make --email optional, saved on enroll and reused on subsequent runs

src/main.rs

@@ -6,6 +6,9 @@ mod ipc;
 mod log;
 mod storage;
 
+use std::fs;
+use std::path::PathBuf;
+
 use clap::Parser;
 use sha2::{Digest, Sha256};
 use zeroize::Zeroize;
@@ -18,7 +21,7 @@ use storage::get_backend;
 #[command(about = "Bitwarden desktop bridge agent")]
 struct Args {
     #[arg(long)]
-    email: String,
+    email: Option<String>,
 
     #[arg(long)]
     password: Option<String>,
@@ -39,6 +42,27 @@ struct Args {
     remove: bool,
 }
 
+fn config_dir() -> PathBuf {
+    let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".into());
+    PathBuf::from(home).join(".cache").join("com.bitwarden.desktop")
+}
+
+fn config_path() -> PathBuf {
+    config_dir().join("agent.conf")
+}
+
+fn save_email(email: &str) {
+    fs::create_dir_all(config_dir()).ok();
+    fs::write(config_path(), email).ok();
+}
+
+fn load_email() -> Option<String> {
+    fs::read_to_string(config_path())
+        .ok()
+        .map(|s| s.trim().to_string())
+        .filter(|s| !s.is_empty())
+}
+
 fn user_hash(email: &str) -> String {
     let mut hasher = Sha256::new();
     hasher.update(email.to_lowercase().trim().as_bytes());
@@ -48,7 +72,14 @@ fn user_hash(email: &str) -> String {
 
 fn main() {
     let args = Args::parse();
-    let uid = user_hash(&args.email);
+
+    let email = args
+        .email
+        .clone()
+        .or_else(load_email)
+        .unwrap_or_else(|| log::fatal("no email provided (use --email on first run)"));
+
+    let uid = user_hash(&email);
     let store = get_backend(args.backend.as_deref());
     let prompt = get_prompter(args.askpass.as_deref());
     log::info(&format!("backend: {}", store.name()));
@@ -56,9 +87,9 @@ fn main() {
     if args.remove {
         if store.has_key(&uid) {
             store.remove(&uid);
-            log::info(&format!("key removed for {}", args.email));
+            log::info(&format!("key removed for {email}"));
         } else {
-            log::info(&format!("no key found for {}", args.email));
+            log::info(&format!("no key found for {email}"));
         }
         return;
     }
@@ -76,8 +107,8 @@ fn main() {
             .or_else(|| prompt("master password:"))
             .unwrap_or_else(|| log::fatal("no password provided"));
 
-        log::info(&format!("logging in as {}", args.email));
-        let (mut key_bytes, server_uid) = auth::login(&args.email, &pw, &args.server, &prompt);
+        log::info(&format!("logging in as {email}"));
+        let (mut key_bytes, server_uid) = auth::login(&email, &pw, &args.server, &prompt);
         log::info(&format!("authenticated, uid={server_uid}"));
 
         let auth = prompt(&format!("choose {} password:", store.name()))
@@ -92,10 +123,11 @@ fn main() {
             .store(&uid, &key_bytes, &auth)
             .unwrap_or_else(|e| log::fatal(&format!("store failed: {e}")));
         key_bytes.zeroize();
+        save_email(&email);
         log::info(&format!("key sealed via {}", store.name()));
         log::info("wiped key from memory");
     } else {
-        log::info(&format!("key ready for {}", args.email));
+        log::info(&format!("key ready for {email}"));
     }
 
     let mut bridge = BiometricBridge::new(store, uid, prompt);