfig, META_FEDERATION_NAME_KEY},
+    config::{ClientConfig, FederationId, META_FEDERATION_NAME_KEY},
     invite_code::InviteCode,
     Amount,
 };
@@ -42,6 +42,9 @@ pub enum Message {
     JoinFederation(InviteCode),
     JoinedFederation(InviteCode),
 
+    LeaveFederation(FederationId),
+    LeftFederation(FederationId),
+
     Send(send::Message),
     Receive(receive::Message),
 
@@ -196,6 +199,44 @@ impl Page {
 
                 Task::none()
             }
+            Message::LeaveFederation(federation_id) => {
+                let wallet = self.connected_state.wallet.clone();
+
+                Task::stream(async_stream::stream! {
+                    match wallet.leave_federation(federation_id).await {
+                        Ok(()) => {
+                            yield app::Message::AddToast(Toast {
+                                title: "Left federation".to_string(),
+                                body: "You have successfully left the federation.".to_string(),
+                                status: ToastStatus::Good,
+                            });
+
+                            yield app::Message::Routes(super::Message::BitcoinWalletPage(
+                                Message::LeftFederation(federation_id)
+                            ));
+                        }
+                        Err(err) => {
+                            yield app::Message::AddToast(Toast {
+                                title: "Failed to leave federation".to_string(),
+                                body: format!("Failed to leave the federation: {err}"),
+                                status: ToastStatus::Bad,
+                            });
+                        }
+                    }
+                })
+            }
+            Message::LeftFederation(federation_id) => {
+                // A verbose way of saying "if the user is currently on the FederationDetails page and the federation ID matches the one that was just left, navigate back to the List page".
+                if let Subroute::FederationDetails(federation_details) = &self.subroute {
+                    if federation_details.view.federation_id == federation_id {
+                        return Task::done(app::Message::Routes(super::Message::Navigate(
+                            RouteName::BitcoinWallet(SubrouteName::List),
+                        )));
+                    }
+                }
+
+                Task::none()
+            }
             Message::Send(send_message) => {
                 if let Subroute::Send(send_page) = &mut self.subroute {
                     send_page.update(send_message)
@@ -444,6 +485,27 @@ impl FederationDetails {
             );
         }
 
+        // TODO: Add a function to `Wallet` to check whether we can safely leave a federation.
+        // Call it here rather and get rid of `has_zero_balance`.
+        let has_zero_balance = self.view.balance.msats == 0;
+
+        if !has_zero_balance {
+            container = container.push(
+                Text::new("Must have a zero balance in this federation in order to leave.")
+                    .size(20),
+            );
+        }
+
+        container = container.push(
+            icon_button("Leave Federation", SvgIcon::Delete, PaletteColor::Danger).on_press_maybe(
+                has_zero_balance.then(|| {
+                    app::Message::Routes(super::Message::BitcoinWalletPage(
+                        Message::LeaveFederation(self.view.federation_id),
+                    ))
+                }),
+            ),
+        );
+
         container = container.push(
             icon_button("Back", SvgIcon::ArrowBack, PaletteColor::Background).on_press(
                 app::Message::Routes(super::Message::Navigate(RouteName::BitcoinWallet(