Login in a more restorable way

src/main.rs

@@ -8,6 +8,7 @@ use matrix_sdk::ruma::events::SyncMessageEvent;
 use matrix_sdk::ruma::UserId;
 use matrix_sdk::{Client, Session};
 use std::convert::TryFrom;
+use std::fs::File;
 use std::sync::Arc;
 use tokio::io::AsyncReadExt;
 use tokio::sync::RwLock;
@@ -79,14 +80,22 @@ async fn main() -> anyhow::Result<()> {
     };
 
     eprintln!("Logging in!");
-    client
-        .login(
-            mxid.localpart(),
-            &config.matrix_password,
-            Some("mxmonzo"),
-            Some("rei's MxMonzo"),
-        )
-        .await?;
+
+    if config.matrix_persist.exists() {
+        let session: Session = serde_json::from_reader(File::open(config.matrix_persist)?)?;
+        client.restore_login(session).await?;
+    } else {
+        let session: Session = client
+            .login(
+                mxid.localpart(),
+                &config.matrix_password,
+                None,
+                Some("rei's MxMonzo"),
+            )
+            .await?
+            .into();
+        serde_json::to_writer(File::create(config.matrix_persist)?, &session)?;
+    }
 
     eprintln!("Syncing once!");
     client.sync_once(SyncSettings::new()).await?;

src/state.rs

@@ -19,6 +19,7 @@ pub struct Config {
     pub matrix_room: String,
     pub matrix_store: PathBuf,
     pub matrix_password: String,
+    pub matrix_persist: PathBuf,
     pub monzo_persist: PathBuf,
     pub monzo_client_id: String,
     pub monzo_client_secret: String,