Add setup instructions

src/main.rs

@@ -1,7 +1,7 @@
 use std::time::{SystemTime, UNIX_EPOCH};
 
 use base32::Alphabet;
-use clap::Parser;
+use clap::{Parser, Subcommand};
 use totp_rfc6238::{HashAlgorithm, TotpGenerator};
 
 /// Get the current time since epoch
@@ -14,6 +14,18 @@ pub fn time() -> u64 {
 #[derive(Parser, Debug)]
 #[clap(author, version, about, long_about = None)]
 struct Args {
+    #[clap(subcommand)]
+    command: SubCommands
+}
+
+#[derive(Subcommand, Debug)]
+enum SubCommands {
+    /// Setup configuration
+    Setup,
+
+    /// Get a TOTP code
+    #[clap(arg_required_else_help = true)]
+    Code {
         /// The secret to use
         #[clap(short, long)]
         secret: String,
@@ -25,20 +37,34 @@ struct Args {
         /// Size of generated secret
         #[clap(short, long, default_value_t = 6)]
         len: usize,
+    },
 }
 
 fn main() {
     let args: Args = Args::parse();
 
+    match args.command {
+        SubCommands::Setup => {
+            println!("To configure TOPT :");
+            println!("1. Please open https://mysignins.microsoft.com/security-info");
+            println!("2. Click on \"Add method\"");
+            println!("3. On the popup that appears, choose \"Authenticator app\" and click \"Add\".");
+            println!("4. Click on \"I want to use a different authenticator app\" and click \"Next\"");
+            println!("5. Click on \"Can't save image ?\" and copy the \"Secret key\"");
+            println!("6. Re-run this program running {} code --secret <SECRET>", std::env::args().next().unwrap());
+            println!("7. Back on the browser, click Next and paste copied code");
+        }
+
+        SubCommands::Code { secret, topt_step, len } => {
             let totp_generator = TotpGenerator::new()
-        .set_digit(args.len).unwrap()
-        .set_step(args.topt_step).unwrap()
+                .set_digit(len).unwrap()
+                .set_step(topt_step).unwrap()
                 .set_hash_algorithm(HashAlgorithm::SHA1)
                 .build();
 
             let key = base32::decode(
                 Alphabet::RFC4648 { padding: true },
-        &args.secret,
+                &secret,
             ).unwrap();
 
             let code = totp_generator.get_code(&key);
@@ -47,3 +73,5 @@ fn main() {
             println!("Secret = {}", code);
             println!("Next update = {} seconds", next_update - time());
         }
+    }
+}